Top 10 Causes of Building Leaks

Building Leaks

Doing building maintenance work has provided some great insights about the buildings that we take for granted. The one standout is the number of buildings that leaks. This list covers the most common causes, not necessarily in order of frequency. These are the items that come up again and again.


Tiled balconies are a key feature of the modern multistorey building. Many of the new apartment buildings and residential homes come fitted with a small or large tiled area outside, located directly above living areas below. It seems like a great idea, outside living area, small garden location, view of the city etc. With the right construction and waterproofing, surely these things can be constructed without leaks. What could possibly go wrong?

The reality, as many apartment owners will confirm, is that they frequently leak. Despite the best efforts of builders armed with silicon guns and test equipment it is exceptionally difficult to stop balcony leaks. Neighbours below are the first ones affected, with collapsing ceilings or just constant water leaks every time it rains heavily. Property managers struggle to deal effectively with the problem.

Shower Leaks

Shower leaks – who would have guessed? Water leaking through walls, through tiles, under shower bases, through tap and shower fittings, through or around glass screens. The possibilities are limited but they are certainly persistent. Some features make showers much more likely to leak and when these are included in a multi-storey building the end result is that neighbour downstairs cops the water from above.

Depending on the cause of the leak, showers can be challenging to fix. Showers are the ultimate test of the builders skill – any shortcomings in waterproofing, drainage, detailing etc can lead to long term leaks.

Roof, Flashings & Box Gutters

At least the roof is the plumbers problem. They should be able to fix it easily – after all this is well proven technology. Well it used to be – but now most designs include such features as low angle roof sheeting, box gutters over living areas, and long lengths of flashing everywhere to protect the building. Undersized box gutters, buckled roof sheets, unsealed flashings etc can all lead to leaks that are difficult to diagnose as they often only leak in heavy rainfalls. These can also be very difficult to diagnose as it is often only peak rainfalls that show up the poor construction and detailing.

Balustrade Anchor Points

Along with tiled balconies came the need for balustrading which is fitted directly onto the tiled surface. Glass balustrading uses vertical stainless steel balusters that have to be securely anchored into the balcony structure. And the bolts go straight through the tiles, the waterproof membrane and down into the timber or concrete below. And the result is a difficult fix leak that everyone seems surprised about.

External Cladding

Unsealed joints in exterior cladding is a common cause of water leaks. When installed, most cladding products are sealed up or jointed in some manner. Weatherboards, sheet cladding, rendered brickwork, bricks etc should all be sealed up as part of the construction process. And mostly this is what happens. It is only after several years of weathering that joints start to come undone and cracks form. If the wall is protected by eaves then generally there is no problem. If no eaves exist then the cracks will leak water directly into the building.


Doors, door frames, sills etc are common causes of leakage. Timber or aluminium both have their own particular common leaks. Providing some weather protection to the door makes a huge difference to the end result. Verandahs, canopies, anything to stop rain from sheeting down the surface of the door helps – especially on the weather side of the building..


Timber windows are a frequent cause of leaks after the timber has started to rot and water gets in around sashes etc. The weather side of the building is the most exposed – so window damage on this side is the most common. Water damage where the sill meets the vertical timber frame is the most common leak point.

Aluminium windows can leak around the outside of frames, against the surrounding cladding if they are not installed correctly. They are much more leak proof than timber windows and they never rot! Problems with subsills is frequent and difficult to fix.


These innocent looking gadgets capture the rain from the roof and run it into the downpipe. Seemingly harmless, they do however have a track record for causing a lot of difficult to find leaks. So if you have mysterious leaks inside somewhere around a rain-head there is a good chance that is the culprit.

Old Brick Walls

There are a number of buildings we have looked at where a major renovation has been constructed up against an existing old brick wall – usually a common wall between two existing properties – often with loose and damaged bricks. The brick wall inside the building may be damp, water stained and there is a suspicion of rising damp. All investigations have led to no result. The answer is frequently that water is finding its way down from the top of the wall, or the vertical face of the wall and running out lower down the wall. Closing up damaged bricks, fitting capping flashings may be part of the solution.


Basements are usually constructed to try and keep water out of the building by draining it away before it enters the building. If the builder did not follow the engineers instructions re drain levels, waterproofing and detailing then basement leaks will result. Slotted drains fitted behind walls have to be fitted at the right level and run to pits so that water can be pumped or drained out of the building somehow. Each situation needs to be carefully looked at find the cause of leak and identify possible solutions. Difficult to come up with good workable solutions as access very difficult.

Hopefully this short list will give you a picture of the most common building leaks – the ones that cause building owners a lot of grief.

Martin can be contacted on 0403 139 994 or via should you have any property repair needs.

The content in this paper is intended only to provide a general overview. You should seek professional advice before acting or relying on any of the content.

The contents of this article or website are only intended to provide a general overview of the topics discussed. The author of this article makes no representations as to the accuracy or completeness of any information and the information is not intended to constitute investment, legal or professional advice. You should seek professional advice before acting or relying on any of the content. This article does not contain references to any specific company, organisation or individual, unless expressly specified.
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