We got a call from a commercial building in Mission that had a leak coming through the ceiling. On a roof like this, finding the leak is most of the job. It is a big flat roof covered in river rock, and the water was getting in somewhere under all of it. Here is what we found, and how we ended up tracking down not one leak but two.
The problem
To even start looking, I had to clear the leak area. This part of the roof sits at a low point, so it ponds water, and there was a lot of standing water sitting on it. I ran my pump and got most of it off, then started shovelling away the river rock ballast to see the membrane underneath. That is when I found the first problem: some old patches that were lifting. The edge of one had let go, and water was running straight in under it.
Once I dried the area off, the lifting edge was easier to see.
Getting the area dry
The tricky part with a low spot is that the water keeps flowing back toward the exact place you are trying to fix. I pumped off what I could, but I could not get all of it, so I used LeakSeal to hold the water back and keep it away from the repair while I worked.
The repair
With the area clean and dry, I re-patched the spots where the membrane had let go and ran lap sealant around every edge so water cannot creep back underneath.
While I was up there, I also cleaned the other existing patches and sealed around them with fresh lap sealant. They were still holding, but a bead of sealant around the edges keeps them holding a lot longer. It is cheap insurance on a roof this size.
The second leak
There was also a second leak on the building. Another trade had been working up there and poked a hole clean through the membrane. This roof is a thin rubber EPDM membrane, and it does not take much to puncture it. The catch is that it is all buried under river rock, so I had to shovel the ballast around the area and hunt for the hole.
Here is what I was looking for. That tiny puncture in front of the broom is the whole leak.
I cleaned the spot and patched it with the proper membrane, with lap sealant around the edge. After that, the leaks stopped.
Why leaks like this are hard to find
On a ballasted commercial roof, the spot where the water drips inside is often nowhere near where it is actually getting in. Water finds the hole in the membrane, then runs along the insulation and the vapor barrier below it, and it can keep running along the metal Q deck until it finds an opening and drops through. So the stain on the ceiling might be twenty feet from the real leak. That is why this work is so labor intensive. There is no shortcut. You shovel the rock off area after area and inspect the membrane until you find the hole. Knowing how the water travels is what makes the difference between chasing a stain and actually fixing the roof.
If you manage a commercial flat roof and you are seeing a leak, do not wait for it to spread. We repair commercial and EPDM roofs across Greater Vancouver and serve Mission and the surrounding area. You can also read how we handled a residential EPDM flat roof leak in North Vancouver. Call 778-389-5564 for a free estimate.