Home Extensions & Additions
Extending your home is one of the most effective ways to add space, value and functionality without the cost and disruption of moving. Whether you are planning a ground floor extension to the rear, enclosing an existing patio, building a second storey above an existing home, or adding a granny flat on a separate structure, Brisbane Structures provides the structural engineering needed to make it happen.
Every home extension that requires a building approval in Queensland needs RPEQ-signed structural engineering drawings and a Form 15 certificate. Brisbane Structures manages the entire structural scope — assessing your existing structure, designing the new elements, coordinating with your architect and builder, and producing council-ready certification that gets your approval through without delays.
We work with homeowners who are managing their own project, building designers who need a structural engineering partner, and builders who require certified drawings for their clients. Our experience with Queensland residential construction — from post-war timber homes to modern steel and concrete — means we understand the structural nuances of adding to an existing building, not just starting from scratch.
Rear extensions, side additions, enclosed patios and carports — increasing ground floor living space.
Adding a full second storey above an existing home — including footing assessment for additional loads.
Structural design for secondary dwellings — freestanding or attached granny flats and dual occupancy.
Structural design and RPEQ certification for elevated decks, pergolas and outdoor entertainment structures.
Full Engineering Scope
A home extension structural engineering package from Brisbane Structures addresses every structural element of the new work — and the interface with the existing building. This interface is where most structural problems occur, and it is where our experience and care makes the difference.
Second Storey Additions
Adding a second storey is the most structurally demanding type of home addition. Unlike a ground floor extension, a second storey places new loads on the existing building — the walls, footings and foundations of the original structure must be assessed and confirmed capable of carrying the additional weight before the new level is designed.
Brisbane Structures assesses the existing structure methodically. We inspect the footing type and depth, check the soil bearing conditions, review the wall framing and connections, and determine whether the existing structure can carry the added loads — or what upgrades are needed. This assessment is the foundation of an accurate and constructible second storey design.
The new structural elements — floor framing, walls, beams, columns and roof — are then designed to integrate with the existing building and to meet all current Australian Standards and Brisbane City Council requirements. Our drawings specify everything needed: footing upgrades (if any), suspended slab or floor joist system, wall framing, roof structure, connections and tie-down details.
We work alongside your building designer or architect so that the structural design integrates seamlessly into the architectural design — minimising the need for costly design changes later in the process.
From concept to council-ready certification
Send us your plans or describe your project. Fixed-fee quote within 24 hours — no surprises.
Our RPEQ engineer assesses the existing structure and site conditions to inform the design.
Complete structural drawings — footings, slabs, framing, beams, connections and schedules.
RPEQ-signed drawings and Form 15 certificate — ready for your building certifier and builder.
Common Questions
Yes. Any home extension in Brisbane that requires a building approval needs RPEQ-signed structural engineering drawings and a Form 15 certificate. Your building certifier will confirm the exact engineering documentation required for your specific project type.
This depends on footing type, depth, soil conditions and the loads the second storey will impose. Brisbane Structures assesses existing footing capacity as part of the structural design. In many cases, existing footings can be used; in others, upgrades are required. The site inspection determines this definitively.
A ground floor extension typically requires structural engineering from $1,500–$3,500. A second storey addition is more complex and typically ranges from $3,000–$7,000 for the full structural design package. We provide a fixed-fee quote within 24 hours — with no hidden fees.
For decks higher than 1 metre above ground and larger pergolas requiring a building approval in Queensland, yes — RPEQ-signed structural drawings are required. Brisbane Structures designs and certifies decks, pergolas and outdoor entertainment structures across Brisbane.
For a standard residential extension, Brisbane Structures typically delivers preliminary structural drawings within 1–2 weeks of the site inspection and receipt of architectural plans. More complex additions may take 3–4 weeks. We confirm a delivery timeline during the initial consultation.
Yes. We work alongside architects, building designers and builders on extension projects across Brisbane. We coordinate structural requirements into the architectural design, liaise with your building certifier, and provide construction-phase support where needed.