Balconies hero


Enclosed decks and balconies are particularly prone to problems associated with damp, as rain can easily get in but not so easily get out.

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What's what

Balconies and decks are both outdoor areas adjoining your house. There are some general rules on safety that you must comply with whether you have a deck or balcony.

Whereas some decks and balconies are open to the elements and have open framing with timber slats, others have waterproof coating or membrane on the floor area and cladding underneath, so the framing isn’t visible. These are commonly known as waterproof decks. A waterproof balcony or deck can function as the roof of a room underneath.

All waterproof balconies and decks should be built with a slope to allow for water to run off to a collection point such as a down pipe. Preferably there should also be a secondary drainage outlet, such as another down pipe or an overflow, positioned below floor level. This is in case the primary water outlet becomes blocked.

A balustrade is a low wall around the deck or balcony designed to prevent people from falling over the edge. A balustrade or some other barrier is required on any deck or balcony where people could fall one metre or more.

The balustrade or barrier has to be one metre high to prevent falls and of adequate strength to cope with people pressing against it. You also need to make sure that there is nowhere on the balustrade where a child can get a foothold between 150mm and 760mm above the deck surface to climb over the balustrade or fall through it.

The NZ Building Code Compliance Document B1/AS2 gives descriptions of suitable barrier types and limitations. If there is a handrail on the balustrade it should be fixed to the side of the balustrade, not through the top where it could cause a leak more easily.


Common on apartments and ‘Mediterranean-style’ homes, enclosed decks and balconies require good design and regular maintenance to ensure adequate drainage.

If water gets into the timber framing it can rot away unseen, posing a serious safety hazard. Enclosed decks and balconies with monolithic cladding are also a risk factor in leaky buildings.

The main things to look for are:

  • Places where water can pool or get into the framing.
  • Insufficient fall.
  • Signs that water has already got in.
  • Damage to the waterproofing.
  • Cladding that is hard down against the deck.
  • Blocked outlets.

Water might get in through holes, cracks, loose cladding or fixings, joints that have separated (this is common with mitre joints), anywhere where the sealant has failed, and any area where water can pool.

Vulnerable areas include:

  • Any horizontal surface including floors and the tops of balustrades.
  • Where the balustrade meets the main wall, on the inside, outside and top of the balustrade.
  • The underside of a cantilevered deck or balcony or where it penetrates the wall.
  • Anywhere the cladding is penetrated (eg by pipes, handrail fixings, nails, bolts etc).
  • Joints.

Signs that water has got in include:

  • Rot (which is especially likely to appear where two materials are joined or anywhere water pools or can be trapped).
  • Cracks and splits.
  • Unusual movement in the balustrade or balcony.
  • Moisture staining or other visible water damage.
  • Musty smells.
  • Blistering or fading paintwork, or bubbling or peeling wallpaper.
  • Mould, moss or discolouration.

Maintaining the external cladding on your balcony

For general maintenance, wash the cladding regularly. You may be required to wash at specific intervals to keep the warranty valid. Follow the manufacturer’s recommendations.

Washing the cladding will extend the life of the materials. It’s particularly important for houses near the sea and where wall areas are sheltered from regular rain washing.

To wash, use a soft brush and low-pressure hose, concentrating on areas rain doesn't reach, like walls sheltered by eaves. For sea spray, moss and lichen, you might have to use specific cleaning products – check with the manufacturer of your cladding and your local hardware store. Rinse off any detergent residue with clean water.

As you wash, check for cracks or damage, particularly in internal corners or joins. Also check the paint coat and look for weathered (thin) paint, particularly on corners or exposed edges. It is very important to maintain the waterproof coating.

Don’t use a water blaster as they can damage claddings and force water through gaps and joints.

Cladding repairs/leaks

You may be able to make minor repairs to cladding yourself, but for any monolithic cladding system you should contact the manufacturer for advice on the correct products to use. If the cladding is a specialised system and less than 15 years old, it could still be under warranty. Again, contact the manufacturer.

If your house is a leaky building, you’ll need professional help.

Ponding water

Water ‘ponding’ on the deck or balcony floor can lead to deterioration of the waterproof membrane, especially at joins in the membrane. Water may enter the structure and cause rot if the membrane fails.

Ponding could indicate:

  • That there is not enough slope on the deck or balcony floor, or
  • That the drainage hole is blocked, or
  • Wind is stopping the water from draining, or
  • Sagging or settlement of the structure.

To deal with it:

  • Check the drainage hole and remove any debris.
  • Make sure the drainage hole’s outlet is at least 50mm below floor level
  • Check the deck or balcony floor after it has rained to see if rainwater drains into the outlet.
  • If water is not draining properly, and especially if water ponds against the house, get professional advice to assess options for improving drainage and check for unseen damage. Note a fully enclosed deck should have two outlets with independent overflows.

Water leaking into house

This can happen if:

  • There isn’t enough of a step down from the house to the deck or balcony and water runs back into the house. If it’s happening in your house, speak to a professional to assess the options for improving drainage from the deck. The Building Code recommends a minimum step down onto the deck of 100mm.
  • There is insufficient up-turn of the membrane up the wall.
  • Water is backing up and not draining away from the wall of the house.
  • The cladding is wicking water up.
  • There are gaps or cracks in the top of the balustrade, or between the ends of the balustrade and adjoining walls, that are letting in water.

If you suspect that any of these could be occurring contact a building professional.

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