Custom home structural engineering — Byron Bay.
Case study: structural engineering and drafting for a 480 m² custom home on a sloping site in the Byron Bay hinterland — engineered timber portals, exposed steel framing and reactive-soil pad-and-beam footings to AS 2870 and AS 1684.
Project overview
ASTCAD provided structural engineering and drafting for a 480 m² architect-designed custom home on a sloping reactive-clay site in the Byron Bay hinterland. The brief required exposed engineered timber portal frames, large cantilevered floor sections and a primary axis aligned to the view rather than the property setback.
The challenge
The reactive Class P site, combined with a 6 m fall across the building footprint, ruled out a slab-on-ground solution. The architect required visible timber portals at the ends of a 9 m cantilever and large unsupported floor spans for an open-plan living area — all while meeting cyclonic-region wind on the exposed ridge.
Our approach
- Pad-and-beam footing design to AS 2870 for reactive Class P soil
- Glulam portal frame design with FEA-validated connection details
- Cantilever floor design using LVL beams with deflection limits at L/600
- Cyclonic Region B wind loading per AS/NZS 1170.2
- Structural integration with passive solar and exposed-services architecture
Deliverables
- Foundation plans with concrete schedule and reinforcement details
- Floor and roof framing plans with bracing layouts
- Glulam portal shop drawings and connection details
- Steel framing details for exposed elements
- Engineering certificate for council and CDC certifier
Outcome
The home was completed within 11 months of structural sign-off. The engineered timber portals — fabricated off-site and craned in — became the defining architectural feature. No structural rework or RFIs were issued during construction.
How we approach custom home structural engineering
Custom home structural engineering in coastal locations like Byron Bay means designing for wind classification, corrosion durability and architectural ambition simultaneously. We engineer to AS 1684 where the framing suits and AS 1720/AS 4100/AS 3600 where steel and concrete take over, resolve the tricky junctions — cantilevered decks, double-height glazing lines, transfer beams over open living spaces — with real detail drawings rather than typical sections, and specify durability provisions appropriate to the exposure zone. The architect’s intent survives because the structure is engineered around it, not despite it.
Structural documentation for custom homes
The package includes footing and slab plans matched to the geotechnical report, framing plans for each level, steel member schedules and connection details, bracing and tie-down design for the site’s wind classification, and certification documentation for the building approval. We coordinate directly with the architect and builder during construction, answering detail queries fast enough that the frame stage never waits on engineering.
If you are designing a custom home on a difficult block — sloping, coastal, reactive soil or bushfire-affected — early structural input keeps the architecture buildable and the budget honest. We work alongside architects and owner-builders across Australia with fixed-fee documentation packages.
Coastal custom homes also carry durability obligations that inland projects never see: stainless or hot-dip galvanised connections in the salt spray zone, timber durability classes matched to exposure, and detailing that sheds water from every steel-to-timber junction. We specify these explicitly on the drawings rather than leaving them to a general note, because a corroding bracket behind cladding is invisible until it is expensive. The engineering premium for doing this properly at documentation stage is small; the rectification cost a decade later is not.