APA Engineered Wodd Handbooks Episode 7 pot

PR TM 40 14" SPACING 12 oc 19.2 oc 24 oc SIMPLE SPAN 24-4 20'-2 MULTIPLE SPAN 25-6 22-1 20'-1 Performance Rated Wood I-Joist for Glued Residential Floors MILL 0000 • PRI-400 PR TM 40 14"

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CHAPTER FIVE PREFABRICATED WOOD

I-JOISTS AND ENGINEERED

RIM BOARD

Edward Keith, P.E.

Senior Engineer, TSD

5.1 INTRODUCTION

While relatively new to the construction industry, when compared to products such

as lumber, plywood, or glued laminated timber, both prefabricated wood I-joistsand engineered rim board products are rapidly becoming the products of choice byquality- and environmentally-conscious builders alike Both of these engineeredwood products are discussed in detail in this chapter, starting with I-joists and thenengineered rim board in Section 5.12

5.1.1 The Development of Prefabricated Wood I-joists and Rim Board

Originally commercialized by the Trus Joist Corporation (now a WeyerhaeuserCompany) in the 1960s, engineered wood I-joists owe their beginning, at least inpart, to a publication developed by the Douglas Fir Plywood Association (a pre-cursor to APA—The Engineered Wood Association) in 1959 entitled DFPA Spec-

ification BB-8, Design of Plywood Beams.1 This specification, later published as

Plywood Design Specification Supplement 2, Design and Fabrication of Glued Plywood-Lumber Beams,2 outlined the original design procedures that ultimatelyprovided the basis for current design recommendations

The first universally recognized standard for wood I-joists was ASTM D5055,

Standard Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I-Joists.3 This consensus standard provides guidelines for theevaluation of mechanical properties, physical properties, and quality of wood I-joists and is the current common testing standard for I-joists However, since ASTMD5055 does not specify required levels of performance, individual manufacturers

of I-joists generally have their own proprietary company standards that govern theeveryday production practice for their products The common sizes and design

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To fill this need for standard performance levels, APA, in conjunction withseveral I-joist manufacturers, is developing performance-based standards forperformance-rated wood I-joist products The first such APA performance standard

is for the use of wood I-joists in residential floors, designated as PRI-400.5It should

be noted that this is a voluntary standard and not all I-joist manufacturers havechosen to produce PRI-400 products

Since APA has promulgated the PRI-400 standard, much of the informationpresented in this chapter will be based on this standard However, this does notpreclude the use of any wood I-joists to achieve similar intended functions Alsomanufacturers who do manufacture the PRI-400 products may also manufacture aproprietary series of I-joists for which they have obtained individual ES or NEScode reports

While clearly a good idea from the start for a number of structural reasons thatwill be discussed in detail in this chapter, the increased use of engineered woodproducts such as wood I-joists and engineered wood rim board in construction willhave a positive impact on the environment, from the standpoint of reducing demandfor products from older-growth forests Historically, residential floors have beenframed with 2⫻ 10s (38⫻235 mm) and 2 ⫻ 12s (38⫻305 mm) These sizeshad to be milled from trees that were at least 18 in (460 mm) in diameter, neces-sitating the use of older-growth trees Engineered wood I-joists and rim board prod-ucts are both made out of a number of engineered wood components, all currentlybeing made economically out of second- and third generation plantation forests Nolonger requiring the log sizes only found in older forests, these engineered woodproducts also permit the use of fast-growing species for which there was no com-mercial value just a few years ago Engineered wood products such as I-joists andrim board have led the way in the early green building movement Figure 5.1illustrates the use of wood I-joists and structural wood panel rim board

5.2 PREFABRICATED WOOD I-JOISTS

5.2.1 Growth of the Industry

Figure 5.2 shows market trends for North American (United States and Canada) joists from 1980 through 2000 The source of the data can be found in the legend

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I-FIGURE 5.1 Engineered wood products used in a residential floor system.

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5.4 CHAPTER FIVE

Web

Flange

FIGURE 5.3 Engineered wood I-joist.

to the graph.6,7The residential market has been the driver in the United States andCanada, accounting for about 90% of the volume increase in the last 4 years.Remodeling and nonresidential construction uses are also increasing, and thesemarkets will provide for even more market volume growth in the future As shown

by Fig 5.2, the total U.S and Canadian I-joist production was approximately 890million lineal feet (271 million lineal meters) in 2000

As engineered wood I-joists only represent about 1⁄3 of the raised floor joistmarket in single- and multifamily residential construction and only a negligibleamount of the wood roof framing market, it can be seen that tremendous domesticmarket potential remains to be tapped

5.2.2 What Is an APA Performance Rated I-Joist?

The APA Performance Rated I-joist (PRI) is an I-shaped engineered wood structuralmember designed for use in residential floor and roof construction (see Fig 5.3).PRI I-joist products are manufactured under the rigorous quality assurance standards

of APA—The Engineered Wood Association Other I-joist products manufactured

in accordance with other proprietary code evaluation reports may fulfill the samepurpose

Performance Rated I-joists are identified by their net depth followed by a ignation such as ‘‘PRI-30’’ that relates to the joist design properties These desig-nations will be covered later in detail In order to be classified as a PRI, the joist

des-is limited to a L / 480 live load maximum deflection (where L⫽ span) for nailed residential floor applications, a criterion that provides superior floor perform-ance

glued-PRIs are manufactured to strict tolerances with the following characteristics:

• Flanges are either sawn lumber or structural composite lumber, typically LVL.The top flange is of the same type and grade of material as the bottom flange.The net flange size depends on the material used

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TABLE 5.1 Designations for APA Performance Rated I-Joists

PRI-30 PRI-40 PRI-50 PRI-60

PRI-30 PRI-40 PRI-50 PRI-60 PRI-70 PRI-80 PRI-90

PRI-50 PRI-60 PRI-70 PRI-80 PRI-90

For SI: 1 in ⫽ 25.4 mm.

• Webs consist of wood structural panels, which can be plywood or OSB All panelsare classified as Exposure 1 or Exterior and are typically 3⁄8 in (9.5 mm) inthickness

• All PRIs are assembled using exterior-type adhesives per ASTM D2559.8

• APA PRIs are available in four depths as shown in Table 5.1

• While PRIs of the same depth may be manufactured with various flange widthsdepending on the product designator, flange width is an important design consid-eration when specifying hangers Unless the designer is very specific on his plans,

he may not know what the actual width of the I-joist installed will be Oftendesigners and builders will insist that the I-joist supplier provide the hangers aswell

• Most mills supply I-joists to distributors and dealers in lengths up to 60 ft (18.30m) These are then cut to frequently used lengths such as 16–36 ft (4.90–11 m).Check local supplier for availability

It should be noted that many manufacturers produce I-joists for the commercialbuilding market that are beyond the scope of APA Performance Rated I-joists TheseI-joists are typically manufactured in depths of 18–30 in or deeper in 2 in depth

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increments Since no industry standard exists for these products, manufacturers mustobtain building code Evaluation Service Reports prior to marketing However, whilethese products are deeper than the PRIs, many of the design and construction phi-losophies presented in this chapter for PRIs are also applicable to other I-joists

5.2.3 I-Joist Manufacturing Process

Wood I-joists are manufactured out of a number of different flange and web terials As such, the manufacturing processes vary slightly to accommodate thematerial differences In general, however, I-joists are manufactured in one of twobasic methods: in fixed lengths or in continuous lines

ma-The fixed-length method gets its name from the fact that the flange stock—usually LVL for this method—arrives at the assembly point in finite lengths, usuallyaround 60–65 ft (18.3–19.9 m) long A wedge-shaped groove is machined into theflange material The geometry of this groove is essential to the manufacturing pro-cess because its wedge shape provides the clamping pressure at the web-to-flangejoint that is required by the adhesive to provide a good glue bond The adhesivesused are fully waterproof and are required by the standard to meet the requirements

of ASTM D2559 After the flanges are initially pressed on to the web, the pleted I-joists are carefully moved to the adhesive curing station of the manufac-turing process Radio frequency, microwave, or simply storing in a hot environmentare three of the curing methods used, depending on the adhesive system used andphysical plant layout Once the adhesive cure has been accomplished, the joists aretrademarked, bundled together and wrapped for shipment to the distributors (seeFig 5.4)

com-The continuous-line method is most often used with sawn lumber flanges Inorder to manufacture long-length I-joists, the flanges must be made in equally longlengths When sawn lumber flanges are used, shorter lengths of lumber are finger-jointed together to form long lengths in a continuous process Because the end joint

is a structural joint, it does not matter where it occurs along the length of the joist After end jointing, the joint moves through a radio frequency or microwavecuring station to cure the adhesive in the joint At the next station in the process,the groove is machined in the continuous flange With two parallel flange linesoperating simultaneously, the output of these lines is joined by the station thatapplies the adhesive to the grooves and inserts the web elements These elementsare initially pressed together as described previously, and the continuous I-joist iscut to usable lengths—as in the fixed length process, about 60–65 ft (18.3–19.9m) The final curing of the flange-to-web joints can occur either before or after thecut-to-size operation depending on the curing method used The I-joists are thentrademarked, bundled, and wrapped for shipment to the distributors (see Fig 5.5)

ENGINEERED WOOD VS LUMBER

All engineered wood composites have many characteristics in common They arestronger, more dimensionally stable, more homogeneous, better utilize availablenatural resources and, are typically more builder-friendly than sawn lumber From

a proper design and detailing point of view, there is another common characteristic

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PR TM

40 14" SPACING 12 oc 19.2 oc 24 oc

SIMPLE SPAN 24-4 20-2 18-0 MULTIPLE SPAN 25-6 22-1 18-0

Performance Rated Wood I-Joist for Glued Residential Floors MILL 0000 • PRI-400

Bundled and wrapped for shipment

Energy applied

to cure adhesive pressed together

Adhesive applied

Grooves machined in flanges ends and edges machined in webs Web stock

Flange stock

FIGURE 5.4 I-joist manufacturing process—fixed-length process.

