Demolition Safety and the Method Statement: OHS Act, Construction Regulations and Site Control

Demolition in South Africa is governed by the Occupational Health and Safety Act 85 of 1993 and the Construction Regulations 2014. Those regulations require a documented demolition method statement prepared before work begins, a competent appointed supervisor on site, and a structural engineer's assessment of the structure before demolition starts. None of the three is optional.

What the law requires

What a method statement contains

1. A description of the structure and how it carries load
2. The demolition sequence, element by element, in order
3. Plant and attachments to be used at each stage
4. Temporary support and how it is installed and struck
5. Exclusion zones and how they are enforced
6. Services present and their isolation status
7. Hazardous materials identified and how they are handled
8. Dust, noise and vibration controls
9. Protection of adjoining property and the public
10. Emergency arrangements and site access for emergency services

A method statement written after work has started is a document, not a control. It is prepared from the engineer's assessment before the first machine arrives.

Exclusion zones

An exclusion zone is sized on the structure rather than on convenience. The working rule is a radius of at least the height of the element being demolished, extended in the direction of any intended fall and widened where debris can bounce or roll. Nobody stands inside it, including the operator on foot. Zones are physically marked rather than verbally agreed, and they move as the work progresses.

Dust control under Cape Town water restrictions

Dust suppression conventionally runs on volume of water, and Cape Town restricts water use. The approach here uses less water for the same result.

• Misting at the source. A fine mist at the breaker head suppresses dust at the point it is generated, using a fraction of the water an open hose needs.
• Staged wetting. The drop zone is wetted immediately before the drop rather than continuously.
• Boundary screening. Debris netting and sheeting catch airborne dust mechanically rather than with water.
• Stop in wind. Dust-generating work stops in a strong south-easter rather than continuing behind screens the wind defeats.
• Damp load-out. Material is damped as it is loaded, and loads are sheeted before leaving site.

Silica

Concrete, brick, block, mortar and tile all contain crystalline silica, and breaking them generates respirable silica dust. That dust causes silicosis, and the exposure is cumulative and irreversible. Water suppression at the source is the primary control, and respiratory protection is the backup rather than the other way round.

The structural engineer's assessment

The Construction Regulations 2014 require a structural engineer to assess a structure before demolition, and the reason is specific: a demolition sequence is only safe if you know how the building carries load, and that is frequently not obvious from looking at it. The assessment answers four questions the method statement is then built on.

1. What carries what. Which walls are load-bearing, where the roof loads go, and what depends on what.
2. What is already compromised. Rot, corrosion, spalling, fire damage, previous alterations and cracking that indicates movement.
3. What must not be removed early. Elements bracing something that stays, including a neighbour's structure.
4. Where temporary support goes. Position, capacity and the order in which it is installed and struck.

Older Cape Town buildings make this more necessary rather than less. A Victorian house that has been altered three times over a century has a load path nobody documented, and assumptions about it are how uncontrolled collapses happen.

The hazards specific to demolition

Working near a structure that stays

Most Cape Town demolitions happen within metres of something that must survive: a neighbour's house, a boundary wall, a retained wing, a public pavement. Four controls apply whenever that is the case.

• Work away from the retained structure, not toward it. The machine pulls material into the site.
• Switch to hand demolition near the boundary, because a machine cannot control the last two metres.
• Stage the breaking where the adjoining structure is old or already cracked, so vibration is intermittent rather than sustained.
• Protect the public interface with hoarding and, where a pavement is involved, the necessary permissions for its closure.

Emergency arrangements

A demolition site is difficult for emergency services to enter: the access is obstructed, the ground is uneven, and the building they would normally use as a reference is coming down. The method statement therefore states how an ambulance reaches the site, where the assembly point is, who is first-aid trained, and how the site is identified to a crew that has never been there. On a site with no street number left standing, that last point matters more than it sounds.

Who is responsible

The Occupational Health and Safety Act 85 of 1993 places duties on the employer for its own employees and on the client for appointing a competent contractor. Neither duty transfers by contract. An owner who appoints on price alone, without checking competence or registration, retains an exposure that no clause removes.