What you need to know about decks & balconies safety in Perth - a structural engineer's perspective

Do you own a house, unit or other building with a balcony or deck? When was the last time you inspected it to make sure it’s safe? People are seriously injured every year in Australia falling from decks and balconies. In some cases this could have been prevented by regular maintenance.

Building your own deck is a great way to transform an outdoor area and to add value to your Perth home. Decking can be described as a flat surface or platform capable of supporting weight, similar to a floor, but typically constructed outdoors. Decking is often elevated from the ground and usually connected to a building.

Building permit and/or development application

It is important to note that all decking requires a Building Permit, regardless of the height or floor area. A Development Application may also be required for decking over 500mm in height from Natural Ground Level.

In most cased, decking may be located up to a side or rear boundary provided it complies with the Residential Design Codes and the Council or Shire legislation relating to fencing.

Decking over 500mm in height is considered to be the same as a Balcony and as such, requires a setback of 7.5m to side and rear boundaries. Reduced setbacks may be considered via an Application to Commence Development (Development Approval). All timber decking must be designed and constructed in accordance with AS 1684.2-2010 (Residential Timber-Framed Construction).

In most cases, a structural engineer is required to provide engineering details or drawings for decking over 500mm in height from Natural Ground Level. The cost to engage a structural engineer in Perth will vary so it is always good to obtain at least three quotes. Structural engineer’s details are not generally required for decking less than 500mm in height from Natural Ground Level, however it will be at the discretion of the Building Surveyor assessing the plans as to whether they will be required.

Not all members of the public are aware that The Department of Mines, Industry Regulation and Safety (formerly The Department of Commerce) contains some useful information regarding this common issue in our community. Here are some useful safety tips:

General deck and balcony safety

Don’t install heavy objects such as spas on a deck or balcony, unless the structure has been designed to withstand this extra load (a structural engineer can provide advice if the structure is suitable for heavy objects). Avoid excessive jumping, dancing or other movement on a deck or balcony, unless the deck or balcony has been designed to withstand this extra load. Remember that with age, decks and balconies deteriorate, reducing their ability to withstand the loads they were originally designed for. Avoid having large numbers of people gather on a deck or balcony, unless it has been specifically designed to withstand this load. Never climb over a balustrade, and never climb from one balcony to another, especially in multi-storey or high-rise buildings. Never sit on top of a balustrade.

Child safety on decks and balconies

Keep kids safe around decks and balconies. Besides always supervising children, you can make your home safer by making a few simple changes:

  • Don’t leave anything climbable on or near the balustrades that kids can grip to help them climb;

  • Keep all outdoor furniture and other climbable objects well away;

  • Ensure furniture and other climbable objects are difficult to move (e.g. use heavy furniture);

  • Install high locks or latches and self-closing devices to doors leading to decks or balconies;

  • Don’t leave furniture or other climbable objects near windows;

  • Don’t rely on fly screens or non-safety-grade glass to protect window openings.

You should inspect your deck at least once a year. Something as simple as rusted nails could cause a collapse that could cause death or injury to those you care for most. Check each part as well as the deck generally to make sure there has not been any excessive structural movement from the stress of swaying and twisting under load, or due to the ground subsiding. If you have any concerns you should contract a chartered professional structural engineer.

It is also recommended that you learn what you should inspect, and what to look for. Here are some key areas to assess:

  • Fixings - check fixings and post brackets for bending, stress, fractures and rust;

  • Nuts, bolts, screws and nails - look out for signs of rusting and replace as soon as needed;

  • Timber posts - make sure the timber is a type that won’t degrade in soil and is treated appropriately.If you see signs of wet rot, fungal growth, or timber that is spongy or fibrous, fix it immediately;

  • Steel posts - check for signs of rust and deterioration around the base where water can pool;

  • Bracing - look for warped, cracked or damaged bracing elements and fixings that are loose or deteriorating;

  • Bearers and joists - inspect bearers and joists regularly for signs of warping or cracking;

  • Balustrades anchor points - inspect where the balustrade is fixed to the deck or balcony, walls and posts, for deterioration;

  • And lastly - ensure handrails are securely fastened, glass balustrades are free from chips or cracks and anchor points are free of rust and wear.

About 6% of Australian houses have a timber deck or balcony. Of these, around 2% could cause fatal injuries if they collapsed, or had a balustrade or railing fail. In other states such as Queensland, the percentage of homes with decks or balconies is even higher. If you have purchased a home with a deck which doesn't have Council you may be able to obtain retrospective building approval. Below are some tips for maintaining your deck or balcony from the Department of Housing and Public Works (State of Queensland).

The case for mandatory decking and balcony inspection

The State of California approved legislation in 2018 that requires a structural building inspection of exterior elevated elements and associated waterproofing elements including decks and balconies by a licensed architect, licensed civil or structural engineer or a registered builder every 6 years. It also states that the building inspector must not be employed by the local jurisdiction while performing these inspections thus providing impartial advice. Based on our experience in Perth and the safety concerns raised, one would suggest that an inspection every 6 years could make a significant difference in reducing injury or worse in the event of a balcony or deck collapse.

General deck and balcony maintenance

Avoid frequently wetting decks and balconies—where possible sweep instead of hosing.If your deck or balcony does get wet, ensure it is adequately ventilated to allow quicker drying. Place pot plants on trays and prevent them from overflowing.Remove shrubs or plants that permanently shade the deck or balcony, and remove creepers from rails or other components (these prevent moisture from escaping).Reapply finishes at regular intervals (depending on the finish type and degree of exposure). Ensure that timber decking is thoroughly cleaned before coating. Avoid using Oregon pine for structural purposes as it won’t last.


Termites can be a major problem in timber structures. Look for any softwood that has been used to construct the deck or balcony discoloured or blistered paint termite mud nests or any build-up of soil around the base of the timber fine 'sawdust' around or below the timber.

Wet rot and moisture

Wet rot and moisture can cause timber to decay and fixings to rust. To help minimise damage:

protect timber exposed to the weather by regularly painting or oiling reduce dampness on the timber by not allowing water to sit or pool on the deck, for example keep trays or feet under pot plants clear away soil and other debris from bearers or joists and deck posts or supports fix any structural problems immediately.

Coastal elements

Salt, sand and wind make deck maintenance even more important. To help protect your structure:

apply oil-based paint to all exposed timber, such as bearers, joists and posts - decking oil alone may not be enough to protect against harsh coastal conditions. Protect metal structures with paint or adequate coating. If metal is left unprotected and starts to rust, it must be rectified promptly before it deteriorates further (image courtesy of

As with any home purchase, be sure to get a thorough pre-purchase building inspection to see whether the house needs any repairs If you have any questions, get in touch with us to discuss your Perth or South West requirements and to obtain a free quote.

Rotaru Building Consultants

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