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TABLE 10.1 Interior Finish ClassificationsInterior finish or flame spread classification Flame spread index Smoke developed index TABLE 10.2 Typical Flame Spread Classification Requireme

CHAPTER TEN FIRE- AND NOISE-RATED

SYSTEMS

John D Rose

Retired Senior Engineer, TSD

When designing or building for fire protection, it is important to recognize thatfireproof buildings do not exist Building contents are a critical factor, and almostall contents can burn Smoke and heat thus generated can cause extensive damageand loss of life long before the building itself begins to burn, regardless of the type

of construction

After studying residential fires involving combustible contents, the USDA ForestProducts Laboratory (FPL) concluded that ‘‘wall and ceiling materials, whethercombustible or noncombustible, had little or no effect on the time or temperature

of the critical point’’—the point at which human life is untenable In the FPLstudies, the critical point was reached in four to seven minutes Other tests haveshown that untenable conditions can occur in as little as two minutes

So-called fireproof building materials do not guarantee safety for occupants orproperty A classic demonstration of this was the 1953 fire in a General Motorsmanufacturing plant in Livonia, Michigan The plant was considered completelynoncombustible, yet was a complete loss due to the collapse of unprotected metalconstruction

Another example was the 1967 disaster at McCormick Place, Chicago’s bition hall All of its structural members, including interior nonbearing walls, werenoncombustible Yet a fire that began in the contents spread with such heat that theentire ceiling fell as steel beams, girders and trusses buckled and collapsed.The type of construction is, of course, important To protect the occupants—always the first concern—as well as to safeguard property, a prompt detection andalarm system and the accessibility of numerous exits are vital Also of importanceare the type of contents and furnishings, interior finishes, degree of sprinkler pro-tection, and availability of adequate fire-fighting equipment

exhi-With proper construction in conformance with model building code regulationsand with recognition of the above factors, fire-safe buildings can be designed withcombustible or noncombustible materials This puts wood framed systems in properperspective Fire- and noise-rated wood floor and roof ceiling systems and wall

systems are being increasingly used for multifamily residential and nonresidentialbuilding construction, for low-rise (three stories and less) and medium-rise (four tosix stories) buildings.

10.1.1 Basics of Fire Protection

In order to evaluate fire safety of a structure, building authorities consider manyfactors, including flame spread and fire-resistance ratings

Flame Spread and Smoke Indexes. Flame spread relates to potential for spread

of fire along the surfaces of the wall and ceiling within a room It is measured bythe flame travel along the surface of materials used for interior finish, such as walls,ceilings, partitions, paint, and wallpaper Not considered in codes are such nonstruc-tural materials as drapes and furnishings, though these may often be primary fuelsources Flame spread is a property of the surface material, not the structure, whenfire has started

The recognized flame spread test is the tunnel test, American Society for Testingand Materials (ASTM) Test Method E84.1A test sample of material, 20 in wideand 25 feet long, is installed as ceiling of a test chamber and exposed to a gasflame at one end The distance of flame spread along the surface of the test sample

is measured during a 10 minute test duration Flame spread index is calculated asthe area under a flame spread distance—time curve, divided by comparable areasfor standard materials (inorganic reinforced cement board and red oak), and mul-tiplied by 100 The flame spread index is 0 for inorganic reinforced cement boardand 100 for red oak

Another property measured in the ASTM E84 test is the opacity of the smokegenerated by the burning material during a 10 minute test exposure A photelectriccell, installed in the test chamber exhaust vent pipe, measures the light absorption(opacity) due to smoke generated during the test, which is compared to the amount

of smoke generated by standard materials (inorganic reinforced cement board andred oak) Smoke developed index is calculated as the area under the light absorp-tion-time curve, divided by the comparable area for standard materials, and multi-plied by 100 The smoke developed index is 0 for inorganic reinforced cementboard and 100 for red oak

Materials with the lowest flame spread index (0–25) are classified as Class A(or I) Such materials are permitted for areas where fire hazard is most severe, forexample vertical exit ways of unsprinklered buildings for public assembly.Materials with a flame spread index from 26–75 are Class B (or II) are permitted

in areas of intermediate severity, such as corridors providing exit way access inbusiness and industrial buildings For exit ways and for most interiors where Class

A or Class B flame spread performance is required, fire-retardant-treated plywood(which falls in Class A) is permitted

Materials with a flame spread index from 76–200 are Class C (or III) Woodstructural panels such as plywood, oriented strand board (OSB), and compositepanels (veneer faces with structural wood core) generally fall in this class and arepermitted in rooms of most occupancies (Exceptions: hospitals, or institutionswhere occupants are restrained.)

