Blog – Expert Roofing Advice & Tips

How to Tell the Difference Between a Roof Leak and Attic Condensation

how to tell the difference between attic condensation or a roof leak

It starts when you spot a brown stain on your ceiling or wall. That’s a sure sign that there’s excessive moisture in your attic. But, while many homeowners presume it’s a roof leak, the truth is that it could be attic condensation.

In either case, you need to solve the problem before you suffer serious water damage to your home and/or belongings. But a roof repair won’t solve a condensation problem and solving a condensation problem won’t plug a leak. So the first step is to learn the difference between attic condensation and roof leaks.

How to Identify a Roof Leak

You can generally spot water leaking into your attic through your roof by tracing the water’s path back from that brown spot you see on the ceiling or wall. Starting in the attic from approximately where the leak is showing on the ceiling, look along the bottom of the roof deck for wet patches.

Water can travel far after leaking into your roof because it always follows the path of least resistance, so the wet patch may not end up being close to where the brown spot is on the ceiling.

Ice dams in winter are a major cause of roof leaks, so be sure to check around the outside edges of your attic.

How to Identify Attic Condensation Issues

You can start to find out if you have an attic condensation problem without even going into the attic. Condensation doesn’t happen unless there’s excess humidity, or water vapour, in the air of your home. If your windows are foggy, or have water droplets on them on cooler nights, then there’s a lot of water vapour in the air.

The air from below the ceiling finds its way into the attic, especially if you don’t have adequate attic insulation.

In cold weather, when warm moist air from the living areas of your home gets into the attic space, it can cause condensation on the bottom of your roof deck, which should be as cold as the outside air. Ideally, a proper level of insulation will reduce the heat transfer into the attic and a good ventilation system will remove the heat and moisture that does leak into the attic.

While the condensation may freeze due to the temperatures in your attic, it will eventually thaw and end up being the source of water damage in your attic, or anywhere in your home.

If you’re not able to spot clear signs of a roof leak, there’s moisture throughout your attic, and/or your attic insulation is damp, it could mean you have an attic condensation issue.

Find Out For Sure

The potential for moisture damage from condensation is quite high in our climate. That’s why it’s so important that there is adequate attic insulation in Toronto and GTA homes. The best way to tell if you have a roof leak or a condensation issue is to get a roof inspection from one of our professionally trained technicians.


Please note: Chouinard Bros. does not recommend any homeowner complete repairs to their roof of their own. Our technicians are skilled at performing this work and have received years of training to understand how to complete repairs safely.

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