In a lightweight frame, standard-sized timber components are spaced relatively close together (typically at 450-600 mm intervals) and nailed or plated into a rigid lattice. The main components comprise vertical studs in the walls, horizontal joists in the floors, and sloping rafters or prefabricated trusses in the roof. Each level of the building is constructed as a platform for the next, with the floor platform established first, then wall frames, and finally the roof framing above.
The result is a strong yet light skeleton of timber to which the exterior claddings and interior linings are attached. Unlike heavy post-and-beam construction, which often leaves massive wood columns exposed, lightweight framing keeps the structural elements hidden beneath cladding (e.g. brick veneer, siding) and linings (e.g. plasterboard) once the building is complete.
Key Takeaways
- Lightweight timber framing is Australia's dominant structural system, used in 70-80% of detached dwellings, and is increasingly extending into low- and medium-rise commercial and institutional buildings.
- The system uses closely spaced timber members (studs, joists, rafters or trusses) nailed or plated into a rigid lattice, built up storey by storey using the platform framing method.
- Framing timber is predominantly locally sourced, plantation-grown softwood, kiln-dried, stress-graded, and preservative-treated for structural use.
- Prefabrication, wall frames, floor cassettes, and roof trusses manufactured offsite and delivered ready to install, is the standard approach across nearly all Australian residential construction.
- The system is governed by AS 1684: Residential Timber-Framed Construction, a fully prescriptive standard recognised by the NCC as a Deemed-to-Satisfy solution for structural compliance in most residential projects.
- Termite management and fire performance are both addressed through well-established, code-compliant detailing, physical and chemical termite barriers, and fire-rated linings capable of achieving FRLs of 60/60/60 or higher.
Why use lightweight timber framing?
Lightweight timber framing is the dominant construction system for Australian houses, accounting for 70 to 80 per cent of detached dwellings. Its greatest contribution has historically been in low-rise housing, but the same system is increasingly extending into low- and medium-rise commercial and institutional buildings, supported by recent expansions to what timber framing can achieve under the National Construction Code.
This prevalence is due to a combination of practical advantages, such as:
- Timber has an excellent strength-to-weight ratio, meaning a relatively light wood frame can support substantial loads.
- Timber frames are lightweight and easy to handle, enabling faster construction with less heavy lifting equipment.
- Prefabricated wall frames, floor cassettes, and roof trusses are manufactured offsite to close tolerances and delivered ready to install, minimising on-site labour and delays. Site-assembled framing is the exception rather than the rule, generally reserved for one-off architectural detailing or remote sites where prefabricated delivery isn't practical.
- The construction process is well understood across the industry, with decades of Australian experience building in timber.
- Designers, tradespeople and other stakeholders are familiar with lightweight timber framed construction.
These factors make timber framing a fast and economical way to build, helping keep material and labour costs lower than some alternative systems.
The timber used in house frames is predominantly locally sourced, plantation-grown softwood - typically radiata pine grown in sustainably managed Australian forests. The wood is kiln-dried and stress graded (e.g. to MGP10 or MGP12) for structural use, and is typically preservative-treated to protect against termites and decay. Most Australian framing timber is sold as treated pine, with specific ratings for different applications.
The framing system, from member sizes and spacings to nailing patterns and tie-down details, is governed by Australian Standard AS 1684: Residential Timber-Framed Construction. Commonly referred to as the Timber Framing Code, AS 1684 provides engineers and builders with prescriptive guidelines, including span tables and connection requirements, to ensure that timber framed houses are structurally safe and compliant with the National Construction Code (NCC).
Sawn Timber to Platform Framing
Timber construction in Australia has evolved from heavy post-and-beam framing, using large hand-worked hardwood members widely spaced apart, to the platform framing system used almost universally today. Machine sawing, mass-produced nails, and industrialised joinery in the early 1900s made lighter, more standardised framing possible, and platform framing was adopted over the alternative balloon framing system for its improved fire safety and easier handling.
This shift suited Australia's post-war housing boom, and AS 1684, first published in 1975, formalised platform framing into national design practice, the same standard that governs timber framed construction today.
