Decks, balconies and balustrades: safety checks that matter
Decks and balconies fail quietly: timber decays where water sits, fixings corrode, and the connection to the house loosens long before anything collapses. Check the posts, bearers and joists for decay, the fixings for rust, and how the deck is attached to the house. Where someone could fall more than 1 metre, current housing provisions require a balustrade at least 1 metre high with gaps that will not let a 125 mm sphere pass, and where the fall exceeds 4 metres, no climbable horizontal elements between 150 mm and 760 mm above the floor. Many older decks predate these rules. Balconies over rooms also need working waterproofing.
- 01FramePosts, bearers, joists and the fixing to the house
- 02Barrier1 m high, gaps under 125 mm, nothing to climb
- 03WaterBalconies over rooms need a membrane and clear outlets
New boards say nothing about the frame beneath them.
Check the structure first
A deck is a small structure exposed to weather on every side. Water sitting on and between timbers drives decay, and decay often starts where you cannot easily see it: the tops of joists under the boards, the ends of bearers, and post bases.
| Check | Good sign | Concern |
|---|---|---|
| Posts and post bases | Sound timber or steel, clear of soil, on stirrups or footings | Soft or crumbling timber at the base, rust, posts buried in soil |
| Bearers and joists | Firm when probed; dry between rains | Soft spots, fungal growth, splits at fixings, sagging |
| Connection to the house | Bolted to the house frame or slab as designed, with flashing above | Nails only, fixings into brick veneer alone, rot or water staining at the junction |
| Fixings and brackets | Galvanised or stainless, tight | Rust, especially near the coast, loose bolts, missing nails |
| Decking boards | Firm underfoot, gaps for drainage | Bouncy or springy boards, rot, cupping from poor ventilation |
| Under the deck | Ventilated, clear of debris | Low and enclosed, damp, leaves and soil packed against timber |
A deck attached to the house must be fixed to the structure, not just the outer leaf of brick veneer, which is cladding rather than structure; see brick veneer vs double brick. A bouncy deck, a gap opening between the deck and the house, or rot at the connection are reasons to keep people off until it has been assessed.
Balustrades: heights, gaps and climbing
The ABCB Housing Provisions set the rules for barriers where people could fall, and councils such as Darebin summarise them for owners.
| Requirement | Rule | Why |
|---|---|---|
| When a barrier is needed | Where it is possible to fall more than 1 metre | Falls from this height cause serious injury |
| Height on decks, balconies and landings | At least 1 metre above the floor | Stops adults toppling over |
| Height on stairs | At least 865 mm above the stair nosings | Matched to the stair geometry |
| Gaps | Must not let a 125 mm sphere pass through | Stops a small child slipping through |
| Climbing | Where the fall exceeds 4 metres, no climbable horizontal elements between 150 mm and 760 mm above the floor | Stops children climbing over |
Many older decks and balconies predate these rules: low balustrades, wide gaps, horizontal rails or decorative infill a child can climb. They are not automatically illegal, but they are a safety question for any household with children, and replacing a balustrade usually means meeting the current rules. Wire balustrades have specific spacing and tension requirements and slacken over time.
Balconies over rooms: waterproofing and drainage
A balcony built over a room or garage is a roof as well as a floor. Its membrane, falls and outlets must carry water away, and a blocked outlet can flood the balcony and push water into the room below. Look for ceiling stains below, efflorescence or cracking on the balcony surface, blocked outlets and missing overflows. The water paths are similar to those in the bathroom waterproofing guide.
In apartments, balconies, balustrades and their waterproofing are often common property, with repairs organised through the owners corporation; see strata risks for owners.
What to ask before you buy
Ask when the deck or balcony was built, whether it had a building permit, and whether it has been maintained or re-stained. Many councils require permits for decks above certain heights, and an unapproved deck can affect insurance and resale. Coastal and high-exposure sites need closer attention to fixings. Record what you learn in your home record.
Common misreads
| What people say | What is closer to right |
|---|---|
| "The boards look new, so the deck is sound" | Re-decking can hide decayed joists and bearers beneath. Check the frame. |
| "Treated pine does not rot" | Treated timber still decays where water sits, especially at cut ends left unsealed. |
| "The balustrade was fine when it was built" | It may predate current rules on height, gaps and climbing. |
| "It is only a small deck, so no permit was needed" | Permit rules depend on height, size and location; check with your council. |
Worked example: a bouncy deck after re-decking
Illustrative reasoning example, not an inspected property. A 1990s deck about 1.5 metres off the ground was re-decked with new boards last year. It now feels bouncy near the house, and the balustrade has horizontal rails with 140 mm gaps.
The new boards say nothing about the frame. The bounce near the house points to the connection or the joists beneath, which need inspecting before anyone holds a party on it. The balustrade fails today’s gap rule, which matters for a household with young children and will matter when it is replaced. The scope is a structural inspection, then a defined repair to the connection and frame, and a compliant balustrade.
Frequently asked questions
How high does a balustrade need to be in Australia?
Under current housing provisions, at least 1 metre above the floor on decks, balconies and landings where it is possible to fall more than 1 metre, and at least 865 mm above the stair nosings on stairs.
What is the maximum gap in a balustrade?
Openings must not allow a 125 mm sphere to pass through, so a small child cannot slip through.
What is the non-climbable zone?
Where it is possible to fall more than 4 metres, balustrades must have no climbable horizontal elements between 150 mm and 760 mm above the floor, so children cannot climb over.
How do I check if a deck is safe?
Check posts, bearers and joists for soft or decayed timber, fixings for rust, how the deck is attached to the house, and whether it feels bouncy. Keep people off a deck that moves or has a gap opening at the house.
Can a deck be fixed to brick veneer?
Not to the brick veneer alone. Brick veneer is cladding rather than structure, so a deck must be fixed to the house frame or slab as designed, or be freestanding.
Do older decks have to meet current balustrade rules?
Existing decks are not automatically non-compliant because rules changed, but replacing a balustrade generally means meeting current requirements, and older designs can be a real risk for children.
How this guide was researched
We check the structure first, then the balustrade rules for new work, then waterproofing for balconies over rooms, with a fictional example.
Limits: Rules shown are for new work under current provisions; older decks may predate them. Structural condition needs safe access and professional assessment.
Sources
- Housing Provisions Part 11.3: Barriers and handrailsAustralian Building Codes Board · accessed
- Handrails and balustradesDarebin City Council · accessed
- Brickwork and blockworkYourHome, Australian Government · accessed
- Waterproofing of wet areasBuilding and Plumbing Commission (formerly the Victorian Building Authority) · accessed