Home Extensions & Additions Sydney
Ground floor rear extensions, second storey additions, and room additions across Greater Sydney. DA and CDC managed. Concept to handover under one contract.
Request a QuoteState Property Development builds home extensions and additions across Greater Sydney. NSW Builders Licence 355555C. $20M public liability. Whether you want to push the back of the house out for a larger open-plan living area, add a second storey, or build a separate studio — we manage the project from approvals through to handover.
Extensions in NSW require either a DA (Development Application) or CDC (Complying Development Certificate) before construction starts. We advise on which pathway applies to your site before you spend money on architect fees, so you’re not caught six months in with the wrong approval type.
What We Build
- Ground floor rear extensions — kitchen, living, open-plan
- Second storey additions — bedrooms, bathrooms, study
- Side extensions and room additions
- Garage conversions and studio additions
- Deck and alfresco extensions integrated with the structure
Cost Ranges — Sydney 2026
- Ground floor rear extension: $2,500–$4,500/sqm. A 40sqm extension runs $100,000–$180,000
- Second storey addition: $3,000–$5,500/sqm. 60sqm addition runs $180,000–$330,000
Engineering, DA, and design fees typically add 10–15% above construction cost. Structural engineer, building designer or architect, and certifier are engaged separately but we coordinate them.
DA vs CDC — Which Do You Need?
A CDC is faster — typically 10–20 days — but only applies if your extension meets the standards in the NSW Housing Code (lot size, setbacks, floor space ratio, height). Extensions that don’t meet CDC criteria need a DA, which takes 40–90+ days at most Sydney councils. We look at your site specifics — lot dimensions, zoning, existing floor area, setbacks — and advise you on which pathway before you pay for design.
Home Extension FAQs
Ground floor: $2,500–$4,500/sqm. A 40sqm rear extension runs $100,000–$180,000 in construction. Second storey: $3,000–$5,500/sqm. 60sqm addition runs $180,000–$330,000. Engineering, design, and DA add 10–15% on top. Full guide here.
Yes — either a CDC (10–20 days, if your site meets NSW Housing Code standards) or a DA (40–90+ days at most councils). We look at your site dimensions, zoning, and existing floor area before you pay for design, so you know which path you’re on.
Ground floor 30–60sqm: 12–18 weeks of construction. Second storey: 16–24 weeks. Total project time including design, engineering, and DA is typically 6–12 months from decision to handover. We give you a realistic programme before you commit.
Usually yes, for ground floor extensions. When the roof is open for new structural connections — typically 1–3 weeks — temporary weather protection is required. For second storey additions, the existing roof is removed and rebuilt, which requires careful weatherproofing management. We plan this as part of the construction sequence.
Home Extension Enquiry — Sydney
Licensed builder. DA and CDC advice before you pay for design. NSW Licence 355555C. $20M public liability.