Façade inspection for falling objects from tall buildings in Singapore

Michael Y.L. Chew (Department of Building, National University of Singapore, Singapore, Singapore)

International Journal of Building Pathology and Adaptation

ISSN: 2398-4708

Article publication date: 4 May 2021

1732

Abstract

Purpose

This paper highlights a crucial public safety issue due to falling objects from tall residential buildings in Singapore. A systematic façade inspection regime and a system of evaluation of severity for the detection and assessment of potential falling objects from tall buildings are presented.

Design/methodology/approach

The research uses qualitative case study approach with 450 tall residential buildings sampled for the study. The common materials, elements, components with high risk of falling objects, the nature and type of the falling, the critical factors affecting the falling, the respective level of severity, and the effectiveness of various diagnostic techniques and protocols, are summarised.

Findings

Façade for tall residential buildings in Singapore comprises mainly cementitious materials cast in situ or precast, with fixtures and architectural features, all of which have potential of falling. The common anomalies arising from each material and fixture/features are identified, the causes evaluated and their implications to future design, construction and maintenance analysed.

Originality/value

This study provides original and significant information to a crucial public safety issue, setting design and construction criteria that will serve as a benchmark for new and existing facades, applicable to all cities dominated by tall buildings. The paper presents original figures, checklists and guides as a basis for readers' consideration to use according to their respective unique conditions.

Keywords

Citation

Chew, M.Y.L. (2021), "Façade inspection for falling objects from tall buildings in Singapore", International Journal of Building Pathology and Adaptation, Vol. ahead-of-print No. ahead-of-print. https://doi.org/10.1108/IJBPA-10-2020-0087

Publisher

:

Emerald Publishing Limited

Copyright © 2021, Michael Y.L. Chew

License

Published by Emerald Publishing Limited. This article is published under the Creative Commons Attribution (CC BY 4.0) licence. Anyone may reproduce, distribute, translate and create derivative works of this article (for both commercial and non-commercial purposes), subject to full attribution to the original publication and authors. The full terms of this licence may be seen at http://creativecommons.org/licences/by/4.0/legalcode


Introduction

In the year 2018, the percentage of public residential building in Singapore exceeding the age of 20 and 30 years were 74 and 56%, respectively (Figures 1 and 2). It is not surprising that more and more incidents of falling objects from height have occurred. The city has reported more than 90 incidents in the past three years where parts of facades fell off (Plate 1). Not only have these cases appeared on media headlines, they have gone all the way into the parliament as a serious public safety issue.

A new legislation on periodic façade inspection (PFI) was passed in Singapore on 6 March 2020, subjecting facades of older tall buildings for a mandatory inspection every seven years by a qualified person for potential falling objects. This new inspection regime is applicable to all buildings taller than 13 m and older than 20 years.

This paper discusses a study designed to evaluate the causes of common falling cases and the roles of relevant professionals in preventing or mitigating such occurrences on the outset of the planning/design stage. A systematic façade inspection regime and a system of evaluation of severity, for the detection and assessment of potential falling objects from tall buildings are presented.

Methodology

The state-of-the-art of regional and global counterparts in terms of standards and best practices for façade inspection and maintainability to prevent falling objects from tall buildings were reviewed. Relevant global standards relating to maintainability factors (e.g. SS, BS, ISO, EN, AS and ASTM) were incorporated in the databank as the foundation phase for the creation of a viable and evidenced based appraisal system.

Case and field study of commonly occurring problems that may lead to falling objects from 450 tall residential buildings were conducted with consideration of factors shown in Table 1.

Face-to-face interviews and workshops with the respective professionals involved in the design, construction and operation of the buildings were conducted for detailed investigation on each problem for their (1) problem types; (2) extent of problem; (3) failure mechanism; (4) good practices in design/construction/FM and (5) environmental issues.

