Flat roof leaks : the possible causes, advices and prevention

Flat roof leaks: what are the causes, how to find them and how to repair them?


A water leak from the roof is an inconvenience you could do without! But it can take a long time from the time water starts seeping through your flat roof to the time you notice it inside your home. How can you detect water infiltration through the roof more quickly and, above all, how can you remedy it? The flat roof experts at Clinique de la toiture FCA give you some possible solutions! 

How to detect water infiltration?

Locating a water infiltration from the roof can sometimes be difficult because it is insidious; indeed, because of runoff, the spot where you see the leak may be very far from its point of origin. There are a few signs that should give you a better idea.

  1. Paint that curls up: whether on walls or ceilings, paint that curls or bubbles is a sign of water build-up, so you must find the source of the infiltration as quickly as possible to stop the damage.
  2. Cracks in the walls or ceiling: it can also be a sign of water leakage through the roof or window frames, for example.
  3. Stains, halos or traces of mould can also hide water infiltration.

Of course, the most telling sign of a roof leak is undoubtedly the presence of water on the floor or when you see water draining from the ceiling! In any case, you must act quickly to stop water leaks in your home, but also to assess the damage. Because a roof that has been leaking for a week is one thing, but it’s another if the problem lasts for months! In the latter case, significant damage may have been inflicted on the structure of the building itself (mould, rotting wood, etc.). 

What are the causes of water infiltration?

Water ingress in a building with a flat roof can come from a variety of sources, including the following. 

Damage to the roof or membrane

If the membrane covering your flat roof is torn or shows signs of wear, there is a high probability of water infiltration! Similarly, if the waterproofing joints are damaged or if they have been poorly made, water can seep in, even through a very small gap. 

Accumulation of water on the roof

New constructions require that there be no standing water on a flat roof for more than 48 hours. If this is the case, it must be remedied quickly as it represents a risk of infiltration. 

Accumulation of snow and ice

We all have images in our heads of roofs that have collapsed under the weight of snow or ice. While not as spectacular, significant damage can be caused to your building by the presence of too much snow or ice, including water infiltration. 

Condensation issues

An insulation or condensation problem in the attic can eventually cause water infiltration. How? By causing an accumulation of ice either in the attic or at the edge of the roof, which can damage the membrane, the structure of the building or simply run inside during thawing season.

Woman cleaning up water damage on the ceiling

How to prevent water infiltration?

Many preventive measures can help you avoid water ingress. First of all, roof maintenance is essential, and even more so if you have a flat roof. In fact, you must be on the lookout for any accumulation of water on your roof that could cause a leak, especially after a heavy rainfall. You must ensure that rainwater drainage is optimal on your roof and that it does not stagnate. If water accumulates frequently and remains there for a long time, it may be a problem with the roof slope, which you will have to adjust to promote better drainage.

Next, check the condition of your gutters and clean them twice a year, in the fall and spring. Gutters that are clogged or obstructed by debris, such as leaves or branches, will not allow water to drain properly, which could cause infiltration. If you wish to limit the risk of debris build-up, you can install gutter guards, which will prevent leaves and other debris from getting inside the eavestroughs.

Finally, regularly inspect the membrane of your flat roof to prevent water infiltration. Regular maintenance will not only prevent leaks and keep your roof healthy for years to come, it will also prevent you from having to replace your roof due to careless maintenance!

Clinique de la toiture FCA can help you with roof maintenance and repairs, as well as provide sound advice on how to maintain your roof! We serve Montreal and Laval.

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