How a Timber-Framed House is Structured
Lightweight timber framing follows a methodical, layered construction process. From the ground up, each component contributes to a structural shell that is strong, stable, and well suited to the needs of Australian housing. The process can vary depending on the site, layout, and project scale, but it almost always follows the platform framing method, where each floor level forms a platform for the level above.
Bearers, Joists, and Subfloors
In a raised timber floor system, the structure begins with a system of bearers and joists supported by vertical elements such as screw piles, stumps, or masonry walls. Bearers span between supports and carry the joists, which are fixed perpendicular to the bearers at regular intervals - typically 450 mm centres, depending on span and floor load requirements. Joists are usually 90x45 mm MGP10 pine in standard domestic construction, but engineered options such as LVL or I-joists are increasingly used for longer spans or reduced floor depths (AS 1684.2).
Once the joists are in place, floor sheeting, commonly structural particleboard, is fixed above to create a strong, flat platform ready for wall construction. Subfloors must be detailed to allow for:
- Ventilation beneath the floor structure
- Moisture control, often via damp-proof membranes or clearances
- Termite protection, including physical barriers such as ant caps or proprietary collars, installed in line with AS 3660 requirements
Slab-on-Ground vs Raised Floor Systems
Many Australian homes, particularly those on level suburban blocks, are built on concrete slab-on-ground foundations. In these cases, the timber wall frames are fixed directly to the slab using anchor bolts and bottom plates. This system eliminates the need for bearers and joists at ground level, resulting in faster construction and minimal site excavation. It's also a popular choice in volume homebuilding, where repetition and flat sites make slab construction economical. However, slab-on-ground systems come with some considerations:
- Limited flexibility for running or modifying plumbing and services, with in-ground services poured into the slab
- Slabs require thorough moisture management, such as vapour barriers and slab edge insulation in cooler climates
- In reactive clay soils or areas with high termite risk, special footing designs or treatments are required
By contrast, raised timber floors, supported on screw piles, stumps, or bearers, provide a resilient, adjustable solution where ground conditions are variable. They:
- Allow for natural subfloor ventilation, which can improve durability in damp or humid regions
- Facilitate future adaptability with plumbing, drainage, or underfloor insulation
- Reduce the risk of slab edge condensation and can be detailed to meet bushfire or flood zone requirements
Both systems are compatible with lightweight timber framing. The choice depends on site-specific factors, local practice, and client or builder preference. AS 1684 supports detailing for both approaches, with design provisions to ensure that either system provides a level, durable and compliant base for the house frame above.
Typical Stud Sizes and Spacing
Wall frames form the vertical structural elements of a timber framed building. They are built flat on the platform floor and then stood upright and fixed in place. A typical wall frame consists of a bottom plate (fixed to the floor or slab), vertical studs, noggings, and one or more top plates, which support the structure above. In residential construction, studs are typically 90x35mm or 90x45mm kiln-dried, machine-graded pine (usually MGP10 or MGP12). Heavier grades or wider members may be used in high-load scenarios such as double-storey external walls or supporting concentrated roof loads.
Studs are usually spaced at either:
- 450 mm centres (common in external, loadbearing, and bracing walls)
- 600 mm centres (permitted for internal non-loadbearing partitions or lightly loaded walls)
These spacings reflect requirements from AS 1684, which balances structural performance with ease of lining installation. Closer spacing improves stiffness and resistance to buckling, while wider spacing reduces material use. Where external cladding or internal linings require specific fixing intervals (e.g. fibre cement sheeting or large plasterboard sheets), additional studs are placed to suit manufacturer requirements.
Double top plates are often used to:
- Support point loads from trusses or upper floors
- Tie adjacent wall frames together across junctions
- Provide additional nailing surface and continuity for lintels
Figure 2: Double top plates - providing extra bending strength and assisting with assembly
Openings, Noggings, and Junctions
Wall frames are regularly interrupted by openings for doors and windows, each of which must be framed out to safely transfer loads around the void. AS 1684 provides prescriptive details and span tables for designing these openings.
