Chapter Maintainability Scoring for Building Subsystems 5.1 Introduction Maintainability is a design parameter and hence should be addressed right from the design phase Traditionally the maintainability guidelines are focussed on design and to a certain extent on construction and installation But Chapter has highlighted that to achieve high maintainability, like design or construction, maintenance should also be ‘designed’ or planned Each subsystem was divided into top-down hierarchy in as many numbers of components as possible and the related defects were graded in terms of cause and criticality These findings were extensively used in current section to develop the best maintainability practices These guidelines in the form of maintainability checklist factors are linked with the defects they can mitigate and such linkage is expressed through the factors’ relative weights Hence this chapter addresses the second objective of this research: ‘Setting benchmark for good design, construction and maintenance practices and provide guidelines for optimum selection of maintenance strategies by developing individual maintainability scoring framework for major building systems’ 5.2 5.2.1 General format of maintainability scoring Mathematical principle The details can be referred back to the research methodology (Section 3.3) Briefly, guidelines for design, construction and maintenance were developed in the form of a checklist The checklist factors are grouped under life-cycle phases (design, construction and maintenance) and further sub-grouped under components For each factor a design scheme can score for compliance and for violation of the given guideline This score is adjusted if for the same factor, different standards are followed in different sections of the building Upon weighted summation, the total score for the subsystem is determined Hence the scoring 132 contains two parts: (1) development of guidelines for the maintainability factors and (2) derivation of their relative weights For derivation of relative weights, details of defects and criticality values should be referred back to the corresponding tables in Chapter Each of the nine subsystems follows the same format 5.2.2 Maintainability Handbook As mentioned, this is the collation of proposed maintainability guidelines and the second main deliverable of this research project It spans about 150 pages and is an extract of more than 400 various sources of literature and practical knowledge elicited from site visits and interviews Apart from its academic contribution of integrating causes and effects of building defects, it aspires to be a benchmark for industry practices Hence it is presented as a standalone document in Appendix C (Section 1-9) 5.3 Maintainability scoring for basement Basements are subjected to a permanent hydrostatic pressure and probable aggressive soil conditions Water-tightness is a critical issue for basement maintainability It depends primarily on the system selection, structural concrete, detailing of waterproofing, drainage system to reduce hydrostatic pressure around basement wall, adequacy of waterproofing over penetrations, projections or joints and coordination with other services located in the basement Additionally the flooring and finishes add to the maintainability as they have direct influence on the ease of usage A basement once constructed has limited scope of repair or replacement upon occurrence of cracks or subsurface seepage In fact maintenance involves only floor, walls and drainage Hence maintainability in terms of water-tightness should be high Sequence of construction and quality control are also critical issues (Chew, 2000) Maintainability guidelines (Appendix C.1) was developed for the major components, namely, water proofing, structural elements, drainage system, finishes on floor and wall and ancillary facilities Out of total 59 maintainability factors, 28 are for design, 21 are for construction and 133 rest are for maintenance and external factors The summary of the factors and their relative weights are presented in Table 5.1 Details of the defects and their criticality index can be referred back to Table 4.4 Table 5.1 Maintainability factors for basement and their RWs Component Critical defect mitigated Design phase Selection /usage A3, A5 Application feasibility A3, A5 Soil condn A3, A5 System / construction A20 method selection Design (mix & rebar) A3, A4 A5 Joint details Pipe penetrations A19 Location A3 Application A3 Material selection A3 Material properties A3, A4 Joint details Pipe penetrations A19 Shape A20 Material A2 Detailing A2 Cavity wall design Masonry block and mortar selection Cavity floor selection A20 Cavity floor design A20 Pump sump A20 Catchments A20 Screed A20 Additives A16 Finishing A16 Paint selection Tile selection Coordination among professions Non-critical defect mitigated Concrete W/P membrane (in Type A system) Waterstop (in Type B system) Cavity (in Type C system) Drainage system Flooring Wall finishes Ancillary facilities a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 a11 a12 a13 a14 a15 a16 a17 a18 a19 a20 a21 a22 a23 a24 a25 a26 a27 a28 RCC a29 W/P install a30 a31 a32 a33 a34 Waterstop Cavity a35 a36 a37 a38 a39 Flooring a40 a41 a42 Construction phase A20 Excavation & formwork Rebar laying Material quality Casting & curing Check & test Substrate & material quality Application Inspect & test Protection Installation Material quality & condition Laying Finishing Screed A20 A3, A4, A5 Wt RW 0.454 0.454 0.454 0.302 0.021 0.021 0.021 0.014 1.117 0.333 0.289 0.258 0.258 0.258 0.622 0.283 0.289 0.571 0.571 0.571 0.065 0.033 0.052 0.016 0.014 0.012 0.012 0.012 0.029 0.013 0.014 0.027 0.027 0.027 0.003 0.002 0.278 0.311 0.278 0.278 0.278 0.229 0.229 0.230 0.061 0.244 0.013 0.015 0.013 0.013 0.013 0.011 0.011 0.011 0.003 0.011 Deign subtotal W/P system Maintainability factors 0.450 A12 0.278 0.013 A1 A11, A17 A1, A12, A17 A17 0.283 0.057 1.110 0.025 0.258 0.013 