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Steel framing basics: light gauge steel for residential construction

Light gauge steel framing for Australian residential builds: AS/NZS 4600, NASH Standard, NCC H1D6, screw patterns, thermal breaks, cyclone ratings.

By Dan Waring. Last updated 10 May 2026. Verified 10 May 2026.

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TL;DR

Light gauge steel (LGS) framing is a factory-fabricated, cold-formed alternative to timber for Class 1 residential buildings: walls, floors, and roof framing using G450-G550 steel sections fixed with self-drilling screws to AS 3566. NCC 2022 H1D6(3) accepts LGS as deemed-to-satisfy under the NASH Standard (Parts 1 and 2) alongside AS/NZS 4600:2018. Frame cost ex-supply is broadly comparable to engineered timber (timber framing runs roughly $35 to $55/m2 of floor area for the wall frame supply-and-fix in 2026); the cost shift is in trades: LGS requires a chippy trained and registered in steel framing, and electrical and plumbing penetrations need grommets throughout. The biggest risk with steel framing is thermal bridging: without R0.2-minimum thermal breaks at every cladding-to-frame contact point, you will lose 0.7 to 1.2 NatHERS stars against your timber-framed equivalent (NCC 2022 7-star requirement). In cyclonic areas (Regions C and D), NASH Part 2C covers C1 and C2 classifications; C3 and C4 require an engineer’s design. Do not mix timber and steel in the one frame without an engineer specifying the connection details.

When you do this

LGS framing is installed after the slab has cured and been set out, and before any external cladding, roofing, or services rough-in. The build sequence is:

  1. Slab on ground or suspended floor (see slab on ground construction)
  2. Wall frame installation (LGS)
  3. Roof framing or truss installation
  4. External cladding and roofing
  5. First fix services (electrical, plumbing, data) through pre-punched service holes with grommets
  6. Insulation and thermal break installation
  7. Internal lining (plasterboard)

LGS walls are not interchangeable with timber mid-project without redesigning connections. Commit to the system before the slab pours.

Who’s involved

  • Builder (principal): specifies the framing system, orders or approves the factory-cut frame package, coordinates trades
  • Chippy (steel-framing certified): installs frame. In most states, installation of structural steel framing requires the chippy to hold relevant licensing (check the state licensing body: NSW Fair Trading, VBA in Vic, QBCC in Qld). Not all chippies are trained in LGS; confirm before engaging.
  • Structural engineer: required for any non-standard configuration, wall heights over those tabulated in NASH Part 2, wind classifications above C2, or any mixed-system details
  • Sparky: AS/NZS 3000 wiring rules apply to steel-framed buildings; the frame must be permanently earthed on completion of the fixing stage
  • Plumber: penetrations through floor joists follow Figure 3.4.2.8 of the NCC; grommets required at all service holes

Steps

1. Confirm the framing design basis

Before ordering a frame, confirm:

For standard residential one- or two-storey construction in wind regions N1-N4 or C1-C2, the NASH Standard Part 2 design solutions (span tables) are the common path. This eliminates the need for bespoke structural design on the wall frame itself, though hold-down and tie-down details still require engineering sign-off.

2. Order the frame package

LGS frames are factory-fabricated off a set of engineer’s drawings. The supplier produces panels cut to length, pre-punched for services, and labelled by wall or floor zone. Typical lead time is 1 to 3 weeks from approved drawings, varying by supplier and season. Confirm:

  • Steel grade (G450 minimum for structural framing members)
  • Coating specification (TRUECORE or equivalent; BlueScope TRUECORE conforms to AS 1397:2021 and uses a zinc-aluminium Activate coating for corrosion resistance)
  • Section dimensions (stud widths of 64 mm, 76 mm, 89 mm, or 92 mm are common for wall studs; section choice driven by NASH span tables and wall height)
  • Delivered or pickup (frames are light but long; a semi with a hiab is typical)

3. Install sole plates and bottom tracks

Mark out the wall positions from the set-out plan on the slab. Sole plate anchoring to the concrete slab is critical: hold-down bolts and anchor positions are set by the engineer’s details, not by the installer’s preference. Anchor bolt positions should have been cast into the slab.

For termite management in LGS systems, the steel frame itself is non-susceptible to termites, but the framing passes through the termite management zone. Physical termite barriers still apply to any timber elements (door jambs, flooring, ceiling battens). Review the termite barrier design against the LGS system with the supplier and your termite barrier installer.

4. Erect wall frames

LGS wall frames are typically erected as pre-fabricated panels. General sequence:

  1. Set bottom tracks to set-out lines, check square and level, fix to slab per anchor schedule
  2. Plumb and brace the first corner panels temporarily
  3. Install intermediate wall panels, checking each for plumb as you go
  4. Fix top plates; check diagonal measurements (equal diagonals = square)
  5. Install any lintels per schedule (lintels in LGS systems are typically C-section or box-beam built-up sections)
  6. Install noggings where required by cladding span or lining fixing schedule

Stud spacings are 450 mm or 600 mm centres. Use 450 mm centres where wind classification, wall height, or cladding weight demand it; 600 mm is the standard spacing for typical residential load conditions.