Results and discussions

Periodic façade inspection

Legislations worldwide similar in principles to that of Singapore's PFI include:

  1. US (ASTM, 2019a, b) –

  • 1990 – Chicago – Maintenance of Exterior Walls and Enclosures (>80 ft, different intervals)

  • 1998 – New York–Periodic Inspection of Exterior Walls and Appurtenances of Buildings (>6 storeys, every 5 years)

  • Other states include: Columbus, Pittsburgh, Boston, Cincinnati, Cleveland, Detroit, Milwaukee, Philadelphia, St Louis, San Francisco

  1. Canada – Quebec – Bill 122 (≥5 storeys, every 5 years)

  2. HK – 2012 - Mandatory Building Inspection Scheme (age>30, every 10 years) (HK Government Building Department, 2017)

  3. Singapore – 2020 – Building Control Act (≥13 m, age>20 years, every 7 years)

Singapore's PFI requires a 2-stage investigation:

  1. Stage 1 - Visual inspection of the entire façade area

  • Visual inspection of the condition of the entire (100%) building façade elements from ground level or other available vantage points and openings; Use of drone mounted with optical cameras and/or infra-red/laser detectors.

  • Detect dilapidation and displacement of façade elements

  1. Stage 2 - Close-up hands-on inspection of each elevation

  • Minimum of 10% close-up “hands-on inspection” to be carried out for each building face (elevation)

  • Inspection may include tapping, localised removal of façade elements or panels for inspections and material testing to ascertain the deterioration level and/or integrity of the façade elements, if required;

  • Determination of whether such defects, deterioration are of any concern; and

  • Recommendation of remedial measures to be carried out.

  • For building with wide spread defects observed, the Competent Person may recommend a full facade investigation of localised areas or the whole building for BCA's consideration and approval prior to the fall.

Types of façade

A building facade essentially falls into one of the following four types:

  1. Mass wall

  • Masonry

  • Reinforced concrete

  1. Barrier wall

  • PC panel, GRP, GRC etc

  • Metal cladding

  • Exterior insulation and finish system (EIFS)

  1. Rainscreen (cavity) wall

  • Brick cavity

  • Rainscreen cladding

  1. Curtain wall

  • Stick system

  • Unitised system

with their characteristics summarised in Figure 3.

As most residential buildings in Singapore fall under Type 1 and Type 2, this paper focuses on mass and barrier walls.

Potential falling objects

Common anomalies of different “materials” and “features” which would lead to falling objects are summarised in Figures 4 and 5 (Chew, 2016, Chew et al., 2018).

One other potentially high fatal falling object is falling windows. Figure 6 shows the statistics of window falling off from tall buildings in Singapore. Investigations show that about 80% of the fallen windows were casement windows. The majority of them had fallen due to corrosion of the aluminium rivets holding the friction stays, as well as improper design; installation; maintenance; and wear and tear of the friction stays.

Façade inspection

Table 2 shows an example of inspection checklist for both Stage 1 and Stage 2.

Stage 1 - visual inspection of the entire façade area

This is the stage to assess the general condition of the building under inspection. Visual aids such as binoculars, cameras with powerful zoom, drones mounted with optical cameras and/or infra-red/laser detectors (Chew et al., 1997, Chew, 1998) are some of the methods used (Plate 2). Areas with dilapidation and displacement of façade elements are identified, together with areas with potential falling objects (latent defects), for detailed investigation in Stage 2.

Stage 2 - close-up hands-on inspection of each elevation

This is the stage to conduct close-up hands-on inspection of at least 10% of each elevation, as identified from Stage 1. This stage requires the deployment of façade access systems. A variety of instrumentation from tapping to non-destructive and destructive tests may be utilised to examine the extent and severity of the anomalies (Chew, 1992, 1999a, b, c, 2000a, b, c, Chew et al., 2001). Recommendations for remedial measures are made based on risk evaluation of the results (Table 3). For building with wide spread defects observed, a full facade investigation of Stage 2 may be recommended.

Summary of results

Tables 4–6 summarise:

  1. Lessons learnt from past and present mistakes, showing the causations of the anomaly, who is responsible for what and how to prevent the occurrence of the anomaly and

  2. Recommendations for new buildings in the future, to consider issues related to design, construction and maintenance at the outset of the planning stage, to prevent the occurrence of falling objects from facades, with relevant international standards specified.

Table 4 shows the concerns for design, construction and maintenance on the outset of the planning/design stage, for structural components, e.g. column, beams, slabs, walls and other load bearing and non-loading components.

