Comprehensive maintainability scoring system (COMASS) for commercial buidings in tropical climate of singapore 2

Structural elements Corrosion & spalling Seepage through joint Efflorescence at joints Seepage through cracks Seepage thru’ porous concrete Finishes on floor wall and ceiling Flakin

Chapter 4 Defect Analysis

4.1 Introduction

This chapter presents the results of the field investigation and questionnaire survey, as well as provides answer for the first research question: “What are the key factors that affect maintainability and how do they influence?” The answer fulfils the first research objective to improve the knowledge-base of building systems, associated defects and their analysis in terms of causes and effects It has already been realized that maintainability essentially means mitigation of defects Hence analysis of the causes and criticality of effects of common building defects can provide a suitable answer Proposed ‘Defect Library’ or DL is a comprehensive central database that contains a brief literature review on defects associated with various building subsystems, analysis of causes and criticality of effects Critical defects are short listed from the entire list Influence of defects on maintainability was first documented during 2002-2004 for facade and wet area (Chew, 2004) In this research those two sections were also dealt along with other seven subsystems The final output of DL was made available online at the research website (www.hpbc.bdg.nus.edu.sg)

4.2 General findings of questionnaire survey

4.2.1 Demographic information

Through 27 individual owners, 9 developers and 22 facility management companies, a total of

89 contacts were made ((31% owner, 20% developer and rest FM company) - 2 cases by each

of last two groups as they have different types of commercial buildings under their supervision Though for questionnaire and discussion total 40 positive replies were received,

34 were finally completed and for case studies FMs of only 14 buildings agreed The sample size of 34 fulfilled the requirement of minimum sample size for a statistically sound analysis (Tan, 2004) Table 4.1 and Fig 4.1 show demography of the case study buildings and the

professionals who provided valid responses respectively The buildings investigated were

3-35 years old, 3-66 storey high, scattered all over the island and had all possible types of commercial usages Slightly higher (57%) responses were received from FMs who maintain their own buildings Probably for the other group, obtaining client’s permission to reveal building defects was difficult

However for questionnaire survey and interviews, instead of building related specific data, generic perception of defects was asked and the response rate was almost equal – 46% from developer/ owner company and rest from FM company Out of 34 respondents, majority (55

%) have 5-10 years of experience, 24% are new in the industry (< 5years), 12% have 10-15% years and 6% of 15-20 years of experience and while rest 3% have a very long experience In fact out of this last two groups, one has been involved in conceptualization of new projects of his company and another person played a key role in the renovation of his building

Table 4.1 Details of case study buildings

Sr

no Main usage Location No Fl (sq m) GFA (yrs) Age tained by Main- Tena- ncy

3 Shopping + community ctr Residential 5 20000 10 Self Multi

14 Hotel + entertainment Commercial 3 96600 3 FMC Multi Note: GFA = Gross floor area FMC = Facility management company

Fig 4.1 Demography of the respondents

4.2.2 Significance of grading criteria and building subsystems

Respondents graded both parameters of defect criticality and subsystems in a 5-point scale Though they had the freedom to add subsystems if necessary, but no new element was suggested Key findings from statistical test (Appendix B.1) are shown in Table 4.2 The t-test

of the means indicated that all the subsystems were considered important for maintainability

of commercial buildings Kruskal-Wallis one-way ANOVA revealed that there was no significant difference between the opinions of respondents from the developer, owner and FM company Henceforth, for defect grading, no discriminations were made among the groups

Table 4.2 Significance of grading criteria and building subsystems

One sample t-test results Mean rank Elements tested Mean SD

KW stat p

Criticality parameters

Freq of occurrence 3.74 0.86 4.96 0.000 19.08 15.00 17.40 0.86 0.652 Impact on economy 3.65 0.73 5.14 0.000 14.54 17.29 19.97 2.39 0.302 Impact on sys perf 3.97 0.67 8.40 0.000 22.33 16.07 14.30 5.62 0.060 Impact on health, safety 3.91 0.75 7.06 0.000 19.71 13.21 17.73 2.18 0.336

Gr1= individual building owner’s FM Gr2= developer’s FM Gr3= FM company employee

4.2.3 Format of defect reporting

These generic rules are applicable to all nine subsystems As per FMECA concept, each subsystem was divided into as many components as possible Defects pertaining to particular subsystems were grouped under relevant components and coded Photographs of visible defects were also grouped in the same manner Basement defects were coded as A1, A2, ,An Similarly defects were coded for other subsystems namely, facade (B1, B2, , Bn); wet area (C1, C2, , Cn); roof (D1, D2, , Dn); sanitary-plumbing (E1, E2, ,En); HVAC (F1, F2, ,Fn); elevator (G1, G2, ,Gn); electrical (H1, H2, Hn); and fire protection (J1, J2, ,Jn) There was

no defect code ‘I’ to avoid confusion with numeric ’1’

Causes of each defect were grouped under four categories, namely, design / specification (D); construction / installation (C); maintenance (M) and external factors (E) Criticality analysis

of defects includes: (1) statistical t-test on ratings for four criticality parameters to identify the critical defects and (2) determination of criticality index Cr The key findings are explained in details in the following sections Detailed SPSS output of t-test for nine subsystems are presented in Section 2- 10 of Appendix B

4.3 Defects in basement

A basement is that part of a building structure that is below ground level and therefore subjected to external hydrostatic pressure Due to their exposure to surrounding soil conditions, basements tend to suffer from a faster rate of deterioration than any other building elements, (Sandeford, 1995) Leakage of water through cracks or vapour transmission through porous surface can cause damage to the structure and make the place inhabitable

Residual soils in Singapore are product of tropical weathering and covers 2/3rd of the area Generally formed above the groundwater table, this soil is usually unsaturated Water carrying contaminants can move over a longer distance along soil strata before reaching the ground water table (Rezaur et al, 2002) As Singapore soils include both their saturated and unsaturated properties (Augus, Leong & Rahardjo, 2001), such unpredictable environment leads to premature deterioration of the under ground structure Defects mainly due to water seepage are common and tedious problem in Singapore (Chew & Egodage, 2003)

Basements are designed, constructed and maintained to keep them free from moisture and dampness Durability is vital for a basement structure as there is limited scope for maintenance and repair (Henshell & Griffin, 1999) From a survey of 61 buildings in Singapore, 987 cases of water seepage and other prevalent defects were identified by building maintainability research team (Chan, 2005; Hing, 2003; Ho, 2003) The major components of basement are: structural members, waterproofing system, finishes and services From field

studies and a thorough literature review, the prevalent defects pertaining to basements are documented in Fig 4.2 and Table 4.3 followed by analysis of causes and criticality

Structural elements

Corrosion & spalling Seepage through joint Efflorescence at joints Seepage through cracks