Each opening includes:
- Lintels: horizontal structural beams above the opening (often 140x45 or larger LVL or solid timber), sized to carry roof or floor loads above
- Trimmer (or jack) studs: vertical members that support the lintel ends
- Jamb studs: full-height studs on either side of the opening, which help distribute loads into the wall
Figure 3: Common definitions in Timber Framed structures
Lintel sizes are selected based on opening width, supported load, and wind classification, with tables provided in AS 1684. Longer or more heavily loaded spans may require engineered timber sections such as LVL or I-beams, especially above wide doors or feature windows.
To provide lateral stability and fixings for linings, noggings (also called blocking) are installed between studs, typically at mid-height in 2.4 m walls. In some cases, multiple rows of noggings are used, especially for taller walls or where cladding requires closer fixing support.
Wall junctions (corners, T-intersections, and returns) require special detailing to:
- Provide continuous load paths between connecting frames
- Ensure there is enough timber for internal linings and external claddings to be fixed securely
Common junction types include:
- Corner studs: paired or tripled studs to form an external corner, often with a return block
- T-junctions: where internal walls meet external walls, often framed with a blocking stud to provide fixing for linings on both walls
- Service cavities: especially in double-stud or acoustic-rated walls, created to route plumbing or wiring without compromising structure or insulation
Timber roof framing completes the structural skeleton of a house, supporting roofing material, ceiling linings, and services.
Prefabricated timber roof trusses, factory-assembled and connected by pressed metal nail plates, are now the default across almost all Australian residential construction, including volume-built and architect-designed projects alike. Engineered to carry roof loads over long spans without internal support walls or beams, prefabricated trusses offer:
- Fast installation time, with a full roof typically installed in a day or two once delivered to site
- Consistent quality and dimensional accuracy, produced under factory conditions to engineered specifications
- Capacity to accommodate complex roof geometries using engineered variants (e.g. scissor trusses, hip sets, girder trusses), designed using purpose-built truss software
Conventional roof framing, individual rafters, ridge boards, ceiling joists and collar ties, cut and assembled on site, remains available where a roofline genuinely can't be achieved with standard truss configurations, or for small-scale and heritage-sensitive work. It offers maximum design flexibility and on-site adaptability, but requires skilled carpenters and significantly more time and labour than a prefabricated system. In the current Australian context, conventional roof framing is best understood as a specialist option rather than a mainstream alternative.
AS 1684 includes provisions for both approaches. In either case, trusses and rafters must be correctly tied down and braced to resist uplift and lateral loads.
Roofs must incorporate:
- Batten or purlin fixing, to support roof cladding (e.g. tile battens or metal roof purlins)
- Bracing appropriate to the roof geometry and wind classification
- Tie-down connectors, such as cyclone straps or triple grips, to resist wind uplift and transfer loads to the walls and footings
Correctly designed and installed roof framing is essential for both structural safety and long-term weatherproofing performance.
Lightweight timber framing in Australia is supported by a well-established set of codes and standards that provide both prescriptive guidance and deemed-to-satisfy compliance pathways for designers, builders, and certifiers. Chief among these is AS 1684 - Residential Timber-Framed Construction, which sets the benchmark for structural safety and consistency across timber framed Class 1 and 10 buildings (e.g. houses, carports, garages).
AS 1684: The Timber Framing Code
AS 1684 is the principal Australian Standard for designing and constructing timber framed houses. It consists of four parts:
- Part 1: Design Criteria - Defines performance-based requirements and loading assumptions
- Part 2: Non-cyclonic Areas - Prescriptive construction practices for wind classifications N1-N4
- Part 3: Cyclonic Areas - Prescriptive construction practices for C1–C4 wind zones
- Part 4: Simplified Non-Engineering Design - For Class 1 structures in lower wind categories
These parts provide comprehensive detail on framing sizes and spacings, bracing wall requirements, tie-down methods and fixings, and span limits for joists, rafters, lintels, and beams. Because AS 1684 is fully prescriptive, it allows most Class 1 residential buildings to be designed without custom structural engineering, provided the building geometry and loads fall within the standard's parameters, and is recognised in the NCC as a Deemed-to-Satisfy solution for structural compliance.