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PR TM 40 14" SPACING 12 oc 19.2 oc 24 oc SIMPLE SPAN 24-4 20'-2 MULTIPLE SPAN 25-6 22-1 20'-1 Performance Rated Wood I-Joist for Glued Residential Floors MILL 0000 • PRI-400

End joints machined Grading

Sawn lumber flange stock

Glue applied to end joints

Continuous joists cut to length Flange stock pressed together

Web stock Stock cutto size Ends

and edges machined

Adhesive added to ends and edges

Flanges and webs pressed together

Energy applied

to cure adhesive

Bundled and wrapped for shipment

FIGURE 5.5 I-joist manufacturing process—continuous-line process using sawn lumber flanges.

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that it is important to understand This characteristic is that all engineered woodcomponents are manufactured in a relatively dry state The moisture content ofengineered wood products at the time of manufacture ranges from approximately4–12% During the manufacturing process, the wood-based resource must be dried

to these levels to ensure that a good glue bond is developed A range of values isgiven because some adhesive systems used in some products have different moisturerequirements

It is also important to realize that these are not average moisture contents astraditionally measured If a certain adhesive system requires a maximum 6% mois-ture content to develop an adequate glue bond, then every piece must meet thatmaximum during fabrication A traditional average where 50% are above the max-imum and 50% are below just doesn’t work Only those pieces at or below themaximum will ever get to the marketplace

Traditional dry lumber, on the other hand, is dried to a much higher moisturecontent, typically 19%, although some lumber is dried to 16% Because of naturalvariability, the range of moisture content of the lumber pieces in a given bundlemay vary widely A given lumber element may even have moisture gradients alongthe length or across the width

In service, however, such as in a residential structure, after four to eight months

of drying, all wood elements will reach an equilibrium moisture content of 6–10%,depending on the season and location of the structure Because the engineered woodproducts are very close to this normal equilibrium moisture content as manufac-tured, and because they are typically shipped in a waterproof protective wrapping,they take on little or no additional moisture during this period As such, theirdimensions vary imperceptibly during this period The sawn lumber, however, driesdown during this period through a relatively large range of moisture content Alongwith drying comes an equally significant shrinkage As Fig 5.6 shows, a 14 in.(337 mm) deep sawn lumber element can shrink as much as3⁄4in (19 mm) in itsdepth as it cycles from the as-dried to in-service equilibrium moisture content Thisdifference in behavior between solid-sawn lumber and engineered wood can lead

to structural failure if the designer is not careful

5.3.1 I-joists and Rim Board Used Together in an Engineered Wood System

APA EWS I-joists and APA EWS Rim Board products (discussed in Section 5.12)are made in 91⁄2, 117⁄8, 14, and 16 in (241, 302, 356, and 406 mm) net depths It

is no accident that these sizes are not compatible with, and are larger than, tional lumber net depths for 2⫻10s, 2⫻12s, 2⫻14s, and 2⫻16s (38⫻241,

tradi-38⫻302, 38⫻356, and 38⫻406 mms) There are many applications in roofingsystems and especially residential floors, where other elements are used in con-junction with the I-joists for the express purpose of transferring load through thefloor system without overloading the floor joists Some examples of these otherelements are blocking panels over an interior bearing wall and rim or starter joists

In these cases, the vertical load from the structure above the plane of the floor istransferred through the floor into the structure / foundation below by way of directbearing on the blocking panels and rim or starter joist

Because the load is transferred in direct bearing, it is essential that the blockingpanels and rim or starter joist be the same height as the floor joist Solid-sawnlumber cannot be used in applications like these because of the very likely potentialfor shrinkage Shrinkage by as little as1⁄ in (3 mm) can be enough to transfer the

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FIGURE 5.6 Shrinkage of glulam compared with sawn lumber.

Load-bearing wall above

I-joist

Lumber blocking Lumber blocking cut to fit at 16% moisture content

Load-bearing wall above

Lumber blocking – after shrinkage Bearing failure

FIGURE 5.7 Effects of differential shrinkage on load transfer.

vertical loads from the walls above directly to the floor joists, thus inducing possiblebearing or reaction overload conditions at these locations The solution to the prob-lem is to use engineered wood products for these applications They are manufac-tured in the correct depths and have the same dimensional stability properties (seeFig 5.7)

While the previous discussion concerns vertical loads, the same is true of lateralloads such as those caused by wind and seismic events The small gap between thefloor sheathing above and the sawn lumber rim joist or blocking panel below re-

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sulting from shrinkage of the lumber members can have a small but negative impact

on the performance of the structure during the design event Even greater however,will be the impact on the deformation of the structure caused by the potential slip

at this location under design lateral loads While not necessarily life threatening,these greater deformations can result in increased damage to the nonstructural com-ponents of the building, such as drywall, windows and doors, cabinets, and interiorand exterior finishes If the deformations are excessive, they can cause the structure

to be irreparable

Every application where solid-sawn lumber is used in conjunction with neered wood must be looked at very carefully with respect to the different moisturestates of materials at the time of construction The safest alternative is to not mixengineered wood with solid-sawn lumber in any situation where load sharing might

engi-be an issue

5.4 ENGINEERED WOOD I-JOIST STANDARD

APA—The Engineered Wood Association, formerly the American Plywood ciation, and before that the Douglas Fir Plywood Association, has long been a leader

Asso-in the development of engAsso-ineered wood standards From the development of thenow nationally recognized plywood standard in the 1950s (see Chapter 2) to thenew standard discussed in Section 5.4.1, APA has developed, or has been instru-mental in the development of most of the glued engineered wood standards in use

in the United States today The APA PRI-I-joist Standard discussed below, is one

of the most recent standards developed for the engineered wood industry

APA—The Engineered Wood Association Member manufacturers are committed

to a rigorous program of quality verification and testing, which ensures predictableproduct performance, regardless of the manufacturer

PRI-400 brings product standardization while providing for a multitude of designand construction situations The standard provides design information for numeroustypes and sizes of I-joists Specifiers, designers, and builders can select and use I-joists from various APA EWS member manufacturers, using just one set of designand installation criteria Because PRIs can be selected based on their allowable spanfor glued uniformly loaded residential floors, it is easy to incorporate them into anydesign Because all APA EWS I-joists share a common set of installation andfastening details, the generation of design drawings is greatly simplified

5.4.2 Identifying I-Joists

All three of the major model building codes as well as the new International ing Code require engineered wood products to be trademarked by an approved

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Build-5.12 CHAPTER FIVE

FIGURE 5.8 Field installation of I-joist and rim board showing APA stamps.

third-party inspection agency before they can be used in code-conforming tion One purpose of these regulations is to allow for easy identification of theproduct The information on these stamps is beneficial to the engineer, contractor,and building official and ultimately to the consumer While the format of the trade-mark stamp may vary depending on the quality assurance agency representing themill, they all contain the same general information An example of a trademarkstamp and an explanation of the information it contains are shown below

construc-I-Joist Trademarking and Identification. The I-joist trademark stamp shown inFig 5.8 and illustrated in detail in Fig 5.9 below contains information valuable tothe specifier, builder, building inspector, and future remodelers In addition to theactual depth of the joist, the trademark contains information on the joists’ specificdesignation, and may contain the allowable spans for both simple and multipleconditions for I-joist spacings of 12, 16, 19.2, and 24 in (305, 406, 488, and 610mm) on center (o.c.)