Seepage thru’ porous concrete

Finishes on floor wall and ceiling

Flaking & peeling Blistering Crazing Rust stain

Tile cracking Damp / dirt stain Dirt / oil stain on floor Stains on false ceiling

Others

Water ponding Water seepage through service penetration

Fig 4.2 Common defects in basement

Table 4.3 Common defects in basement and their causes

Cause gr Defects & coding Possible causes of defects D C M E

Structural elements

Poor design detailing E.g congestion of rebar ▲ Discontinuity at joints or poorly finished joints ▲ ▲

Improper installation of water proofing or waterstops ▲ Wrongly selected or bent waterstops unable to provide

protection

▲ ▲

Water leakage

through joints (A1)

Aging of water proofing membrane or waterstops ▲Leaching of soluble salt or un-hydrated lime from cement Poor

quality control for cement and improper curing ▲

Efflorescence at

joints (A2)

Delayed repair of leakage and irregular cleaning ▲ Inappropriate waterproofing technique & unsuitable material ▲ Deterioration of waterproofing with time or due to exposure to

aggressive condition which is not considered in design ▲ ▲Concrete is porous due to poor mix design or bad workmanship ▲ ▲

Water leakage

through concrete

(A3)

Wrong location, installation of waterproofing or its damage

Delayed repair of initial cracks, allows moisture to reach rebars

The corrosion product has higher volume and causes spalling

▲ ▲Concrete is exposed to water if the waterproofing is not properly

installed or damaged with time

▲ ▲

Seepage though

cracks Usually

with rust staining

and may lead to

efflorescence (A4) Poor lay out of rebars that hinders vibration or poor compaction

around rebars that leave concrete porous at certain places ▲ ▲ Plastic settlement cracks if water cement ratio is excessive or

Plastic shrinkage cracks if inadequate curing is done especially

in warm and windy weather

▲ Insufficient vibration and pouring leaves voids and honeycombs ▲ Concrete is attacked by aggressive chemicals in soil No use of

corrosion resistant bars, corrosion inhibitor in such special cases ▲

Corrosion &

spalling of concrete

(A5)

Inner cavity wall

Material has high water absorption and low water resistance ▲ Rising damp if cavity is not designed or constructed properly to

Damp patches (A6)

Clogged and overflowing cavity Moisture bridging by debris ▲ ▲

Finishes

Blistering (A7) Paint applied on wet (> 6% of moisture content) and warm

surface traps moisture underneath the paint causing blistering

This problem is especially prominent in poorly ventilated basements

▲

Unsuitable selection or poor quality of paint A breathable system that allows excess moisture to evaporate is preferable ▲ Poor surface preparation for substrate Dirt or other

contaminants reduce adhesion between the surfaces ▲

Paint peeling &

flaking (A8)

Failed water proofing membrane allows water seepage that push off the paint film

▲ ▲ ▲Paint is applied on wall suffering from shrinkage cracks ▲ Paint crazing (A9)

Contaminated substrate, tools, water /thinner ▲ Damp and dirt

patch (A10)

Fatty acid of alkyd based paint and alkali of concrete causes saponification or damp patches of soluble soap

▲ Rust stain (A11) Leaching from corroded fittings or rebars ▲ ▲ ▲

Differential settlement of basement or shrinkage cracks of basement No proper movement joint provided to mitigate these ▲ ▲ Tile cracking (A12)

Cause gr Defects & coding Possible causes of defects D C M E

Use of incompatible or poor quality grout ▲ ▲

No cleaning of tile surface after laying or dirt from other works ▲

Dirt & stains on

patches on ceiling

(A15) Condensation and water seepage from HVAC ducts damage false ceiling boards

▲ Dirt and oil stains from vehicles remains unattended due to

Oily patches due to saponification from paints ▲ Carbonation from CO2 form vehicles is confined in one place

Dirt and oil stains

on floor (A16)

Trapped moisture if finishing coat is applied on damp substrate

Excess seepage through deep / wide crack ▲ ▲ ▲ Concrete is porous or weak at poorly prepared construction

joints

▲ ▲ Leaching of soluble salts or unhydrated lime from cement Poor

quality control for cement and improper curing ▲

Efflorescence on

floor (A17)

Delayed repair of leakage and irregular cleaning ▲ Poor ventilation and natural lighting ▲ Biological (algae,

fungi) staining on

surface (A18) Lack of inspection and cleaning Delayed repair of leakage ▲

Others

Poor detailing and installation of water proofing around the pipe

E.g no angle fillets at sharp turn, improper lapping etc

Water ponding

(A20)

Uneven ground settlement due to massive change in ground water table or poor compacting of compressible soil ▲ ▲ ▲

4.3.1 Criticality analysis of defects in basement

Out of 20 defects 8 were found critical according to one or more grading parameters The results are shown in Table 4.4 Statistical tests and detailed calculation of Cr can be found in Section B.2 It was observed that most of the critical defects are related to water seepage through cracks, joints, penetration or concrete itself This observation is in agreement with earlier findings by Chew & Egodage (2003) Blistering on paints and dirt on floor are

common issues as mostly basements are used for service areas and parking Leakage through joints, concrete, cracks or service penetration was found critical as they affect the water tightness of basements Water ponding on floor is usually regarded as a nuisance and people prefer to avoid such parking options Hence the economic performance suffers

Table 4.4 Criticality analysis of defects in basement

Code Defects in basement ⎯X FR ⎯X EC ⎯X SP ⎯X HS Sv Cr

Structural elements

▲ A1 Leakage at joints 2.79 2.82 3.97* 2.71 3.17 0.354 A2 Efflorescence at joints 3.82 1.47 3.03 2.56 2.35 0.360

▲ A3 Water leakage through concrete 2.21 3.76* 4.32* 2.88 3.66 0.323

▲ A4 Seepage through cracks & rust stain 3.09 3.47* 3.82* 2.53 3.27 0.404

▲ A5 Corrosion & spalling of concrete 1.62 3.24* 4.18* 3.91* 3.77 0.244

Inner cavity wall

A10 Damp & dirt patch 3.62 1.94 1.50 1.47 1.64 0.237

A12 Tile cracking 2.44 1.06 1.32 1.32 1.24 0.121 A13 Dirt & stains on tiles 2.68 1.68 1.29 2.24 1.74 0.186

A15 Dark, damp patches on ceiling 4.12 1.79 2.12 1.65 1.85 0.305

▲ A16 Dirt and oil stains on floor 3.62* 2.56 2.21 1.18 1.98 0.287 A17 Efflorescence on floor 2.44 1.29 1.24 1.35 1.29 0.126 A18 Bio-growth on surface 3.12 2.03 1.65 3.21 2.29 0.286

