Façade inspection for falling objects from tall buildings in Singapore

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.

Citation

Chew, M.Y.L. (2023), "Façade inspection for falling objects from tall buildings in Singapore", International Journal of Building Pathology and Adaptation, Vol. 41 No. 6, pp. 162-183. https://doi.org/10.1108/IJBPA-10-2020-0087

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.Appendix

Figures

Figure 1

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

Figure 2

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

Plate 1

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

Figure 3

Four major types of building façade

Figure 4

Common anomalies from different façade materials

Figure 5

Common anomalies from different façade features

Figure 6

Statistics of falling window from tall buildings in Singapore

Plate 2

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

Table 1

Factors considered for case and field studies

Façade components	Factors considered
Structural	Cracks Alkali-silica reaction (ASR) Movement Joints Rising Dampness Corrosion of RC
Architectural	Material selection and handling Sealant deterioration Corrosion of metal cladding Delamination of façade Weather-tightness Window / Fenestration Staining
Services	Façade access Fixtures and fittings

Table 2

An inspection checklist for both Stage 1 and 2

Table 3

A recommended benchmark for risk index

Risk index	Description	Definition
High risk	Intolerable	Blow whistle. Activate emergency SOP. Provide immediately temporary public safety features, e.g. netting, cordon etc.
Medium risk	Undesirable	Latent defects imminent. Inform all relevant parties. Recommend remedial actions
Low risk	Tolerable	Documentation for future maintenance and inspection to ensure the risk is kept to minimum

