(Almost) Everything You Need To Know About Building Water Leaks

A leak in a commercial building, school or residential complex can be costly. It can cause thousands of dollars in damage, pose health and safety risks and lead to lost revenue.

Even the smallest of leaks can cause significant damage, but while we can all spot a burst pipe or an overflowing toilet, some leaks are much more difficult to detect and resolve. Leaks from upper-floor bathrooms, for example, cause damp patches on the ceiling of the lower floor and result in mould and structural damage. These leaks typically occur as a result of a low-quality or damaged waterproofing membrane (so it’s important to take care of minor concerns before they worsen).

To prevent the worst from happening, keep your buildings in excellent condition and call in the building maintenance experts at the first sign of a serious water problem. In this blog, we’re going to talk about the signs and causes of leaks, as well as how to go about building leakage repair. 

What are the warning signs of building leakage?

  • Musty odours

When absorbed into building materials — i.e. carpet, woodwork, drywall — the moisture will create a strong, musty smell.

  • Mould

Moisture allows mould to grow… and it can grow on almost any substance if moisture is present. 

  • Discolouration and wet stains

Off-colour walls, water spots and copper stains on ceilings and walls indicate a hidden water leak. 

  • Warping walls

When water is absorbed by the drywall, plasterboard or whatever is behind the wall, it will swell and “warp” the wall. You will either see cracks or peeling paint as a result. 

  • Buckling or sagging floors

Water under the floor can cause the floor to detach from the substrate (foundation) and either curve upwards or begin feeling “spongy” underfoot. 

  • Unusually high water bills

If water consumption habits haven’t changed but your bill has increased, it could be that there’s a water leak somewhere in the building.

  • Very low water pressure 

If the water supply is normal but you experience low water pressure, there’s either a problem with the water main or the pipes in the building.

  • Accumulated water

Bodies of water, wet carpets or areas of standing or pooling water are the most obvious sign of a leak in the building.

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What are the most common causes of building water leaks in schools, commercial buildings and residential complexes?

  • Roof and balcony water seepage

A leaky roof is a serious structural problem that poses several health and safety risks. These leaks could be caused by environmental damage (wind, rain, hail, heavy snowfall), low-quality roofing materials, clogged gutters or improperly installed or secured roof components, i.e. roof flashing, pipes, drains or valleys (where two sloped sections of the roof come together).

Skylights can also contribute to the problem, especially if they’re not watertight or fitted correctly. 

  • Improper specification 

Every construction project is based upon drawings and specifications handed to the contractor — this includes what to build and the quality of the materials to use. However, while the materials may meet the specified size and colour requirements, they’re not strong enough or resilient enough to weather day-to-day conditions.

As a result, issues only become apparent after construction. These are “latent defects”. Examples include inadequate foundations causing subsidence, under-strength concrete or misplaced reinforcement and defective basement tanking leading to water penetration. 

These defects are also progressive — they get worse over time as they are exposed to the general wear and tear of use and/or natural forces. For example, pavement that gives way due to the deterioration of the substrate or roofs that use the wrong flashing material. 

  • Defective pipes and/or changes in temperature

Broken water supply pipes and deteriorated sewer lines are the most common causes of water damage in a building. They can easily burst due to: extreme changes in temperature, high water pressure, corrosion, tree roots and even foundation shifts. 

If ignored for long enough, they can wreak havoc on an entire building or school — mould, flooding, warped and stained walls are just a few of the problems they can cause. 

  • Clogging 

Hair, grease, food, toilet paper — there’s no shortage of things that can cause clogs in drainage. If a clog causes the pipe’s internal pressure to increase, the water needs to find another way out of the pipe. If the pipe is damaged (or there are loose seals), it will force its way out or cause a burst.

Once the clogs form, an easy way to detect them is to see how quickly your sinks, baths, showers and toilets are draining. If it’s much slower than usual, call in an expert to check.


How can you repair building leakages?


For smaller, less complex leaks, there are several things you can do yourself. First, find the source of the leak by inspecting the underside of the roof. Trace the water’s route from the damaged area to the entry point. 