Services

▲ A19 Seepage at service penetration 2.62 3.53 3.71* 3.12 3.45 0.361

Note: * Represents the t-value that is higher than critical t-value (1.6931)

▲ Represents critical defects

Exposed brick masonry

Cracking Staining Unevenness & spalling Efflorescence

Rising dampness Biological growth Sealant deterioration

Cracks & spalling Biological attack Sealant failure & stain Cracks & shattering

Plastered wall

Surface cracks Delamination Biological growth Dirt stains

Efflorescence Crazing

Painted wall

Alligorating Blistering and peeling Chalking Discolouration

Biological growth Yellowing Staining & dirt streaks

Fig 4.3 Common defects in facade

Tile cladding

Cracking Tile delamination Biological growth Staining

Efflorescence Tile chipping

Natural stone cladding

Staining: rust, chemical

or dirt stain

Biological growth : fungal or algal growth

Efflorescence: salt stain, patch

Coating discolouration or colour change

Cracking Fixing failure Scratches & abrasion Joint failure

Misalignment of joint Sealant failure

Fig 4.3 Common defects in facade(Continued)

Falling tiles, detached panels, broken windows, corroded rivets that pop up metal cladding are few examples of facade defects that can affect public safety (Venning, 1995) Incomplete detailing, lack of supervision (Pavitt & Gibb, 2003; Waring & Gibb, 2001) or poor construction accelerate facade deterioration process and reduce its durability Similarly lack

of scheduled maintenance and documentation of faults can be held responsible for premature failure or downtime loss (Richardson, 2001)

Table 4.5 Common defects in façade and their causes

Cause gr Defects &

Exposed masonry

Differential structural and thermal movement between steel, concrete and brick masonry Expansion joints should have been provided ▲ Drying shrinkage of mortar Non-durable blocks crack ▲ Slight expansion of bricks on water absorption Process is not totally

reversible As the material dries out and can cause stresses in the wall ▲

Cracking

(B1)

Inadequate structural support, anchoring, or provision for stress ▲ Severe efflorescence caused by soluble sulphates in clay used for brick ▲ Sources of sulphates may also come from acid rain or rising damp if

(B3)

Brick is prepared from clay that contains excess amount of soluble salts such as manganese sulphates, chlorides, silicates, calcium compounds, manganese colouring compounds

effect as dirt is carried and then re-deposited a short distance away ▲

A thin film of rain water adhering to the surface retains dirt and spores

If crack remains unattended, seepage or dirt accumulation occurs there ▲

Stain: dirt &

Pre-cast concrete (PC) cladding

Structural issues such as differential structural movement of joint

Cracks (B7)

No site checking of quality of delivered product Careless storage or rough handling may also damage the panels ▲ ▲

Cause gr Defects &

Inadequate compression joints between floors to take deformation of

Sulphate attack when sulphates from groundwater or acid rain penetrate and react with the concrete constituents Provision of DPC helps

▲ ▲Alkalinity of concrete is lost through carbonation This can be prevented

by adopting controlled curing at factory ▲ Chloride attack from atmosphere It reduces alkalinity of concrete ▲Improper detailing (e.g conc cover) of rebar in design or construction ▲ ▲ Inadequate structural provision for deflection control ▲

(B9) Unattended cracks allow seepage and salt leaches out at that part ▲

Dirt accumulates in gap of 2-stage horizontal joints between precast panels or at design features such as ledges and protrusions ▲

Biological &

dirt stain

(B10)

Concrete absorbs and retain thin film of rain, dirt and organic particles

Algae and fungi thrives there (Chew, 1999) Regular cleaning helps ▲

coating Often the topcoat, with the undercoat of splatter dash adhering

to it, come away cleanly Powdery coating may also be found on delaminated side of detached plaster (Chew, Wong & Kang, 1998)

Incorrect application technique and handling of plaster, e.g hardening of

The rough / porous texture of the plaster collects dirt and other organic material acting as nutrients for biological growth (Pharnham, 1997) ▲ Facade features may concentrate runoff and keep certain areas damp ▲

(B14)

Unattended surface cracks allow seepage and leaching of salts ▲ High suction of substrate if proper wetting of substrate is not done ▲ Crazing, web /

Cause gr Defects &

Paint or colour sensitive to adverse environmental conditions ▲ Paints of vibrant colours with organic particles are susceptible to UV

rays Discolouration is rapid for exposed areas compared to shaded ones ▲ ▲

excessive dampness - esp seen on light surface ▲ Rust bleeding (Chew & Tan, 2003) – usually from poor RCC detailing ▲ Inadequate cleaning Often internal corners aren’t reachable by gondola ▲ ▲

contraction of tiles due to temperature and moisture, esp for large tiles ▲ Normal service load for a long time or overloading ▲ ▲

contaminated tile/ substrate leads to a loss of adhesion ▲ Efflorescence remains unattended (Kresse, 1982) ▲ Porous tiles if not soaked properly before laying, absorb water from

mortar backing and affect the bond strength (Chew, 1999) ▲ ▲ Moisture ingress through unattended cracks dissolves some compounds

in adhesive to make it weak

(Vickers et al, 1996) Runoff tends to be diverted to these areas and the dirt retained is washed away and re-deposited on the tile surface

(B25) Water seepage through unattended cracks causes leaching of lime products from backing wall with high salt content ▲ ▲

Rough handling or poor workmanship in installation ▲

Tile chipping

(B26)

No protection of finished trades - at corners of building, especially at pedestrian level, tiled walls should be protected ▲

Natural stone cladding

Inadequate expansion joint to cater differential movement of backing

Cause gr Defects &

Insufficient joint thickness or use of hard mortar to absorb movement

Stones are susceptible to thermal shock caused by alternate cycle of sunshine and rain

▲ Warping due to non uniform expansion-contraction of minerals in

freshly cut stones upon water absorption ▲ Insufficient expansion joints cause slabs to push against each other and

few slabs may jut out (BCA, 2003a; Vickers et al.,1996; Kresse, 1982) ▲ ▲

Uneven

surface (B28)

Capillary suction of gr water in porous stone (Driscoll & Gates,1993) ▲ Rising damp-

Rainwater penetrates through unattended cracks into backing and reacts with potassium sulphate in cement used for backing ▲ Water penetration through joints that are too narrow for effective

application of mortar or pointed badly

Water retention on stone by capillary action in absence of DPC ▲ Rainwater contains high amount of industrial pollutant ▲Cladding stone has high porosity or clay minerals ▲ Parts of the facade may be sheltered from direct sunlight and remain

during handling (Shohet, 2002)

