Why water does not fall in a straight line
A roof is made of layers. Water that gets through the first one meets the next and follows the slope until it finds an opening. That is what makes a roof leak so misleading.
On a sloped roof, water slips under a shingle, runs along the underlayment, finds a nail or a joint in the decking, then runs down a rafter. It lands on the insulation, spreads over the vapour barrier and finally comes out at a ceiling joint or around a light fixture.
On a flat roof, the path is even longer. Water enters at a seam or an upstand, spreads through the insulation under the membrane and comes out at a low point, sometimes at the other end of the unit. The insulation can hold water for days before releasing it.
What we will ask you
Before going up, we ask questions. Your answers guide the whole search.
- How long have you been seeing water?
- Is it with every rain, or only with wind?
- Which direction was the wind coming from?
- Did it happen in winter, during a thaw?
- Was there recent work on the roof, such as an antenna, an air conditioner or a skylight?
The search, step by step
Inside first. We look at the stain, its shape and its position relative to the exterior walls. If the attic is accessible, we look for marks on the wood, such as dark streaks, rusty nails or compressed or damp insulation. Following these marks brings us closer to the entry point.
Then the roof. We start with the spots that leak most often, located higher than the stain. Flashing, vents, the chimney, valleys, skylights and edges come before the open surface.
The water test. When nothing stands out, we wet the roof section by section, starting from the bottom. One person watches inside. When water appears, the last section wetted is the right one. The test is slow, but it avoids repairing at random.
Instruments. On a flat roof, a moisture meter or a thermal camera helps locate wet insulation under the membrane. We can also make a small test cut to see the condition of the layers, then close it up.
Frequently asked questions
Can I look for the leak myself?
You can look into the attic from the hatch, with a flashlight, without going in. Spot the water marks on the wood and take photos. Do not touch insulation that looks like vermiculite. Do not go up on the roof. Leave that part to us.
Do you charge for leak detection?
Billing for leak detection varies from one contractor to another. Some include it in the repair, others bill the search time separately, especially for a water test. Ask us before the visit.
The leak came back after the repair. What should I do?
Write again to the contractor who did the repair, to us if it was our work, and describe the conditions in which the water came back. There may be two entry points, or the first repair may have targeted the wrong spot. This is where the written warranty matters.