Table 5 shows the concerns for design, construction and maintenance on the outset of the planning/design stage, for architectural components, e.g. finishes, furnishings and other elements that contribute to the aesthetic value and liveability.

Table 6 shows the concerns for design, construction and maintenance on the outset of the planning/design stage, for service components which include vertical and horizontal circulation systems, electro-mechanical and sanitary connections.

Conclusions

Falling objects from tall building façades including materials, components and features/fixtures are life threatening public safety issue that have been reported globally. It is imperative that all façades must be designed, constructed and maintained adequately with public safety in mind, preventing falling objects from height. The new legislation Singapore recently implemented on PFI is discussed and guides and checklists are recommended. In addition to existing buildings, the paper sets quality benchmarks for future new buildings, spearheading the integration of designers, constructors and facility managers on the outset of the planning/design stage, by providing easy to read tables summarising (1) knowledge learnt from past mistakes and (2) quality benchmarks. Based on predictive/preventive approach, the tables serve to define acceptable standards in design, construction and operation practices to prevent falling objects from facades.

Figures

Percentage of public residential building in Singapore exceeding the age of 20 years

Figure 1

Percentage of public residential building in Singapore exceeding the age of 20 years

Percentage of public residential building in Singapore exceeding the age of 30 years

Figure 2

Percentage of public residential building in Singapore exceeding the age of 30 years

Examples of recent cases of falling objects from height of public residential buildings in Singapore

Plate 1

Examples of recent cases of falling objects from height of public residential buildings in Singapore

Four major types of building façade

Figure 3

Four major types of building façade

Common anomalies from different façade materials

Figure 4

Common anomalies from different façade materials

Common anomalies from different façade features

Figure 5

Common anomalies from different façade features

Statistics of falling window from tall buildings in Singapore

Figure 6

Statistics of falling window from tall buildings in Singapore

Stage 1 - visual investigation for 100% of the façade surface area

Plate 2

Stage 1 - visual investigation for 100% of the façade surface area

Factors considered for case and field studies

Façade componentsFactors considered
Structural
  1. Cracks

  2. Alkali-silica reaction (ASR)

  3. Movement Joints

  4. Rising Dampness

  5. Corrosion of RC

Architectural
  1. Material selection and handling

  2. Sealant deterioration

  3. Corrosion of metal cladding

  4. Delamination of façade

  5. Weather-tightness

  6. Window / Fenestration

  7. Staining

Services
  1. Façade access

  2. Fixtures and fittings

An inspection checklist for both Stage 1 and 2

A recommended benchmark for risk index

Risk indexDescriptionDefinition
High riskIntolerableBlow whistle. Activate emergency SOP. Provide immediately temporary public safety features, e.g. netting, cordon etc.
Medium riskUndesirableLatent defects imminent. Inform all relevant parties. Recommend remedial actions
Low riskTolerableDocumentation for future maintenance and inspection to ensure the risk is kept to minimum

