Yes. Steel wall frames, floor joists and roof trusses can be used for many home extensions. With appropriate engineering, steel framing for home extensions can connect to existing timber framing, brickwork, concrete and structural steel.
The most important part is the junction between the existing house and the new extension. Foundations, framing, load paths, movement, waterproofing and services should all be resolved before manufacturing begins.
Can Steel Framing Be Added to Any Existing House?
Steel framing can suit many ground-floor and upper-storey additions.
Its relatively low weight can be useful where structural loads need to be carefully managed, while factory manufacturing can provide accurate wall lengths, openings and roof components.
However, the existing house must be assessed first. The condition of the existing structure, footings, roof, walls and proposed openings can all affect the extension design.
An upper-storey addition will generally create different structural requirements from a ground-floor extension supported on new foundations.
Inspect the Existing House First
Existing drawings may not reflect later renovations, structural changes, damage or movement.
Before designing the connection, the project team may need to verify:
- Existing wall and roof framing
- Supporting walls and beams
- Footing and foundation conditions
- Existing bracing and tie-downs
- Floor and ceiling levels
- Roof pitch and support points
- Cracking, settlement or moisture damage
- Plumbing and electrical services
This information helps determine whether the new structure can connect directly to the existing building or requires more independent support.
Plan the Load Path Before Manufacturing
A properly designed extension needs a continuous load path from the roof and walls through the frame and foundations.
Do not assume an existing wall can support new roof trusses, beams or an upper floor.
The engineer may require new:
- Posts
- Beams
- Bracing
- Footings
- Strengthened walls
- Independent structural supports
Removing an external wall can also remove existing structural support or bracing. Temporary propping and permanent structural support may therefore be required.
Should New and Existing Foundations Be Connected?
Not always.
Existing and new foundations can behave differently because of settlement, soil conditions, excavation and changes to drainage.
The engineer may specify a connection between the foundation systems or a controlled joint that allows appropriate movement.
The extension’s footing and slab design should be coordinated with the steel frame from the beginning. Floor levels, slab edges, set-downs and connection points all need to align.
Connecting Steel Wall Frames to the Existing Structure
Steel framing can connect to timber, masonry, concrete or existing steel, but the connection must transfer loads into suitable structural elements.
Depending on the design, connections may use:
- Brackets
- Plates
- Bolts
- Anchors
- Screws
- Engineered connection systems
The appropriate connection depends on the materials, loads and condition of the existing structure.
Existing walls may also be out of square or out of plumb. Allowing for measured tolerances, packing or finishing zones can prevent problems when the new steel frame meets the old structure.
Joining New and Existing Floors
Floor levels should be established early.
The design needs to account for the structure as well as floor sheeting, finishes, slabs and any wet-area set-downs.
Where a new raised floor meets an existing floor, structural support should not simply rely on existing floorboards.
Moisture protection, subfloor ventilation and termite management should also be coordinated where applicable.
Connecting the Roof
The new roof may continue the existing roof pitch, sit below it or create a new valley.
New trusses require properly designed bearing points and tie-downs. They should not be supported from an unverified fascia, batten or other non-structural element.
Roof junctions also require careful waterproofing. Valleys, flashings, gutters and drainage paths should be designed as one system.
For steel framing for home extensions, roof geometry and structural support should be finalised before trusses are manufactured.
Allow for Movement
New and existing construction can move differently because of settlement, temperature, soil conditions and different materials.
Depending on the design, a movement joint, slip detail or flexible sealant may be required.
Structural connections, waterproofing, cladding and internal finishes should all accommodate the movement requirements identified by the designer.
Coordinate Bracing, Insulation and Services
The extension needs appropriate bracing and tie-down design.
Large openings can reduce available bracing space, so this should be resolved before the frame is manufactured.
Insulation and thermal-break details should also be coordinated with the wall and roof construction.
Service routes should be identified before production. Cutting studs, joists, tracks or trusses on site to solve service clashes should not be done without appropriate approval.
What Approvals and Documents Are Needed?
The approval pathway for a NSW extension depends on the proposal, site and applicable planning controls. Depending on the project, this may involve a development application, complying development pathway or other approval process.
The project may require:
- Architectural drawings
- Structural engineering
- Site or survey information
- Soil information
- Energy-efficiency documentation
- BASIX where applicable
- Certification and approval documents
Cold-formed steel design may involve AS/NZS 4600 and applicable NASH requirements, while other standards may apply to structural loads, foundations, materials and connections.
The designer, engineer and certifier should confirm the requirements for the specific project.
What Should You Provide Before Ordering the Frame?
For accurate steel framing for home extensions, provide the manufacturer with the latest approved:
- Architectural and engineering drawings
- Existing-building measurements
- Floor and roof levels
- Demolition information
- Footing and slab details
- Beam and post locations
- Connection requirements
- Bracing and tie-down details
- Window, door and cladding information
- Service penetrations
- Heavy fixture locations
Do not release the frame for manufacture while important junction or connection details remain unresolved.
Build the Extension as One Coordinated System
Steel framing can work effectively when extending an existing home, even when the original house uses timber, brick or other construction.
The key is to investigate the existing structure, establish the new load path and coordinate the foundations, walls, floors and roof before manufacturing.
Early coordination gives the steel framing package the correct dimensions, openings, supports and connection zones, helping reduce site modifications and rework.
About Prime Steel Frames & Trusses
Prime Steel Frames & Trusses supplies steel wall frames, roof trusses, floor joists and structural steel solutions for residential and commercial projects.
Based in St Marys, NSW, the team works with builders, designers and engineers to manufacture accurate steel framing packages from coordinated project drawings.
Contact Prime Steel Frames & Trusses early to discuss existing-building measurements, connection zones, roof layouts and the framing requirements of your extension.