Top 10 Causes of Building Leaks

At Strata Management Consultants, we know building leaks can be the cause of significant inconvenience and financial strain for strata property owners and tenants. When it comes to water infiltration, structural integrity, mould growth, and the deterioration of building materials come into question.

To prevent and effectively remediate these issues promptly, it is imperative to know and explore the top 10 causes of building leaks and provide insights into these specific water leaks. By identifying these top leaks through our strata consulting services and new body corporate management process, strata-tilted property owners can take proactive steps to protect their building structures and mitigate any dangerous strata risks associated with building leaks.

Here are the 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. Building leaks occur when there is an unwanted entry into the building’s interior, generally within roofs, balconies, windows, doors and so much more. These leaks can enter through cracks, gaps or material breakage, which compromises the integrity of the building.

And as strata professionals, the one standout is the number of strata properties dealing with building leaks. This list covers the most common causes, not necessarily in order of frequency. These are the common components that come up again in our assessments.

Balcony Leaks

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 the 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 balcony leaks. What could possibly go wrong?

The reality, as many apartment owners will confirm, is that balcony leaks are quite frequent. 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 Leak & Water Leaks

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

Depending on the cause of the shower leak, it can be challenging to fix. Showers are the ultimate test of the builder’s skill – any shortcomings in waterproofing, drainage, detailing etc can lead to long-term water leaks.

Roof Leaks, Flashings & Box Gutters

At least the roof is the plumber’s 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 in poor construction and roof leak detailing. Supported by a professionally changed strata manager, you can rest assured the roof leak can be arranged to be fixed.

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 for this top leak that everyone seems so surprised about.

External Cladding

Unsealed joints in exterior cladding are 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.

Door Leaks

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

Window Leaks

Timber windows are a frequent cause of window 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 for potential window leaks. Water damage where the sill meets the vertical timber frame is the most common window leak point.

Aluminium window leaks arise around the outside of frames, against the surrounding cladding if they are not installed correctly. They are much more leakproof than timber windows and they never rot! Problems with sub sills are frequent and difficult to fix.


These innocent-looking gadgets capture the rain from the roof and run it into the downpipe. Rainheads may seemingly be harmless, they do however have a track record for causing a lot of difficult-to-find leaks. So if you have mysterious leaks somewhere around rainheads 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, and water stained and there is a suspicion of rising dampness.

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, and fitting capping flashings may be part of the solution of these top leaks.

Basement Leaks

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 engineer’s instructions regarding 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 the basement leak and identify possible solutions. Difficult to come up with good workable solutions as access is very difficult.

At Strata Management Consultants, we are hopeful this short list will give you a picture of the most common building leaks – the ones that cause building owners and owners corporations a lot of grief.

If you wish to find an insightful analysis of your strata building, whilst reducing costs and changing your strata manager to address these issues relating to the top leaks promptly, then contact us today at 1300-917-848 or via

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.
March 18, 2023
Contributed by
Martin Speller
The Leak Professionals
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