0.003 0.052 0.001 0.012 A1 A1 0.830 0.541 0.258 0.895 0.024 0.039 0.025 0.012 0.042 0.001 0.278 0.032 0.278 0.013 0.002 0.013 A12 A1, A111, A17 A1, A12, A17 A8 A1 A1 A1 A1 A6, A11 A6 A6 A17 A8, A10 A12, A13 A15 A3 A3, A19 A3 A3 A2, A4 A1 A12 A20 A14 A20 134 Component Critical defect mitigated Maintainability factors a46 a47 a48 a49 Tiling General Drainage system Flooring Tiles Painted wall External factors 5.4 Joints Checking Substrate & material quality Application Screed & tile prep Tiling Protection a50 a51 a52 a53 a54 a55 a56 Inspection Check Clean Clean Clean Clean Soil permeability a57 a58 a59 Paint & plaster a43 a44 a45 Aggressive chemical Depth Building age A20 A7 Maintenance phase A4, A5, A15, A19 A20 A20 A20 A16, A20 A1, A3, A5 A1, A3 A1, A3 A1, A3, A4 Non-critical defect mitigated A17 A17 A8, A9 Wt RW 0.025 0.303 0.219 0.001 0.014 0.010 0.212 A12, A14 0.056 A13, A14 0.070 A13 0.037 Construction subtotal 0.010 0.003 0.003 0.002 0.285 A2, 18 1.569 0.278 0.278 0.360 0.419 0.266 0.541 0.074 0.013 0.013 0.017 0.020 0.012 0.025 0.541 0.541 0.865 Maintenance subtotal Total 0.025 0.025 0.041 0.265 1.000 A17 A10, A18 Maintainability scoring for facade Facade as building envelope needs to meet the primary requirement of weather exclusion Hence water tightness is the key concern for facade maintainability followed by aesthetics Various facade options ranging from traditional brick or block masonry to modern metal or glass curtain wall vary largely in these two aspects Each system should be carefully detailed to minimize problems during the service life Apart from system selection, wall shape, grid and joint details should be considered Additionally, complexity in building profile affects accessibility and exposure condition influences facade durability Considering these factors, materials are usually chosen that can facilitate cleaning and partial removal However facade maintainability remains incomplete without addressing the issues of window They are weak points in facade fabric allowing a path for seepage and control run-off profile Moreover, windows require more frequent cleaning compared to the rest part of the facade Hence it is necessary to have safe and easy cleaning provisions These aspects were taken into considerations while developing maintainability scoring for facade (Table 5.2, Appendix 135 C.2) Corresponding defect information can be found in Table 4.6 Total 78 factors were identified for various types of facades 42, 26 and 10 number of factors were attributed to design, construction and maintenance phase respectively, Table 5.2 Maintainability factors for facade and their RWs Component System selection Maintainability factors b8 Water resistance Complexity Removeability Accessibility Availability Water resistance : traditional wall -Do-: curtain wall/ cladding Cleanability b9 b10 b11 b12 b13 b14 b15 b16 b17 b18 b19 b20 b21 b22 Inspect Freq Masonry block Plaster Stone Tiles Paint Coating Metal Glass Water resistance Grid size Exposure Drainage Location b23 b24 b25 b26 b27 b28 b29 Rigidity Type Geometry Backer rod Exposure Plan Massing Regularity b32 b33 b34 b35 b36 b37 b38 b39 Projection Type Coverage Number Position Panel detail Louvre detail Shading b40 b41 b42 Drainage detail Accessibility Structural b7 Material Wall joint Expansion joint Sealant Building shape Access system Window Ancillary Wt RW 0.351 0.192 0.192 0.060 0.192 0.298 0.016 0.009 0.009 0.003 0.009 0.014 B43 B40 0.261 0.012 B5,B13,B21,B43, B49 B49 B3, B5 B13 B10, B24, B31 1.250 0.059 0.192 0.560 0.241 0.330 0.097 0.318 0.069 0.338 0.413 0.298 0.074 0.075 0.261 0.332 0.009 0.026 0.011 0.015 0.005 0.015 0.003 0.016 0.019 0.014 0.003 0.004 0.012 0.016 0.127 0.006 0.273 0.065 0.243 0.243 0.066 0.980 0.013 0.003 0.011 0.011 0.003 0.046 B48 B9, B10, B24 0.252 1.457 0.012 0.068 B48 0.252 0.192 0.192 0.192 0.213 0.213 0.915 1.128 0.012 0.009 0.009 0.009 0.010 0.010 0.043 0.053 0.213 0.219 B1, B2, B10, B22, B23, B35 0.640 Design subtotal 0.010 0.010 0.030 0.677 Spacing b30 b31 Finishes b1 b2 b3 b4 b5 b6 Critical defect Non-critical defect mitigated mitigated Design phase B3 B4, B9, B14, B25, B29, B30 B49 B49 B48 B49 B3 B9, B14, B25, B30 B21 B33 B43, B44 B3 B43 B3 B44 B44 B44 B13, B21, B31, B49 B49 B5, B13, B21, B31, B33, B43 B49 B49 B49 B49 B46 B46 B5, B13, B21, B33 B5, B13, B21, B33, B46 B46 B47 B7, B8, B21 B1, B2, B10, B14, B25 B27 ,B28, B29, B30, B31 B23, B24, B26 B16, B18, B19, B20 B34, B39 B32,B35,B36,B38,B41, B42 B9, B14, B25, B30 B6, B22, B27, B35 B6, B10 B40 B1,B11, B27, B28, B35, B36 B22, B23, B27, B28, B35, B36 B35, B36, B45 B6, B42 B6, B42 B6, B42 B42, B45 B48 B9, B10 B9, B10 136 Component Brickwork Maintainability factors b64 b65 Material quality Laying Finishing Material quality Laying Finishing Preparation Erection & jointing Substrate prep Material quality Application & curing Substrate prep Material quality Application Base prep Tile prep Tiling Grouting Inspection Protection Material quality & preparation Setting fixings Panel erection Sealant application b66 b67 b68 Substrate prep Material quality Application Clean b69 b70 b71 b72 b73 b74 b75 b76 b77 Masonry Conc & plaster Painted Stone cladding Tile cladding Glass curtain Metal cladding Building age Exposure b78 Height Block masonry PC Plastering Painting Tiling (ceramic & stone) Metal External 5.5 b43 b44 b45 b46 b47 b48 b49 b50 b51 b52 b53 b54 b55 b56 b57 b58 b59 b60 b61 b62 b63 Critical defect Non-critical defect mitigated mitigated Construction phase B3, B5 B1, B2 B4 B3 B4 B1, B2 B4 B3 B7 B8 B10 Wt RW 0.463 0.036 0.233 0.035 0.036 0.197 0.030 0.173 0.022 0.002 0.011 0.002 0.002 0.009 0.001 0.008 0.061 0.123 0.309 0.003 0.006 0.014 B16, B17 0.069 B16 0.022 B17 0.047 B22, B23, B28 0.049 B23, B26 0.046 B23, B27, B28, B30 0.079 B24 0.051 B22, B23, B24, B26 0.112 B24, B26 0.073 B32, B34, B35, B37, B38, 0.159 B40 B44 B32, B37, B40 0.275 B44 B32, B34, B35,B36,B40, 0.318 B41 B44 B6, B42, B45 0.274 B6, B42, B45 0.096 B43 B6, B42, B45 0.331 Construction