▲ Unplanned cutting of panel forms weak points at the support, perforation

Galvanic corrosion by dissimilar metals used together in design or at site ▲ ▲

Inferior make (varying temperature, orientation, duration, base material and paint batches during fabrication) Before installation any visual defect should be noted

▲

Failure to ensure that panels are cut and formed from sheets placed in same orientation - esp one with metallic paint containing flakes ▲ Failure to match colour tones during installation ▲

vulnerable locations such as corners, street level etc ▲ Rigidity of fixings within panel – all three sides should not be fixed ▲ ▲

Cause gr Defects &

Inadequate thickness of panel, especially after routing and folding forms weak point (Chew, 1999) Lack of stiffener/ core and overlapping ▲ ▲ Inadequate support causes stress built-up at folded edge ▲ Rigid fixings Stresses due to thermal expansion and external loading

cannot be relieved through them

▲ ▲ Fixing failure

(B37) Fixing details are pre-tested by manufacturer Field adjustment or use of insufficient / improper tools/ accessories causes such failure ▲

Material not suitable for rough usage is employed in areas susceptible to

Insufficient joint overlap – non compliance with specification ▲ Imperfect fit between top and bottom panels (Ng, 1995) – fixings are not

Joint failure &

seepage (B40)

Fixing failure (Waring & Gibb, 2001) ▲ Field adjustment due to non-adherence to detail ▲ Required alignment tolerance is not maintained ▲

Improper joint width-to-depth ratio of sealant bed and allowance for

Adhesion failure due to dirt, grease and other foreign substances present

on improperly prepared substrate (Hutchinson, 1995) ▲ Poor mixing and wrong / no primer (Woolman, 1994) ▲

Sealant failure

(B42)

Incompatibility of sealant with substrates may cause failure, staining etc ▲

Glass curtain wall

Moisture attached to glass (hydrophilic) traps dust, dirt Needs cleaning ▲ Microscopic irregularities on glass surface capture dirt and dust ▲ Facade features allow dirt particles to accumulate and be re-deposited by

rainwater runoff Inadequate cleaning

▲ ▲ Stain (B43)

During rainfall, dust / dirt trapped in tiny gaps of glass frames / on sealants may trickle down to the glass panels below ▲ ▲ Poor make: presence of impurities, esp nickel sulphide in tempered/

toughened glass shows thermal expansion-contraction (Barry, 1993) ▲

No / poor design consideration for differential movement of glass facade relative to the supporting building frame when temperature and moisture changes (Beason & Morgan, 1984)

▲ Inadequate horizontal and vertical movement joints produce distress ▲ ▲

Sealant failure

(B45)

Cause gr Defects &

Window

Seepage

(B46)

Difficult access – need outdoor access system, hence cleaned only when the whole facades cleaned at a comparatively longer interval ▲

Dirt & stain

access (B48) Access to facade/ window from outside only ▲

Facades made of various elements with different inspection and cleaning cycle along with varied cleaning method

▲ Facade material is not easily available for replacement ▲

No scope of partial removal or replacement–very high downtime ▲ Inefficient access system– poor coverage, too many types or numbers ▲

Maintenance

is unusually

complex

(B49)

Very tall structure with extensive exposure and needs high tech access ▲ ▲

4.4.1 Criticality analysis of defects in facade

For eight types of common facade systems, 49 different types of defects were identified, however only 13 defects (26.5%) were found critical (Table 4.6) Almost all types of facade including the window are prone to suffer from stains either from dirt or biological growth Many respondents considered up-keeping the building image is also a part of facade performance and hence graded stain or dirt critical in terms of both economy and system performance impact Cracks and spalling of concrete as well as the seepage through window were observed to lower the system performance significantly Only two defects those showed significant impact on health and safety are shattering of glasses and unusual difficulty in maintenance Interestingly they affect the pedestrians and maintenance team respectively and hence it shows that facade has less direct impact on building users This finding is in union with Venning;’s (1995) observation

Table 4.6 Criticality analysis defects in facade

Code Defects in facade ⎯X FR ⎯X EC ⎯X SP ⎯X HS Sv Cr

B38 Scratch & abrasion in coating 1.09 1.32 2.38 1.03 1.58 0.069 B39 Discolouration or colour change 1.18 1.82 1.26 1.06 1.38 0.065 B40 Joint failure & seepage 1.47 1.53 3.15 1.97 2.22 0.130

4.5 Defects in wet area

High usage and continuous exposure to moisture keep wet areas under constant maintenance Though such areas mainly comprising of toilets in commercial buildings, is a mere fragment

of less than 10% of a buildings’ gross floor area, the annual maintenance cost for wet areas including cleaning, repair and replacement can be as high as 50% of the building’s total maintenance cost (Chew, De Silva & Tan, 2004) More than 50% of the newly built buildings suffer from internal water leakages problems within a year after occupation (The Straits Times, 13th January, 1996) From a condition survey of 56 non-residential buildings in Singapore 14 major defects in wet area were reported by Chew and De Silva (2002) Water leakage followed by the corrosion of pipes and spalling of concrete are the most frequent problems The major components of wet area those contribute to the water seepage in one way or other are: floor drainage, waterproofing, finishes on wall and floor, sanitary-plumbing system, fixture-fittings and ancillary facilities such as ventilation Chew (2005) identified five key factors that contributes to the majority of the wet area defects, namely, water-tightness, spatial integrity, ventilation, material and plumbing From site investigation and review of previous studies, 19 various defects pertaining to wet areas were identified The list

is presented in Table 4.7 and visual signs of defects are illustrated in Fig 4.4

Table 4.7 Common defects in wet area

Cause gr Defects &

Structural elements

Premature failure of the poor quality or incompatible membrane or insufficient water-tightness due to poor application ▲ ▲ Deterioration of the waterproofing membrane with time Need

Ineffective accommodation for movement between 2 elements (slab &

wall) can damage the membrane Fibreglass mesh at joints is preferred

▲ Dry zone (usually without waterproofing) is not segregated from wet

Aging of waterproofing Also influenced by type, quality, durability, feasibility of application and level of usage ▲ ▲ ▲

Cause gr Defects &

Porous concrete (improper mix design or inadequate mixing) may retain water and remain damp for long Together with faulty waterproofing, water can leak through the surface

▲ ▲

Dry zone is not segregated from wet zone and water ponding ▲

Leaching of soluble salt or unhydrated lime from cement – a result of poor quality control for cement and improper curing ▲

Efflorescence

& leakage

through cracks

C3) Water seepage due to cracks resulting from excessive shrinkage of the concrete (v low water cement ratio or inadequate curing) ▲ ▲

Permeability of concrete is high due to v low water cement ratio, no

Poor specification of rebars E.g epoxy coating, steel bars, use of corrosion inhibitors etc

