Main page › Guides › Building materials

What prefab and modular homes are built from

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

A prefab or modular home's material and its construction method are separate questions. About 73% of detached Australian houses built in 2017–18 were timber-framed; timber framing follows AS 1684, and residential steel framing follows the NASH Standard referenced in the National Construction Code.^[1][2][3] Termite management under AS 3660.1 applies to new building work, and steel framing needs a thermal break of at least R0.2 where external cladding and internal lining are attached to it.^[4][5]

When a builder describes a "steel modular home", two separate facts are being stated at once. One is the material the structure is made of. The other is the method by which it was manufactured and delivered. The two travel together in marketing language, but they are independent choices, and they carry different consequences for the person buying the house.

Material and method are separate questions §

Material is what the load-bearing frame or shell is made of: sawn timber, engineered wood, light gauge steel, structural steel, or concrete. It is the question that governs how the home behaves over decades — how it responds to moisture, pests, fire and heat, and what maintaining it involves.

Method is how the building is produced and assembled. Volumetric modular construction delivers complete three-dimensional boxes. Panelised construction delivers flat wall, floor and roof elements for assembly on site. Kit or componentised systems deliver a set of parts. Method governs transport limits, design flexibility, how much work happens on your block, and where the risk of delay sits.

Almost any material can be used with almost any method, which is why the two questions have to be asked separately. A timber-framed home can arrive as complete modules or as a stack of panels. A steel-framed home can do the same. Knowing that a builder uses steel tells you nothing about how finished the product will be when it reaches your land.

The structural materials in use §

Timber

Timber framing is the default in Australian detached 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; the share was considerably lower — around 46 per cent — for Class 2 dwellings in buildings up to three storeys^[1]. Those figures are now some years old and should be read as an indication of scale rather than a current measurement.

Residential timber framing is governed by AS 1684, a four-part standard covering design criteria, building practices, tie-downs, bracing and span tables. Complying with it is a deemed-to-satisfy pathway under the National Construction Code for Class 1 and Class 10 buildings^[2].

Engineered timber and mass timber panels

Cross-laminated timber (CLT) is a solid timber panel made by bonding layers of boards at 90 degrees to one another, producing large-format elements used as walls, floors and roofs. It is manufactured in factory conditions and is described as well suited to prefabrication, since panels are cut to size before they leave the plant^[6].

Light gauge steel

Cold-formed light gauge steel framing has an established position in Australian residential construction. For residential work the National Construction Code calls up the NASH Standard — Residential and Low-rise Steel Framing as a deemed-to-satisfy solution^[3][7]. Australia was an early adopter of higher-strength G550 steel, allowing thinner and lighter members, and aluminium/zinc alloy coatings replaced galvanising as the standard corrosion protection^[3].

Steel's relevance to off-site construction is partly a manufacturing one: wastage during prefabrication is generally reported at under 1 per cent^[3].

Concrete and structural steel

Heavier systems — precast concrete panels and hot-rolled structural steel — appear in Australian off-site construction mainly in multi-residential, commercial and institutional work rather than detached housing. Detailed treatment of these systems in a residential context is not covered by the sources compiled here, and is not inferred from their use in other building classes.

Where the choice of material actually shows up §

Four areas account for most of the practical difference.

Pests. Australia has approximately 350 termite species, around 30 of which have achieved pest status^[8]. Termite management for new building work is regulated under AS 3660.1, which covers both physical and chemical systems and applies regardless of framing material — a termite management system is required for the building, not only for its timber^[4].

Heat transfer. Steel conducts heat far more readily than timber, which creates thermal bridging through repeating frame members. Under NCC 2022 this is handled explicitly: thermal bridging calculations apply to repeating steel frame elements and are not applied to timber-framed construction, and steel-framed dwellings are modelled so as to align with the performance of an equivalent timber-framed dwelling^[9]. Where external lightweight cladding and internal lining attach directly to the same member, a thermal break of at least R0.2 is required^[5].

Weight. Weight determines footing design, transport load and crane requirements. It is a significant variable for modules that must travel to site, though the specific effect depends on the design and cannot be generalised from material alone.

Fire and bushfire. Construction in bushfire-prone areas is governed by its own requirements, and material choice interacts with the Bushfire Attack Level assigned to a site. This is addressed in the guides on individual materials rather than summarised here.

Comparison §

What published sources do not tell you about cost §

There is no independent Australian comparison of the delivered cost of a house by structural framing material that is covered by the sources compiled here. Prices published by builders are commercial guidance for their own products, not survey data, and they bundle material together with design, finish level, factory completion percentage and inclusions — which means two quotes using the same material can differ substantially for reasons that have nothing to do with the material.

The practical consequence is that "steel is cheaper than timber", or the reverse, is not a claim this site can support in either direction. Cost differences that matter to you will be visible in the quotes themselves rather than in the material.

Questions worth asking a builder §

• What is the structural frame made of, and which standard is it designed to?
• What proportion of the home is completed in the factory before it leaves?
• Is the building delivered as volumetric modules, as panels, or as a kit?
• What termite management system is proposed, and what inspection does it require afterwards?
• If steel-framed: are thermal breaks required for this design, and how are they detailed?
• What is the delivered weight, and what does it mean for footings and crane access on my block?

References §