subtotal Maintenance phase B5 0.230 B8, B13 B9, B10, B14 0.466 B21 B17 0.278 B31 B30 0.257 B23, B24, B25, B26 0.146 B43 B47 0.454 B33 B32, B38, B39 0.274 B8 B10, B20, B22, B35 0.219 B5, B7, B8, B31 B2, B10, B19, B20, B39, 0.676 B42, B45 0.192 Maintenance subtotal Total 0.003 0.001 0.002 0.002 0.002 0.004 0.002 0.005 0.003 0.007 B12 B13 B15 B11, B12, B14, B15 B11, B12 0.013 0.015 0.013 0.005 0.016 0.173 0.011 0.022 0.013 0.012 0.007 0.021 0.013 0.010 0.032 0.009 0.149 1.000 Maintainability scoring for wet area Wet area needs to fulfil the requirement of internal water tightness to prevent leakage and keep a safe and healthy environment Water-tightness relies mainly on the adequacy of waterproofing over the floor and wall surfaces punctured by unavoidable penetrations, projections and joints Therefore, proper selection, detailing of a waterproofing system and 137 sound workmanship should be in focus The finishes on wall and floors are the first barrier to water infiltration and hence should be durable Additionally, the material should allow easy maintenance in terms of resistance against stain, chipping, cracking and cleaning material or cleaning methods Wet area contains many elements of sanitary-plumbing system Efficient plumbing design not only reduces number of penetrations, but also allows adequate space for regular inspection and cleaning Considering these issues, the maintainability factors of wet area were identified (Table 5.3) The detailed guidelines are presented in Appendix C.3 and background information of defects is documented in Table 4.8 Table 5.3 Maintainability factors for wet area and their RWs Component Floor Water proofing Plumbing Fixture and fittings Maintainability factors c1 c2 c3 c4 c5 c6 c7 c8 c9 c10 c11 c12 c13 c14 c15 c16 c17 c18 c19 c20 c21 c22 c23 c24 Tiles on floor & wall Paints Ancillary facilities c25 c26 c27 c28 c29 c30 c31 c32 Zoning Gradient Concrete slab Screed Material select Material property Application feasibility Joint details Penetration details Fixture detailing Wet wall or layout Penetration plan No of fl./ wall penetration Pipe accessibility Wall accessibility Gen quality Basin selection Basin layout WC & urinal selection WC & urinal layout Bath selection Shower layout Bathtub layout Piping material selection Movement joint location Movement jt detail Tiles selection Bedding material Grout selection Paint property Water resistance Coordination among professions Critical defect mitigated Design phase C2 Non-critical defect mitigated Wt RW C2, C4 C2, C4 C2, C4 C1, C11 C18 C1, C3, C5, C6, C11 C1, C5, C6, C11,C18 C1, C11 C1, C11 C11 0.163 0.024 0.350 0.118 0.290 0.290 0.259 0.010 0.002 0.022 0.008 0.019 0.019 0.017 C4, C15, C16 C2 C2,C13 C2, C4, C15, C16 C4, C15 C1, C11 C11 C11 C11 C11 C11 0.055 0.547 0.131 0.428 0.655 0.340 0.004 0.035 0.008 0.028 0.042 0.022 C11, C12, C17 C7 0.385 0.313 0.238 0.296 0.296 0.296 0.025 0.020 0.015 0.019 0.019 0.019 C18 C12, C17 0.296 0.320 0.296 0.024 0.280 0.019 0.021 0.019 0.002 0.018 C5, C6, C8 0.076 0.005 C5, C6 C5, C6, C7, C8 C6, C8 C6, C7, C9 C11 C11 C14 0.040 0.092 0.039 0.059 0.432 0.320 0.549 0.003 0.006 0.003 0.004 0.028 0.021 0.035 Design subtotal 0.533 C2, C4 C4, C15 C13 C19 C13 C13 C13 C13 C13 C13 C19 C10, C13 C13 C13,C16 C18 138 Component Critical defect mitigated Construction phase C2, C4 C4, C15, C16 Non-critical defect mitigated c33 c34 Water proofing Tiles on floor & wall c40 c41 c42 c43 c44 c45 c46 c47 c48 c49 c50 Paints Fix.& fittings General Tile finish Marble Granite Paints Fix fittings External factors 5.6 c35 c36 c37 c38 c39 c51 c52 c53 c54 c55 c56 c57 c58 c59 Slab casting Embedding of services Laying the slope Substrate condition Quality of material Application Inspection & testing Protection Base (substrate & screed) preparation Preparation of tiles Tiling Grouting Inspect & check Protection Substrate prep Material quality Application Fixing & connection Inspection Cleaning Cleaning Cleaning Cleaning Cleaning Building age level of usage Vandalism C2, C4 C2, C4 C2, C4, C15, C16 C2, C4 C4, C15, C16 C10 C10 C10 C15, C16 Maintenance phase C4,C15 C13 C13 C13 C13 C19 C2, C4, C16 C19 C13, C19 Wt RW C1, C3, C6, C11,C12 C11 0.352 0.547 0.023 0.035 C18 C1, C11 C1, C11 C1, C11 C1, C11 0.024 0.290 0.290 0.686 0.290 0.002 0.019 0.019 0.044 0.019 C11 C6, C8 0.547 0.059 0.035 0.004 C6, C8, C9 C5, C6, C8, C9 C6, C7, C9 C5, C6, C7, C9 C5, C6 C11 C11 C12 C11, C14 0.079 0.096 0.059 0.076 0.040 0.135 0.135 0.131 0.282 0.005 0.006 0.004 0.005 0.003 0.009 0.009 0.008 0.018 Construction subtotal Floor Maintainability factors 0.265 C1, C11, C12, C17 0.416 0.296 0.296 0.296 0.296 0.238 C1, C11 0.497 C7 0.254 C7 0.550 Maintenance subtotal Total 0.027 0.019 0.019 0.019 0.019 0.015 0.032 0.016 0.035 0.202 1.000 Maintainability scoring for roof Among various forms of roofing systems, accessible type reinforced concrete flat roof is most commonly used in commercial buildings of Singapore Flat roof is defined as a roof with pitch less than 5° to horizontal (SS CP 82) The regular components are: deck, waterproofing, insulation, and protective surface (Baskaran, 1996) Various types of roof have various arrangements of these elements selected according to the usage and exposure condition Flat roofs can either be (1) inaccessible i.e access for cleaning and repair only or (2) accessible i.e can host various human activities (BS 6399-3) Flat roofs not only should carry both the 139 live load and abundant rainfall, but also withstand the exposure condition Roof components should be compatible with each other to form a durable structure together Except the drainage or finished surface other roof elements are beyond the scope of regular inspection or maintenance and hence should be constructed well to avoid costly re-roofing Maintainability aspects of roof are described in Table 5.4 along with detailed guidelines in Appendix C.4 Relative weights (RW) of the factors are determined based on the associated defect criticality (Table 4.10) A