Table 10.1 shows flame spread and smoke developed index values of somecommonly used construction materials Table 10.2 shows typical flame spread re-quirements, as specified in the International Building Code (IBC) The Flame spreadindex for untreated wood structural panels falls within Class C, but ratings vary,

TABLE 10.1 Interior Finish Classifications

Interior finish or flame spread classification Flame spread index Smoke developed index

TABLE 10.2 Typical Flame Spread Classification Requirements for Interior Finish Based

on the 2000 International Building Code

Unsprinklered Group

Vertical exits and exit passagewaysa,b

Exit access corridors and other exitways

Rooms and enclosed spacesc

aClass C interior finish materials shall be permitted for wainscoting or paneling of not more than 1000

ft 2 of applied surface area in the grade lobby where applied directly to a noncombustible base or over furring strips applied to a noncombustible base and fireblocked.

bIn vertical exits of buildings less than three stories in height of other than Group I-3, Class B interior finish for unsprinklered buildings shall be permitted.

cRequirements for rooms and enclosed spaces shall be based upon spaces enclosed by partitions Where

a fire-resistance rating is required for structural elements, the enclosing partitions shall extend from the floor

to the ceiling Partitions that do not comply with this shall be considered enclosing spaces and the rooms

or spaces on both sides shall be considered one In determining the applicable requirements for rooms and enclosed spaces, the specific occupancy thereof shall be the governing factor regardless of the group clas- sification of the building or structure.

dLobby areas in A-1, A-2, and A-3 occupancies shall not be less than Class B materials.

eClass C interior finish materials shall be permitted in places of assembly with an occupant load of 300 persons or less.

fFor churches and places of worship, wood used for ornamental purposes, trusses, paneling, or chancel

depending on species, thickness, and glue type In general, for plywood, panelswith exterior adhesives perform better than those with interior adhesives; thickpanels better than thin; and low density species better than heavier species.2,3

Fire-Resistance Ratings. Though codes are concerned with how fast fire canspread on a room’s surface, they are even more specific about fire resistance: themeasure of containment of fire within a room or building It is defined as protectionagainst fire penetrating a wall, floor, or roof, either directly or through a high rate

of heat transfer that might cause combustible materials to be ignited on the side ofthe wall or floor away from the actual fire Thus, it is a property of an assembly

of several materials, including fastenings, and of the workmanship

Fire-resistive construction provides time to discover a fire, restrict or suppress itbefore it spreads, and evacuate the building if necessary

The standard test for measuring fire resistance is ASTM E119.4Ratings of semblies are determined by test procedures somewhat simulating actual fire con-ditions Floor-ceilings and roof-ceilings are tested flat while loaded to their fullallowable stress Walls are tested vertically, either as bearing walls under full orlimited axial load or as nonbearing walls under no load The resistance rating isexpressed in hours or minutes before some limiting condition is reached (flamepassage or heat transmission on the unexposed surface, or structural collapse) Itapproximates the time an assembly would be expected to withstand actual fireconditions

as-A one-hour rating, for example, is taken to mean that an assembly similar tothat tested will not collapse, nor transmit flame or a high temperature, while sup-porting its full load, for at least one hour after the fire commences

Thermal Barrier Index. When foam plastic insulation is used in building struction, an approved thermal barrier material is required to serve as a protectivemembrane to separate the interior of the building from the insulation, which is oftenhighly flammable when exposed to fire conditions The fire performance of thethermal barrier is evaluated by a special standard fire testing method (ICBO),5withfire exposure for 15 minutes on the bottom surface of a 3⫻ 3 ft horizontal testspecimen of the thermal barrier material The thermal barrier material is backedwith noncombustible1⁄2in thick calcium-silicate board for the test, to standardizetesting conditions Temperature rise on the unexposed surface is limited to an av-erage of 250⬚F A product meeting these requirements is defined as a thermal barriermembrane and is classified as having a thermal barrier index of 15, which is theminimum specified in the codes for applications where foam plastic insulation isused Thermal barrier membranes are not required by codes for certain applications

con-of foam plastic insulation, such as:

• When used as roof insulation that is separated from the interior of the building

by minimum nominal7⁄16in wood structural panels

• When used as a substrate for fire-classified roofing

• For insulation in attics or underfloor crawl spaces with limited access, whereinsulation is protected against ignition by minimum nominal1⁄4in wood struc-tural panels or other prescriptive materials specified in the codes

• For insulation in cooler and freezer walls when the foam plastic insulation meetsspecified requirements

As for thermal resistance in fires: because of its superior insulating qualities,wood structural panels may be expected to develop a finish resistance (based on

time to develop an average temperature rise of 250⬚ on the back of the panel) ofapproximately 20 or more minutes per inch of thickness when subjected to heatand flame based on the ASTM E119 time-temperature curve Pressure treatmentwith fire-retardant chemicals does not materially affect the finish resistance, thoughcoating with fire retardant paints may be somewhat more effective.

Fire-Retardant Treated Wood and Fire-Retardant Coatings. treated (FRT) wood or plywood is pressure-impregnated with fire-retardant chem-icals in water solution in accordance with American Wood-Preservers’ AssociationStandards AWPA C27 (plywood) or C20 (lumber), to inhibit combustion and retardflame spread under fire exposure conditions However, no treatment processes orstandards have been developed for fire-retardant treatment of other wood structuralpanels (oriented strand board, or com-ply) or engineered wood composite framingmembers such as structural glued laminated timber (glulam), I-joists, laminatedveneer lumber, parallel strand lumber, or oriented strand lumber

Fire-retardant-When tested for 30 minutes under ASTM Standard E84, FRT wood and plywoodhave a flame spread index of 25 or less and show no evidence of significant pro-gressive combustion Also, there is a maximum limit on the flame travel during thetest FRT wood reduces its fire hazard classification and qualifies it for lower flamespread (at least as low as gypsum wallboard) and smoke index ratings

