In short: Lenders rarely add the full build cost of a granny flat to a property's value; an uplift of roughly half what you spend is common. Most will not count the second dwelling's rent at all, and those that do shade it hard. Funding is usually an equity release or a construction loan, and some lenders decline security whose value depends on a secondary dwelling.
A granny flat looks like the cleanest possible investment: you own the land, the build is a fraction of a house, and the rent lands on a property you already hold. The finance side is where the plan meets resistance, and that is worth understanding before you sign a build contract.
Granny flat, dual occupancy or subdivision
These three words get used interchangeably and mean very different things to a lender.
| Small second dwelling (granny flat) | Dual occupancy | Subdivision | |
|---|---|---|---|
| What it is | A self-contained second home on the same title | Two dwellings on one lot, often of similar size | The lot is split into two titles |
| Title | One | One | Two |
| Sold separately | No | No | Yes |
| Typical finance | Equity release or construction loan on the whole property | Construction loan, sometimes restricted | Subdivision finance, then two builds |
| Valuation | Small uplift on the existing property | One property with two dwellings | Two securities once titled |
| Lender appetite | Reasonable, with conditions | Narrower | Narrower again, often treated as development |
Value follows title. Two dwellings on one title cannot be sold to two buyers, so the market is smaller than the arithmetic suggests. Only a subdivision creates a second saleable asset, and that is a planning process, not a building one.
The planning reality
Planning rules for secondary dwellings are set by state government and administered by councils, and they differ everywhere. In Victoria, changes from December 2023 removed the planning permit requirement for a small second home of 60 square metres or less on a lot of at least 300 square metres, provided the land carries no flood, environmental or heritage overlay. A building permit is still required, the dwelling cannot be subdivided or sold separately, and anyone can live in it, including a tenant.
Other states have their own thresholds, minimum lot sizes, setbacks and occupancy rules. Check the specific address with the council before you cost anything. Consumer Affairs Victoria's building and renovating pages cover the permit and contract side.
How lenders value a granny flat
Spending $150,000 does not add $150,000 to the valuation. A valuer works from comparable sales, and few houses with a granny flat trade, so the uplift is modest rather than cost-based. Common outcomes:
- An uplift well below cost. Roughly half the spend is a reasonable planning assumption, and in some markets less.
- A more conservative figure and a longer estimated selling period, because there are fewer comparables.
- In some cases no uplift at all, particularly where the second dwelling consumes the backyard of a family home.
- Occasionally a reduction, because the buyer pool for a four-bedroom house with no yard is smaller.
Some lenders will not accept a security whose value materially depends on a secondary dwelling, and some restrict the maximum LVR on properties with two dwellings on one title. If the valuation comes back short, read what to do about a low valuation.
Does the rent count towards your borrowing power
Sometimes, and less than you would like. Rent from a normal investment property is shaded to 70% to 80% for vacancy, agent fees and repairs — see rental income and how lenders shade it. Granny flat rent is treated more cautiously again:
- Some exclude it entirely on an owner-occupied property, because the arrangement is informal and the tenancy is hard to verify.
- Some count it at the standard shading where there is a formal lease and an agent's rental appraisal for the second dwelling.
- Some count it only where the dwelling is legally permitted and separately metered, and will ask for the occupancy permit.
If the rent is what makes the numbers work, this single policy point decides whether the plan proceeds. Confirm it before the build contract is signed.
How to fund it
Equity release
The most common route. You increase the loan against your existing property to a comfortable LVR and pay the builder yourself: no progress-payment mechanics, and funds available before work starts. The limit is your existing equity — model it with the equity calculator and read how to use equity. Smaller conversions of an existing outbuilding can sometimes sit under a renovation loan instead.
Construction loan
Where you lack the equity to fund the build up front, a construction loan progresses against a fixed-price contract, releasing funds at each stage. It requires a registered builder, but it draws on the end value rather than only the current value. See construction loans and progress payments. The catch: the "on completion" valuation is the same conservative one described above, so a $150,000 build that adds $75,000 does not fund itself.
Worked example: a $150,000 granny flat on a $780,000 property
You own a house in Melbourne's north valued at $780,000 with a $400,000 loan, so your LVR is $400,000 ÷ $780,000 = 51.3%. You plan a 60 square metre second dwelling costing $150,000 including permits, connections and landscaping.