total of 64 factors were identified out of which 35, 21, and rest were dedicated to design, construction and maintenance respectively Table 5.4 Maintainability factors for roof and their RWs Component Roofing system Deck WP membrane LAM Preformed Insulation Tile/ panel Sealant Roof drainage Outlet RWDP Ancillary facility Maintainability factors d1 Selection d2 d3 d4 d5 d6 d7 d8 d9 Struct concrete Bearing capacity Deflection Movement jt Vapour barrier Parapet Pipe & equip Selection d10 d11 d12 d13 d14 d15 d16 d17 d18 d19 d20 d21 d22 d23 d24 d25 d26 d27 d28 d29 d30 d31 d32 d33 d34 d35 Jt detail Penetration Jt detail / flashing Penetration Venting Properties Material Properties Type Joint geometry Bk rod detail Design rate Effective runoff Angle of slope Uniformity of slope Ease of construction Size & No Location Protection Size & material Slope Access Fixing Jointing Termination Coordination Critical defect mitigated Design D3 D3, D5, D21 D5, D21 D3 D5 D3, D25 D3 D3, D22, D25 D3 D3, D22, D25 Non-critical defects mitigated Wt RW D11, D15 0.230 0.014 D1 D11 D6, D11 D2, D4, D11, D16 D6, D12 D4 0.025 0.679 0.538 0.280 0.060 0.235 0.323 0.152 0.001 0.040 0.032 0.017 0.004 0.014 0.019 0.009 0.224 0.602 0.248 0.602 0.038 0.045 0.477 0.050 0.043 0.064 0.064 0.235 0.235 0.235 0.499 0.477 0.235 0.477 0.235 0.235 0.235 0.235 0.235 0.268 0.098 0.387 0.013 0.036 0.015 0.036 0.002 0.003 0.028 0.003 0.003 0.004 0.004 0.014 0.014 0.014 0.030 0.028 0.014 0.028 0.014 0.014 0.014 0.014 0.014 0.016 0.006 0.023 Design subtotal 0.553 D6, D10, D11, D12, D13, D14 D4, D14 D4, D14 D2, D4, D14 D4, D14 D6 D4, D11 D5,D21 D16, D17 D18 D18, D20 D18, D20 D22 D22 D22 D5, D21 D5, D21 D22 D5, D21 D22 D22 D22 D22 D22 D22 D23 D3, D27 D4 D24 D14, D24, D26 140 Component Deck WP-LAM Insulation Tiles/ panels Sealant Drainage Roof surface Drainage Details External factors 5.7 Maintainability factors d36 d37 d38 d39 d40 d41 d42 d43 d44 d45 d46 d47 d48 d49 d50 d51 d52 d53 d54 d55 d56 Concreting Precast unit Propping Const joint Curing Protection Finished surface Storage & prep LAM apply Membrane application Joint & penetration Protection Testing Layout Base Tiling Substrate Quality check Application Jointing Testing d57 d58 d59 d60 d61 d62 d63 d64 Check Clean Check Clean Check Usage Building age Exposure Critical defect mitigated Construction phase Non-critical defects mitigated Wt RW 0.047 0.025 0.025 0.204 0.063 0.259 0.817 0.117 0.141 0.429 0.003 0.001 0.001 0.012 0.004 0.015 0.049 0.007 0.008 0.025 0.757 0.054 0.477 0.031 0.282 0.019 0.043 0.043 0.064 0.745 0.745 Construction subtotal 0.045 0.003 0.028 0.002 0.017 0.001 0.003 0.003 0.004 0.044 0.044 0.320 Maintenance phase D3, D19 D2, D7, D8, D20 0.425 D5, D19 0.375 D4, D12 0.257 D12 0.235 D3, D5 D2 0.417 D7, D8, D9, D15 0.097 D3 D2, D18, D20 0.268 D15, D18 0.071 Maintenance subtotal Total 0.025 0.022 0.015 0.014 0.025 0.006 0.016 0.004 0.127 1.000 D3 D3 D3, D5, D21 D21 D3, D5,,D21 D1, D4 D1 D1 D2 D1, D6 D2, D9, D11 D2,D4, D6,D9, D11,D12 D6, D9, D10, D11 D6, D9, D12, D14, D15 D6, D9, D10, D13, D14, D15 D4,D11, D14,D24 D9, D14 D5, D21 D21 D5, D21, D22 D5, D21, D22 D16 D17 D17 D18 D18 D18, D20 D24 D24 Maintainability scoring for sanitary-plumbing system Main functions of sanitary and plumbing system are hot and cold water supply along with removal of liquid waste or liquid borne solid waste (Heerwagen, 2004) Health and convenience are the two major main focus of this system Outbreak of SARS brought into limelight the importance of a well-maintained, hygienic sanitary-plumbing system as the disease spreads as a result of infected water droplets (Watts, 2003) Additionally in Singapore due to limited land of water catchments, efficiency of the system has been emphasized by Ministry of Environment and Water Resources (MEWR) As sanitary-plumbing system consists of different types of pipes (cold & hot water supply and waste disposal) passing in 141 7.2.11 Scoring for entire building Probing into each subsystem, following general conclusions can be drawn about the building under investigation: ● The design and specification is good in general, but the designers faced the problem of site restriction in CBD As a result few incidents of space planning were compromised ● For M&E systems, some approved material or method had better options, which was not implemented probably for cost ● In later stage, design team for addition-alteration works did not pay much attention to the existing services Hence few functional elements became useless and added utilities were not seamlessly synchronised ● The construction process seemed to have taken place in hurry or without greater concern for perfection leading to wrong sequence, inadequate timing, field adjustments etc ● Maintenance in terms of specialized contracts (elevator, electrical etc) is as per specification, but for works under central facility management suffers from a slight time lag This may be proved hazardous especially in case of fire protection system For the entire building, weighted sum of the maintainability scores for nine subsystems were obtained (Table 7.10) A value of 85.989% indicates the building poses ‘Excellent’ grade of maintainability However there are drawbacks which can be overcome Fig 7.1 illustrates the relative contribution of each subsystem From such comparison, overall implication of decision making can be obtained Table 7.10 Prototype scoring for entire building RW MS (%) Wtd MS Civil-architectural system Basem Wet San – Facade Roof ent area plumb 0.046 0.131 0.091 0.078 0.061 72.427 82.002 89.928 90.166 85.217 3.331 10.742 8.183 7.033 5.198 Total: 85.989 Mechanical-electrical system EleElecHVAC vator trical 0.249 0.171 0.118 82.560 91.331 92.851 20.557 15.618 10.956 Fire prot 0.055 79.832 4.391 195 300 250 RW x 1000 200 Score 150 100 Wtd score x 10 50 Fire prot Electrical Elevator HVAC San.plumb Roof Wet area Faỗade Basement Subsystems Fig 7.1 Variance of MS and RW for subsystems 7.3 Sensitivity analysis via Monte Carlo