Fire-retardant (FR) coatings can be used on wood and wood structural panelsfor nonstructural interior finish applications such as wall and ceiling paneling toreduce flame spread ratings to 25 or less (Class A) or from 26–75 (Class B),depending on the coating selected FR coatings are tested per ASTME 84 for 10minutes, as compared to 30 minutes for FRT wood FR coatings can be factory- orfield-applied as interior finish coats over new or existing wood surfaces; some FRcoatings are available with proprietary topcoat finishes for exterior use FR coatingsare available as opaque or clear finishes

10.1.2 Model Building Code Provisions (2000 International Building Code)

In the past, four model building codes have been used in the United States Theseare the Standard Building Code (primarily used in the South); Uniform BuildingCode (primarily used in the Midwest and West); National Building Code (widelyused in the Northeast); and the One- and Two-Family Dwelling Code Most of theregional and state codes in the country are similar to or adaptations of these codes.Building code provisions have the authority of law (unlike insurance requirements,which are optional)

Beginning in the year 2000, two new national codes were promulgated to replacethe model codes These were the International Building Code (IBC)6 and the In-ternational Residential Code for One and Two Family Dwellings (IRC).7Adoption

of these codes by local and state jurisdictions will occur over a period of yearswith the model codes remaining in effect in the interim

In addition, the National Fire Protection Association (NFPA) will be publishing

an alternative national building code in 2002 Therefore, designers are cautioned tocheck their local area for the applicable code

Types of Construction. The International Building Code standardized the types

of construction prescribed in the previous model building codes, as shown in Table10.3 Construction-type classifications are based on fire-resistance ratings of struc-tural elements Of the three types of wood construction, Type IV (Heavy Timber)construction is permitted for multistory buildings (up to four stories, or five stories

TABLE 10.3 Typical Types of Construction Permitting Wood Systems Based on 2000 International Building Code

Non-wood systems

Types I and II construction Noncombustible structural building elements.

Includes subtypes A and B with specific fire-resistive ratings required for each building element These construction types permit untreated or fire-retardant-treated wood for certain building elements such as partitions, roof framing, decking, etc Heavy timber construction permitted for roof framing and decking, where one-hour

or less fire-resistance rating is required See code for specifics.

Wood systems

building elements of light framing with protected or unprotected wood members Includes sub-types A and B with specific fire-resistive ratings required for each building element.

Type IV contruction (heavy timber) Noncombustible exterior walls, interior

building elements of heavy timber wood members without concealed spaces.

walls of light framing with protected or unprotected wood members throughout Includes subtypes A and B with specific fire-resistive ratings required for each building element.

for certain occupancies) such as educational, religious, manufacturing, warehouse,supermarket; and permits the largest areas The next largest areas are permitted forType III construction, commonly used for commercial or public buildings up tothree or four stories high, or five stories for some occupancies Finally, Type Vconstruction is used in 80% of all residential and many commercial, institutional,industrial and assembly buildings

If the building requires a larger area than is permitted for the type of constructionselected, the designer has several choices, including breaking up the area with firewalls, adding sprinklers, increasing property line setbacks, and specifying a morefire-resistant construction (See Building Area Increases.)

In most cases, conventional wood-frame construction with wood structural panelsheathing and regular gypsum wallboard interior finish provides ample fire safetyand is completely acceptable for one- and two-family residential applications.Certain building applications, such as multifamily residential construction, andnonresidential construction, require additional protection In these cases, the de-signer’s options include protected construction or Heavy Timber construction Forcertain applications, fire-retardant-treated wood is permitted for construction

Protected Construction Protected construction consists of conventional

wood-framed assemblies, such as floor-ceiling or wall, with a fire-resistive material added

to give primary protection to the wood framing The material may be fire-resistive

TABLE 10.4A Fire-Resistance Rating Requirements for Building Elements (Hours) Based

on 2000 International Building Code

Building element

Type III

Type IV HT

2 0

2

1 / HT

1 1

0 0 Nonbearing walls and partitions

Exterior

Interiord

See Table 602 See Section 602 Floor construction

Including supporting beams and joists

Roof construction

aThe structural frame shall be considered to be the columns and the girders, beams, trusses, and spandrels having direct connections to the columns and bracing members designed to carry gravity loads The members

of floor or roof panels that have no connection to the columns shall be considered secondary members and not a part of the structural frame.

b1 Except in factory-industrial (F-I), hazardous (H), mercantile (M) and moderate hazard storage (S-1) occupancies, fire protection of structural members is not required, including protection of roof fram- ing and decking where every part of the roof construction is 20 ft or more above any floor imme- diately below Fire-retardant-treated wood members are allowed to be used for such unprotected members.