Façade – structural

Façade – Architectural

Façade – Services

Normative references/standards referred to for facade

ASTM C33/C33M-16e1Painting of buildings. Code of practice
ASME A120.1Code of practice for cleaning and surface repair of buildings. Metals (cleaning only)
ASTM A380/A380M-17Workmanship on construction sites. Introduction and general principles
ASTM C1193–16Calculating domestic water consumption in non-domestic buildings. Code of practice
ASTM C1260–14Code of practice for the sampling and monitoring of hot and cold water services in buildings
ASTM C1293–20Code of practice for the selection of water reuse systems
ASTM C1401–14Specification for masonry units. Clay masonry units
ASTM C1487–19Products and systems for the protection and repair of concrete structures. Definitions, requirements, quality control and evaluation of conformity. Concrete injection
ASTM C1496–18Eurocode 2: Design of concrete structures. General rules and rules for buildings
ASTM C1521–19Eurocode 2. Design of concrete structures. Liquid retaining and containing structures
ASTM C1567–13Adhesives for ceramic tiles. Requirements, assessment and verification of constancy of performance, classification and marking
ASTM C1722–18Gravity drainage systems inside buildings. Sanitary pipework, layout and calculation
ASTM C227–10Workmanship on building sites. Cementitious levelling screeds and wearing screeds. Code of practice
ASTM C295/C295M-19Workmanship on building sites. Internal and external wall and floor tiling. Ceramic and agglomerated stone tiles, natural stone and terrazzo tiles and slabs and mosaics. Code of practice
ASTM C618–19Screeds, bases and in situ floorings. Concrete bases and cementitious levelling screeds to receive floorings. Code of practice
ASTM C639–15Screeds, bases and in situ floorings. Concrete wearing surfaces. Code of practice
ASTM C856/C856M-20Guide to facilities maintenance management
ASTM C920–18Code of practice for design and installation of damp-proof courses in masonry construction
ASTM C926–20Code of practice for cleaning and surface repair of buildings. Cleaning of natural stone, brick, terracotta and concrete
ASTM C989/C989M-18aCode of practice for cleaning and surface repair of buildings. Surface repair of natural stones, brick and terracotta
ASTM E1667–95aPaints and varnishes. Corrosion protection of steel structures by protective paint systems. Types of surface and surface preparation
ASTM E2112–19cNon-destructive testing. Infrared thermographic testing. General principles
ASTM E2128–17Code of practice for ceramic wall and floor tiling
ASTM E2266–11Ceramic tiles – Part 1: Sampling and basis for acceptance
ASTM E2270–14Ceramic tiles – Grouts and adhesives – Part 1: Terms, definitions and specifications for adhesives
ASTM E241–09(2014)e1Guidelines for simplified seismic assessment and rehabilitation of concrete buildings
ASTM E2513–07Ceramic tiles – Definitions, classification, characteristics and marking
ASTM E2841–19Ceramic tiles – Grouts and adhesives – Part 5: Requirements, test methods, evaluation of conformity, classification and designation of liquid-applied waterproofing membranes for use beneath ceramic tiling bonded with adhesives
ASTM E903–12Paints and varnishes. Examination and preparation of test samples
BS 1139–2.2Code of practice for cleaning and surface repair of buildings – Part 1 : Cleaning of natural stone, brick, terracotta, concrete and rendered finishes
BS 1881–210Code of practice for cleaning and surface repair of buildings – Surface repair of natural stones, brick, terracotta and rendered finishes
BS 4873Code of practice for painting of buildings
BS 5427Code of practice for waterproofing of reinforced concrete buildings
BS 5974Admixtures for concrete, mortar and grout – Part 2 : Definitions, requirements – Concrete admixtures – Definitions, requirements, conformity, marking and labelling
BS 6037–1Eurocode 2: Design of concrete structures, Part 1–1 General rules and rules for buildings
BS 6093Code of practice for design of joints and jointing in building construction
BS 6150Painting of buildings. Code of practice
BS 6213Selection of construction sealants. Guide
BS 6398Specification for bitumen damp-proof courses for masonry
BS 6576Code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp-proof courses
BS 8000–0Workmanship on construction sites. Introduction and general principles
BS 8004Code of practice for foundations
BS 8102Code of practice for protection of below ground structures against water from the ground
BS 812–123Bases for the design of structures – Deformations of buildings at the serviceability limit states
BS 8204–1Screeds, bases and in situ floorings. Concrete bases and cementitious levelling screeds to receive floorings. Code of practice
BS 8204–2Screeds, bases and in situ floorings. Concrete wearing surfaces. Code of practice
BS 8210Guide to facilities maintenance management
BS 8213–4Windows and doors. Code of practice for the survey and installation of windows and external doorsets
BS 8215Code of practice for design and installation of damp-proof courses in masonry construction
BS 8221–1Code of practice for cleaning and surface repair of buildings. Cleaning of natural stone, brick, terracotta and concrete
BS 8221–2Code of practice for cleaning and surface repair of buildings. Surface repair of natural stones, brick and terracotta
BS 8298–1Code of practice for the design and installation of natural stone cladding and lining. General
BS EN 1004Mobile access and working towers made of prefabricated elements. Materials, dimensions, design loads, safety and performance requirements
BS EN 10088–2Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion resisting steels for general purposes
BS EN 10346Continuously hot-dip coated steel flat products for cold forming. Technical delivery conditions
BS EN 12152Curtain walling. Air permeability. Performance requirements and classification
BS EN 12153Curtain walling. Air permeability. Test method
BS EN 12154Curtain walling. Watertightness. Performance requirements and classification
BS EN 12179Curtain walling. Resistance to wind load. Test method
BS EN 12810–2Facade scaffolds made of prefabricated components. Particular methods of structural design
BS EN 12811–1Temporary works equipment. Scaffolds. Performance requirements and general design
