How Construction Loans Work for Granny Flats
General information only. PremiumRea holds no Australian Credit Licence, is not a credit assistance provider, and does not recommend lenders, loan products or borrowing structures. Speak to a licensed mortgage broker or your lender. Figures below are illustrative mechanics, not quotes, offers or predictions.
Construction lending releases funds in stages against builder invoices as work progresses, rather than as a lump sum at settlement.
On "as-if-built" valuations. Some lenders will assess a proposed build on an as-if-completed basis. The assessed figure is the valuer's opinion and we have seen it come in both above and below the build cost on comparable projects. We have removed an earlier version of this section which asserted a ~$150,000 assessed uplift on a $110,000 build, a $120,000 advance at 80% LVR, and a potential "$0 out of pocket" outcome — we cannot substantiate those as a general expectation. Assume you are funding the build, and treat any valuation uplift as an upside you do not control.
Loan structure:
- Construction loans are typically a separate "split" on your existing mortgage
- Interest rate: Slightly higher than standard home loan rate
- Interest-only during construction (you only pay interest on drawn funds)
- Converts to standard loan after construction completion and OC
4-stage draw-down (matching builder's payment schedule):
- Deposit: 5% ($5,390 on $107,800 build)
- Demolition/foundation stage: 35% ($37,730)
- Lock-up stage: 40% ($43,120)
- Final payment: 20% ($21,560)
Each stage requires builder's invoice + bank inspection before funds are released.
Alternative Financing Options
Not everyone qualifies for a construction loan addition. Here are alternatives:
Cash build (most common for granny flats):
- Many investors use savings or equity from refinancing the main property
- No construction loan fees or bank inspections
- Faster process (no bank approval for each draw-down)
- Builder can often offer better terms for cash builds
Equity release from existing property:
- Refinance your existing property before construction
- Extract equity at 80% LVR
- Use extracted funds to pay builder directly
- Example: Property worth $750K with $500K loan → refinance to 80% ($600K) → extract $100K for granny flat build
Line of credit:
- Flexible draw-down as needed
- Higher interest rate than standard mortgage
- Good for investors building multiple granny flats across properties
Personal loan (not recommended):
- Higher interest rate (8–12%)
- Not tax deductible unless funds are clearly used for investment purposes
- Shorter repayment term increases cash flow pressure
SMSF restriction: You cannot build a granny flat on a property held with an active SMSF loan. The granny flat construction is considered "changing the character of the property" which violates LRBA rules.
The Complete Granny Flat Finance Timeline
Month 1–2: Pre-construction finance
- Request property revaluation from your lender (if refinancing)
- Apply for construction loan split or equity release
- Obtain builder quotes and contract
- Building permit application (~$3,000)
- Soil testing (~$4,400)
Month 2–3: Approval
- Bank approves construction loan / equity release
- Building permit issued
- Builder's insurance confirmed (~$5,500)
- Construction commencement
Month 3–6: Construction & draw-downs
- Stage 1 payment (foundation): Released on invoice
- Stage 2 payment (lock-up): Released after bank inspection
- Stage 3 payment (completion): Released on builder's completion certificate
- Final payment: Released after OC obtained
Month 6–7: Post-construction
- Occupancy Certificate obtained (~3 days)
- Tenant placed (advertising begins 5 days before OC)
- First rental income received
- Request bank revaluation of completed property
Month 9–12: Refinance
- Bank revalues property with completed granny flat
- Refinance at 80% LVR of new value
- Extract equity (up to $120K on a $110K build)
- Deploy equity toward next investment
Total timeline: 6–12 months from finance application to equity recovery. During this period, the granny flat is already earning $370–$500/week in rent.