Step 1: the valuation
The bank's on-completion valuation comes back at $855,000, an uplift of $75,000 on $150,000 spent. Half the money has gone into the property and not into the balance sheet.
- New loan: $400,000 + $150,000 = $550,000
- New LVR: $550,000 ÷ $855,000 = 64.3%
- Had the valuation added the full cost ($930,000), LVR would be 59.1%
Step 2: what it costs to hold
- Extra borrowing $150,000, for illustration at 6.00% p.a. over 30 years: $899 a month, or $10,788 a year
Step 3: what it earns
- Rent at $420 a week: $420 × 52 = $21,840 a year
- Less agent fees at about 6.6% of rent: $1,441
- Less extra rates, water, insurance and maintenance: about $2,400
- Net rent: $21,840 − $1,441 − $2,400 = about $18,000 a year
Step 4: the actual return
- Cashflow before tax: $18,000 − $10,788 = $7,212 a year, about $600 a month
- Net return on the $150,000 spent: $18,000 ÷ $150,000 = 12.0% a year
- Equity effect on day one: negative $75,000 against the cash spent
Step 5: what the lender counts
Shaded at 70%, the lender counts $21,840 × 0.70 = $15,288. A lender that excludes granny flat rent counts nil, while still counting the full $899 a month against you. Same build, same tenant, two very different borrowing capacities. The cashflow return is strong; the equity return is poor for several years. Which matters depends on whether you intend to hold or sell.
Tax, land tax and other consequences
Renting out a granny flat on your own home has consequences beyond the loan:
- The rent is assessable income and associated expenses are generally deductible, apportioned to the part producing income.
- Using part of your main residence to produce income can reduce the main residence capital gains tax exemption. See capital gains tax on property.
- Victoria's principal place of residence land tax exemption is not automatically lost by renting a granny flat, but the position depends on the facts. Read land tax in Victoria explained.
- Depreciation on a new second dwelling can be significant. See depreciation and tax deductions for investors.
- Insurance must cover a tenanted secondary dwelling, which is not an ordinary home policy.
Get the tax position from your accountant before you build.
Frequently asked questions
Does a granny flat add its full cost to a property's value?
Usually not. Valuers work from comparable sales, and houses with a second dwelling trade rarely, so the uplift is typically well below build cost. Roughly half the spend is a reasonable planning assumption, and in some markets there is no uplift at all. Budget on the cashflow return rather than an immediate equity gain.
Will the bank count granny flat rent in my borrowing power?
It depends entirely on the lender. Some exclude rent from a secondary dwelling on an owner-occupied property. Some count it at the usual 70% to 80% shading where there is a formal lease and an agent's appraisal for the second dwelling. Some require an occupancy permit and separate metering. Confirm the policy before you sign a build contract.
Do I need a planning permit for a granny flat?
It depends on the state, the council and the site. In Victoria, a small second home of 60 square metres or less on a lot of at least 300 square metres has not needed a planning permit since December 2023, provided the land is not affected by flood, environmental or heritage overlays. A building permit is still required. Check the specific address with the council.
Is a construction loan or an equity release better for a granny flat?
An equity release is simpler and faster if you have the equity: funds are available before work starts and there are no progress-payment mechanics. A construction loan draws on the completed value rather than only your current value, which helps when equity is tight, but it requires a registered builder, a fixed-price contract and staged valuations.
Talk to GNT Finance
Before you sign a building contract, let us confirm two things: how much value the lender is likely to add, and whether it will count the rent. Those answers change the whole plan and cost nothing to obtain. Gorakh Timilsina assessed loan files as a senior credit officer before founding GNT Finance, so you get the credit view.
Book a free consultation or call 0426 403 703.
This page is general information only and not legal, tax or financial advice. Laws change — confirm current rules with the State Revenue Office, the ATO or a licensed professional.
Written by Gorakh Timilsina
Founder, CEO & Senior Mortgage Consultant at GNT Finance. Gorakh started as a broker assistant, spent years as a senior credit officer assessing loan applications, and now helps Melbourne families get the right loan approved. English, Nepali and Hindi spoken.