2 In all occupancies, heavy timber is allowed where a one-hour or less fire-resistance rating is required.

cAn approved automatic sprinkler system shall be allowed to be substituted for one-hour rated construction, provided such system is not otherwise required by other provisions of the code or used for an allowable area increase or an allowable height increase The one-hour substitution for the fire resis- tance of exterior walls is not permitted.

fire-resistance-dFor interior nonbearing partitions in Type IV construction.

gypsum wallboard, plaster, or acoustical tile The fire-resistive material, in junction with wood structural panel sheathing, prevents flame passage and temper-ature rise while reinforcing framing against collapse under load Tables 10.4A and10.4B are examples of typical fire-resistive requirements in model building codes.Fire-rated floor-ceiling and wall assemblies have been developed for one- and two-hour ratings using wood systems, for building applications in the United States InCanada, fire-rated assemblies for 45-minute and 11⁄2-hour ratings are permitted bythe National Building Code of Canada

con-Heavy Timber Construction con-Heavy Timber construction provides fire

protec-tion through use of noncombustible exterior walls in conjuncprotec-tion with interior tural elements of large, solid wood members, including solid lumber girders, col-umns, and floor and roof decking, glued laminated wood, and engineered woodframing, installed without concealed spaces See Table 10.5 for code definitions ofminimum sizes of members for Heavy Timber construction

struc-The requirements for Heavy Timber construction in model building codes donot constitute one-hour fire resistance The terminology is descriptive of early east-ern U.S textile mills, where it was known as mill construction, plank-on-timber,

or slow-burning Although outside surfaces of wood members may char duringexposure to fire, the surface char layer acts as insulation The strength and size of

TABLE 10.4B Typical Fire-Resistance Rating Requirements for Exterior Walls Based on Fire Separation DistanceaBased on 2000 International Building Code

0 1

0 1

fire-cSee Section 503.2 of 2000 IBC for party walls.

TABLE 10.5 Dimensions of Components for Heavy Timber Construction

Heavy Timber construction is defined in the 2000 International Building Code by the following minimum sizes for the various members or portions of a building:

in., nominal Columns

Supporting floor loads 8 ⫻ 8 Supporting roof and ceiling loads only 6 ⫻ 8 Floor framing

Beams and girders 6 wide ⫻ 10 deep Arches and trusses 8 in any dimension Roof framing—not supporting floor loads

Arches springing from grade 6 ⫻ 8 lower half

6 ⫻ 6 upper half Arches, trusses, other framing springing from top of walls, etc 4 ⫻ 6 Floor (covered with nominal 1 in flooring, or 1 ⁄ 2 in wood structural

panels, or other approved surfacing)

Splined or tongue-and-groove planks 3 Planks set on edge 4 Roof decks

Splined or tongue-and-groove planks 2 Planks set on edge 3 Tongue-and-groove wood structural panels 1 1 ⁄ 8

wood members are such that they continue to support its load, so the chance ofbuilding collapse is greatly diminished

Based on comparative fire tests, 11⁄8in thick wood structural panels with and-groove edges are accepted as an alternative to nominal 2 in thick planks (orlaminated planks at least 3 in wide and set on edge) for Heavy Timber roof decks.See Fig 10.1 Oriented strand board (OSB) wood structural panels, having a min-

tongue-Built-up roofing

Strength axis Structural glued laminated timber (glulam) or solid timber beams (4x6 minimum)

1 1 /8" APA T&G wood structural panels with exterior glue (Exposure 1) – APA RATED STURD-I-FLOOR 48 oc typical

FIGURE 10.1 Heavy timber roof construction.

imum nominal thickness of 13⁄32in and tongue-and-groove edges, also are nized as an alternative to 11⁄8 in wood structural panels for Heavy Timber roofdecks in the Uniform Building Code

recog-This code recognition can simplify roof construction practices while providingfire protection Performance of Heavy Timber construction is superior to most un-protected ‘‘noncombustible’’ (metal) structures, under fire conditions There are noconcealed spaces where fire can spread Firefighting is simpler and safer Firefight-ers who have had long experience with wood’s structural integrity under fire con-ditions can more accurately predict how long wood will carry its load than theycan with other materials, enabling them to stay on or in the building to combat thefire

Codes also permit15⁄32or1⁄2in wood structural panels over nominal 3 in planksfor Heavy Timber floors These provisions allow structural design of the building

to resist wind or seismic loading, based on utilizing the wood structural paneldiaphragm capacity for floor and roof decks

Guidelines for structural evaluation of the effect of damage to Heavy Timbermembers and glulam after a fire are available.8,9

Fire Retardant Treated (FRT ) Construction Fire-retardant-treated (FRT) wood

or plywood is permitted for certain applications in the model building codes FRTwood reduces its fire hazard classification and qualifies it for lower flame spread(at least as low as gypsum wallboard) and smoke index ratings When FRT wood

is identified by a code-recognized testing agency label, it is rated on a parity withnoncombustible construction by many fire insurance rating bureaus

Span ratings for wood structural panels, and load capacities for wood framingand plywood wood structural panels are based on untreated materials and may notapply following fire-retardant treatment Structural performance characteristics anduse recommendations for FRT wood and plywood should be obtained from thecompany providing the treatment and redrying service For structural applications,use only FRT wood that has recognition through building code evaluation servicereports

When considering use of FRT wood, first determine through thorough gation that it is the best overall solution Required fire protection at lowest con-struction cost, and cost of annual building insurance, should be taken into consid-eration FRT wood is more expensive than untreated wood, which in most casescan be used in structural floor, wall, and roof assemblies to meet fire-resistiverequirements in regard to both life safety and protection of property

investi-Calculated Fire Resistance. The International Building Code (as well as the threemajor model building codes) permits calculation as an alternative to prescriptive ortested assemblies for one-hour fire-rated wood-framed floors, roofs, and load-bearing and nonbearing walls The codes provide tables of assigned times for com-ponents, which have been developed empirically from extensive studies of assem-blies tested with nominal 2 in wood framing in accordance with ASTM StandardE119 End-point criteria in the standard also were considered A one-hour fire-ratedassembly can be determined by combining the individual component times of theassembly in accordance with the method and limitations in the codes, thereby pro-viding additional choices for the designer.