5.5 I-JOISTS DESIGN PROPERTIES

For those applications not covered specifically by this Handbook, Table 5.2 is vided Table 5.2 contains the allowable design capacities for APA EWS perform-ance rated I-joists Similar design properties are also available from manufacturersfor non-PRI-400 products The values listed are single-joist, normal-duration designvalues Duration of load adjustments may be applied to all of the values in the table

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Performance Standard for APA EWS I-Joists.

can be achieved for a glued-nailed floor system at the indicated spacing for a live load of 40 psf and a dead load of 10 psf (optional)

Joist designation The on-center spacing

of the I-joists (optional)

Mill number Conforms with APA

Standard PRI-400,

Performance Standard for APA EWS I-Joists

FIGURE 5.9 Sample of a Performance Rated I-joist trademark stamp with explanation of elements.

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Repetitive lbf-ft

2180 2800 2355 3290 3245

2265 2910 2520 3420 3470

1120 1120 1120 1120 1120

1700 1905 2160 2040 2160

830 945 1080 1015 1080

4.94 4.94 4.94 4.94 4.94

2910 3715 3145 4375 4335 5600 6130 7770

3025 3860 3365 4550 4635 5820 6555 8080

1420 1420 1420 1420 1420 1420 1420 1925

1700 1905 2500 2040 2500 2335 2760 3355

830 945 1200 1015 1200 1160 1280 1400

6.18 6.18 6.18 6.18 6.18 6.18 6.18 6.18

3860 5350 5320 7120 7525 9535

4130 5560 5690 7405 8050 9915

1710 1710 1710 1710 1710 2125

2500 2040 2500 2335 3020 3355

1200 1015 1200 1160 1280 1400

7.28 7.28 7.28 7.28 7.28 7.28

4535 6270 6250 8350 8845 11,205

4850 6520 6685 8680 9460 11,650

1970 1970 1970 1970 1970 2330

2500 2040 2500 2335 3020 3355

1200 1015 1200 1160 1280 1400

8.32 8.32 8.32 8.32 8.32 8.32 For SI: 1 lbf ⫽ 4.45 kN, 1 lbf ft ⫽ 1.356 N m, 1 lbf in 2 ⫽ 0.00287 N m 2 , 1 in ⫽ 25.4 mm.

a The tabulated values are design values for normal duration of load All values, except for EI and K,

are permitted to be adjusted for other load durations as permitted by the code for solid sawn lumber.

bBending stiffness (EI ) of the I-joist.

c Moment capacity (M ) of a single I-joist When I-joists are in contact or spaced not more than 24 in.

on-center, are not less than three in number, and are joined by floor, roof, or other load-distributing elements adequate to support the design load, repetitive moment shall be permitted for use in design.

d Shear capacity (V ) of the I-joist.

eIntermediate reaction (IR) of the I-joist with a minimum bearing length of 3 1 ⁄ 2 in without bearing stiffeners.

ƒ End reaction (ER) of the I-joist with a minimum bearing length of 1 3 ⁄ 4 in without bearing stiffeners For a bearing length of 4 in (5 in for 14 in and 16 in PRI-50 joists), the end reaction may be set equal

to the tabulated shear value Interpolation of the end reaction between 1 3 ⁄ 4 and 4 in (5 in for 14 in and 16

in PRI-50s) bearing is permitted For end-reaction values over 1550 plf, bearing stiffeners are required with the exception of PRI-90, which requires bearing stiffeners when end reaction values exceed 1,885 lbf.

g Coefficient of shear deflection (K ) For calculating uniform load and center-point load deflections of

the I-joist in a simple-span application, use Eqs (1) and (2).

EI⫽ bending stiffness of the I-joist (lbf-in 2 )

K⫽ coefficient of shear deflection (lbf)

␻ ⫽ uniform load (lbf / in.)

ᐉ ⫽ design span (in.)

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except the EI value and the K value Values for moment (M) capacity in the table

are given for both repetitive and nonrepetitive applications

There are a several significant differences in designing for I-joists compared todesigning for solid-sawn lumber The first is in calculating deflection In calculatingdeflection of solid-sawn lumber beams, the deflection due to shear deformation isminimal and is accounted for by adjusting the published design MOE values toinclude shear deformation effects With I-joists, however, the deflection due to shearcan be a significant contributor to the overall deflection of the member and, as such,

must be calculated separately Footnote (g) of Table 5.2 provides the equations

necessary to compute the total deflection for uniformly loaded or center loaded single spans

point-The second significant difference in designing for I-joists vs solid sawn lumberjoists is related to the necessity to consider the intermediate and end reactions inI-joist design Because of the narrow cross section of the I-joist web, the web exerts

a potential splitting force in the flange of the joist This is a design considerationforeign to solid lumber design, but may be critical in I-joist design Notice that theassigned values are different for an intermediate reaction (IR) and an exterior re-action (ER) This is because the intermediate reaction capacity presupposes a min-imum bearing length of 31⁄2in (89 mm), where an exterior reaction is based on aminimum required bearing length of 13⁄4in (44 mm) If a designer were considering

a cantilever situation where the support adjacent to the cantilever was fully porting the I-joist over an area at least 31⁄2 in (89 mm) long, the intermediatereaction (IR) value would be appropriate at this location

res-For those applications where stone or ceramic tile is desired for a finish floorsurface, similar tables are provided based on a live load of 40 lb / ft2(1.9 kN / m2)and 20 lb / ft2(0.96 kN / m2) for dead load Again two tables are provided, Table 5.6for simple-span applications and Table 5.7 for multiple-span applications Thesetables would also be applicable for the case of using a lightweight concrete orgypsum topping

Discussion of L / 480—Deflection Criteria for Floors. The maximum spans listed

in Tables 5.4–5.7 are all based on a live-load deflection criteria of L / 480 (where

L ⫽ span) for glued-nailed residential floor applications This deflection criteria,

33% stiffer than the traditional code-recognized deflection criteria of L / 360, was

selected during the development of APA’s I-joist performance standard, PRI-400,

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Strength axis

Note:

Provide adequate

ventilation and use

ground cover vapor

retarder in crawl

space Panels must be

dry before applying

finish floor.

Carpet and pad 2x rim joist or APA Rim Board

Tongue-and-groove edges (or 2" lumber blocking between supports) Stagger end joints Site-applied glue, both joints and tongue-and-groove joints (or between panels and edge blocking) 1/8" spacing is recommended at all edge and end joints unless otherwise indicated by panel manufacturer 2x joists, I-joists or floor trusses –16", 19.2", 24", or 32" o.c (4x supports for 48" o.c spacing)

APA Rated Sturd-I-Floor

16, 20, 24, 32 or 48 oc

FIGURE 5.10 Wood structural panel floor nailed and glued for maximum performance.

to provide superior floor performance under live load applications A detailed cussion of this decision by APA is provided in Section 5.8.7

dis-The Glued-Nailed Floor System. In order to achieve the allowable spans that areshown in Tables 5.4 through 5.7, floor sheathing must be field glued-nailed to theI-joist flanges as shown in Fig 5.10 Spans must be reduced by 1 foot (0.3048meters) when the sheathing is nailed only

In addition to achieving greater span, by gluing the wood structural panels tothe I-joists:

• Floor stiffness is increased appreciably, particularly when tongue-and-groove(T&G) joints in the floor panels are glued

• The possibility of floor squeaks, excessive deflection, vibration, bounce, and popping is greatly reduced

nail-• The number of cracks that can leak airborne noise is also reduced, thereby creasing the acoustical performance of the floor-ceiling assembly

in-The Glued-Nailed Floor System Panels recommended for glued floor

construc-tion are T&G APA-Rated Sturd-I-Floor for single-floor construcconstruc-tion, and APARated Sheathing for the subfloor when used with a separate underlayment or withstructural finish flooring An additional layer of underlayment, or veneer-facedSturd-I-Floor with ‘‘sanded face’’ should be applied in areas to be finished withresilient floor coverings such as tile, linoleum, vinyl or fully adhered carpet In both

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cases, Sturd-I-Floor and subflooring panels should be installed continuous over two

or more spans with the long dimension or strength axis across the I-joists Othernon-APA trademarked panels complying with either PS-19or PS-210 may also beused

Tongue-and-groove panels are highly recommended for single-floor construction.Before each panel is placed, a line of glue is applied to the I-joist with a caulkinggun The panel’s T&G joint should also be glued, although less heavily to avoidsqueeze-out If square-edge panels are used, edges must be supported between I-joists with 2⫻ 4 (38 ⫻ 89 mm) blocking Glue panels to blocking to minimizesqueaks Blocking is not required under structural finish flooring, such as woodstrip flooring, or if a separate underlayment is installed

Important Note: Wood structural panels must be glued with an adhesive meeting APA Specification AFG-01 11 or ASTM D3498 12 to achieve the allowable spans shown in Tables 5.4–5.7 If the floor structure is built using OSB panels with sealed surfaces and edges, only solvent-based glues should be used Always follow the specific application recommendations of the adhesive manufacturer.