For a practical entry point, AS 1684 is also published as a series of ten-page guides covering common construction scenarios - a useful quick reference alongside the full standard. See the AS 1684 guides on the Technical Design Guides hub.
Span Tables, Bracing, and Tie-Down Schedules
At the core of AS 1684's utility are its span tables and bracing/tie-down schedules, which allow framing members and connectors to be selected directly from tables based on load type, timber grade and size, roof pitch, wind classification, and member spacing.
For example, a builder can determine the appropriate size of a lintel above a window, or a floor joist span, based on MGP10 pine at 450 mm centres, without needing to perform manual calculations. Bracing wall requirements are allocated according to wind classification and building dimensions, and tie-down is addressed using connector schedules linking each structural element together, from rafters and trusses through to wall frames and footings. Each connection type is given a minimum capacity (in kN), with acceptable solutions such as cyclone ties, framing anchors, triple grips, and bolted fixings specified alongside nail size, embedment, and corrosion resistance requirements.
These tools make AS 1684 an essential day-to-day resource for residential designers and builders.
Cyclonic vs Non-Cyclonic Provisions
AS 1684 is split into two main construction practice guides: Part 2 for non-cyclonic regions (wind classifications N1 to N4), and Part 3 for cyclonic regions (C1 to C4). Cyclonic provisions, required in northern Queensland, coastal NT, and parts of WA, call for closer stud and truss spacing, stronger bracing systems, enhanced tie-down detailing (e.g. continuous rods, upgraded connectors), and more stringent fixing schedules.
Builders working in cyclonic regions must be aware of the expanded detailing obligations, particularly when using prefabricated frames. By following the correct version of AS 1684 and the appropriate wind classification, designers and builders can ensure that a timber framed house will perform safely and reliably under local conditions.
National Construction Code (NCC)
While AS 1684 provides detailed construction guidance, it sits beneath the National Construction Code (NCC), which sets out the performance and compliance requirements for all buildings in Australia. Timber framing, when constructed to AS 1684, is recognised by the NCC as a Deemed-to-Satisfy (DTS) solution for structural compliance, significantly reducing the need for engineering sign-off or custom design for standard housing projects.
Deemed-to-Satisfy Pathways
In NCC Volume 2, timber framing built in accordance with AS 1684 Parts 2-4 is explicitly listed as a Deemed-to-Satisfy pathway for Class 1 and 10 buildings. This means a builder following AS 1684 is considered to have met the NCC's structural performance obligations without further justification.
In NCC Volume 1, for Class 2-9 buildings such as low-rise apartments, hotels, and aged care facilities, timber framing may also be used under DTS pathways where the structure remains within height, fire, and acoustic performance limits. Otherwise, Performance Solutions (e.g. fire modelling, alternative compliance documentation) may be required, particularly for taller or mixed-use timber framed buildings. The expansion of mid-rise timber allowances has further increased the scope for using timber framing in larger buildings, including up to 25 metres (typically 4-8 storeys), when combined with appropriate fire and acoustic systems.
Termite Management and Fire Performance
Two areas where NCC compliance intersects heavily with timber framing are termite protection and fire performance. In termite-prone zones, NCC Volume 2 Part 3.1.4 requires a termite management system, which may consist of:
- Physical barriers, such as stainless steel mesh or graded stone
- Chemical systems, such as soil treatments or reticulated chemical zones
- Resistant materials, such as H2-treated timber framing above ground
For timber framing, it is common to use envelope-treated softwood (e.g. blue or red H2 pine) in combination with physical barriers at ground level (e.g. ant caps on stumps, slab edge systems). These measures must be detailed in the building plans and maintained throughout the building's life.
For fire performance, timber framed walls must meet the stipulated Fire Resistance Level (FRL) in applications such as boundary walls, where separation from other buildings is required, and intertenancy walls, where acoustic and fire separation is needed (e.g. in townhouses or Class 2 apartments).