simulation Scores were selected at random using a Monte Carlo simulation (software: @Risk student version) so that the results of many combinations of scores, including a complete ranking, can be explored At each run only one sub-system was tested and the maintainability score of subsystem was defined as output which is actually weighted sum of the inputs Such simultaneous change of inputs allows the analysis of relative weights in a detailed manner (Furlanetto, Cattaneo & Mastriforti, 1991) It was assumed for a good, moderate and bad quality building, the scores will uniformly vary in the range of (5 to 3), (4 to 2) and (3 to 1) respectively Additionally a case was tested where the input covers the full range i.e to In these four cases, if the grading framework is robust, the scores should be normally distributed around 80% (4 in 5), 60%, 40% and 60% respectively Then simulation was run with 1000 iterations In first case a basement was tested where maintainability was assumed to be poor It was found that the resulting values are concentrated around 40% as expected (Fig 7.2) The judgmental variances of to were not affecting the MS, but majority of results fell between a narrow range of 38% to 44% Hence this can be concluded as satisfactory Similar results were obtained for all 36 cases (4 ranges, sub-systems), which can be found in Appendix E 196 Fig 7.2 Simulated maintainability score for a basement of poor quality 7.4 Web based application of COMASS COMASS has been designed to work as a web based decision enhancement tool and is a part of the NUS-BCA research website ‘Maintainability of Building’ (www.hpbc.bdg.nus.edu.sg) It contains three main sections – Defect Library, maintainability scoring system that contains Maintainability Handbook and COMASS for the calculation (Fig 7.3) Mathematically the application is built on criticality index of defects, relative weights of maintainability factors and relative weights of nine subsystems for buildings of various locations and heights The users are not required to deal with the complex working principles while generating score for their buildings 7.4.1 Defect Library Common defects occurring in different elements in buildings, their causes and photographs are compiled in Defect Library in a hierarchy of three levels, first: the four civil –architectural elements and mechanical-electrical (M&E) Next five M&E elements are grouped together for ease of browsing In each section defects are organized at component level (Fig 7.4) and detailed descriptions are presented in tabular form (Fig 7.5) 197 Fig 7.3 Interface of ‘Maintainability of Buildings’ website Fig 7.4 Three level hierarchy of Defect Library interface Fig 7.5 Compilation of defects, photos and analysis of causes 7.4.2 Maintainability Scoring System It covers Maintenance Handbook for all nine building systems and calculators under COMASS icon (Fig 7.6a) In the handbook suggested guidelines and corresponding scores 198 are displayed (Fig.7.6b) List of references is also appended at the end of each section for further reading In the calculator part, users can enter values ranging from to and for non-applicable factors As help, links to Handbook and prototype scoring are provided For a conscious decision making, associated defect of each factor and their criticality profile can be obtained as a pop-up window once the folder icon next to the factor is clicked (Fig 7.6c) (a) Section of maintainability scoring system (b) A part of Maintainability Handbook (c) Interface of calculator Fig 7.6 Interface of maintainability scoring system 199 COMASS essentially belongs to the third generation or level scoring system (Section 2.6.1) that can handle a building holistically, address variability of influence of input parameters and generate project specific results Usually such systems have limited application due to complex nature, costly simulation / documentation, fuzzy nature of weighting, user dependence etc (Lee & Burnett, 2006) On the contrary, COMASS was expected to overcome most of these limitations From its simple yet informative interface ensures achievement of these goals and hence the third research objective was fulfilled But it should be remembered that COMASS was never claimed to replace a designer or a decision maker i.e it cannot take decision on behalf of user, but helps to provide the framework for conscious decision making 7.5 Summary The validity, sensitivity and predictive accuracy of proposed scoring system were tested and found satisfactory The whole scoring process, application of logic and computations were demonstrated through a hypothetical commercial office tower The system was successful in finding drawbacks, chain effect of defects and difference in consequence of same defect in different situation Hence it can be inferred that using COMASS, future defects for new or existing building can be predicted It proves hypothesis A user-friendly yet informative and precise version of COMASS was designed for web based application This chapter delineates all these topics along with the justification of COMASS as a decision enhancement tool 200 Chapter Conclusions 8.1 Introduction With growing complexity of building services, higher user expectation and decreasing budget, modern buildings should have higher maintainability This is an issue of ‘perform or perish’ in Singapore commercial building sector due to two additional reasons, namely, (1) higher deteriorating effect of tropical climate and (2) dependence of country’s economy on the fact that building facilities can not be compromised to attract and retain global clientele In spite of plethora of performance-based standards and their strict implementation, defects in buildings are prevalent leading to poor maintainability In order to probe into this paradox this study was conducted and the focus was cast on Singapore commercial buildings This chapter will summarize the research, present the key findings, highlight academic and practical