Application For best results, follow these application procedures:

1 Wipe any mud, dirt, water, or ice from I-joist flanges before gluing.

2 Snap a chalk line across the I-joists 4 ft in from the wall for panel edge

align-ment and as a boundary for spreading glue

3 Spread only enough glue to lay one or two panels at a time, or follow specific

recommendations from the glue manufacturer

4 Lay the first panel with tongue side to the wall, and nail in place This protects

the tongue of the next panel from damage when tapped into place with a blockand sledgehammer

flange of a single I-joist Apply glue in a serpentine pattern on wide areas,such as with double I-joists

6 Apply two lines of glue on I-joists where panel ends butt, to ensure proper

gluing of each end

7 After the first row of panels is in place, spread glue in the groove of one or

two panels at a time before laying the next row Glue line may be continuous

or spaced, but avoid squeeze-out by applying a thinner line (1⁄8 in [3 mm])than used on I-joist flanges

8 Tap the second row of panels into place, using a block to protect groove edges.

between all end joints and 1⁄8 in (6 mm) space at all edges, including T&Gedges, is recommended (Use a spacer tool or an 8d common (3.3⫻64 mm)nail to ensure accurate and consistent spacing.)

10 Complete all nailing of each panel before glue sets Check the manufacturer’s

recommendations for allowable cure time (Warm weather accelerates glue ting.) Use 6d ring- or screw-shank (3 ⫻ 51 mm) nails for panels 3⁄4 in (19mm) thick or less, and 8d ring- or screw-shank (3⫻64 mm) nails for thickerpanels Space nails per Table 5.3 Closer nail spacing may be required by somecodes, or for diaphragm construction The finished deck can be walked on rightaway and will carry construction loads without damage to the glue bond

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Fastening: glued-nailedc(in.)

Nail size and type

Maximum spacing (in.) Supported panel

edges

Intermediate supports

For SI: 1 in ⫽ 25.4 mm.

aSpecial conditions may impose heavy traffic and concentrated loads that require construction in excess

of the minimums shown.

bPanels in a given thickness may be manufactured in more than one allowable span Panels with an allowable span greater than the actual joist spacing may be substituted for panels of the same thickness with

a allowable span matching the actual joist spacing.

cUse only adhesives conforming to APA Specification AFG-01 or ASTM D3498, applied in accordance with the manufacturer’s recommendations If OSB panels with sealed surfaces and edges are to be used, use only solvent-based glues; check with panel manufacturer.

dRecommended minimum thickness for use with I-joists.

e8d common (3.3 ⫻ 64 mm) nails may be substituted if ring- or screw-shank nails are not available.

5.6.2 I-Joist Allowable Span Tables—Residential Floor

I-joist allowable span tables for residential applications are provided in Tables 5.4

to 5.7

Design Assumptions. The floor span tables provided for both simple and multiplespan are based on the following assumptions:

• Span for calculation purposes equals clear span⫹0.25 ft (76 mm) (Spans given

in Tables 5.4–5.7 equal the vertical projection measured between inside faces ofsupports.)

• Allowable spans are calculated based on the use of glued-nailed constructionutilizing adhesives meeting the requirements of APA Specification AFG-01 orASTM D3498

• Bending capacities are adjusted for repetitive member stresses (1.04 for compositeflanges and 1.07 for sawn lumber) as is applicable to all wood products whenmultiple members are spaced 24 in (610 mm) on center or less

• Bending stiffness and coefficient of shear deflection and other design propertiesare as listed in Table 5.2

Joist Identification. All APA PRIs are identified by an allowable span designatedfor uniformly loaded residential floor construction at various I-joist spacings There-fore, the specific I-joist needed for a given application is easily determined by

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TABLE 5.4 Allowable Floor Spans for APA PRI I-Joists (simple-span only), Based on a Live Load of 40 psf and a Dead Load of 10 psf

Depth

I-joist

designation

Simple-span floor I-joist spacing

12 in o.c 16 in o.c 19.2 in o.c 24 in o.c 32 in o.c 48 in o.c.

9 1 ⁄ 2 ⴖ PRI-20 16 ft, 7 in 15 ft, 2 in 14 ft, 4 in 13 ft, 4 in 11 ft, 3 in 8 ft, 2 in PRI-30 17 ft, 1 in 15 ft, 8 in 14 ft, 10 in 13 ft, 11 in 12 ft, 10 in 9 ft, 4 in PRI-40 18 ft, 0 in 16 ft, 6 in 15 ft, 7 in 14 ft, 1 in 11 ft, 9 in 9 ft, 7 in PRI-50 17 ft, 10 in 16 ft, 4 in 15 ft, 15 in 14 ft, 5 in 13 ft, 5 in 10 ft, 0 in PRI-60 19 ft, 0 in 17 ft, 4 in 16 ft, 4 in 15 ft, 4 in 13 ft, 10 in 10 ft, 8 in.

11 7 ⁄ 8 ⴖ PRI-20 19 ft, 11 in 18 ft, 2 in 17 ft, 2 in 15 ft, 5 in 12 ft, 4 in 8 ft, 2 in PRI-30 20 ft, 6 in 18 ft, 9 in 17 ft, 9 in 16 ft, 7 in 14 ft, 0 in 9 ft, 4 in PRI-40 21 ft, 6 in 19 ft, 7 in 18 ft, 2 in 16 ft, 3 in 13 ft, 7 in 11 ft, 1 in PRI-50 21 ft, 4 in 19 ft, 6 in 18 ft, 5 in 17 ft, 3 in 15 ft, 1 in 10 ft, 0 in PRI-60 22 ft, 8 in 20 ft, 8 in 19 ft, 6 in 18 ft, 3 in 16 ft, 0 in 11 ft, 10 in PRI-70 23 ft, 0 in 21 ft, 0 in 19 ft, 10 in 18 ft, 7 in 17 ft, 3 in 11 ft, 5 in PRI-80 24 ft, 11 in 22 ft, 8 in 21 ft, 4 in 19 ft, 11 in 18 ft, 6 in 12 ft, 8 in PRI-90 25 ft, 8 in 23 ft, 4 in 22 ft, 0 in 20 ft, 6 in 19 ft, 0 in 13 ft, 10 in.

14 ⴖ PRI-40 24 ft, 4 in 22 ft, 1 in 20 ft, 2 in 18 ft, 0 in 15 ft, 1 in 11 ft, 10 in PRI-50 24 ft, 4 in 22 ft, 3 in 21 ft, 0 in 19 ft, 8 in 15 ft, 1 in 10 ft, 0 in PRI-60 25 ft, 9 in 23 ft, 6 in 22 ft, 2 in 20 ft, 9 in 17 ft, 9 in 11 ft, 10 in PRI-70 26 ft, 1 in 23 ft, 10 in 22 ft, 6 in 21 ft, 0 in 17 ft, 3 in 11 ft, 5 in PRI-80 28 ft, 3 in 25 ft, 9 in 24 ft, 3 in 22 ft, 8 in 19 ft, 1 in 12 ft, 8 in PRI-90 29 ft, 1 in 26 ft, 6 in 24 ft, 11 in 23 ft, 3 in 20 ft, 10 in 13 ft, 10 in.

16 ⴖ PRI-40 27 ft, 0 in 24 ft, 0 in 21 ft, 11 in 19 ft, 7 in 16 ft, 4 in 11 ft, 10 in PRI-50 27 ft, 0 in 24 ft, 8 in 23 ft, 4 in 20 ft, 2 in 15 ft, 1 in 10 ft, 0 in PRI-60 28 ft, 7 in 26 ft, 1 in 24 ft, 7 in 23 ft, 0 in 17 ft, 10 in 11 ft, 10 in PRI-70 29 ft, 0 in 26 ft, 5 in 24 ft, 11 in 23 ft, 1 in 17 ft, 3 in 11 ft, 5 in PRI-80 31 ft, 4 in 28 ft, 6 in 26 ft, 11 in 25 ft, 1 in 19 ft, 1 in 12 ft, 8 in PRI-90 32 ft, 2 in 29 ft, 3 in 27 ft, 7 in 25 ft, 9 in 20 ft, 10 in 13 ft, 10 in For SI: 1 in ⫽ 25.4 mm, 1 ft ⫽ 304.8 mm.

1 Allowable clear span applicable to simple-span residential floor construction with a design dead load

of 10 psf (0.48 kN / m 2 ) and live load of 40 psf (1.9 kN / m 2 ) The live load deflection is limited to span / 480.

2 The tabulated spans are based on a composite floor with glued-nailed sheathing meeting the ments for APA rated sheathing or APA rated Sturd-I-Floor conforming to PRP-108 13 , PS 1, or PS 2 with a minimum thickness of 19 ⁄ 32 in (15 mm) ( 40 ⁄ 20 or 20 oc) for a joist spacing of 19.2 in (488 mm) or less, or

require-23 ⁄ 32 in (18.3 mm) ( 48 ⁄ 24 or 24 oc) for a joist spacing of 24 in (610 mm) Adhesive must meet APA Specification AFG-01 or ASTM D3498 Spans must be reduced 12 in (305 mm) when the floor sheathing

is nailed only.