Methods also provide for determining the required size of exposed timber beamsand columns with a minimun nominal dimension of 6 in., including structural gluedlaminated timber, for fire-resistance ratings up to one hour.6,10(See Chapter 4 for

a further discussion.)

Building Occupancy, Area, and Height Limitations. All buildings must meetcode requirements with respect to permissible heights and floor areas These re-quirements are based on certain characteristics of the building, including the firezone, type of occupancy, construction materials and systems, setbacks from propertylines, exits, and automatic extinguishing systems

Fire Zones Some cities have established one or more geographic fire zones

(or fire limits), which restrict type of use or occupancy, percentage of lot coverage,and type of construction permitted The purpose is to make fire protection easier

by concentrating in one area those buildings of similar fire hazard Usually, frame building construction is not permitted in central fire zones, where congestionand closeness of other buildings would make fire spread most likely and fire fightingmost difficult

wood-Occupancy Codes traditionally have specified use or occupancy classifications,

including assembly, business, educational, factory and industrial, hazardous, tutional, mercantile, residential, storage, and utility or miscellaneous Within oc-cupancy classifications, codes also consider whether manufacturing or storage is ofpotentially explosive or dangerous materials; whether the residents are elderly, dis-abled, or confined, etc Unprotected wood construction is not permitted in specifichigh-hazard or medical institutional occupancies

insti-Setbacks Codes traditionally have recognized the advantage of large open areas

around buildings, to make fire fighting easier and prevent fire spread When ings have more than 25% of their perimeter on a 20 ft minimum open space, orface on a street with a 20 foot minimum width, the International Building Codepermits a building with larger area than when buildings are closer to property lines

build-or other buildings

Exits The number and type of exits required depend on occupant load and

travel distance to exits All exit assemblies are classified by fire-resistance ratings,and except for certain high-hazard or institutional occupancies, protected woodconstruction is usually permitted The maximum distance to an exit is 200 ft inaccordance with the International Building Code, for most occupancy classificationswithout sprinklers including business or residential buildings Previous codes dif-fered somewhat in these provisions

Sprinklers Sprinklers are another option that can be used to increase building

height and / or area, expanding the options for using wood systems in large family residential and non-residential buildings With sprinkler protection, coderequirements for flame spread and fire-resistance ratings may be relaxed It may be

multi-possible to add another story or increase building area Reduced annual insurancepremiums for buildings and contents mean that sprinklers generally will pay forthemselves within a few years, depending on the value of the building and itscontents The difference in insurance rates between sprinklered wood and sprink-lered unprotected steel buildings is usually minimal.

Building Area Increases. Building codes place limitations on the height and area

of a building according to compliance with certain established criteria that are based

on safety of occupants and fire services These criteria include occupancies, types

of construction, and location within fire zones

Light-frame wood construction is often the best choice from the standpoint ofcost and simplicity However, the basic allowable areas may limit the size of thebuilding It is to the designer’s advantage to utilize permitted construction featuresthat allow increases in allowable building area, in order to take advantage of theeconomy and versatility of wood framed construction systems The following sug-gestions, and the data in Table 10.6, help to identify these features

increased when one-hour fire resistance is provided for all structural elements inthe building, including beams and columns, floors, walls, and roofs

to be increased when an automatic sprinkler system is installed throughout thebuilding For example, under the 2000 IBC, a 200% increase is permitted forone- and two-story buildings An additional benefit is the likelihood of substan-tially lower insurance rates with sprinklers Sprinkler systems can be connected

to a central alarm system for additional protection

on two or more sides of a building Under the 2000 IBC, a 150% increase isallowed if all sides face toward public streets

unlimited area buildings for industrial, storage, or business uses Generally, theremust be large areas of open space surrounding the building, and the building must

be completely sprinklered

of properly constructed fire walls In effect, two contiguous buildings are erectedbut are separated by a rated wall or partition, with all openings protected

The 2000 IBC provides a simple formula that can be used to determine areaincreases for the values shown in Table 10.6 This is given as:

where A a⫽adjusted allowable area (ft2)

A t⫽area per Table 10.6

lƒ⫽area increase due to open frontage

l ⫽area increase due to sprinkler protection

TABLE 10.6 Typical Allowable Height and Building Areas Based on 2000 International Building Code Height limitations shown as stories and feet above grade plane; area limitations as determined by the definition of ‘‘area building,’’ per floor

Group

HGT (ft)

HGT (story)