5. Screw-fix all members

Self-drilling screws to AS 3566 are the standard fastener. Key requirements:

  • Class 3 corrosion resistance: minimum for structural connections in sheltered conditions and where not in contact with H2 treated timber. Use Class 4 in coastal environments (within 1 km of ocean) or where in contact with H3 treated timber.
  • Screw gauge: 10 and 12 gauge Tek screws are typical for structural connections; follow the NASH Part 1 connection schedule and the frame supplier’s fixing schedule.
  • Do not substitute: rivets, pneumatic nails, and timber screws are not interchangeable with self-drilling screws for structural LGS connections. Follow the frame supplier’s fixing schedule exactly.

Inspect connections before cladding. Once lined, missing or under-fixed connections are invisible.

6. Install bracing

Bracing in LGS systems is typically either:

  • Steel strap bracing: flat strap diagonals fixed to studs and top/bottom plates, tensioned to manufacturer specification
  • Sheet bracing: structural plywood or LGS bracing panels, where wind classification or plan geometry requires

Bracing walls and their positions are shown on the engineer’s or supplier’s bracing layout. Do not relocate or omit. LGS buildings without correct bracing are underbraced even if everything else is right.

7. Install thermal breaks before cladding

This is the step most commonly missed on LGS builds. NCC 2022 raised the energy efficiency target to 7-star NatHERS equivalent for Class 1 buildings. Steel has approximately 400 times the thermal conductivity of timber, so direct metal-to-cladding contact creates a significant thermal bridge. Without intervention, expect a 0.7 to 1.2 star NatHERS penalty against your timber-framed equivalent (verified 2026-05-10 via NatHERS Assessor Handbook and steelselect.com.au NCC 2022 guidance).

Minimum requirement: thermal break with R-value of R0.2 or greater at all points of contact between the external cladding and the metal frame. This includes:

  • At every stud-to-cladding contact point
  • Under wall cladding battens fixed through to studs
  • At lintels and headers where metal is exposed to the external environment

Foam or fibre thermal break strips (typically 10-15 mm thick, pre-cut to stud width) are the standard solution. Install before the cladding goes on; retrofitting is destructive. Confirm the NatHERS assessor has modelled the thermal break correctly.

8. First fix services

The LGS frame is supplied with pre-punched service holes (knockout holes) in studs and floor joists at regular heights for electrical cables, plumbing pipes, and data conduit. Key requirements:

  • Grommets: plastic cushioning grommets must be snapped into all service holes where cables or pipes pass through. Grommets protect against abrasion damage to cable insulation and plumbing from frame edges and long-term expansion/contraction movement.
  • Earthing: the steel frame must be permanently electrically earthed on completion of the fixing stage. This is a requirement under AS/NZS 3000 (wiring rules) and is typically done by the sparky during rough-in, not the chippy. Confirm responsibility before handover of the frame.
  • Structural zone: do not drill or cut in the structural zone of a stud (typically within 40 mm of the stud edge). Cuts or holes in the structural zone weaken the member. Any additional penetrations beyond the pre-punched pattern require engineer approval.
  • Plumbing floor joists: penetrations through LGS floor joists must comply with NCC Figure 3.4.2.8; larger pipes may require structural assessment.

Tolerances and acceptance

Per current HIA Guide to Materials and Workmanship and the relevant state Guide to Standards and Tolerances. Verified numerical values pending HIA member access.

AttributeToleranceSource
Wall frame plumb (per storey height)[HIA-079]HIA Guide (pending)
Individual stud bow or twist[HIA-080]HIA Guide (pending)
Top plate level deviation[HIA-081]HIA Guide (pending)
Stud spacing from nominal±5 mmNASH Standard Part 1 (general manufacturing tolerance; verify with frame supplier)
Frame opening size vs. schedule±3 mmNASH Standard Part 1

At frame completion and before cladding, the inspector should check:

  • All walls plumb and square (diagonal measurements equal)
  • Bracing installed and tensioned per layout
  • Service holes grommetted
  • No cut or drilled structural zones
  • Screw fixing complete per schedule (spot-check with the frame supplier’s schedule)
  • Thermal break ordered and on site before cladding starts

Documents needed

  • Engineer’s drawings and specifications (structural and hold-down details)
  • Frame supplier’s fixing schedule (screw type, spacing, connection details per joint)
  • NASH Part 2 or Part 2C span table reference (to confirm design basis)
  • Bracing layout (from engineer or frame supplier)
  • Thermal break specification (for NatHERS compliance and site instruction)
  • Frame delivery docket (confirm steel grade, coating, section sizes match order)

Common holds

  • Hold-down anchor positions in slab incorrect: LGS frames rely on precisely positioned hold-down bolts cast into the slab. If bolts are out by more than the manufacturer’s tolerance, the frame will not seat correctly. Check bolt positions before the slab pours; rectification after is expensive.
  • Frame order delay: factory fabrication of LGS frames is not a same-day turnaround. Finalise structural and architectural drawings before you need the frame on site, not after.
  • Tradesperson not LGS-trained: confirm the chippy has current experience in LGS installation. The screw patterns and fixing details differ significantly from timber; an untrained installer working from habit creates compliant-looking but non-compliant frames.
  • Thermal break not specified before cladding: once cladding is fixed, retrofitting thermal breaks is destructive. Flag this to your NatHERS assessor and confirm the break spec before the first batten goes on.
  • Earthing not arranged before lining: the sparky needs access to the bare frame to install earthing connections. Once plasterboard goes on, earthing the frame is disruptive.

References

See also

Last updated: 2026-05-10. Verified: 2026-05-10. Quarterly review for currency.

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