BS EN 12845Fixed firefighting systems. Automatic sprinkler systems. Design, installation and maintenance
BS EN 13022–1Glass in building. Structural sealant glazing. Glass products for structural sealant glazing systems for supported and unsupported monolithic and multiple glazing
BS EN 13139Aggregates for mortar
BS EN 13369Common rules for precast concrete products
BS EN 13561External blinds and awnings. Performance requirements including safety
BS EN 13830Curtain walling. Product standard
BS EN 13914–1Design, preparation and application of external rendering and internal plastering. External rendering
BS EN 14630Products and systems for the protection and repair of concrete structures. Test methods. Determination of carbonation depth in hardened concrete by the phenolphthalein method
BS EN 14992Precast concrete products. Wall elements
BS EN 1504–2Products and systems for the protection and repair of concrete structures. Definitions, requirements, quality control and evaluation of conformity. Surface protection systems for concrete
BS EN 1504–3Products and systems for the protection and repair of concrete structures. Definitions, requirements, quality control and evaluation of conformity. Structural and non-structural repair
BS EN 1504–5Products and systems for the protection and repair of concrete structures. Definitions, requirements, quality control and evaluation of conformity. Concrete injection
BS EN 1504–9Products and systems for the protection and repair of concrete structures. Definitions, requirements, quality control and evaluation of conformity. General principles for use of products and systems
BS EN 15651–1Sealants for non-structural use in joints in buildings and pedestrian walkways. Sealants for facade elements
BS EN 15651–3Sealants for non-structural use in joints in buildings and pedestrian walkways. Sealants for sanitary joints
BS EN 1932External blinds and shutters. Resistance to wind loads. Method of testing and performance criteria
BS EN 1992-1-1Eurocode 2: Design of concrete structures. General rules and rules for buildings
BS EN 1992-1-2Eurocode 2. Design of concrete structures. General rules. Structural fire design
BS EN 1992–3Eurocode 2. Design of concrete structures. Liquid retaining and containing structures
BS EN 1993-1-4Eurocode 3. Design of steel structures. General rules. Supplementary rules for stainless steels
BS EN 1994-1-1Eurocode 4. Design of composite steel and concrete structures. General rules and rules for buildings
BS EN 1995-1-1Eurocode 5: Design of timber structures. General. Common rules and rules for buildings
BS EN 39Loose steel tubes for tube and coupler scaffolds. Technical delivery conditions
BS EN 485–1Aluminium and aluminium alloys. Sheet, strip and plate. Technical conditions for inspection and delivery
BS EN 74–1Couplers, spigot pins and baseplates for use in falsework and scaffolds. Couplers for tubes. Requirements and test procedures
BS EN 752Drain and sewer systems outside buildings. Sewer system management
BS EN ISO 11600Building construction. Jointing products. Classification and requirements for sealants
BS EN ISO 12631Thermal performance of curtain walling. Calculation of thermal transmittance
BS EN ISO 12944–8Paints and varnishes. Corrosion protection of steel structures by protective paint systems. Development of specifications for new work and maintenance
CP 14Code of practice for scaffolds
CP 4Code of practice for foundations
CP 52Code of practice for automatic fire sprinkler system
CP 65–1Code of practice for structural use of concrete – Design and construction
CP 65–2Code of practice for structural use of concrete – Special circumstances
CP 7Code of practice for structural use of timber
CP 81Code of practice for precast concrete slab and wall panels
CP 96Code of practice for curtain walls
EN 1997Geotechnical design
ISO 11600Building construction – joint-sealing products–Classification and requirements of sealants
ISO 13823General principles on the design of structures for durability
ISO 15099Thermal performance of windows, doors and shading devices – Detailed calculations
ISO 16938–1Buildings and civil engineering works – Determination of the staining of porous substrates by sealants used in joints – Part 1: Test with compression
ISO 28278–2Glass in building – Glass products for structural sealant glazing – Part 2: Assembly rules
ISO 28841Guidelines for simplified seismic assessment and rehabilitation of concrete buildings
ISO 6589Joints in building – Laboratory method of test for air permeability of joints
ISO 7361Performance standards in building – Presentation of performance levels of facades made of same-source components
ISO 7729Typical vertical joints between two prefabricated ordinary concrete external wall components – Properties, characteristics and classification criteria
ISO 7845Horizontal joints between load-bearing walls and concrete floors – Laboratory mechanical tests – Effect of vertical loading and of moments transmitted by the floors
SS 150Specification for emulsion paint for decorative purposes
SS 212Specification for aluminium alloy windows
SS 509–1Code of practice for cleaning and surface repair of buildings – Part 1 : Cleaning of natural stone, brick, terracotta, concrete and rendered finishes
SS 509–2Code of practice for cleaning and surface repair of buildings – Surface repair of natural stones, brick, terracotta and rendered finishes
SS 542Code of practice for painting of buildings
SS 555–1Protection against lightning – Part 1: General principles
SS 555–2Protection against lightning – Part 2: Risk management
SS 555–3Protection against lightning – Part 3: Physical damage to structures and life hazard
SS 555–4Protection against lightning – Part 4: Electrical and electronic systems within structures
SS 598Code of practice for suspended scaffolds
SS 599Guide for wayfinding signage in public areas
SS 637 (formerly CP 82)Code of practice for waterproofing of reinforced concrete buildings
SS EN 12620Specification for aggregates for concrete
SS EN 1992-1-1Eurocode 2: Design of concrete structures, Part 1–1 General rules and rules for buildings
SS EN 1992-1-2Eurocode 2: Design of concrete structures, Part 1–2 General rules – Structural fire design
SS EN 1994-1-2Eurocode 4 – Design of composite steel and concrete structures – General rules – Structural fire design
Appendix