Excessive shrinkage cracks due to lack of curing of concrete backing ▲

Tiles are porous and if not soaked properly draws up water from

un-▲ un-▲

Efflorescence

on tiles (C6)

Cracks in tile (C5) or grout (C9) allows water to seep in It may lead

to leaching of soluble salts in concrete backing

▲ ▲

Tiles are not stain-resistant or selected as per colour consistency ▲ ▲

Grout material is not durable With contact of water, joints erode and

Inadequate cleaning especially for inaccessible parts or cleaning with harmful material or methods Cleanability is poor ▲ ▲

Staining or dull

patch on tiles

(C7)

Inadequate provision or wrong detailing of expansion joints ▲ ▲

Poor bonding between incompatible tile and bedding ▲

Excessive drying shrinkage of the substrate due to wrong mix design

Tile debonding

or adhesive

failure (C8)

Poor bonding by inadequate mechanical keys at the tile back ▲ ▲

Poor quality of grout – inferior standard, or improperly mixed ▲ ▲

Dirt on the tile edge may cause poor bonding ▲

Inconsistency in size, thickness or alignment ▲

Failure of

pointing (C9)

The tiled surface is not properly cleaned after tile installation ▲

Poor preparation of the substrate may cause peeling due to improper bonding between the paint film and substrate ▲

Paint peeling

and flaking

(C10) Use of a paint of poor grade or one with expired shelf life ▲ ▲

Cause gr Defects &

Painting done on a surface which is warm or the moisture content is >

Substrate remains wet due to seepage from upper floor at pipe penetration (C15), floor trap (C16), joints (C1) or floor (C2) ▲ ▲ ▲ ▲Migration & leaching of corrosion products to the surface May be by

corrosion of concrete rebars (C4), piping (C17) or fittings (C19) ▲ ▲ ▲ ▲

Rust stain

(C12)

Painting on substrate already having rust stains In such cases a primer

Main source of water remains unattended and untreated Prolonged dampness helps in abundant growth of algae and fungi This is prevalent in inaccessible areas behind or between fixtures or with frequent splashing of water from basin or bath Problem increases with more number of wet walls

▲ ▲

Poor ventilation maintains a damp humid condition ▲

Paint is not fungi or algae resistant or absorbs water (non-washable) ▲

Unsuitable or irregular cleaning, careless usage, vandalism ▲ ▲

Biological /

other stain on

floor / walls

(C13)

First sign of algae / fungi remain unattended and not scrubbed off

Many times poor accessibility is the reason ▲ ▲ Water leakage of pipes/ HVAC ducts above the ceiling Corrosion

resistant plastic pipes or proper jointing required ▲ ▲

The plaster board material retains moisture that attracts the growth of micro-organisms (esp poorly ventilated areas) ▲

Main water source remains undetected and unattended ▲

‘Short discharge pipe or gully pipe due to improper laying) ▲

Porous infill of the cold joint at the penetration (usually unplanned) ▲ ▲

Poor detailing or application of membrane around pipe ▲ ▲

Leakage

through floor

trap(C16)

Deterioration of the membrane with time may result in lost of

Water carrying acidic iron salts may lead to the corrosion of cast iron pipes PVC pipe is recommended

▲ ▲

No / wrongly placed floor trap beneath the bathtub to handle water

If the bath is not enclosed, there is high amount of splash on floor ▲

environment (usually industrial area) may cause pitting Selection of corrosion resistant material (e.g PVC) recommended

▲ ▲

High chloride content in water can destroy the passive film to form corrosion products Suitable material should be selected ▲ ▲Inadequate cleaning especially for inaccessible parts or cleaning with

harmful material or methods

Internal finishes (wall, floor and ceiling)

Crack in tiles Tile efflorescence Grout staining Tile debonding

Failure of pointing Dull patch on stone Paint peeling & flaking Blistering

Rust staining Bio-growth: Algae Bio-growth: fungi Patch on false ceiling

Fixture & fittings

4.5.1 Criticality analysis of defects in wet area

Out of 19 various types of defects, 7 (36.8%) were found critical (Table 4.8) All of them have root cause of high exposure to the water Wet area i.e bathroom or toilets are in regular use unlike other civil-architectural elements Hence inconvenience caused to the user was reflected as both economic loss and health-safety-comfort impact of 43% of critical defects Dirt or biological staining and peeling of paint in damp environment are common problems, but do not have severe impact On the contrary, leakage through floor trap often turns into complaints and affect system performance Concrete spalling especially from ceiling due to seepage and fungal growth on the surfaces are taken seriously in terms of health and safety

Table 4.8 Criticality analysis of defects in wet area

Code Defects in basement ⎯X FR ⎯X EC ⎯X SP ⎯X HS Sv Cr

C1 Seepage through structural joints 1.76 2.26 3.21 1.18 2.22 0.156

▲ C2 Leakage through wall or floor 1.26 2.76 4.00* 1.24 2.67 0.135 C3 Efflorescence & leakage through cracks 1.32 1.68 2.79 1.12 1.86 0.099

▲ C4 Corrosion & spalling of concrete 1.06 3.12 4.03* 4.15* 3.76 0.159

Finishes

C6 Efflorescence on tiles 2.62 1.18 1.12 1.03 1.11 0.116 C7 Staining or dull patch on tiles 1.91 1.06 1.06 1.06 1.06 0.081 C8 Tile debonding or adhesive failure 2.76 1.88 1.71 1.32 1.64 0.181 C9 Failure of pointing 1.97 1.03 1.68 1.03 1.25 0.098

▲ C10 Paint peeling and flaking 3.29* 1.03 1.09 1.06 1.06 0.140

▲ C15 Leakage at pipe penetration & joints 2.09 3.18 3.09 2.21 2.82 0.236

▲ C16 Leakage through floor trap 1.94 3.44* 3.26* 3.29 3.33 0.259

C18 Water ponding under bathtub or on floor 1.38 1.38 1.94 3.12 2.15 0.119

▲ C19 Staining of fixtures and fittings 3.59* 2.91 1.32 1.97 2.07 0.297 Note: * Represents the t-value that is higher than critical t-value (1.6931)

▲ Represents critical defects

4.6 Defects in roof

Flat roofs are the most vulnerable part of building envelope due to its direct exposure to weathering elements (Brifett, 1995) This issue has exacerbated in the case of tropical climatic conditions due to heavy rainfall and high temperature together forming wet-dry cycle leading

to thermal shock (Das & Chew, 2007) Early detection of defects is tough as flat roofs are either inaccessible-catering only to building services or host human activities like roof garden