Type of construction Type III

Type IV 65

2 8,500

3 15,000

2 11,500

1 5,500

A

3 14,000

2 9,500

3 15,000

2 11,500

1 6,000

A

3 14,000

2 9,500

3 15,000

2 11,500

1 6,000

A

3 14,000

2 9,500

3 15,000

2 11,500

1 6,000

A

UL UL

UL UL

UL UL

UL UL

UL UL

A

5 28,500

4 19,000

5 36,000

3 18,000

2 9,000

A

3 23,500

2 14,500

3 25,500

1 18,500

1 9,500

A

3 19,000

2 12,000

4 33,500

2 14,000

1 8,500

A

4 28,500

3 18,000

5 50,500

3 21,000

2 13,000

A

1 9,500

1 7,000

1 10,500

1 7,500

NP NP

A

2 9,500

1 7,000

2 10,500

1 7,500

1 3,000

A

4 17,500

2 13,000

4 25,500

2 10,000

1 5,000

A

5 28,500

3 17,500

5 36,000

3 18,000

2 6,500

A

3 28,500

3 19,000

3 36,000

3 18,000

2 9,000

A

4 16,500

3 10,000

4 18,000

3 10,500

2 4,500

A

1 12,000

NP NP

1 12,000

1 9,500

NP NP

A

2 10,500

1 7,500

2 12,000

2 7,500

1 5,000

A

3 23,500

2 13,000

3 25,500

1 18,500

1 9,000

A

4 18,500

4 12,500

4 20,500

3 14,000

1 9,000

A

4 24,000

4 16,000

4 20,500

3 12,000

2 7,000

TABLE 10.6 Typical Allowable Height and Building Areas Based on 2000 International Building Code Height limitations shown as stories and feet above grade plane, area

limitations as determined by the definition of ‘‘area building,’’ per floor (Continued )

Group

HGT (ft)

HGT (story)

Type of construction Type III

Type IV 65

4 UL

4 UL

3 UL

3 UL

A

4 24,000

4 16,000

4 20,500

3 12,000

2 7,000

A

3 26,000

3 17,500

4 25,500

3 14,000

1 9,000

A

4 39,000

4 26,000

5 38,500

4 21,000

2 13,500

A

3 14,000

2 8,500

4 18,000

9 9,000

1 5,500

UL ⫽ unlimited.

lƒmay be determined by the following equation:

where lƒ⫽area increase due to frontage (percent)

F⫽building perimeter fronting on public way or open space

P⫽perimeter of entire building

W⫽minimum width of public way or open space

max-Protected Floor and Roof Ceiling Systems. There are numerous fire-rated blies combining wood framing and wood structural panels with fire-resistive gyp-sum wallboard that are especially suitable for nonresidential and multifamily resi-dential buildings They include one-hour rated and several two-hour rated protectedwood-frame floor-ceiling and roof-ceiling systems.

assem-In these assemblies, materials such as gypsum wallboard, plaster, and acousticaltile provide primary fire protection The panel floor or roof acts to prevent flamepassage and temperature rise, as well as to reinforce wood framing members againstcollapse under load after the effectiveness of the ceiling has been lost

Because these systems contain wood and possibly other combustible materials,they are designated as combustible constructions At present, codes don’t permitthem in so-called noncombustible (Type I or II) structures, even though their testedperformance meets performance requirements that are the same as for assembliesclassified as noncombustible

Full-scale tests on assemblies representative of intended floor- or roof-ceilingconstruction are conducted by fire testing laboratories that are recognized by build-ing code evaluation services Many of these laboratories publish a listing directorythat is updated annually or periodically, describing the materials and construction

of the tested assemblies, and the fire endurance rating obtained in the test Onesuch directory is the Underwriters Laboratory Inc (UL) Fire Resistance Direc-tory;11 others are listed under Additional Reading at the end of this chapter Over

40 wood floor-ceiling (or roof-ceiling) systems using wood structural panels arelisted in the UL directory Listed designs in fire directories of recognized fire testinglaboratories are used by architects and designers for building design and construc-tion, and are accepted by building code officials for fire-rated construction.Selected examples of fire-rated floor-ceiling construction options with lumberjoists and engineered wood framing (wood I-joists or trusses) are shown in Fig.10.2

Many systems consist of a double layer floor of plywood subfloor and layment (15⁄32in and 19⁄32in., respectively) For fire-rated roof-ceiling assemblies,codes permit omission of the top layer of plywood More recently, fire-rated floor-ceiling assemblies have been developed, which have a single-layer floor system of

under-19⁄32 in or thicker wood structural panels for combination subfloor-underlayment;these systems are more frequently specified than those having a two-layer floor.Any finish flooring material may be used over the underlayment or single-layerfloor Many systems permit lightweight concrete or gypsum concrete floor topping,applied over the single-layer floor or over the subfloor in lieu of the top plywoodunderlayment layer, for one- and two-hour floor-ceiling assemblies Other systemsusing a single-layer23⁄32in wood structural panel floor with wood I-joists or trussesalso are shown in this figure

Based on comparative tests, wood structural panels such as oriented strand board(OSB) or composite panels containing veneer faces and a wood structural core(COM-PLY) may be used in tested plywood floor- or roof-ceiling systems withoutjeopardizing fire-resistance ratings In double-layer wood systems, minimum7⁄16in.oriented strand board may be used in lieu of a 15⁄32 in plywood subfloor Othersubstitutions are based on equivalent panel thickness For all assemblies, specifiedthicknesses and dimensions for sheathing and framing components are minimums,and thicker or larger materials may be used For framing members, spacing may

be reduced without affecting the fire rating

As previously discussed, model building codes also include procedures for culating fire resistance of one-hour fire-rated floor- or roof-ceiling systems, using

cal-a component cal-additive method with stcal-andcal-ard building components The

time-19 / 32 " T&G APA plywood underlayment(b)(c) (Most codes do not require the top layer of two-layer rated assemblies when used for roofs.)

