Do I need a permit to build a deck in Perth?
If you've been Googling permit rules for decks in WA, you've probably noticed something frustrating: most results give you national information that doesn't apply in Western Australia.
Here's the short answer: in Perth, almost all decks require a building permit. Unlike sheds, patios, and pergolas — which have size-based exemptions — decks sit in a different legal category under WA building law. This trips up thousands of homeowners every year.
Why decks are different from patios and sheds
In Western Australia, building permit exemptions for residential structures are governed by the Building Act 2011 (WA) and its associated regulations. For most common backyard structures, Schedule 4 lists specific exemptions based on size, height, and attachment. Sheds under 10 m² and patios under 10 m² can be built without a permit if freestanding and under 2.4 m high. Pergolas get a more generous 20 m² exemption. But decks don't appear in the exemptions list the same way.
The only potential exception: ground-level decks under 300 mm
An on-grade deck — sitting directly on or very close to the ground, no more than 300 mm above it — may be treated as cosmetic/non-structural work in some councils. The reasoning is that a deck at this height doesn't create fall risk and doesn't require balustrades.
Summary: when a deck permit is required in Perth
| Deck type | Permit required? |
|---|---|
| Raised deck (over 300 mm) — any size | Yes — always |
| Deck attached to the house — any height | Yes — always |
| Deck with stairs or balustrades | Yes — always |
| Freestanding ground-level deck under 300 mm | Maybe — check with council |
| Second-storey deck or balcony | Yes — always |
The building permit process in WA
Certified application (faster)
You hire an independent registered Building Surveyor to assess your plans. They issue a Certificate of Design Compliance (CDC), which you lodge with your council. The council has 10 business days to issue the permit.
Uncertified application (slower)
You lodge plans directly with the council. The council has 25 business days to respond. Cheaper but adds 3 weeks to your timeline.
What happens if you build without a permit?
- Fines — penalties of $50,000 or more for unauthorised building work
- Demolition orders — councils can require you to pull down unauthorised structures at your own expense
- Insurance void — if an unpermitted structure causes damage, your insurer can deny the claim
- Problems at sale — unauthorised structures must be disclosed at settlement
How much does a deck cost in Perth?
- Budget (treated pine): $500–$850 per m²
- Mid-range (merbau or composite): $850–$1,600 per m²
- Premium (hardwood, custom design): $1,600–$2,800 per m²
A 30 m² deck at mid-range rates comes in at roughly $25,000–$48,000 installed. Perth's 1.18× regional multiplier applies. Add $200–$800 for permit fees depending on your council.
Get your exact estimate in 60 seconds
Enter your deck size and finish level — the calculator checks permit rules and gives you a Perth-adjusted cost range.
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