Timber roof trusses and fire regulations

A timber roof.PHOTO: sourced
A timber roof.PHOTO: sourced

WHILE there are a few misconceptions around timbers fire performance, structural timber for roofing is both commonplace and performs well under fire conditions. As with every aspect of building, timber roof trusses must be manufactured and erected in line with the National Building Regulations and SANS 10400, which provide for fire safety.

Building regulations, set in place by the South African Bureau of Standards (SABS) after extensive research and consultation with industry experts, consider all aspects of a given building material’s composition and properties to ensure that it meets the same safety and performance standard as any other building material in the same application.

Fire regulations relating to timber roof trusses state the following:

• Each independent dwelling unit situated on either side of a fire wall must have its own bracing system within its roof structure, regardless of the fire wall projecting above the roof covering or not.

• The fire regulations do not state the size of a permissible gap between timber members bearing on either side of the fire wall. However, trusses passing through a fire wall must be split into separate trusses.

• The regulation states that “No part of the roof assembly, made of wood or any other combustible material shall pass through the separating wall.”

• No tile underlay or insulation may pass over the fire wall.

The Department of Public Works’ revised Guide to Architects on the subject of fire safety (1998: pp. 3), addresses the matter of fire walls in roof spaces as follows:

“Fire walls, where required, shall be carried up tightly against the underside of the floor except that combustible minor structural members, such as battens, to which roofing material is directly fastened, may be permitted. Purlins must not penetrate a fire wall for a distance greater than 80 mm, but if they penetrate from both sides of the wall, at least 80 mm of non-combustible material must separate them.”

While the Institute for Timber Construction South Africa (ITC-SA) does not make the regulations governing timber construction in South Africa, as part of its endeavours to promote and protect the industry, its players and the general public, it interprets and disseminates them. It is the responsibility of all players, from the manufacture to erection and inspection of timber roof trusses to enforce the regulations; even engineers who sign off on a non-compliant roof structure could well be put to task by the Engineering Council of South Africa.

Professor Walter Burdzik of the Department of Civil Engineering at the University of Pretoria confirms. “Any failure of a truss plant or roof inspector to insist on the separation of roofs per fire regulations needs to be reported to the ITC-SA. The same principle applies to low-cost housing, just because a roof is over a low-cost house does not justify deviating from National Building Regulations.”

The Institute thus urges all responsible along the timber roof truss value chain to play their part and act in accordance with the National Building Regulations SANS 10400 and Building Standards Act 103 of 1977.

We live in a world where facts and fiction get blurred
In times of uncertainty you need journalism you can trust. For only R75 per month, you have access to a world of in-depth analyses, investigative journalism, top opinions and a range of features. Journalism strengthens democracy. Invest in the future today.
Subscribe to News24
Lockdown For
Voting Booth
Who do you think is going to win the 2020 US election?
Please select an option Oops! Something went wrong, please try again later.
Biden is going to take it
46% - 6206 votes
It's four more years for Trump
54% - 7295 votes
Brent Crude
All Share
Top 40
Financial 15
Industrial 25
Resource 10
All JSE data delayed by at least 15 minutes morningstar logo