23 /32" T&G

adhesive at trusses and T&G edges

Type X gypsum wallboard

ceiling; resilient channels

required in some assemblies

Wood I-joists or

trusses 24" o.c.

*For proprietary names see latest

U.L Fire Resistance Directory

1 /2" proprietary* Type X gypsum wallboard ceiling

(2 layers)

Resilient channels spaced 16" o.c.

Some rated assemblies incorporate proprietary products When designing and specifying,

check the Underwriters Laboratories Fire Resistance Directory for complete details on a

particular assembly A change in details may affect fire resistance of the assembly.

1 Two-layer floor systems with joists (a) For details, see U.L Design Nos L001, L003,

L004, L005, L006, L201, L202, L206, L208 (1-1/2 hr), L209, L210, L211 (2 hr), L212, L501, L502, L503, L505 (2 hr), L511 (2 hr), L512, L514, L515, L516, L519, L522,

L523, L525, L526, L533, L535, L536 (2 hr), L537, L541 (2 hr) and L545 Also see U.L Designs No L524 and L527 (1-1/2 hr single layer) with steel joists spaced 24" o.c., and L521 with wood trusses spaced 24" o.c.

2 Single-layer floor systems with wood I-joists or trusses For details, see U.L Design

Nos L528, L529, L534, L542 and L544 (shown) Also see U.L Design No L513 for

single-layer floor system with lumber joists spaced 24" o.c.

fire-resistance ratings Substitution is based on equivalent panel thickness, except that 7/16" OSB

subfloor panels may be used in place of 15/32" plywood subfloor panels in two-layer assemblies

OSB panels are listed as alternates to plywood subflooring or finish flooring in U.L Design Nos L501, L503, L505 (2hr), L508, L511 (2hr), L513, L514, L516, L521, L526, L528, L529, L532 (1-1/2 hr),

L539, L540, L543, L544, L546, L548, L550, L551 and L552.

(c) Lightweight concrete or gypsum concrete floor topping permitted over single-layer floor or as

alternate to plywood underlayment in many assemblies (check details).

FIGURE 10.2 One-hour fire-rated combustible floor-ceiling or (roof-ceiling) semblies.

as-APA Rated Siding Exterior or other

exterior finish (code-approved type)

Min 7 /16" APA Rated Sheathing Exposure 1 OSB or plywood

Glass fiber insulation (R-13 minimum, kraft paper or foil facing)

or unfaced mineral wool insulation; min 3 1 /2" thick

5 /8" Type X gypsum wallboard

Min 2x4 studs @ 16" o.c.

FIRE SIDE

FIGURE 10.3 Load-bearing exterior wall system.

assigned values for these components are based on analysis of full-scale fire testsconducted with nominal 2 in framing members; thus, values should not be applied

to framing systems using lightweight engineered wood framing members However,fire-rated floor-ceiling or roof-ceiling systems that use proprietary engineered woodframing members, are recognized by model building code evaluation services, underevaluation reports issued to individual manufacturers or trade associations

Wall Systems. Options for fire-rated wall systems for light-frame wood tion include conventional wood-framed walls with wood structural panel sheathing

construc-or siding, commonly in conjunction with fire-resistive (Type X) gypsum wallboardinterior finish

Protected Exterior Walls Protected light-frame construction, with fire-resistive

(Type X) gypsum wallboard interior finish, is rated by codes between ordinaryunprotected and Heavy Timber construction in terms of fire performance

Under 2000 IBC provisions, when separation between buildings is greater than

5 feet, the fire-resistive rating for the wall applies only to fire exposure from theinterior side of the wall Fire-resistive (Type X) gypsum wallboard sheathing is notrequired on the exterior side of the wall Figure 10.3 illustrates a one-hour fire-rated wall construction based on UL Design No U356 that is applicable underthese code provisions

In populated regions subject to urban wildfire hazards, such as the western andsouthwestern United States, or where buildings are separated by 5 ft or less, exteriorwalls must be rated for fire exposure from the exterior side as well as the interiorside to comply with requirements of the 2000 IBC and the Urban-Wildland InterfaceCode (IFCI) In such applications, fire-resistive (Type X) gypsum wallboard sheath-ing is required on the exterior side of the wall, either under or over wood structuralpanel sheathing, over which an approved exterior finish is applied Wood structuralpanel siding also can be installed over fire-resistive gypsum wallboard sheathing.Alternatively, noncombustible exterior finishes such as brick veneer or portlandcement plaster (stucco) can be applied over wood structural panel sheathing on theexterior side of the wall to provide one-hour fire endurance when subjected to fireexposure on the exterior side of the wall

An example of protected wall construction, rated for fire exposure on both sides,

is shown in Fig 10.4 Such walls consist of minimum 2⫻ 4 studs, spaced 16 in

or 24 in o.c with wood structural panel siding over5⁄8in Type X gypsum sheathing

on the exterior side, and5⁄8in Type X or proprietary Type X (Type C or G) gypsumwallboard on the interior side Another option permitted in the 2000 IBC usesstucco over wood structural panel sheathing Protected wall constructions qualifyfor the same ratings if other materials are added; e.g., siding may be attached tothe outside of a fire-rated wall to add shear-wall value without impairing the rating.Also, wood structural panel sheathing can be added between the gypsum wallboardfire-resistive membrane and wood framing, on either the interior or exterior side ofthe wall

(a) Generic, non-proprietary assembly based on GA File No WP8105 listed in

Gypsum Association Fire Resistance Design Manual, referenced in the model

building codes Mineral or glass fiber batt insulation (optional).