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Further reading

Chew, M.Y.L. (2001a), “Curing characteristics and elastic recovery of sealants”, Building and Environment, Vol. 36 No. 8, pp. 925-931.

Chew, M.Y.L. (2001b), “A modified on-site water chamber tester for masonry walls”, Construction and Building Materials, Vol. 15 No. 7, pp. 329-337.

Chew, M.Y.L. (2004a), “Cyclical movement of PU under outdoor environment”, International Journal of Architectural Science, Vol. 5 No. 1, pp. 5-10.

Chew, M.Y.L. (2004b), “Retention of movement capability of polyurethane sealants in the tropics”, Construction and Building Materials, Vol. 18 No. 6, pp. 455-459.

Chew, M.Y.L. and Egodage, N.D.D.S. (2004), “Factorial method for performance assessment of building facades”, Journal of Construction Engineering and Management, ASCE, Vol. 130 No. 4, pp. 525-533.

Chew, M.Y.L. and Lee, D.Y. (1997), “Elastic recovery of sealants”, Building and Environment, Vol. 32 No. 3, pp. 187-193.

Chew, M.Y.L. and Tan, P.P. (2003a), “Façade staining arising from design features”, Construction and Building Materials, Vol. 17 No. 3, pp. 181-187.

Chew, M.Y.L. and Tan, P.P. (2003b), Staining of Façades, World Scientific, Singapore.

Chew, M.Y.L. and Zhou, X. (2002), “Enhanced resistance of polyurethane sealants against cohesive failure under prolonged combination of water and heat”, Polymer Testing, Vol. 21, pp. 187-193.

Chew, M.Y.L., Goh, S.H., Kang, L.H. and Tan, N. (1999), “Applicability of infra-red specstrocopy for sealant degradation studies”, Building and Environment, Vol. 34, pp. 49-55.

Corresponding author

Michael Y.L. Chew can be contacted at: bdgchewm@nus.edu.sg

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