Structural member

Cracks at drainage Crack at expansion jt Leakage thru’ slab Water ponding

Water proofing membrane

Blistering Tearing of blister Alligatoring Crocodiling

Delamination Lifted lap Ridging & splitting Erosion & chalking

Secondary roof concrete panel and tiles

Crack in panel Tile popping Failure of sealant Bulging of sealant

Biological growth

Roots in sealant joint Algae on parapet Algae & moss on surface in general

Services

Leakage at pipe base Clogged outlet Clogged / inadequate drainage system

Fig 4.5 Common defects in flat roof

It camouflages the signs of deterioration Hence, necessary guidelines for inspection and maintenance of roof are essential (Baker, 1980; Rossiter, Cullen & Mathey, 1995) But the

existing framework provides only partial solution due to lack of tools and service life data (Lacasse, Vanier & Kyle, 1997; Vanier & Lacasse, 1996) Many of the major components of roof including the waterproofing and structural deck are beyond regular maintenance and repair Herbert (1989) argued that a number of roof specifications are written by architects and quantity surveyors without consulting a roof specialist As a result specifications are blindly copied from past projects without prior considerations of the particular situation and any defect of the prototype design gets repeated

Cash & Bailey (1993) have reported on the premature failure phenomena, causes and prevention of specific roof types, components, and materials Various defects, their causes and significances are noted by Harrison (2006); Cash (2003); McCampbell & Harrison (1991); Patterson & Mehta (2001); Scharff & Kennedy (2000) etc Major problems identified

by them are: (1) water ponding and leakage; (2) sealant defect; (3) blistering; (4) premature membrane failure; and (5) cracking Other defects are seepage through pipe penetration, microbial growth and tile popping Defects found in concrete flat roof in Singapore commercial buildings are presented in Fig 4.5 and Table 4.9 along with analysis of causes

Table 4.9 Common defects in flat roof and their causes

Cause gr Defects &

Structural elements

Poor workmanship in casting the deck along with precast drain ▲ Plastic shrinkage due to wrong mix design & improper curing ▲ ▲ Adjacent structures act as thermal restraint during curing ▲

Cracks at roof

drainage: on side

/base of scupper

drain (D1) Inadequate support to edges along scupper drain ▲ ▲

Non provision / damaged metal capping exposes the sealant and concrete kerb to direct sunlight and UV radiation

▲ ▲ Wrong dimension (depth: width ratio) of joint ▲ ▲

Construction joint lacks bonding if not properly treated ▲ Gap in joints is filled up during careless grouting ▲

Cause gr Defects &

Omission of detailing in waterproofing ▲ ▲ Steep slope of surface near perimeter causes ponding at base ▲ ▲ Differential movement of roof slab and parapet- poor struct design ▲

Slab lifting due to inadequate thickness / excessive spacing of expansion joints with /without proper insulation ▲ ▲

Waterproofing : sheet or LAM

No vapour barrier is used on deck for membrane or LAM of low water vapour transmitivity (WVT) or breathability ▲ ▲ LAM applied on substrate which is not properly cured and contains

excess moisture

▲ ▲

Adhering air / rainwater on deck is not broomed out ▲

No venting of waterproofing esp hot-applied bitumen to remove excess moisture on or in the felts during construction ▲ Voids or un-adhered areas remain in the bonding coat ▲ ▲

Excessive and irreversible stretching of hot membrane ▲

Wrongly stored felts absorb water that evaporates under the sun ▲

Tearing or puncturing of small blisters which are not treated in time ▲ Tearing of large

blister exposing

Water seepage through overlooked hairline cracks makes the substrate loose Under heavy traffic, the surface caves in a bit, causing the roof to crack in an “alligatored” fashion

▲ ▲Alligatoring &

crocodiling (D8)

Crocodiling is severe form of alligatoring and happens if the initial

Use of inferior quality materials (quality deteriorates by careless and prolonged storage or prepared wrongly) ▲ Poor workmanship to achieve adequate dry film thickness (DFT) of

LAM Usually 3 coats should provide min 1.2mm overall thickness

▲ Poor embedding of felts due to low volume or temp of bitumen

between felts, inadequate brooming or underweight mopping ▲

bottom layers not scraped off and a gap at laps remain ▲ Insufficient overlapping between two layers ▲ Insufficient pressure applied to joint during installation ▲ Blistering at lap due to laying upper layer on wet base layer ▲ Pulling felt during application, using felt with damp edges or

flattened rolls may cause laps to lift or have wrinkles

No / inadequate number or dimension of movement joints to mitigate shrinkage cracks and expansion Hence ridging and splitting occur almost in longitudinal direction of the felts

▲

Movement joints in deck are improper, filled by grout or not carried

Cause gr Defects &

New equipment or usage without consideration of structural adequacy, leads to stress concentration ▲ Few membranes have limited elongation and no recovery characteristics E.g standard asphalt and fibreglass felts The problem is severe if the membrane is fully bonded

▲

Without a suitable thermal insulation or protective layer, membrane becomes brittle upon prolonged exposure to solar heat & UV rays ▲ Water absorption on felts and drying shrinkage of wet felts ▲ Poorly bonded roof assembly undergoes relative movement due to

mechanical reasons (deflection, stress concentration) ▲ Unskilful laying of membrane E.g inadequate stretching, too thin

or non-uniform application of the hot asphalt layer

▲

In the absence of vapour barrier, moisture from the building interior rises through the roof deck and condenses within the base felt In the long run, the felts swell and buckle, forming ridges directly above the insulation joints

Membrane unable to handle excessive thermal movement Can be avoided by using LAM

▲

Wrinkling: ridge

in irregular

Poor workmanship to achieve adequate DFT of LAM ▲ Differential movement of membrane and surface due to use of

partial bonding system or insufficient mopping ▲ ▲

Poor detailing or finishing of edge termination points are vulnerable

to water flow The edge is disturbed by such flow and once loosened, it allows water seepage

▲ ▲

Careless maintenance of rooftop equipment, e.g dropping of tools, erection of ladder Co-ordination among disciplines is needed

& chalking(D15) Accelerated degradation from wrong application of coats ▲

Protective or surface elements

Cracks in conc

panel (D16) Excessive stresses built-up due to improper thermal joints Separation layer and wire meshing are helpful ▲ ▲

Use of closed joints or a thin layer of cementitious adhesive The tile layer becomes very rigid against thermal movement ▲ Tiles are not durable for large thermal cycles in the long run and

show sign of delamination from substrate ▲ Inadequately cured screed shows excessive shrinkage ▲

of solar UV rays, temperature, oxygen, ozone, moisture, air pollutants and microbial factors

▲ ▲

Use of product which is not compatible or has crossed shelf life ▲ ▲

Improper batching and mixing of sealant components ▲

sealant (D18) Contaminants (dirt, grease and other foreign substances) on a poorly

prepared substrate hinder adhesion with the sealant ▲ Biological

growth on

sealant (D19)