3 Minimum bearing length must be 1 3 ⁄ 4 in (44.5 mm) for the end bearings.

4 Bearing stiffeners are not required when APA PRI joists are used with the spans and spacings given

in this table, except as required by hanger manufacturers.

selecting the span needed and then choosing the I-joist that meets the span, spacing,and loading criteria

Tables 5.4 and 5.5 may be used when it is known that a simple- or a span application is involved These tables indicate the allowable clear span forvarious joist spacings under typical residential floor loads (40 lb / ft2 [1.9 kN / m2]live load and 10 lb / ft2 [0.48 kN / m2] dead load) for glued-nailed systems Forloading conditions with 40 lb / ft2(1.9 kN / m2) live load and 20 lb / ft2 (0.96 kN /

multiple-m2) dead load, Tables 5.6 and 5.7 are provided

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Multiple-span floor I-joist spacing

1 Allowable clear spans applicable to multiple-span residential floor construction with a design dead load of 10 psf (0.48 kN / m 2 ) and live load of 40 psf (1.9 kN / m 2 ) The end spans must be 40% or more of the adjacent span The live load deflection is limited to span / 480.

2 The tabulated spans are based on a composite floor with glued-nailed sheathing meeting the ments for APA rated sheathing or APA rated Sturd-I-Floor conforming to PRP-108, PS 1, or PS 2 with a minimum thickness of 19 ⁄ 32 in (15 mm) ( 40 ⁄ 20 or 20 oc) for a joist spacing of 19.2 in (488 mm) or less, or

is nailed only.

3 Minimum bearing length must be 1 3 ⁄ 4 in (44.5 mm) for the end bearing, and 3 1 ⁄ 2 (89 mm) in for the intermediate bearing.

While any of the PRIs shown in the allowable span tables in this chapter may

be available in a specific market area, availability of any specific PRI product should

be verified

Example To illustrate the selection of a performance rated I-Joist product, assume a normal residential floor load (40 lb / ft 2 live load and 10 lb / ft 2 dead load) with a design simple span of 16 ft, 1 in For architectural reasons, the joist depth is limited to 11 7 ⁄ 8 in., joist spacing to 19.2 in on center, and a simple span is desired From the 11 7 ⁄ 8 ⴖ

portions of Table 5.4, looking down the 19.2 in o.c spacing column, it can be seen

that any joist designation will work.

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TABLE 5.6 Allowable Floor Spans for APA PRI I-Joists (simple-span only), Based on a Live Load of 40 psf and a Dead Load of 20 psf

Depth

I-Joist

designation

Simple-span floor I-joist spacing

1 Allowable clear span applicable to simple-span residential floor construction with a design dead load

of 20 psf (0.96 kN / m 2 ) and live load of 40 psf (1.9 kN / m 2 ) The live load deflection is limited to span / 480.

is nailed only.

3 Minimum bearing length shall be 1 3 ⁄ 4 in (44.5 mm) for the end bearings.

t4 Bearing stiffeners are not required when APA PRI joists are used with the spans and spacings given

If the owners later decided that they wanted ceramic tile on the first floor, the designer would use Table 5.6 to check his design Again from the 11 7 ⁄ 8 ⴖ portions of

Table 5.6, looking down the 19.2 in o.c spacing column, it can be seen that any joist

designation will work except for the PRI-20 However, if the spacing of the I-joists were changed to 16 in on center, then any joist designation would work for the floor

under the ceramic tile installation.

Substituting APA Performance Rated I-Joists for Other APA PRIs

Uniformly Loaded Applications The most common type of joist substitution

is to substitute one PRI for another having the same depth For PRIs that have beenselected based on the use of the allowable span tables for uniformly loaded appli-

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Multiple-span floor I-joist spacing

1 Allowable clear spans applicable to multiple-span residential floor construction with a design dead load of 20 psf (0.96 kN / m 2 ) and live load of 40 psf (1.9 kN / m 2 ) The end spans shall be 40% or more of the adjacent span The live load deflection is limited to span / 480.

is nailed only.

3 Minimum bearing length shall be 1 3 ⁄ 4 in (44.5 mm) for the end bearing, and 3 1 ⁄ 2 in (89 mm) for the intermediate bearing.

cations, this is a simple substitution All that is needed is to select a PRI with anequivalent or greater allowable span from a given series classification

Example Referring to Table 5.4, it can be seen that a 9 1 ⁄ 2 ⴖ PRI-60 can be substituted

for a 9 1 ⁄ 2 ⴖ PRI-40 for all on-center spacings listed Note also that a 9 1 ⁄ 2 ⴖ PRI-50 is NOT

a suitable substitution for a 9 1 ⁄ 2 ⴖ PRI-40; its allowable spans are not as great.

If a designer wants to give the builder the greatest possible latitude in selectingPRI I-joists, they can design for the minimum allowable spans for each depth andthen just specify PRI by depth, e.g., ‘‘91⁄2ⴖPRI.’’

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However, it is important to note that mills manufacture specific products based

on flange resource availability and manufacturing limitations This means that whilethe depths of a given series will be constant, not all series may be available in agiven geographic area Since flange width may vary for a given series, it may bebest practice for a designer not to specify the hanger width but instead to specify

‘‘a flange-width-compatible hanger.’’

Example All 9 1 ⁄ 2 ⴖ PRIs have a depth of 9 1 ⁄ 2 in regardless of flange type—the flange width may vary If metal hangers are required, it is important to verify the appropriate hangers when a subsitution is being considered.

As an option, the designer can design the application for the minimum allowable span or section properties for the desired I-joist depth and then specify the depth and

a flange-width-compatible hanger For example: ‘‘Floor joists use 9 ⁄ 12 ⴖ APA PRIs with

flange-width-compatible hangers ’’

Nonuniformly Loaded Applications In some situations, a PRI may be designed

to support nonuniform loads such as from a load-bearing wall above or from aconcentrated point load In these cases, a direct substitution based on the allowablespan tables may not be possible Because of variations in the design properties andphysical dimensions of I-joists, each design property given in Table 5.2 must becompared to verify a candidate for product substitution

Example Assume a substitution of a 9 1 ⁄ 2 ⴖ PRI-60 for a 9 1 ⁄ 2 ⴖ PRI-50 joist is desired.

As indicated by Tables 5.4 or 5.5, the 9 1 ⁄ 2 ⴖ PRI-60 joist has greater span capabilities

than a 9 1 ⁄ 2 ⴖ PRI-50 joist for all spacings listed and could be substituted on a uniform

load design basis However, as noted by comparing the design properties in Table 5.2, the moment capacity for the PRI-60 joist is lower than the value for the PRI-50 Thus,

if the design is based on other than uniform load conditions, it would need to be verified that the design moment does not exceed the capacity of the 9 1 ⁄ 2 ⴖ PRI-60 before the

substitution can be made.

PRI Joists Substituted for Sawn Lumber

Uniformly Loaded Applications Substituting PRIs for sawn lumber in uniform

load applications is relatively simple Table 5.8 illustrates several span comparisons

of PRIs with sawn lumber joists for typical residential uniform loading For the

sawn lumber joists, a live-load deflection criterion of L / 360 applies and the joists

are assumed to be simple span For the PRI joists, the live-load deflection criterion

is L / 480 and this is applicable to simple or multiple span applications.

Example Assume 9 1 ⁄ 2 ⴖ PRIs are to be substituted for 2 ⫻ 10 sawn lumber joists spaced

16 in on center From Table 5.8, it can be seen that the maximum span for nay of the sawn lumber species tabulated is 16 ft, 1 in for southern pine A 9 1 ⁄ 2 ⴖ PRI-30 could

be directly substituted for any of the lumber joists, other than the southern pine joists,

at the same on-center spacing when used in either a simple or multiple span A 9 1 ⁄ 2 ⴖ

PRI-40 could be substituted for any of the lumber species shown at this for either simple or multiple spans.

Example For the same conditions as the example above but assuming the PRIs are used in a multiple-span-only application, the 9 1 ⁄ 2 ⴖ PRI-30 joists could be spaced at 19.2

in on center and substituted for all of the lumber species listed This results in fewer joists to be handled and installed while still maintaining the superior deflection performance characteristics of a PRI.

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Multiple span SPF (south)b

19.2 in o.c 19.2 in o.c.

span

Multiple span SPF (south)b

19.2 in o.c 19.2 in o.c.

19.2 in o.c 19.2 in o.c 19.2 in o.c.

For SI: 1 in ⫽ 25.4 mm, 1 ft ⫽ 304.8 mm.

aUniform live load ⫽ 40 psf (1.9 kN / m 2 ) Uniform dead load ⫽ 10 psf (0.48 kN / m 2 ).

bWestern Lumber Use Manual—Base Values for Dimension Lumber.

cSouthern Pine Use Guide—Empirical Design Values for Dimension Lumber.