contributions, discuss the limitations and finally identify the scope of future research 8.2 Research summary showing achievement of research goal The research statement comprising of research questions, aim, objective and hypothesis laid the foundation of the entire research process Their precise details can be referred back to Chapter This section will summarize this whole process in order to establish the achievement of each of the statement of research goal This topic being challengingly multifaceted, a thorough literature review was done on various related areas, namely, building systems, associated defects, priority setting in building maintenance, maintainability in general, building scoring systems and MCDA principles The absence of a holistic maintainability grading tool was palpable In order to find the key maintainability factors, their influence and the method to quantify those factors to select the best building alternative, the research objectives were set in the form of deliverables They are: (1) Defect Library: improved knowledge-base on common building defects, their causes and effects; (2) Maintainability Handbook: benchmarking the selection process of design, 201 construction and maintenance practices in order to achieve a highly maintainable building; (3) COMASS or Comprehensive Maintainability Scoring System to evaluate major building elements and integrate them to obtain a final score COMASS was planned as an online decision analysis tool for judging maintainability profile of proposed or existing buildings Inspirations were drawn primarily from two established fields, (1) FMECA used for maintainability in system engineering and (2) sustainability tools for holistic grading of buildings Based on the literature review, the hypotheses were formulated First was the logical assessment and integration of various building elements in terms of maintainability Second was the feasibility to identify future defects and predict maintainability potential of both new and existing building The research methodology developed continually – first on the findings from literature review and later was guided by preliminary findings Fourteen detailed case studies and discussion with 34 experienced facility managers helped in developing the defect list along with photographs pertaining to nine major building elements referred here as subsystems Probable causes of defects were noted under design, constriction, maintenance and external factors Results of questionnaire survey graded defects by criticality in terms of (1) frequency and (2) severity given by impact on economy, system performance and health-safety-comfort This exhaustive list of common defects in Singapore commercial buildings is called ‘Defect Library’ – the first deliverable that fulfils the first research objective of a systematic defect database and it provides answer for the first research question i.e ‘What affects maintainability and how they influence?’ Next, using literature and knowledge elicited from field studies and interviews, the existing design-construction-maintenance guidelines for nine subsystems were collated in the format of checklists 731 guidelines for their selection in terms of maintainability were suggested through scores for each option This comprehensive segment for benchmarking for the 202 selection of the options formed the Maintenance Handbook – the second deliverable of this research Relative weights of the factors were extracted from the criticality index of defects it can mitigate Hence weighted sum of scores against each factor can yield maintainability score for a subsystem As it helps in conscious decision making and allows the user to improve maintainability score by altering the selection for design, construction or maintenance of the whole building system, it fulfils the second research objective of system selection framework Maintainability is reflected in facility management strategies and they highly depend on subjective parameters apart from technical issues of defect mitigation The nine subsystems cannot be integrated based on objective parameters as they don’t share any technical aspect Hence for integration, subjective parameters were dealt by AHP The relative numeric weights of nine subsystems and grading criteria matched exactly with the logic provided by expert respondents during face to face interviews Hence the integration of nine subsystems in a building system was seamless in terms of maintainability fulfilling the third research objective and proving the first hypothesis Simultaneously, it provides answer for the second research question, ‘how to measure maintainability to select the best alternative?’ In final stage the proposed COMASS tool was checked for operational validity and sensitivity analysis by Monte Carlo simulation COMASS was able to predict defects based on particular set of design-construction-maintenance and moreover was able to identify the chain effects of the defects Hence the second hypothesis was proved true Once the predictive accuracy of COMASS was found satisfactory, the web-based interface was built 8.3 Key findings The key findings of this research are as follows: ● The major elements or services that contribute significantly to the maintainability of a building are: (1) basement; (2) facade; (3) wet area; (4) roof; (5) sanitary-plumbing; (6) 203 HVAC; (7) elevator (8) electrical and (9) fire protection system The first can be grouped as civil-architectural (C&A) systems and rest as mechanical-electrical (M&E) systems ● A total of 319 defects were identified for 62 major components of these nine subsystems, out of which 145 (45.45%) are critical Though in general design has the highest contribution (84.64%) in defects, but C&A and M&E systems were found to show different traits For C&A subsystems which have more design options, constructed at site, life span almost same as the building itself and exposed to external environment, have influence of