Demolition safety: what supervisors need to know

Why it matters

Demolition takes a structure apart while people stand next to it. Every cut changes how the load travels. A wall that stood for forty years can fall in a second once its support is gone.

Singapore's recent fatal cases show the pattern. In November 2024 a worker hacking a concrete wall alone at a private house was pinned when the wall fell on him. In December 2024 part of a concrete structure toppled onto an excavator cab and killed the operator. In both cases the structure came down in a way nobody planned.

Collapse is the big killer, but not the only one. Workers fall through openings and fragile roofs. Debris drops on people below. Hidden asbestos, live cables and dust add their own harm.

Before demolition starts: surveys and the plan

Demolition safety is mostly decided at the planning stage. The WSH Council asks for a site survey, a structural survey and a risk assessment before work begins. The aim is to know how the remaining structure will stay up at every stage.

Get the drawings if they exist. Find out what the building was used for, since old tanks and pipes may hold chemicals or flammable residue. Check that the building is empty.

• Structure. A professional engineer works out the safe working load of each floor, counting debris and machines. Floors are not loaded past it.
• Services. Gas, power, water, steam and other lines are shut off and capped. Any line that must stay live is moved or covered.
• Hazardous materials. Asbestos, chemicals and flammables are found and dealt with before the structure is touched.
• Neighbours. The stability of adjacent walls, slabs and buildings is checked before and during the work.
• The demolition plan. Site and layout plans, scope, machines and tools, the sequence and method, the supervision plan and the debris plan.

Order of controls

• Eliminate. Keep people out of the collapse zone altogether. Use remote-controlled demolition machines or robots for the riskiest areas.
• Substitute. Choose a method that brings parts down in small, controlled pieces. Cut and lift sections instead of letting them fall.
• Engineer. Props, shoring and bracing for walls and slabs that could become unstable. Catch platforms, hoardings, covered walkways, enclosed chutes and barricades.
• Administer. Permit-to-work, a written sequence, a competent supervisor on site, daily briefings and regular checks of the remaining structure.
• Personal protection. Helmets and safety boots for everyone. Add eye and hearing protection, respirators, gloves and fall protection as the task needs.

Sequence and stability

The sequence is the most important safety control on a demolition job. Write it in the method statement and brief it every morning. Workers must not invent their own shortcuts.

Go from the top down, storey by storey. Finish all work above a floor before you weaken the supports under it. Break large walls into small sections so no big panel can fall at once. On framed structures, take out horizontal beams before columns, in a controlled way.

Never leave a wall or part of a structure standing so that wind or vibration could bring it down. If a wall or slab will lose its support, prop or brace it first. Props must be strong enough to hold the load if the part starts to move.

Stop work in high winds. Weakened structures fail more easily in bad weather.

Machines on demolition jobs

Excavators with breakers, crushers and shears do most of the heavy work. Match the machine to the size of the structure and its reach to the height. Only trained, competent operators should run them.

Mark out the collapse zone and work so the piece being demolished lands inside it. When two or more machines work on the same structure, work in the same direction and coordinate the sequence. The supervisor checks the zone is empty of people and equipment before work starts.

Moving machines between floors can overload a slab. Do not build ramps from rubble. Use proper ramps such as steel ramps, or lower the machine by crane, as a PE has planned.

Debris, chutes and openings

Debris must not pile up until it becomes a hazard. It also adds load to floors that may already be weak. Clear it as you go, by chutes, buckets, hoists or another method that does not endanger anyone.

Chutes are fully enclosed apart from the loading and discharge openings. Side openings stay closed when not in use. The discharge end goes into a gated enclosure at least 2 metres high, or into a skip with sides at least that high. Openings used to drop debris are enclosed or barricaded, with warning signs below.

Protecting the public and the site

Put up a solid barricade with warning signs along every pavement or road next to the work. Use hoardings and covered walkways to move pedestrians past safely. Lock the gates outside working hours.

Fit catch platforms when you demolish an exterior masonry wall or a roof, unless a full external scaffold gives the same protection. Keep safe, protected routes into and out of the building throughout the job. Guard every open edge where someone could fall more than 2 metres.

What the rules require (Singapore)

Part X of the Workplace Safety and Health (Construction) Regulations 2007 covers demolition. Most duties fall on the occupier of the worksite. The WSH Council also notes that most demolition works need BCA approval of the structural plans and a permit before work starts, with the plan prepared by a Qualified Person.

• Permit-to-work for all demolition work. The supervisor applies, the safety assessor checks, and the project manager issues it (regs 10 to 15).
• Exterior glass and cladding removed, and all supply lines shut off and capped, before demolition starts (reg 70).
• Stability of adjacent structures assessed before and during the work, and supported where needed (reg 71).
• Removal of load-bearing parts done with regard to the remaining structure and to a PE's method statement (reg 72).
• Walls taken down systematically. With hand tools, walls are not left more than one storey above the floor people work on (reg 73).
• Protected access and egress at all times; barricades and signs along public routes; catch platforms for exterior walls and roofs (regs 74, 75).
• Swinging weights only on structures up to 24 m, with a zone of 1.5 times the height. Clamshell buckets need an 8 m zone. Only essential people inside barricaded zones (reg 76).
• Debris removal by safe means, enclosed chutes, and PE-designed chutes over 12 m (regs 50 to 56).

Common mistakes

• Starting before the survey, the method statement or the permit is ready.
• Removing walls that turn out to carry a slab, with no props in place.
• Hacking walls from the bottom, or leaving tall panels standing overnight.
• One worker hacking alone with nobody watching the structure.
• Rubble ramps for machines, and debris piled on weak floors.
• Two excavators working towards each other on the same structure.
• People walking through the collapse zone to save time.

Use it on site: the demolition checklist and the toolbox talk to brief your crew.

Sources

1. Workplace Safety and Health (Construction) Regulations 2007, Singapore Statutes Online (AGC).
2. WSH Advisory: Demolition workplace fatal injuries in 2H2024, WSH Council.
3. Technical Advisory for Demolition, WSH Council.
4. Demolition (topic page), WSH Council.
5. When do I need to conduct an asbestos survey?, Ministry of Manpower.
6. If I suspect that I have asbestos materials in my house or workplace, what should I do?, Ministry of Manpower.
7. Code of practice on safety and health in construction (revised 2022), International Labour Organization.

This is practical guidance, not legal advice. Laws and codes of practice change; always check the current official text and your site's own procedures.