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Similar comparisons could be made for the other joists shown in Table 5.8, orfor any PRI tabulated in Tables 5.4 or 5.5 based on uniformly loaded residentialfloors.

Nonuniformly Loaded Applications As with the substitution of PRIs for one

another, substituting a PRI for a sawn lumber joist when the joist selection is based

on nonuniform loading conditions is more complicated than just comparing spancapabilities In these cases, an engineering analysis may be required before makingthis substitution Table 5.2 is provided for such applications

5.7 I-JOIST INSTALLATION DETAILS—FLOORS

5.7.1 Installing Performance Rated I-Joists—Floors

Because they are simple to install, I-joists provide many benefits to the designerand contractor alike However, as with any construction material, it is essential tofollow proper installation procedures

I-joists are to be installed as shown in Fig 5.11 and in accordance with thefollowing guidelines, which show methods recommended for most applicationsfound in common situations of residential floor construction

General Installation Guidelines for All I-Joist Products

• I-joists must be plumb and anchored securely to supports before floor sheathing

is attached

• Supports for multiple-span joists must be level

• To minimize settlement when using hangers, I-joists should be firmly seated inthe hanger bottoms

• Leave a1⁄16in (1.5 mm) gap between I-joist ends and headers

• Except for cutting to length, I-joist flanges should never be cut, drilled, or

notched

• I-joists must be protected from the weather prior to installation

• I-joists must not be used in places where they will be permanently exposed toweather or will reach moisture content greater than 16%, such as in swimmingpool or hot tub areas

• They must not be installed where they will remain in direct contact with concrete

or masonry

Typical PRI Floor Framing and Construction Details and Installation Notes

1 Installation of APA PRIs must be as shown in Fig 5.11.

2 Concentrated loads should only be applied to the top surface of the top flange.

At no time should concentrated loads be suspended from the bottom flange withthe exception of light loads (ceiling fans, light fixtures, etc.)

intermediate bearing length must be at least 31⁄2in (89 mm)

4 Ends of floor joists must be restrained to prevent rollover Use performance rated

rim board or I-joist blocking panels

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Some framing requirements such as erection bracing and

blocking panels have been omitted for clarity

Holes may be cut in web for plumbing, wiring and duct work See Tables 5.12 and 5.13 and Figures 5.20 and 5.21.

Figures 5.17-5.19 Figures 5.17-5.19

Use hangers recognized

in current ICBO ES, SBCCI PST & ESI, BOCA ES, or NES reports

5.11j

5.11f

5.11h 5.11k

5.11j 5.11m FIGURE 5.11 Typical Performance Rated I-joist floor framing and construction details.

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PRI blocking panel vertical load transfer = 2000 plf maximum, Performance Rated Rim Board blocking vertical load transfer =

2750 plf maximum for 1" thick, and 4400 plf for 1 1 / 8 " thickness.

All nails shown in the details 5.11a through 5.11m are assumed to be

common nails unless otherwise noted 10d box nails may be substituted

for 8d common shown in details Inividual components not shown to

scale for clarity

(a)

Performance Rated Rim Board vertical load transfer = 2750 plf maximum for 1" thick, and 4400 plf for 1 1 / 8 " thickness.

One 8d nail at top and bottom flange

Attach Performance Rated Rim Board to top plate using 8d box toenails @ 6" o.c.

of I-joist Nails may be driven

at an angle to avoid splitting

of bearing plate.

(b)

Attach rim joist to

top plate per 5.11a

PRI rim joist vertical load transfer

= 2000 plf maximum

Attach rim joist to floor joist with one nail at top and bottom Nail must provide 1 inch minimum penetration into floor joist For

2 1 / 2 " and 3 1 / 2 " flange widths, toe nails may be used.

Minimum 1 3 / 4 " bearing required (2x6 bearing required for rim joists with 2 5 / 16 " or greater flange widths)

Attach I-joist

per 5.11b

(c)

FIGURE 5.11 (a–c) Typical Performance Rated I-joist floor framing and

construction details (Continued )

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Attach

squash block

with one 8d nail

into top and

16 "

for lumber squash blocks

Vertical load transfer capacity per pair of squash blocks as shown:

Pair of Squash Blocks (lb)

bearing area of blocks

below to post above.

(e)

Performance Rated Rim Board may be used in lieu of I-joists Backer is not required when Performanc Rated Rim Board is used.

Provide backer for siding attachment unless nailable sheathing is used

Wall sheathing,

as required

Use single I-joist for loads

up to 2000 plf, double I-joists for loads up to 4000 plf, (filler block

not required)

(f)

FIGURE 5.11 (d–f) Typical Performance Rated I-joist floor framing and construction details.

(Continued )

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Blocking required over all interior supports

8d nails

at 6" o.c.

Joist attachment per detail 5.11 b

Load bearing wall above shall align vertically with the wall below Other conditions such

as offset walls are not covered

by this detail.

PRI blocking panel vertical load transfer = 2000 plf maximum Performance Rated Rim Board blocking vertical load transfer =

2750 plf maximum for 1" thick, and 4400 plf for

1 1 / 8 " thickness.

(g)

FIGURE 5.11 (g) Typical Performance Rated I-joist

floor framing and construction details (Continued )

5 I-joists installed beneath bearing walls perpendicular to the joists must have full

depth blocking panels, performance rated rim board, or squash blocks (crippleblocks) to transfer gravity loads from above the floor system to the wall orfoundation below

6 For I-joists installed beneath bearing walls parallel to the joists, the maximum

allowable vertical load using a single I-joist is 2000 plf (2.94 kN / m) and 4000plf (5.9 kN / m) if double I-joists are used

7 Continuous lateral support of the I-joist’s compression flange is required to

pre-vent rotation and buckling In simple-span uses, lateral support of the top flange

is normally supplied by the floor sheathing In multiple-span or cantilever plications, bracing of the I-joist’s bottom flange is also required at interior sup-ports of multiple-span joists and at the end support next to the cantilever exten-sion The ends of all cantilever extensions must be laterally braced as shown inFigs 5.17, 5.18, and 5.19

ap-8 Nails installed perpendicular to the wide face of the flange must be spaced in

accordance with the applicable building code requirements or approved buildingplans but should not be closer than 3 in (75 mm) o.c per row (4 in [100 mm]o.c for I-joists with composite flanges 11⁄2in [38 mm] wide) for 6 or 8d com-mon (2.9 ⫻ 61 mm or 3.3⫻ 64 mm) nails If more than one row of nails isused (not permitted for I-joists with composite flanges 11⁄2 in [38 mm] wide),the rows must be offset at least1⁄2in (12.5 mm) Nails installed parallel to thewide face of the veneers in LVL flanges must not be spaced closer than 3 in.(75 mm) o.c for 8d common (3.3⫻64 mm) nails, and 4 in (100 mm) o.c for10d common (3.8⫻76 mm) nails

9 Figure 5.11 details on the following pages show only I-joist-specific fastener

requirements For other fastener requirements, see the applicable building code

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Backer block (use if hanger load exceeds 250 lbs.) Before installing

a backer block to a double I-joist, drive 3 additional 10d nails through the

webs and filler block where the backer block will fit Clinch Install backer

tight to top flange Use twelve 10d nails, clinched when possible Maximum

capacity for hanger for this detail = 1280 lb.

BACKER BLOCKS (Blocks must be long enough to permit required

nailing without splitting)

* Minimum grade for backer block material shall be Utility grade SPF (south)

or better for solid sawn lumber and Rated Sheathing grade for wood

structural panels.

Backer block required (both sides for face-mounted hangers) For hanger capacity see hanger manufacturer’s recommendations Verify double I-joist capacity to support concentrated loads

Filler block per Figure 5.14, Table 5.9

Double I-joist header Top- or

face-mounted hanger

(h)

Note: Unless hanger sides laterally support the top flange, bearing stiffeners shall be used (see Figure 5.16)

FIGURE 5.11 (h) Typical Performance Rated I-joist floor framing and construction details (Continued )

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Glulam or multiple structural composite lumber (SCL) beams

For nailing schedules for multiple SCL beams, see the manufacturer‘s recommendations

Note: Unless hanger sides laterally support the top

flange, bearing stiffeners shall be used (see Figure 5.16)

Top- or face-mounted hanger installed

per manufacturer‘s recommendations

(i)

2x plate flush with inside face of wall

or beam

Top-mounted hanger installed

per manufacturer‘s recommendations

Note: Unless hanger sides laterally support the top flange, bearing stiffeners shall be used

(see Figure 5.16)

(j)

Filler block, per Figure 5.14, Table 5.9

Backer block attach per 5.17h Nail with twelve 10d nails, clinch when possible.

Maximum support capacity = 1280 lb.

Install framing anchor

per manufacturer‘s

recommendations

(both sides of stringer)

Multiple I-joist header with full depth filler block shown Glulam and multiple SCL headers may also be used.