Water and dirt held in cracks of sealants facilitate germination of seeds and pores carried by birds or wind If unattended, deep roots can damage the roof

▲ ▲

Cause gr Defects &

Wrong joint geometry makes sealant sink if both panels contract with temperature drop Sealant bulges out if both panels expand ▲ ▲

Bulging of

sealant (D20)

With time, sealants harden, lose flexibility and stay bulged at

Drainage system

Excessive deflection either due to inadequately supported very long span, or inability to support dead and live load ▲ Uneven substrate E.g no screed on the top of precast slabs ▲ Fall is non-uniform due to poor detailing or workmanship or post-

Outlet not at lowest elevation or misaligned slope ▲ ▲

Installation of new equipment / elements without checking the safe

Bulging at poorly finished waterproofing at joints Should be

Under-sized rainwater outlets cause build-up of excessive head of water, inadequate drainage and ponding ▲ Insufficient number of outlets to cater for the flow rate Effective

run-off should be considered in calculation ▲ Inadequate fall design of roof keeps water standing Esp if the

volume is not large, water flows slowly to the outlets ▲ Leakage at poorly detailed/ finished joint between outlet & RWDP ▲ ▲

The water is discharged directly at lower level without proper

Services on roof

Base supports are mounted directly on roof without any concrete insulation pad to absorb the vibration from equipment So deck deflection takes place

▲

If machinery is bolted directly on finished roof, there is a small gap

Water ponding

at the base of

mechanical

equipment (D24)

Leakage from the installation such as tank, condenser ▲

Penetrations are not pre-planned and hacked at later stage ▲

Too many pipes passing very closely are not grouped and it is difficult to seal efficiently each pipe separately ▲ Poor design or workmanship for flashing at the penetration E.g the membrane upturn sleeve missing, < 150mm or merely finished off with a layer of cement and sand

▲ ▲

Leakage at pipe

penetration

(D25)

Poor jointing and alignments of rainwater pipes ▲ ▲

The support is not strong enough for the imposed load ▲

Concrete insulation pad is not provided to cater vibration ▲

Cracking at

service support

(D26) Temporary gondola system is used without adequate structural

Stains under

equipment (D27) Rust dripping from corroded fittings made of poor quality or not coated with special antirust paint ▲

4.6.1 Criticality analysis of defects in roof

30% (8 out of 27) defects were graded as critical Biological growth on surface and sealant is very common (Table 4.10) In terms of impact, mainly (50%) system performance was at risk

It was attributed to water ponding and leakage through slab or service penetrations Flooding

of lower level (plaza / podium) due to improper roof drainage was regarded as hindrance to

business while seepage through interior though a rare issue showed the highest impact

Table 4.10 Criticality analysis of defects in roof

Code Defects in roof ⎯X FR ⎯X EC ⎯X SP ⎯X HS Sv Cr

D1 Cracks at roof drainage (scupper drain) 2.15 1.24 2.03 1.12 1.46 0.125

D2 Cracks at const or expansion joint 1.97 1.26 2.38 1.06 1.57 0.124

▲ D3 Leaking roof lead to paint peel, fungi,

efflorescence at ceiling 1.65 3.29* 3.41* 3.50* 3.40 0.224

D4 Cracks at base of parapet wall 1.91 1.15 2.06 1.12 1.44 0.110

▲ D5 Algal growth on roof elements 3.68* 2.53 1.06 1.85 1.81 0.267

Waterproofing : sheet or LAM

D7 Tearing of large blister exposing substrate 1.68 1.12 2.97 1.09 1.73 0.116

D8 Alligatoring & crocodiling 1.24 1.12 2.38 1.06 1.52 0.075

D9 Delamination of membrane 2.26 1.09 3.00 1.12 1.74 0.157

D10 Lifting of lap & fish mouthing 2.06 1.03 2.38 1.09 1.50 0.124

D12 Ridging: long parallel un-dulation on roof 1.74 1.18 2.50 1.06 1.58 0.110

D13 Wrinkling: ridge in irregular pattern 1.82 1.12 2.47 1.03 1.54 0.112

D14 Tearing of membrane: may result in leakage 1.32 1.88 3.18 1.24 2.10 0.111

D15 Surface erosion & chalking 2.71 1.06 1.68 1.06 1.26 0.137

Protective or surface elements

D16 Cracks in conc panel 2.12 1.53 2.85 1.06 1.81 0.154

Sealant

D18 Adhesion or cohesion failure 3.09 1.09 3.15 1.03 1.75 0.217

▲ D19 Biological growth on sealant 3.38* 1.03 2.38 1.06 1.49 0.202

D20 Bulging of sealant 1.65 1.06 2.71 1.03 1.60 0.105

Drainage system

▲ D21 Water ponding at local depressions on roof 2.71 2.24 4.03* 2.85 3.04 0.329

▲ D22 Water ponding / leakage at outlets 2.76 2.50 3.68* 1.79 2.66 0.294

▲ D23 Lower level flooded with rainwater 1.24 3.38* 1.06 3.03 2.49 0.123

Services on roof

D24 Water ponding at base of mech equipment 2.41 1.06 3.03 1.06 1.72 0.166

▲ D25 Leakage at pipe penetration 1.50 2.12 3.35* 3.50* 2.99 0.179

D26 Cracking at service support 2.53 1.18 2.18 1.03 1.46 0.148

Note: * Represents the t-value that is higher than critical t-value (1.6931)

▲ Represents critical defects

4.7 Defects in sanitary-plumbing system

Apart from wasting precious energy and water, sanitary-plumbing system can trigger fatal

contamination unless it is designed, constructed and maintained properly Only visibly clean

water cannot be considered satisfactory Particularly in Singapore abundant rainfall, high

temperature and humidity, coupled with high population density can cause waterborne

diseases to spread quickly unless a high standard of public health is maintained (PUB, 2004)

Today’s design professionals emphasise notably on occupant’s health (Hassanain, 2005)

