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Timber framing and engineered wood in prefab homes

From Modular Living Australia — the independent knowledge base Last updated: 8 Oct 2026

About 73% of detached houses built in Australia in 2017–18 were timber-framed, and residential timber framing is built to AS 1684.^[1][2] Preservative-treated timber is classified under AS/NZS 1604 into hazard classes H1 to H6, with H2 typical for internal framing protected from the weather, and termite management under AS 3660.1 applies to new buildings whatever the frame.^[3][4]

Timber is the default structural material in Australian detached housing, and most factory-built homes are framed in it. But "timber" covers several quite different products — sawn softwood studs, laminated veneer beams, and solid engineered panels that arrive as whole walls. They share a raw material and very little else, and the questions worth asking differ for each.

Where timber sits in Australian housing §

An industry study estimated that around 73 per cent of detached houses built in 2017–18 used timber framing, down from about 76 per cent for the 2015 calendar year. For Class 2 dwellings in buildings up to three storeys the share was considerably lower, at around 46 per cent^[1]. These figures are now some years old and are best read as an indication of scale rather than a current measurement.

The framing standard §

Residential timber framing is governed by AS 1684, a four-part standard covering design criteria, building practices, tie-downs, bracing and span tables. It is referenced in the National Construction Code as an acceptable construction standard for Class 1 and Class 10 buildings, and in the deemed-to-satisfy provisions for timber structures in Class 2 to Class 9 buildings^[2].

As with steel, "designed to AS 1684" is a checkable claim rather than a marketing phrase, and a builder should be able to produce the documentation behind it.

Engineered wood products §

Three products appear regularly in off-site construction, and they do different jobs.

Laminated veneer lumber (LVL)

Made by bonding rotary peeled or sliced veneers under heat and pressure. It is used for beams, lintels, purlins, truss chords and formwork, and is described as stronger, straighter and more uniform than solid sawn timber, with less tendency to shrink or warp^[6].

Glued laminated timber (glulam)

Multiple layers of dimensioned timber bonded with structural adhesive, with the grain of all layers running parallel to the length of the member. It produces beams, columns, arches and portal frames, and enables spans and curved forms that solid sawn timber cannot achieve. It has been manufactured in Australia since the 1950s^[7].

Cross-laminated timber (CLT)

A solid panel made by bonding layers of boards at 90 degrees to one another, used as walls, floors and roofs. It is manufactured in controlled factory conditions, and its high level of prefabrication is described as reducing on-site adjustment^[8].

The relevance to a buyer is that these are engineered to defined and repeatable properties, which is what makes them suited to a factory process where components are cut from digital files before anyone sees the site.

Treatment and hazard classes §

Timber durability in Australia is managed through the preservative treatment system in AS/NZS 1604, which defines six biological hazard classes. H1 covers borers only; H2 termites; H3 moderate decay; H4 severe decay; H5 very severe decay; and H6 marine borers. H1 and H2 apply where the wood is fully protected from weather and wetting — that is, inside a building^[3].

H3 protects against decay fungi and insects including termites, in above-ground situations exposed to weather or periodic wetting. Within H3 there are two retention levels: the lower level, branded H3A, applies only to vertical water-shedding applications that can be regularly maintained, and must not be used in load-bearing applications where routine inspection and maintenance cannot readily be carried out^[9].

One structural limitation is worth knowing: the heartwood of most hardwood species and some softwoods cannot currently be treated to certain levels of protection^[9]. Treatment is not universally available for every species and every application.

Treated timber sold in Australia should carry a registered brand identifying its H class, applied by the treater before the wood leaves the plant. Buyers are advised to check that the branding matches the intended use^[10].

Cut ends and on-site modification §

Where treatment is applied as an envelope rather than through the full section, cutting exposes untreated material. Applying a brush-on preservative to cut ends of envelope-treated plywood, LVL, glue-laminated timber and reconstituted wood-based products is described as very important^[11].

This is a specific point on which off-site construction has an argument in its favour — cutting is done in a factory under a controlled process — and a specific point on which to ask what happens when modifications are made on site.

Termites §

Australia is home to approximately 350 termite species, around 30 of which have pest status. Termites eat cellulose, which includes timber and timber products^[12].

Termite management for new building work is regulated under AS 3660.1, covering both physical and chemical systems^[4]. It applies to the building rather than to the frame alone, so it is required whether or not the frame is timber — but for a timber-framed home the structural stakes are higher, and the ongoing inspection regime is correspondingly more important to understand before signing.

Thermal performance §

Timber conducts heat far less readily than steel. The regulatory consequence is direct: under NCC 2022, thermal bridging calculations apply only to repeating steel frame elements and are not applied to timber-framed construction^[5]. A timber-framed home does not require thermal breaks for this reason, which removes a detailing question that steel framing introduces.

This is a difference in one specific area, not a general verdict. Overall energy performance is determined by the whole building envelope — insulation, glazing, air-tightness, orientation — rather than by framing material alone.

Summary §

What published sources do not cover §

No independent Australian comparison of the delivered cost of a timber-framed versus steel-framed house is covered by the sources compiled here, and builder-published prices bundle framing together with design, finish and inclusions in a way that cannot be separated.

Comparative service life of timber and steel framing in Australian residential conditions is likewise not covered here. Both are accepted under the National Construction Code when correctly specified, treated where required, and maintained.

Embodied carbon comparisons between framing materials are not covered here. Claims on this subject are common in marketing from all sides, and the sources compiled for this site do not include an independent Australian assessment.

Questions worth asking §

• What H class is the framing timber, and is that appropriate for where it sits in the building?
• Can I see the treatment branding or a certificate of treatment?
• Which engineered products are used, and for what — beams, panels, or the whole structure?
• If the frame is cut or modified on site, how are cut ends treated?
• What termite management system is proposed, and what inspection does it require afterwards?
• How are panels and framing protected from weather between factory and lock-up?

References §