Verify double I-joist capacity to support concentrated loads.

(l)

FIGURE 5.11 (i,j,l) Typical Performance Rated I-joist floor framing and construction

details (Continued )

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Engineered wood blocking panels:

• Shape and rigidity of blocking panel prevent roll-over of floor or roof joists.

• Vertical capacity of blocking panel transfers vertical loads.

• Fastening at top and base of blocking panel transfer shear.

FIGURE 5.12 Engineered wood blocking panel used in I-joist floor system.

5.7.2 Other Framing Elements Essential to Engineered Wood Floor Construction

When designing or working with I-joists for the first time, the user will be duced to a number of new and sometimes esoteric terms While some of theseterms almost exclusive to I-joists are intuitive and therefore easy to grasp, there are

intro-a few thintro-at intro-are intro-a little difficult to understintro-and in terms of their intro-actuintro-al function Thefollowing sections are an introduction to these terms

Blocking Panels

Definition / Function As far as the installation of I-joists is concerned, a

block-ing panel is a rectangular piece of engineered wood (I-joist, rim board, or I-joistcompatible LVL) that is placed between adjacent joists at various locations de-scribed below (see Fig 5.12) Blocking has three major functions:

1 To provide lateral support to the floor joists—to prevent them from physically

rolling over due to lateral loads This is analogous to preventing overturning in

a shear wall This is accomplished by the rectangular shape and stiffness of theblocking panel

2 To provide a means of transferring shear / lateral loads from the walls above to

the floor / foundation below This is accomplished by nailing into the top andbottom flanges

3 To provide a means of transferring vertical loads from the wall above to the

foundation / floor below The blocking is used in bearing to accomplish this

Physical Description Blocking is often site-fabricated out of engineered wood

materials on hand It is essential that engineered wood materials be used becausethe shrinkage that can be anticipated with the use of sawn lumber would make the

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Attach

squash block

with one 8d nail

into top and

1/16"

for lumber squash blocks

Vertical load transfer capacity per pair of squash blocks as shown:

1-1/8" Rim Board x 3-1/2 in 3000 1" Rim Board x 3-1/2 in 2700

FIGURE 5.13 Installation of squash / cripple blocks to transfer vertical

loads around floor joists.

blocking unable to perform the vertical load transfer function and could seriouslyimpede its ability to transfer shear / lateral loads

Fabricate the blocking panels from engineered wood products of compatible sizes and cut to fit snugly between the floor joists

I-joist-Use Recommendations.

1 Blocking panels are required at the ends of floor joists not otherwise restrained

from overturning by band joist or rim board and at all other supports

2 Blocking panels are required between floor joists supporting load-bearing walls

running perpendicular to the joists

3 Blocking panels are required between floor joists at the interior support adjacent

to a nonload-bearing cantilever in the floor system.

4 For a load-bearing cantilever, blocking panels are required between floor joists

at the interior support adjacent to the cantilever as well as for 4 ft along thesupport on either side of the cantilevered joists

Squash Blocks / Cripple Blocks

Definition / Function A squash block is a block of wood that is installed

ad-jacent to an I-joist to prevent the I-joist from carrying a point load that it is notdesigned to support (see Fig 5.13)

When acting as a bending member, in addition to checking bending strength,shear strength, and deflection, the I-joist designer must also consider the exteriorreaction (ER) and intermediate reaction (IR) as possible design controls This is theforce in the upward direction at the support locations that balances or resists thedownward force on the I-joist—the live and dead loads The reason for needing toconsider each of these reaction points is the propensity for the thin web to knifethrough the bottom flange of the I-joist, as a web-bearing failure In some cases,the span of the I-joists will be limited by this design check Even when not limited

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by the IR or ER, when an I-joist is at or near its maximum span, there is littleexcess IR or ER capacity left within the joist to support other than the uniformload as the majority is used up by the floor loads

The problem is that in conventional platform construction there are situationswhere loads from above are transferred down through the floor into the wall orfoundation below This occurs where load-bearing walls fall on floors or whereposts supporting headers are located within the walls Beneath these wall and pointloads, the I-joists usually do not have enough IR or ER capacity remaining to safelytransfer these loads without exceeding the design web bearing capacity of the I-joist floor joists The solution is to place extra load-carrying members in line with

these loads and insure that they carry the load and not the I-joists For line loads

like load-bearing walls, blocking panels (described in above under Blocking Panels)are normally used as described below to transfer these additional loads around theweb of the floor joist In the case of point loads, squash blocks are more oftenspecified

Physical Description A squash block is a 2⫻4 (38⫻89 mm) or 2⫻6 (38

⫻ 240 mm) lumber block that is oriented with the grain of the wood runningparallel to the vertical axis of the web of the joist The squash block is cut justslightly longer than the I-joist is deep, usually1⁄16in (1.5 mm) longer This is done

to ensure that the block will pick up the vertical load and not the I-joist The grain

is oriented parallel to the vertical axis to minimize the impact of shrinkage by thelumber block

The minimum grade of the squash blocks is utility grade spruce-pine-fir (SPF)(south)

In addition to lumber blocks, performance rated rim board may be cut intoblocks and used for such applications Because the rim board material is alreadycut to a compatible size for use with the I-joist, its use as a squash block eliminatesthe real danger associated with the inadvertent use of undersized squash blocks

Use Recommendations.

1 Each lumber squash block has a capacity of at least 2000 lbf (8.9 kN) Because

squash blocks are usually placed in pairs—to minimize load eccentricity—atleast 4000 lbf (17.78 kN) is appropriate for a pair of blocks with full bearing

on the top / sole plates Often the designer will simply match the area of thesquash blocks with that of the posts above

A pair of 11⁄8 in rim board squash blocks has a total capacity of 3000 lb(13.34 kN), and a pair of 1 in rim board squash blocks has a total capacity of

2700 lb (12.0 kN)—the capacity is reduced in direct proportion to the rim boardthickness Again, the above numbers assume full bearing on the top / sole plate

the joist to ensure that the squash block carries the load (Remember that the joist is ‘‘busy’’ carrying the floor load and may have little capacity remainingfor the additional wall load.)

I-3 Squash blocks are installed with the wide side of the block flush with the edges

of the I-joist flanges When possible, they will be fully seated on the top / soleplate below They will be attached to the top and bottom flange of the I-joistwith one 8d (3.3 ⫻ 64 mm) common nail at each location The extra 1⁄16 in.(1.5-mm) of the lumber squash block is to stick up above the surface of the topflange of the I-joist

4 The use of squash blocks in lieu of blocking for the entire length of a

load-bearing wall is not recommended They could be used, however, to transfer

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Filler block

(see below)

Offset nails from opposite face by 6"

1 Support back of I-joist web during nailing to prevent damage to web/flange connection.

2 Leave a 1/8-inch gap between top of filler block and bottom of top I-joist flange.

3 Filler block is required between joists for full length of span.

4 Nail joists together with two rows of 10d nails at 12 inches o.c (clinched when possible) on each side of the double I-joist Total of 4 nails per foot required If nails can be clinched, only 2 nails per foot are required.

FIGURE 5.14 Multiple I-joist construction showing filler blocks and attachment details.

vertical loads in an occasional joist space to allow for the passage of a duct.The model building codes, however, require blocking under load-bearing walls

to provide lateral stability and prevent rollover of the joists, as well as to transfervertical load While the squash blocks can transfer the vertical loads, they have

no ability to provide lateral stability Leaving out an occasional blocking panel

and putting in squash block could be justified from an engineering perspective

Multiple-I-Joist Construction. Some applications require that multiple I-joists beused to achieve the necessary span Multiple joists may be required to frame open-ings, support concentrated loads, or support any other loads, which would exceedthe capacity of a single I-joist In these instances, an engineering evaluation may

be required Figure 5.14 illustrates the construction details required to assemble two

or more I-joists, and Table 5.9 provides detailed requirements for installing therequired filler blocks covered in below under Filler Blocks

When Multiple-I-joist Construction Is Required.

