Most Australian homes are built with a lightweight frame of timber or steel. Your Home calls lightweight framed construction the most common construction system used in Australia. Both materials offer design freedom at a competitive cost. The right pick depends on your site, your budget and how you want the house to perform.

This guide compares the two on cost, termites, rust, fire, comfort and environmental impact. It draws on the Australian Government’s Your Home guide to lightweight framing. Neither material wins on every count. Knowing the trade offs helps you have a better conversation with your builder.

How lightweight frames are built today

Modern construction generally favours making trusses and wall frames off site. Frames built on site have one advantage, as they can help overcome small set out errors or variations in the slab and flooring. Both timber and steel frames need bracing to stay rigid. Sheet bracing gives much more rigidity in a shorter length of wall, and it must be installed to the relevant Australian Standard.

Lightweight framing also makes later changes easier. Your Home says it allows future changes to the structure to be made more readily. That is handy if you plan to renovate one day. Our guide to second storey additions is a good read if you might build up later.

Comparing the cost

Timber framing is the lower cost option, according to Your Home. The catch is that timber may be attacked by termites if termite proofing is inadequate. Prices vary between suppliers and over time, so get quotes for both. Look at the whole cost, including termite management and insulation, rather than the frame alone.

Termites

Timber is vulnerable to termite attack. That is a big reason some owners look at steel. But a steel frame does not remove the need for termite protection. Termites can still infest steel framed homes by eating the paper linings on plasterboard.

Whatever you choose, the home needs proper termite management. Your Home points to Australian Standard AS 3660 for termite management. Timber can also be chemically treated. Protection levels range from H1, the lowest, to H3 for exposed outdoor uses, with H4 used for timber in the ground.

Rust, moisture and weathering

Timber is an organic material and deteriorates with weathering. It is subject to mould and rot when exposed to water or condensation. Steel has its own weak point, which is rust. Modern steel frames typically use zincalume with an extra polymer coating to minimise rust.

Rust is possible if the coatings get damaged. Your Home says steel should be treated to suit how corrosive the site conditions are. It refers to AS 1397 for hot dip metallic coated steel sheet and strip. Ask your supplier which coating suits your location.

Wet areas need care with either frame. Keeping water out of the wall cavity protects timber from rot and steel from rust. When you plan a bathroom, choosing the right shower screen helps keep water where it belongs. Kitchens also have plumbing in the walls, which is one reason we suggest leaving kitchen renovations to experienced trades.

Fire

Timber maintains its structural integrity longer than steel in a fire. Steel loses strength rapidly when it is exposed to heat. That may surprise people who assume a metal frame is always safer. In bushfire prone areas, fire risk standards apply where timber is used extensively outside and around the house. Your Home names AS 3959 for construction in bushfire prone areas.

Comfort, insulation and condensation

This is where the two materials differ most. Timber is a natural insulator and a poor thermal bridge. Steel is an excellent conductor of heat. It always needs an effective thermal break to stop heat moving through the frame.

Without proper insulation, a steel frame acts as a thermal bridge and raises the risk of condensation. In practice, that means paying attention to how insulation and thermal breaks are detailed. With either frame, bulk insulation should sit neatly between the structural members without being compressed. Ask your builder how the insulation will be fitted and checked.

Strength, spans and connections

Steel has greater tensile strength than timber. That strength can help with longer spans, though your engineer will set the final sizes. Joints and connections are closely linked to tie down and bracing requirements, and accredited frame fabricators usually design and certify them. If your project includes bolted steel connections, it helps to know how to use a manual torque wrench safely.

Environmental impact

Timber has low embodied energy and absorbs carbon while it grows. Timber from approved sustainable sources is a renewable building material. Certification schemes include the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC). Ask for certified timber when you get quotes.

Steel has high embodied energy, because making it takes large amounts of energy. On the other hand, steel is 100 per cent recyclable. Around 80 per cent of steel is currently recycled. New steel frames include 30 to 40 per cent recycled steel.

Which one should you choose?

There is no single right answer. Timber suits owners who want lower cost, lower embodied energy and better natural insulation. Steel suits those who want a frame that will not rot, and who will pay attention to thermal breaks and coatings. Either way, termite protection and good insulation are still needed.

Frequently asked questions

Do steel framed homes need termite protection?

Yes. A steel frame does not remove the need for termite protection. Termites can still infest a steel framed home by eating the paper linings on plasterboard. Your builder should still follow the termite management standard.

Is timber or steel framing cheaper?

Your Home describes timber framing as the lower cost option. Both materials still offer a competitive cost overall. Prices vary between suppliers and over time, so compare current quotes. Remember to include termite protection and insulation in the comparison.

Can steel frames rust?

Rust is possible if the protective coating on a steel frame gets damaged. Modern frames usually have a polymer coating to minimise rust. Steel should be treated to suit how corrosive the site conditions are. Handle frames carefully on site to avoid scratching the coating.

Which frame performs better in a fire?

Timber maintains its structural integrity longer than steel in a fire. Steel loses strength quickly when heated. In bushfire prone areas, building standards apply to how the house is built. Your builder can tell you if your block is in a bushfire prone area.

Both timber and steel can make a sound, comfortable home. The details matter more than the label on the frame. Get quotes for both, ask how termites, insulation and coatings will be handled, then choose the one that fits your site.