design, construction ,maintenance and external factors in decreasing order (89.77%, 78.17%, 46.60% and 36.64% respectively) ● On the contrary, M&E subsystem have more components but standardized factory tested products which are installed at site, often maintained through specialized contract and unexposed to external environment In this case maintenance has the highest emphasis (84.43%), followed by design (82.86%), installation (61.14%) and external factor (22.83%) Here the influence of external factor is due to daily operation by building occupants and maintenance team ● In terms of effect, C&A system has 33.25% of critical defects compared to 55.15% of M&E system Though M&E critical defects have 57.48% less probability of occurrence (M&E:16.92% vs C&A: 39.80%), their direct impact on users and maintenance team in terms of health-safety-comfort issue is 222.47% of C&A defects (M&E: 52.26% vs C&A: 23.49%) However economic loss from C&A defects are more (C&A: 30.01% vs M&E: 20.1%) and affect system performance almost equally (C&A: 49.66%, M&E: 50.52%) ● It was observed that C&A defects can be easily identified with visual inspection while M&E defects cannot be For example crack, seepage, staining vs shock, vibration, noise, over heating etc It was also found that the same defect may have different consequences in different situation Malfunctioning of emergency power supply is poor system performance for electrical system but a safety hazard for fire protection system ● Based on this defect analysis, findings from discussion with facility managers and review of more than 400 codes, standards, industry practices, defect mitigating guidelines in form 204 of 731 maintainability checklist factors were proposed These guidelines for each of the nine subsystems were first grouped under design, construction, maintenance phases and then under various components Design related guidelines were maximum in number (52.26% in average) But construction had 75.6% higher emphasis for C&A subsystems while maintenance were 104.4% more influential for M&E subsystems ● However the overall maintainability of a building was found to depend on these technical viability objective in nature and as well as on subjective parameters expressed as business profile Maintainability of a building of same floor area and facilities were found to vary if the location and height of the building varied Hence for overall maintainability of the entire building, nine subsystems were integrated based on both of these criteria ● The subjective opinion of 34 experts who participated in AHP survey, and their objective values of grading matched seamlessly The validity of 10% threshold of inconsistency in human judgement as proposed for classical AHP was reaffirmed It was also observed that people with longer (≥ 15 years) experience provide consistent judgement ● From this process, relative weights of nine subsystems for 12 sets of building location – height combinations were derived HAVC showed the highest influence followed by elevator and faỗade Throughout the research process it was mentioned by almost all respondents that maintainability decisions should be judged by value-driven performance rather than cost whether initial or life cycle Building owners are eager to invest on better performance if it can generate higher return 8.4 Knowledge contribution Previous researchers and C21 committee have stressed upon (1) development of knowledge on maintainability through a centralized online defect database; (2) setting up of a maintainability benchmark and (3) establishment of a maintainability assessment system to grade the performance of buildings There has been plethora of advanced design– 205 construction-maintenance guidelines Similarly defect diagnosis and individual building components are well-addressed topics But maintainability is the linkage between them and has remained a highly neglected subject This research has tried to bridge this gap Such holistic grading system for building maintainability is first of its kind Building defects have not been communicated by maintenance team back to the design or construction team Hence same defects get repeated and the differences in perception of maintainability prevail In this study, information was collected from facility management team and archived defect data This information was used to trace back impact of design and construction on maintainability Alike other grading tools, score generated by COMASS is an indicator where higher value means higher maintainability By virtue of inherent building profile (age, height, usage) and surroundings, it is not always possible to achieve 100% maintainability score But a score in 80-100% strata implies an overall good maintainability profile Two alternative detailed schemes for same building can be directly compared Though Singapore scenario was focussed while developing COMASS, its generic principle can be used to extend this decision analysis tool for other climates AHP is a highly recognised method in MCDA But by matching the objective data generated by AHP and subjective opinion of the expert respondents (consistent in judgement and usually with work experience of ≥ 15 years), the method was established as a suitable decision analysis and knowledge acquisition tool in facility management, where information is scarce and decisions are mostly intuitive It was realized that maintainability in today’s context needs the keyword ‘improve’ to be added to the formal definition provided by BS 3811 Hence the proposed new definition is: ‘The ability of an item, under conditions of use, to be retained in, restored and improved to a state in which it can perform its required functions, when maintenance is performed under stated conditions and using prescribed procedures and resources’ 206 Interestingly it was observed that the traditional emphasis on design might not be true in all cases There is no straightforward ratio of design, construction, and maintenance