Table 4

Façade – structural

Table 5

Façade – Architectural

Table 6

Façade – Services

Table A1

Normative references/standards referred to for facade

ASTM C33/C33M-16e1	Painting of buildings. Code of practice
ASME A120.1	Code of practice for cleaning and surface repair of buildings. Metals (cleaning only)
ASTM A380/A380M-17	Workmanship on construction sites. Introduction and general principles
ASTM C1193–16	Calculating domestic water consumption in non-domestic buildings. Code of practice
ASTM C1260–14	Code of practice for the sampling and monitoring of hot and cold water services in buildings
ASTM C1293–20	Code of practice for the selection of water reuse systems
ASTM C1401–14	Specification for masonry units. Clay masonry units
ASTM C1487–19	Products and systems for the protection and repair of concrete structures. Definitions, requirements, quality control and evaluation of conformity. Concrete injection
ASTM C1496–18	Eurocode 2: Design of concrete structures. General rules and rules for buildings
ASTM C1521–19	Eurocode 2. Design of concrete structures. Liquid retaining and containing structures
ASTM C1567–13	Adhesives for ceramic tiles. Requirements, assessment and verification of constancy of performance, classification and marking
ASTM C1722–18	Gravity drainage systems inside buildings. Sanitary pipework, layout and calculation
ASTM C227–10	Workmanship on building sites. Cementitious levelling screeds and wearing screeds. Code of practice
ASTM C295/C295M-19	Workmanship 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 C618–19	Screeds, bases and in situ floorings. Concrete bases and cementitious levelling screeds to receive floorings. Code of practice
ASTM C639–15	Screeds, bases and in situ floorings. Concrete wearing surfaces. Code of practice
ASTM C856/C856M-20	Guide to facilities maintenance management
ASTM C920–18	Code of practice for design and installation of damp-proof courses in masonry construction
ASTM C926–20	Code of practice for cleaning and surface repair of buildings. Cleaning of natural stone, brick, terracotta and concrete
ASTM C989/C989M-18a	Code of practice for cleaning and surface repair of buildings. Surface repair of natural stones, brick and terracotta
ASTM E1667–95a	Paints and varnishes. Corrosion protection of steel structures by protective paint systems. Types of surface and surface preparation
ASTM E2112–19c	Non-destructive testing. Infrared thermographic testing. General principles
ASTM E2128–17	Code of practice for ceramic wall and floor tiling
ASTM E2266–11	Ceramic tiles – Part 1: Sampling and basis for acceptance
ASTM E2270–14	Ceramic tiles – Grouts and adhesives – Part 1: Terms, definitions and specifications for adhesives
ASTM E241–09(2014)e1	Guidelines for simplified seismic assessment and rehabilitation of concrete buildings
ASTM E2513–07	Ceramic tiles – Definitions, classification, characteristics and marking
ASTM E2841–19	Ceramic 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 E903–12	Paints and varnishes. Examination and preparation of test samples
BS 1139–2.2	Code of practice for cleaning and surface repair of buildings – Part 1 : Cleaning of natural stone, brick, terracotta, concrete and rendered finishes
BS 1881–210	Code of practice for cleaning and surface repair of buildings – Surface repair of natural stones, brick, terracotta and rendered finishes
BS 4873	Code of practice for painting of buildings
BS 5427	Code of practice for waterproofing of reinforced concrete buildings
BS 5974	Admixtures for concrete, mortar and grout – Part 2 : Definitions, requirements – Concrete admixtures – Definitions, requirements, conformity, marking and labelling
BS 6037–1	Eurocode 2: Design of concrete structures, Part 1–1 General rules and rules for buildings
BS 6093	Code of practice for design of joints and jointing in building construction
BS 6150	Painting of buildings. Code of practice
BS 6213	Selection of construction sealants. Guide
BS 6398	Specification for bitumen damp-proof courses for masonry
BS 6576	Code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp-proof courses
BS 8000–0	Workmanship on construction sites. Introduction and general principles
BS 8004	Code of practice for foundations
BS 8102	Code of practice for protection of below ground structures against water from the ground
BS 812–123	Bases for the design of structures – Deformations of buildings at the serviceability limit states
BS 8204–1	Screeds, bases and in situ floorings. Concrete bases and cementitious levelling screeds to receive floorings. Code of practice
BS 8204–2	Screeds, bases and in situ floorings. Concrete wearing surfaces. Code of practice
BS 8210	Guide to facilities maintenance management
BS 8213–4	Windows and doors. Code of practice for the survey and installation of windows and external doorsets
BS 8215	Code of practice for design and installation of damp-proof courses in masonry construction
BS 8221–1	Code of practice for cleaning and surface repair of buildings. Cleaning of natural stone, brick, terracotta and concrete
BS 8221–2	Code of practice for cleaning and surface repair of buildings. Surface repair of natural stones, brick and terracotta
BS 8298–1	Code of practice for the design and installation of natural stone cladding and lining. General
BS EN 1004	Mobile access and working towers made of prefabricated elements. Materials, dimensions, design loads, safety and performance requirements
BS EN 10088–2	Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion resisting steels for general purposes
BS EN 10346	Continuously hot-dip coated steel flat products for cold forming. Technical delivery conditions
BS EN 12152	Curtain walling. Air permeability. Performance requirements and classification
BS EN 12153	Curtain walling. Air permeability. Test method
BS EN 12154	Curtain walling. Watertightness. Performance requirements and classification
BS EN 12179	Curtain walling. Resistance to wind load. Test method
BS EN 12810–2	Facade scaffolds made of prefabricated components. Particular methods of structural design
