Timber vs Steel Roof Trusses: Which Is Right for Your Build?

Timber and light gauge steel are the two main choices for roof trusses in South Africa. Both can give you a safe, compliant roof when they are properly engineered. The right choice depends on your budget, your span, where you are building and what you plan to put on top.

Here is a straight comparison, based on what we see every day at our plants across the country.

The quick comparison

	Timber trusses	Light gauge steel trusses
Typical cost for houses	Usually lower	Usually higher
Weight	Heavier	Lighter
Termites and borer	Needs treated timber in risk areas	Not affected
Rot	Must be kept dry and ventilated	Does not rot, but must be protected from corrosion at the coast
Long spans	Good, with girders for wide spans	Very good
Fixing ceilings, brandering and fittings	Easy with standard nails and screws	Needs specific screws and fixings
Availability of trades	Most roofers and builders work with timber	Needs installers familiar with steel systems
Fire	Chars at a predictable rate	Does not burn, but loses strength at high temperatures

Timber roof trusses

Most South African homes are roofed with timber trusses made from structural SA pine and joined with galvanised nail plates. There are good reasons for that.

Advantages of timber

• Cost. For a typical house, timber is usually the most economical option.
• Familiar to every trade. Builders, roofers, electricians and ceiling installers all know how to work with timber.
• Easy to alter and fix to. Ceilings, downlights, geysers and solar mounting can be fixed with standard fasteners.
• Locally grown. South African plantation pine is a renewable material.
• Proven. SANS 10400-L and SANS 10243 cover timber roof design and manufacture in detail, so compliance is well understood.

Things to watch with timber

• Timber grade. Structural members must be properly graded and stamped. SANS 10400-L calls for at least grade 5 softwood with a visible grade mark.
• Treatment. In coastal areas and where termites or borer are a risk, the timber must be preservative treated.
• Moisture. Timber must be kept dry. Roof leaks and poor ventilation shorten its life.

Light gauge steel roof trusses

Light gauge steel trusses are made from cold-formed, galvanised steel sections that are screwed or bolted together.

Advantages of steel

• Immune to termites and rot. A strong argument in parts of KwaZulu-Natal, Mpumalanga and Limpopo where termites are common.
• Light and straight. Steel members are dimensionally consistent, which helps with flat ceilings.
• Long spans. Steel performs well on wide spans such as halls, churches, warehouses and showrooms.
• Non-combustible. Steel does not add fuel to a fire.

Things to watch with steel

• Cost. For standard houses, steel is often more expensive than timber.
• Corrosion. Near the sea, the galvanising class and detailing matter. Cut ends and scratched coatings must be protected.
• Trades. Electricians, ceiling contractors and solar installers need the right fixings for steel.
• Heat in a fire. Steel does not burn, but it loses strength quickly at high temperatures.

Which should you choose?

Choose timber if

• You are building a typical house or townhouse and want the best value.
• Your roof has hips, valleys and changes of direction, where timber is easy to detail.
• You want the widest choice of builders and roofers.

Consider steel if

• You are in a high termite risk area and do not want to rely on timber treatment.
• You need long clear spans, for example on a hall, school, church or commercial building. See our services for long-span work.
• The building owner specifically requires non-combustible construction.

Whichever you choose, the truss design must suit your roof covering, span and wind zone, and an engineer must take responsibility for it. Read our guide to roof truss regulations in South Africa for what that involves.

Where you build makes a difference

South Africa’s climate zones change the timber versus steel question more than most people expect.

Coastal areas

Along the KwaZulu-Natal, Eastern Cape and Western Cape coasts, salt in the air attacks steel coatings and fixings, and humidity is hard on untreated timber. Timber trusses must use treated timber, and steel trusses need a galvanising class and fixings rated for the coastal zone. Both work well when they are specified for the site. Our KwaZulu-Natal, Eastern Cape and Western Cape branches design for coastal conditions every day.

Termite and borer areas

The warmer, wetter parts of the country, including much of Mpumalanga, Limpopo and KwaZulu-Natal, have higher termite activity. Correctly treated timber performs well here, but some owners choose steel for extra peace of mind. Our Mpumalanga plant supplies the Lowveld, Limpopo and eSwatini.

Highveld and inland areas

Inland, in Gauteng, the Free State and North West, the main roof hazards are wind and hail. Here the choice usually comes down to cost and span, and timber is the most common choice for houses. The bigger risk is poor bracing and tie-downs, which matter equally for timber and steel.

What about cost?

On a typical house, the timber roof structure (trusses, battens and bracing) usually comes in below an equivalent steel structure. The gap narrows on simple, long-span buildings. Our roof truss price guide explains how roofs are priced and what affects the cost.

Frequently asked questions

Do steel roof trusses last longer than timber?

Both can last the life of the building if they are designed correctly, installed properly and kept dry. Timber needs protection from moisture and insects. Steel needs protection from corrosion, especially at the coast.

Are timber roof trusses safe in termite areas?

Yes, when the timber is correctly treated and the building is detailed to keep termites out. In high-risk areas many owners still prefer steel for peace of mind.

Can I put solar panels on timber trusses?

Yes, but the extra load must be checked. Tell your truss designer if you plan to add solar panels or a geyser in the roof so the trusses can be designed for it.

Does Truss Master make steel trusses?

Truss Master supplies engineered timber and steel roof trusses. Talk to your nearest branch about which suits your project.