for influencing maintainability It ‘depends’ When a system is built at site, construction plays a bigger role On the contrary M&E systems with standard factory made products but with high number of components, impose a higher emphasis on maintenance 8.5 Industry contribution Contribution to the industry can be reflected through three deliverables, namely, the Defect Library, Maintainability Handbook and COMASS Their contents are explained in previous section Now their implications are discussed Defect Library collates both critical and noncritical defects Hence it tries to develop the knowledge base of defect data which is scarce Secondly the serious defects are reported in usual cases It is like tip of iceberg where real defect may be 30,000 times more but remain undocumented (Floyd, Eastwood & Liggett, 1998) Defects however trivial cause loss and may spark a serious defect Hence the comprehensive defect list along with their criticality index provides useful information Facility managers instead of brainstorming an unusual problem may use Defect Library as reference It is built on extensive literature and the knowledge shared by other professionals Maintainability Handbook may appear mere collation of codes, standards or guidelines at first glance But actually it is different due to the explanation of reason for every single guideline In reality, scenario with ideal design, construction or maintenance scheme rarely exists Decision makers need to compromise to an acceptable extent By foreseeing the long-term effect of their actions, it is easier to take conscious decisions COMASS (Comprehensive Maintainability Scoring System) is a holistic tool for assessment of a new or existing building and for any phase of life cycle This ‘whole to part’ and ‘part to whole’ concept allows versatile use of the proposed framework It not only indicates the maintainability potential of a building but also clearly identifies the drawbacks and provides a scope for improvement It should be noted that the intention of COMASS was never to 207 replace a decision maker; neither can it serve as a standalone encyclopaedia for design, construction or maintenance, but it aids in structured planning, for example in selection of tenders Its user-friendly design and informative contents are aimed at the users of various credentials The use ranges from simple referencing to extensive assessment Being webbased, the scoring system carries immense potential for application and improvement 8.6 Limitation of the study COMASS is developed from the generic viewpoint of facility managers Cutting-edge defect analysis and recommendations were considered beyond the scope especially for complex defects whose causes are difficult to determine Secondly, during defect analysis it was realized that few defects can have chain effect, e.g inadequate cover for concrete reinforcement hairline cracks water ingress corrosion and spalling However such chain effects were dealt only up to two levels, not to the fullest extent according to FMECA rules Also it was not feasible to address any possibility of multicolinearity (high correlation of two independent variables, in this case defects) due to scarcity of sufficient amount of defect data 8.7 Scope for future research Discussion on the validation of the proposed framework (Section 3.5.1), has revealed that COMASS can be tested fully with real life data if a building’s design, construction and maintenance phases are closely monitored to document compliance or violation of given maintainability guidelines Next phase should be to check whether the predicted defect profile (if any) matches with actual one This will allow any refinement in this work The present trend of innovative use of material or components for sustainable building design requires to define maintainability of such elements in order to become sustainable in true sense (Chew & Das, 2008) If their service life and long term performance can be assigned using suitable methods, such as accelerated aging, this information can be added to 208 COMASS Apart from enriching the tool, this process will help to determine maintainability potential of a proposed scheme already graded fit by sustainability standards It may help to promote the green concept by eliminating common apprehension and hesitance in using a new techniques or materials if their long term performance and maintainability is known Regarding the influence of time, it should also be noted that, COMASS scores rely on today’s perception of defect criticality and performance requirement Change of these two factors with time is inevitable In order to remain relevant, this scoring system requires to accommodate such changes Adding a component as a result of newer technology is not an issue, but addressing time-dependent decision making is a complex phenomenon Saaty (2007) has referred it as Dynamic AHP (DAHP) He indicates the probable methods as: (1) structural: scenarios and time periods are included as elements in decision making structure; (2) functional: time is explicitly involved in the judgment process; and (3) hybrid of these two Extension of COMASS as a dynamic framework is a worthy attempt 8.8 Concluding remarks "Not everything that counts can be counted and not everything that can be counted, counts" –Albert Einstein Through this exploratory research, effort has been made to count major technical and subjective parameters of maintainability Integration of various phases of building lifecycle and components is its main knowledge contribution COMASS was designed to predict the possible outcome of a decision taken for any phase of building lifecycle or building component The other deliverables, namely, Defect Library and Maintainability Handbook can serve as a centralised defect database and benchmark for maintainability practices respectively As a result COMASS is expected to work as decision-enhancement framework 209 ... 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