1 Double I-joists are required along the foundation or lower support wall line when

the vertical load from above is between 2000 plf (2.94 kN / m) and 4000 plf(5.89 kN / m) and no other means of supporting the vertical load is provided

2 When reinforcing the floor for cantilevers caused by vertical wall offsets as

shown in Fig 5.19, double I-joists are one reinforcing option available

3 Double I-joists are used under interior braced walls or shearwalls running

par-allel to the floor joists where required by code

4 Double I-joists are used when determined by engineering calculation.

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Definition / Function Filler blocks are used to fill the rectangular space between

a pair or more of I-joists designed to act as a single bending member The purpose

of the blocks is to transfer load from one I-joist to the next to achieve load sharing.This is accomplished by forcing each of the joists to deflect the same amount underthe applied load When used between two joists subjected to a line load runningthe full length of the joists, the filler blocks must also be placed the full length ofthe double I-joists Filler blocks do not, however, have to be continuous—they can

be made up of shorter lengths of lumber and / or wood structural panels (see Fig.5.14) provided the attachment is designed to transfer the point / noncontinuous load

Physical Description Filler blocks are made up of lumber, rim board, or wood

structural panel (WSP) materials on hand—whatever it takes to meet the size quirements of Table 5.9 The minimum grade of WSP would be Rated Sheathing;minimum lumber grade is utility grade SPF (south) or better Any PerformanceRated Rim Board product would also work satisfactorily

re-The depth of the filler block should equal the distance between the flanges ofthe joist minus1⁄8 in (3 mm) This gap is placed between the filler block and thetop flange There is nothing scientific about the 1⁄8 in (3 mm) gap Ideally, thecarpenter would cut the blocks so they would just fit between the flanges Ratherthan too tight a fit being risked, and possible damage to one or both of the flange-to-web joints, a slightly loose fit is recommended

In a similar manner, the thickness of the filler block is also important Too thick

is better than too thin If the filler block is too thick, the result is a small gapbetween the flanges, which will not cause a problem Too thin can cause problemswhen the nailing schedule shown in Fig 5.14 is attempted Notice that the nailsare placed near the top and bottom of the filler block This puts them very close

to the flanges of the joist If there is a gap between the web of the joist and filler

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block, the mechanics of driving a nail will attempt to close up that gap This can

do one of two things The first is that it can damage the web or the web-to-joistglue bond If repeated every 12 in (3.5 mm), this can cause a failure of the I-joist.The second is that it can cause the flange of the I-joist to rotate, making for anuneven surface and / or reducing the capacity of the I-joist due to the induced ec-centric loading

Use recommendations.

1 Follow the attachment recommendations of Fig 5.14.

2 Size filler blocking in accordance with Table 5.9.

3 Filler blocks are not required where double I-joists occur under a load-bearing

wall and are supported by the foundation or wall below as in the case of adouble starter joist In this case, the I-joists are not being used as bending mem-bers, so load sharing between joists is not required

Backer Block Construction

Definition / Function Backer blocks (shown in Fig 5.15) are used to fill the

rectangular space between the outside edge of the I-joist flange and the web of theI-joist A backer block is very similar to a half-thickness filler block The backerblock does not run the full length of the I-joist The purpose of the backer blocks

is to provide a flat, flush surface by which surface- or top-mounted hangers or otherstructural elements can be attached to I-joists, and thus it is only as long as it needs

to be to transfer these loads without splitting

With top-mounted hangers, the backer block prevents rotation on the lower

por-tion of the hanger by filling the void between the hanger and the web If the mounted hanger does not rely on any attachment into the side of the I-joist sup-porting it, the backer block is really only providing bearing and an additional backer

top-block on the other side of the I-joist web is not required Backer top-blocks are NOT required if load on top-mounted hanger is less than 250 lbf (1.11 kN ).

With face-mounted hangers, the backer block provides anchorage for the hanger

nails It also provides a means whereby the hanger load is transferred to the web

of the I-joist For such applications, backer blocks on both sides of the web arealmost always required

Physical Description See Physical Description for Filler Blocks (above) for

description of acceptable materials

The depth of the backer block should equal the distance between the flanges ofthe joist minus 1⁄8 in (3 mm) Backer blocks should always be installed tight to the top flange This is to minimize the possibility of inadvertent loading of the

bottom flange in a direction perpendicular to the web-to-flange joint

The thickness of the backer block can be critical If the backer block extends

out beyond the edge of the flange when a top-mounted hanger was being used, this

could cause insufficient bearing on the horizontal fold of the hanger or provide

insufficient space for the required nails This may not be so critical for the mounted hanger, depending on the nailing pattern of the hanger If the backer block

face-is too thin, it could cause the hangers to be installed with a slight rotation towardthe web This can have a detrimental impact on the bearing surface area and / orultimate capacity of the hanger A plus or minus tolerance of 1⁄8 in (3 mm) istypically recommended For tolerance verification and further information pleasecontact the hanger manufacturer

As mentioned previously, the backer block doesn’t have to run the full length

of the I-joist The backer block should be long enough to fully support the flanges

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a) For face-mounted hangers, backer blocks required on both sides of

I-joist If double I-joists are used, filler block between acts as second backer

block.

b) Before installing a backer block to a double I-joist, drive 3 additional 10d

nails through the webs and filler block where the backer block will fit

Clinch Install backer tight to top flange Use twelve 10d nails, clinched

when possible Maximum capacity for hanger for this detail = 1280 lb.

BACKER BLOCKS (Blocks must be long enough to permit required nailing

without splitting)

* Minimum grade for backer block material shall be Utility grade SPF (south)

or better for solid sawn lumber and Rated Sheathing grade for wood

structural panels.

** For face-mount hanger use net joist depth minus 3-1/4 in for joists with

1-1/2 in thick flanges For 1-5/16 in thick flanges use net depth minus

2-7/8 in.

Backer block (hanger not shown for clarity)

Performance Rated I-Joist

Additional nails required for face-mounted hangers

(See notes.) Backerblock must be long enough to

permit required nailing without splitting.

FIGURE 5.15 Backer block installation and connection details.

of the hanger and the required nailing without splitting the block The hanger widthplus 4–6 in (100–150 mm) will be sufficient if wood structural panel blocking isused If the backer block is to be made out of lumber, then additional length may

be required to prevent splitting

Use Recommendations.

1 For top-mounted hangers, backer blocks are normally required on one side of

the I-joist web only Exceptions:

• When the load on the top-mounted hanger exceeds 1000 lbf (4.45 kN), thesecond backer block is required to act as a web stiffener See above underBacker Block Construction

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• When the top-mounted hanger requires additional face nails to reach full pacity, the second backer block will be required (See Recommendation 3 forface-mounted hangers below.)

ca-• When the load on the top-mounted hanger does not exceed 250 lbf (1.11 kN),

a backer block is not required

2 For top-mounted hangers the backer block will be mounted tight to the top

flange (The load is applied to the I-joist through the top flange To preventknife-through of the top flange by the web, the joint between the backer blockand the top flange must be tight.)

For face-mounted hangers backer blocks are required on both sides of a singleI-joist This is to allow sufficient nail penetration in the main member (the block-joist-block assembly) to develop the nail capacity It also allows for a pseudo-double-shear connection at the I-joist web As with the top-mounted hanger, thebacker block should be mounted tight against the top flange

Because the purpose of the backer block is to transfer the load from thehanger into the web of the I-joist, and because the web of the I-joist in only3⁄8

in (10 mm) thick, additional fasteners (fasteners other than those supplied withthe hanger) are required These are the fasteners that attach the backer block tothe web of the I-joist Approximately one additional fastener for each 120 lbf(0.53 kN) of load on the hanger is required In addition, the fasteners that attachthe hanger to the backer block must be long enough to penetrate the web andinto the backer block on the far side

3 When face-mounted hangers are used, care must be exercised in selecting the

material used for the backer blocks The fastening requirements specified bymost hanger manufacturers are established based on a specified species or spe-

cific gravity (G ) of the material receiving the fastener If the hanger installations are based on a G of 0.50, then only OSB, Structural I plywood, or Douglas fir

or southern yellow pine (SYP) lumber may be used for the backer blocks

4 When a piece of lumber is being nailed parallel to and up against the side of

an I-joist, as seen in Fig 5.18 for a non-load-bearing cantilever, the backer block

is only required on the lumber-side of the I-joist when the attachment nails can

be clinched

5 When installing the backer block to multiple I-joists, drive three additional 10d

(3.8 ⫻ 79 mm) common nails, through the webs and filler block where thebacker block will fit, clinch if possible The blocks should be fitted tight againstthe top flange for both top- and face-mounted hangers)

Web Stiffeners

Definition / Function A web stiffener, as shown in Fig 5.16, is a wood block

that is used to reinforce the web of an I-joist at locations where:

1 The webs of the I-joist are in jeopardy of buckling out of plane This may occur

in the deeper I-joist when they exceed their maximum exterior reaction (ER)capacity

2 The webs of the I-joist are in jeopardy of knifing through the I-joist flanges.

This can occur at any I-joist depth when the design reaction capacities are ceeded

ex-3 The I-joist is supported in a hanger and the sides of the hanger do not extend

up to the top flange With the top flange unsupported by the hanger sides, thejoist may collapse to the side, putting a twist in the flange of the joist The web

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(4) 8d nails, 10d required for I-joists with 3-1/2" flange width (PRI-80s)

Flange width

1-3/4"

or less

Flange width greater than 1-3/4"

FIGURE 5.16 Performance rated I-joist web stiffener requirements.

Tiêu đề	Prefabricated Wood I-Joists And Engineered Rim Board
Tác giả	Edward Keith, P.E.
Trường học	APA—The Engineered Wood Association
Chuyên ngành	Engineering
Thể loại	Chương

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Số trang	157
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