BS EN 12811–1	Temporary works equipment. Scaffolds. Performance requirements and general design
BS EN 12845	Fixed firefighting systems. Automatic sprinkler systems. Design, installation and maintenance
BS EN 13022–1	Glass in building. Structural sealant glazing. Glass products for structural sealant glazing systems for supported and unsupported monolithic and multiple glazing
BS EN 13139	Aggregates for mortar
BS EN 13369	Common rules for precast concrete products
BS EN 13561	External blinds and awnings. Performance requirements including safety
BS EN 13830	Curtain walling. Product standard
BS EN 13914–1	Design, preparation and application of external rendering and internal plastering. External rendering
BS EN 14630	Products 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 14992	Precast concrete products. Wall elements
BS EN 1504–2	Products 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 1504–3	Products 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 1504–5	Products and systems for the protection and repair of concrete structures. Definitions, requirements, quality control and evaluation of conformity. Concrete injection
BS EN 1504–9	Products 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 15651–1	Sealants for non-structural use in joints in buildings and pedestrian walkways. Sealants for facade elements
BS EN 15651–3	Sealants for non-structural use in joints in buildings and pedestrian walkways. Sealants for sanitary joints
BS EN 1932	External blinds and shutters. Resistance to wind loads. Method of testing and performance criteria
BS EN 1992-1-1	Eurocode 2: Design of concrete structures. General rules and rules for buildings
BS EN 1992-1-2	Eurocode 2. Design of concrete structures. General rules. Structural fire design
BS EN 1992–3	Eurocode 2. Design of concrete structures. Liquid retaining and containing structures
BS EN 1993-1-4	Eurocode 3. Design of steel structures. General rules. Supplementary rules for stainless steels
BS EN 1994-1-1	Eurocode 4. Design of composite steel and concrete structures. General rules and rules for buildings
BS EN 1995-1-1	Eurocode 5: Design of timber structures. General. Common rules and rules for buildings
BS EN 39	Loose steel tubes for tube and coupler scaffolds. Technical delivery conditions
BS EN 485–1	Aluminium and aluminium alloys. Sheet, strip and plate. Technical conditions for inspection and delivery
BS EN 74–1	Couplers, spigot pins and baseplates for use in falsework and scaffolds. Couplers for tubes. Requirements and test procedures
BS EN 752	Drain and sewer systems outside buildings. Sewer system management
BS EN ISO 11600	Building construction. Jointing products. Classification and requirements for sealants
BS EN ISO 12631	Thermal performance of curtain walling. Calculation of thermal transmittance
BS EN ISO 12944–8	Paints and varnishes. Corrosion protection of steel structures by protective paint systems. Development of specifications for new work and maintenance
CP 14	Code of practice for scaffolds
CP 4	Code of practice for foundations
CP 52	Code of practice for automatic fire sprinkler system
CP 65–1	Code of practice for structural use of concrete – Design and construction
CP 65–2	Code of practice for structural use of concrete – Special circumstances
CP 7	Code of practice for structural use of timber
CP 81	Code of practice for precast concrete slab and wall panels
CP 96	Code of practice for curtain walls
EN 1997	Geotechnical design
ISO 11600	Building construction – joint-sealing products–Classification and requirements of sealants
ISO 13823	General principles on the design of structures for durability
ISO 15099	Thermal performance of windows, doors and shading devices – Detailed calculations
ISO 16938–1	Buildings and civil engineering works – Determination of the staining of porous substrates by sealants used in joints – Part 1: Test with compression
ISO 28278–2	Glass in building – Glass products for structural sealant glazing – Part 2: Assembly rules
ISO 28841	Guidelines for simplified seismic assessment and rehabilitation of concrete buildings
ISO 6589	Joints in building – Laboratory method of test for air permeability of joints
ISO 7361	Performance standards in building – Presentation of performance levels of facades made of same-source components
ISO 7729	Typical vertical joints between two prefabricated ordinary concrete external wall components – Properties, characteristics and classification criteria
ISO 7845	Horizontal joints between load-bearing walls and concrete floors – Laboratory mechanical tests – Effect of vertical loading and of moments transmitted by the floors
SS 150	Specification for emulsion paint for decorative purposes
SS 212	Specification for aluminium alloy windows
SS 509–1	Code of practice for cleaning and surface repair of buildings – Part 1 : Cleaning of natural stone, brick, terracotta, concrete and rendered finishes
SS 509–2	Code of practice for cleaning and surface repair of buildings – Surface repair of natural stones, brick, terracotta and rendered finishes
SS 542	Code of practice for painting of buildings
SS 555–1	Protection against lightning – Part 1: General principles
SS 555–2	Protection against lightning – Part 2: Risk management
SS 555–3	Protection against lightning – Part 3: Physical damage to structures and life hazard
SS 555–4	Protection against lightning – Part 4: Electrical and electronic systems within structures
SS 598	Code of practice for suspended scaffolds
SS 599	Guide for wayfinding signage in public areas
SS 637 (formerly CP 82)	Code of practice for waterproofing of reinforced concrete buildings
SS EN 12620	Specification for aggregates for concrete
SS EN 1992-1-1	Eurocode 2: Design of concrete structures, Part 1–1 General rules and rules for buildings
SS EN 1992-1-2	Eurocode 2: Design of concrete structures, Part 1–2 General rules – Structural fire design
SS EN 1994-1-2	Eurocode 4 – Design of composite steel and concrete structures – General rules – Structural fire design