Supply piping

Damaged outdoor pipe Corrosion of pipe Scaling in pipe Broken pipe brace

Leaky joint wetting the

floor

Corroded & broken valve Scaling in hot water pipe Corrosion & pitting in

hot water pipe

Broken manhole cover Corroded iron pipe

Fig 4.6 Common defects in sanitary-plumbing system

In a survey on residential buildings, 56 significant problems were identified (Chew, Das, DeSilva & Foon, 2008) in spite of many codes of practice, standards of design and operation handbooks (Manas, 1957; PUB, 2004; SS CP 48; Woodson, 2006), along with detailed consideration for certain major issues such as piping (NAHB, 2006), valves (Lauer, 1990), pumps (Karassik, 2007) and life cycle costing (Cheng, 2001) etc Yet major problems all round the world such as leakage resulting in water scarcity (Taipei Times: 3.10.2003), sewage contamination of potable water causing sickness (ENV & PUB, 2000) or recurrent cases of Legionella (Mathys, Stanke, Harmuth, Mathys, 2007) are reported frequently, The root cause

of many of these problems is derived from corrosion and wearing of metallic parts which are common in pipelines, particularly in the consumer's plumbing fittings Corrosion favours bacterial growth, developing high concentration of lead and copper components within the system and hence leading to dirty and contaminated water (Plottu-Pecheux et al., 2001) Researchers have drawn attention to various problems related to sanitary-plumbing system, such as lead contamination (Fertmann et al., 2004), biofilm formation (Percival et al., 1998) etc Defects identified in this study are analysed in Table 4.11 and their visible signs are presented in Fig 4.6

Table 4.11 Common defects in sanitary-plumbing system and their causes

Cause gr Defects &

Coding 1 Possible causes of defects

D C M E

Supply pipes in general

Pipe type and joint not suitable for underground condition and suffer

from uneven settlement

▲

Inadequate longitudinal support to cater traffic vibration and load ▲ Careless backfilling: poor compaction, inadequate depth (<500mm),

Wearing of external protective coat of metal pipe exposes it to

Ageing, hardening of PVC pipe under prolonged exposure to sun ▲ ▲

Degraded

pipe: rusting,

pitting etc

(E2)

Thermal stress from close proximity of hot water pipes if very limited

freedom for thermal movement is provided ▲ Interference of potable and non-potable water due to poor planning/

workmanship, e.g sewers placed above supply lines

▲ ▲ Contami-

nation: users

fall sick (E3) Wrong position of draining tap allows drained water in certain parts of

the building, interferes with the supply to other parts of the building ▲

Cause gr Defects &

Coding 1 Possible causes of defects

Dirt enters by seepage through wall or with dirty testing tools ▲ ▲ Stagnation inside large tanks if outlets are not diagonally opposite to

the inlets Lack of ventilation aggravates the problem ▲ Mosquito breeding, entry of other creature, leaves, dust in tank if the

net at overflow or vent pipe is omitted / damaged or cover is left open ▲ ▲ Underground pipe is corroded, leaky or ruptured or penetration at

Seepage through pipe joints which are not water tight (wrong jointing

Irregular cleaning of tanks or flushing of distribution pipes This

problem is more frequent if cleaning is difficult (E7)

make) or at joints which are not finished smooth or have projections ▲ ▲ Oversized pipe or under capacity pump unable to deliver right

pressure

▲ Loss of pressure by faulty pumps Regular testing can detect the fault ▲ Hunched pipes, wrong hydraulic gradient or wrong size of valve

orifice cause airlock

▲ ▲ Dirt accumulation at joints - bad fixing detail, and irregular flushing ▲ ▲

Inadequate/

poor supply

(E5)

Design details unable to prevent water hammer, splashing or noise

Inadequate support / anchor blocks at every bend, branch & dead-end

results in hydraulic thrust

▲

Noisy /

turbulent

flow (E6)

Hunched pipes, wrong hydraulic gradient or wrong size of valve

Pipes are difficult to access if laid at a depth more than 2m below

ground, covers of pipe work are not easily removable or embedded in

structural element or insufficient servicing space

▲ Haphazard layout – poor design or non-compliance with drawing ▲ ▲

Difficult

maintenance

(E7)

Interrupted supplies during repair if stop valves at every level or at

convenient places / on branch pipes are not planned Hence repair at

one part disturbs supply to other parts of building

▲

Underground & overhead storage tank

Poor application / peeling and delamination of coat (steel tank) or

Corroded

tank, parts

(E8) Parts (e.g pipes/ strainer) not corrosion resistant or changed regularly ▲ ▲

Cracks due to corrosion or poor structural design ▲

Leakage,

flooding (E9)

Poor detailing / workmanship at pipe penetration cause leakage ▲ ▲

Cause gr Defects &

Coding 1 Possible causes of defects

D C M E

Inadequate provision to cater overflow - poor drainage of receiving

Damaged float valve or liquid level indicator unable to control

Inadequate space around the tank or access is not proper ▲

Wash out pipes / sumps not provided or wrongly constructed ▲ ▲

Difficult

cleaning

(E10) Tanks are not compartmentalized – hence cleaning results in shutting

of the whole supply and causes inconvenience ▲

Hot water supply

Wrong design results in excessive ‘dead leg (the pipe length of cold

water allowed to run off before hot water appears at tap spout) ▲

The primary and / or secondary circuit is not insulated to prevent heat

Water not

enough hot /

takes long

time to

appear (E11) Short circuiting in the piping of the primary and secondary circuit

Combustible insulation of the primary and secondary circuit of the hot

water cylinder needs replacement at regular interval

▲ ▲

Piping material not corrosion resistant or galvanic corrosion Timely

Protective coating lost /damaged during installation or done wrongly ▲

Corrosion &

scaling (E12)

Hard water reaches a temperature > 60ºC and forms scales ▲

General and sewage pumps

Impeller goes out of balance if not designed for large range of head

Wear & tear of parts – especially if not cleaned or lubricated Esp if

maintenance is hindered by poor accessibility ▲ ▲

Excessive

vibration,

noise over

heating (E13)

Automatic pressure release valve unable to provide circulation of

sufficient water and pump becomes hot Needs servicing ▲ Chocked

(E14)

Hunched pipes, wrong hydraulic gradient or wrong size of valve

orifice cause airlock

▲ ▲ Long fibrous material or solids of dia ≥ 64mm are common in sewage

and causes clogging if strainer / baffle is not installed

▲ ▲ Clogged

sewage pump

Material is not corrosion-resistant or not suitable for pumped medium

Corrosion

(E16)

Corrosion in parts is neglected No cleaning of rust, painting or

No more auto

inter-change

of pumps

(E17)

The auto control is done through many elements working together -

the float switch, lead/lag selector switch, hour run meters for each

pump or high level alarm Any of them goes faulty and not rectified

▲

Sanitary appliances

Inadequate or harsh cleaning of fixture & trap If the material in not

vitreous or surface is scratched, cleaning is difficult ▲ ▲ ▲ Backflow or back siphonage If the preventive devices (stop valves,

vacuum breaker, check valve etc) are damaged with time or from

mishandling Parts should be replaced after certain interval

▲

Clogged /

soiled fixture

(E18)

Inadequate trap-seal or venting to prevent backflow ▲

Inadequate grading of flooring towards the WC pan ▲ ▲ Connection of fixture & discharge pipe is not watertight Flexible type

connectors (collar, flange) or seals can handle fixture movement and

remain watertight if installed properly