Decks in Melbourne: building, repairs and permits

New deck, or repairs to an old one?

Replacing a few worn boards is a carpentry repair. Replacing posts, bearers or joists, or building a new deck, is structural work, which can need a building permit and, above $10,000, a registered builder. Say which you think it is, and let the carpenter confirm once they've looked underneath.

• The deck's size and height above the ground at its highest point
• What's showing: soft or split boards, loose railings, rot at the base of posts, rusty brackets or bolts
• Whether it's attached to the house, and whether it has stairs
• The timber or decking material now, and what you'd like

Does it need a building permit?

The Building and Plumbing Commission says decks typically use a structural subfloor and need a building permit. Timber slats laid straight onto concrete or soil generally aren't treated as a deck.

A registered building surveyor issues building permits, and your council can tell you if a planning permit is needed too, for example in a heritage area. Sort both out before work starts: the builder or carpenter quoting should be able to tell you what the job needs.

Who can build it

If the contract price is more than $10,000, the BPC says to appoint a registered builder, and the work needs a major domestic building contract. The deposit can't be more than 10% for a contract under $20,000, or 5% from $20,000. For eligible contracts over $20,000 signed from 1 July 2026, the builder must also take out Home Warranty insurance.

Under $10,000, a carpenter can do the work without builder registration, but the permit question doesn't go away, and the quote should still be in writing.

Balustrades and safety

Balustrades must be at least one metre high, measured from the deck's finished floor. Check yours: a rail that's rotted, rusted, loose or wobbly needs fixing before anyone leans on it.

The BPC suggests looking over decks and balconies every year: the base of timber posts for rot, and brackets and bolts for rust. If you're worried a deck isn't stable, keep people off it until a structural engineer or other qualified building practitioner has assessed it.

Before anyone digs

New footings mean digging. Before You Dig Australia is a free service that gets plans of underground pipes and cables from the companies that own them; use it before any digging, at any depth.

What the quote should cover

• Design and documentation, and who applies for the permit
• Footings, subfloor (posts, bearers and joists) and the decking boards: material, grade and size
• Stairs, and balustrades built to the building code's height rules
• Fixings suited to outdoor use
• Oiling, staining or sealing, or a note that it's excluded
• Removing the old deck, and disposal
• How hidden rot found during a repair will be priced and approved

Example brief

“Existing backyard deck in Mitcham, about 4 m × 3 m and 70 cm off the ground, attached to the house. Several boards are soft and two posts look rotten at the base; the railing wobbles. Please inspect the subfloor and quote either repairs or a rebuild, and tell me whether it needs a building permit.”

Before booking a carpenter or builder

• Repair or rebuild, decided after looking underneath
• Building permit, and planning permit if your council needs one
• A registered builder and contract above $10,000
• Balustrades at least one metre high
• Before You Dig Australia before footings go in

Ready to describe it? Start a job request or browse carpentry jobs. Paying in stages? See paying a tradie. Availability depends on real postings, and registration must be enabled to submit.