Home Extensions in Adelaide

The 10-step framework

1. STEP 1

   Nail the extension type before you scope a builder

   Second-storey add, ground-floor rear addition, side extension, or wing conversion. Each has a completely different structural profile, planning risk and price band. Most extension regrets trace back to picking the wrong extension type for the block, not picking the wrong builder. Match the type to your block shape, orientation, and existing structure before spending anything on design.

2. STEP 2

   Get a structural feasibility check first

   For a second-storey add, the existing footings and ground-floor frame have to carry the new load. Book a structural engineer for a 90-minute site visit (typically $500 to $900) before you spend anything on architectural drawings. If footings need underpinning, that alone can change your budget by tens of thousands - and it's often the deal-breaker on 1950s-70s Adelaide homes with strip footings not sized for a second storey.

3. STEP 3

   Check planning rules for your council BEFORE you design

   Adelaide councils each interpret setbacks, height, overshadowing and site coverage differently. A ground-floor rear extension in Unley is a different approvals path than the same extension in Playford. Read your council policy or hire a planning consultant ($1,500 to $3,500) up front. Cheaper than redesigning after refusal - refusal averages $8k-$15k in wasted design fees.

4. STEP 4

   Decide living arrangement during the build

   Ground-floor extensions can often be built while occupied. Second-storey adds usually require you to move out for 8 to 16 weeks. Renting elsewhere ($4k-$8k per month for a comparable Adelaide home), keeping utilities running, and short-term storage add real cost. Factor this into the budget conversation with your builder before signing - many homeowners underestimate temporary housing by $15k-$25k.

5. STEP 5

   Match the extension type to a specialist builder

   Volume home builders rarely do extensions. Custom builders sometimes will. Dedicated extension specialists (often smaller firms) will. Verify the builder has completed 3+ jobs in your exact extension type in the last 24 months. Ask to speak to those homeowners - and specifically ask about scope creep, delay cost, and dispute handling.

6. STEP 6

   Match rooflines, brickwork and floor levels carefully

   The tell-tale sign of a bad extension is a floor step, a mismatched brick course, or a roof pitch that fights the original. Force your designer to model the extension in 3D against the original elevations. Match brick suppliers exactly (BrickWorks and PGH keep colour-matched stock for older Adelaide bricks - just ask). Detail the transition zone at design stage, not at fitout.

7. STEP 7

   Get the party wall + boundary conversation done early

   Extensions within 1m of a boundary trigger neighbour notification in SA. Extensions attached to a shared wall need a party wall agreement. Both add 4 to 8 weeks if left until construction. Handle them at design stage. Most builders will not chase these for you - it becomes your problem in month four when the neighbour objects.

8. STEP 8

   Ask for a fixed price with itemised inclusions

   Extension quotes are notoriously variable because every existing home is different. Insist on a fully itemised fixed-price quote covering: existing structure works, new build works, transition works (roofing tie-in, bricking-in, plaster patch), electrical rewiring, plumbing tie-in. Beware quotes that lump these into "provisional sums" - that's where 20-40% cost blowouts hide.

9. STEP 9

   Verify insurance covers extensions specifically

   Some SA builders licence covers new builds but excludes major additions. Check the builder is licensed for extensions in SA (Consumer & Business Services SA licence register) and confirm their public liability + home indemnity insurance names extensions as a covered activity. Extensions are the highest-claim category in HBCF - insurance gaps become your problem.

10. STEP 10

    Pressure-test the contract on transition risk

    Standard HIA contracts assume greenfield. Extensions have unique risks: discovering asbestos in existing walls (common in pre-1985 Adelaide homes), discovering foundation issues after opening up, discovering non-compliant existing work. Contract should assign these risks fairly. Spend $400 to $600 having a building contract lawyer review it - the ROI is enormous on an extension.

FAQs