(b) Exterior layer of gypsum sheathing not required under the National and

Standard Building Codes, or the International Building Code, when separation is

greater than 5 feet Check local provisions See U.L Design U356 in U.L Fire

Resistance Directory.

FIGURE 10.4 One-hour fire-rated exterior load-bearing wall assembly.

2000 IBC provisions also permit determination of one-hour fire-rated wall tems using procedures for calculated fire resistance of components

sys-Interior Walls and Partitions Building code regulations require a flame spread

index of 200 maximum on materials used for interior finishes on exposed surfaces(in areas other than certain exit ways and corridors, as noted earlier) Flame spreadindex ratings for wood structural panels generally fall within Class A (FSI 76-200)and thus are within the range of acceptable materials

For interior areas requiring lower flame spread ratings, fire-retardant-treated wood paneling is acceptable Panels identified by labeling from a recognized firetesting laboratory or quality assurance agency indicating conformance to a Class Aflame spread rating, are accepted by code officials Fire retardant paints, properlyapplied, also may be used to reduce the flame spread rating to Class A or B, andare often recognized by building officials

ply-In single-family residential use, Class C flame spread rating is acceptable forinterior wall and ceiling finishes Softwood plywood paneling is well within theacceptable range, and has been used for interior as well as exterior walls, whereplywood is used to resist wind or seismic loading on the structure

Roofing Systems. Fire-resistance ratings of roofing materials (built-up or ply roofing; prepared roofing such as asphalt composition shingles; or wood shin-gles or shakes) are classified as Class A, B, or C in descending order of fire pro-tection afforded Their use is prescribed by building codes, and also affectsinsurance rates The standard test for measuring the fire characteristics of roofcoverings is ASTM E108.12 This standard specifies fire testing of roofing over

single-untreated plywood as a roof deck substrate However, fire classification of roofingover other types of wood structural panels, such as oriented strand board for roofdeck substrates, is permitted if roofing fire tests are conducted over the intendedroof deck substrate materials, by recognized fire testing laboratories Listing direc-tories published by recognized fire testing laboratories should be consulted for in-dividual roofing specifications and minimum requirements for the roof deck sub-strate, for built-up or single-ply roofing membranes, spray-applied foam insulationand roof coating systems, or prepared roof covering materials such as shingles,shakes, cement tile, and metal roofing panels.

Structural Glued Laminated Timber (Glulam). Procedures are available in themodel building codes to calculate the size of sawn timber and glulam beamsrequired for projects in which one-hour fire resistance is required.13 A structuralmember’s fire resistance is measured by the time it can support its design loadduring a fire An exposed beam or column sized for a minimum one-hour fireresistance will support its full design load for at least one hour during standard firetest conditions that simulate an actual fire As with all other structural framing,final specifications of members designed to have one-hour fire resistance should becarefully checked by a professional engineer or architect to ensure compliance withall local building codes

The following is a brief discussion of the fire performance of Heavy Timbermembers such as glulam See Section 4.6.3 for a detailed discussion of the fireperformance of glulam

Beams Charring of wood surfaces during a fire places a premium on

cross-sectional area Charring weakens a wood member’s cross-section slowly because

of the insulating characteristics of the developing char layer Glulam beams with aminimum width of 51⁄8in (nominal 6 in.) can be adapted to a one-hour fire rating

in accordance with procedures recognized by the model building codes, althoughthe beam bending capacity is reduced

For 63⁄4in and 83⁄4in widths, there is a minimum depth at and above whichall members with these widths can be adapted at 100% of the allowable designload for a one-hour fire rating The minimum depth increases when the design callsfor the beam to be exposed on four rather than three sides See Table 4.21A

To adapt beams whose dimensions qualify for one-hour fire rating, the basiclay-up must be modified as shown in Fig 4.13 One center core lamination adjacent

to the tension laminations is replaced by an additional tension lamination to ment the beam bending capacity provided by the tension laminations

aug-Fire resistance for glulam beams also may be provided by covering the exposedsurfaces with two layers of fire-resistive 5⁄8 in Type X gypsum wallboard Thismodification has been demonstrated to provide one-hour fire resistance for beamshaving a minimum size of 41⁄2in wide by 91⁄2in deep (nominal 5⫻10 in beam).10With such gypsum wallboard protection, a standard glulam beam or Heavy Timbermember can be rated for one-hour fire resistance A glulam beam, meeting theabove lay-up requirements for a one-hour fire rating, can be upgraded to two-hourfire resistance when also protected with gypsum wallboard in accordance with therecognized fire-rated design

Columns Columns are produced with a single grade of laminations throughout,

and therefore need no special lay-up to qualify for a one-hour fire rating For glulambeams having 83⁄4 in and 103⁄4 in widths, columns meeting the minimum sizestandard satisfy the one-hour fire rating requirement at 100% of the allowable de-sign load

However, column length plays a significant role in determining minimum sizefor one-hour ratings The column size needed for a one-hour fire rating is deter-