Once you’ve found the entry point, simulate a downpour with a garden hose so you can see how your roof would (or wouldn’t) withstand it. This approach requires two people: one inside with a torch to check areas for leakage, and the other on the roof, wetting it section by section. Also, look out for cracks, broken tiles or breaks in the flashing material. These are all common signs of damage. 

After finding the points of weakness, it’s time for the building leakage repair. There are a few methods you could use, depending on the construction of the roof. The below focuses on metal (colorbond roofs):

  • Flashing

Common roof leaks are caused by rusted, damaged or missing roof flashings which allow water to push up under roof sheets. We normally see this type of leak when heavy downpours are combined with high winds. Sometimes these leaks are hard to diagnose. 

  • Broken down roof sealants

Roof sealant such as silicone breaks down in the sun, and over time it stops protecting water from getting into areas it shouldn’t be going. Regular roof inspections and sealant replacement programs prevent costly water ingress repairs. 

  • Dektites

The pipes that come out of your roof have a rubber seal around them called a “dektite”. Over time, the rubber breaks down, and allows water in. Usually, we see water in bathrooms and kitchens (where the pipes originate), as the water runs down the pipes into the ceiling underneath. Regular roof inspections and dektite replacements often save costly water ingress repairs.


First, start by determining if the leaking is happening within the building. Turn off the water completely and check the reading on the water meter. Check back after a few hours: if the number has risen then a leak is most likely causing this. Also, check to see if there are any broken sprinkler pipes inside and if the drainage is working optimally to reduce water levels.

Next, check the gutters and downpipes. If they are clogged, clear them out and install gutter guards or undertake regular gutter cleaning from a company like Guttersucker. Additionally, scrape off and replace any old caulking to ensure it isn’t capturing water and allowing it into the walls. 

However, if the leak is coming from the inside of the building, consider asking a professional to help as you will need to cut out the wall, concrete and pipe to replace what’s damaged. 

Underground car park areas

Water leaks in underground car parks are very common. Most underground car parks are designed to take a certain amount of moisture, however when water is coming through the ceiling and walls regularly, you know you have a problem.

Repairing underground car park leaks can be technical and costly, as it often relies on sealing where the water is coming from. If the water is coming from underneath tiles from a podium above, or a retained area of earth adjacent to the building, repairs may not be economically viable.

There are temporary and longer term repair options available, such as negative waterproof membrane, epoxy injections and silane sealing of tiles. These are maintenance systems that will slow the water ingress and will need to be completed at regular intervals. 

Bringing in the experts 

While some building leakage repairs can be undertaken yourself, internal leaks — if not dealt with quickly and properly — can be devastating. 

The best way to mitigate problems is to enlist professionals to regularly maintain your buildings. While these professionals can work on any type of building — commercial, residential or academic — it’s worth checking they’ve got experience in these environments. That way you’re sure repairs will disrupt your day as little as possible. 

When should you bring in contractors? 

  • For complex leaks that need immediate resolution

Small building leaks can be repaired relatively easily, but for instances where the structure has deteriorated or the leak is larger than initially anticipated, it’s best to bring in a team of contractors to manage the problem. They’ll be able to identify the issues, propose a plan of action and deliver a solution quickly.

  • When health and safety is a major concern

Ensuring the health and safety of the people inside your buildings is crucial. This is especially true if you operate a school, as children are naturally curious and may not heed warnings. Leakages can cause structural damage, slips, falling debris, electrocution and the like. 

  • When you might make the problem worse

If you attempt a complex building leakage repair on your own, you may end up doing more harm than good and paying for it twice. Instead, get it right the first time by enlisting contractors. They’ll provide a fair price and outline what they can do to help. 

At First Response, we specialise in building maintenance. This includes building refurbishment, painting, landscaping and grounds maintenance, refurbishment, carpentry, electrical systems installation and design, roofing repairs, flooring, plastering and more. This means that no matter what kind of building leak you have, we have the experience and expertise to deliver. 

If you want to find out more about our services and get a tailored quote, please click the button below. We’d be glad to help. 

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