Blenheim Ontario Flat Roof Leak Causing a Basement Flood

This week we are out in the countryside, in Blenheim Ontario. We are at a beautiful Spanish style residential home with a flat roof. The client contacted Legacy Flat Roofing as they were having a lot of issues with their roof, so they called us in to locate the roof, and find the most cost effective and professional flat roof repair to stop leaks.

The client reported water coming into the house, and flooding the basement. It wasn’t just a few drips either, the client reported literally buckets of water leaking into their home. This was a really bad leak that needed urgent addressing. This job took more than a day as we had to take some time to locate what the actual cause of the roof leak so we could properly address it.

The roof system was a 2ply modified bitumen built up roof system.

We could tell from our initial investigation that this wasn’t a pinhole leak, something more significant was going on, like some metal detail was missing, or there was a larger hole letting in water. It took some time to find this one, fortunately we have had years of investigating flat roof leaks, and know some of the warning signs to look out for when looking for a vulnerability in a building envelope.

You can see in the video where the ceramic roof tile transitions to the roof membrane, where the angle meets the flat section. There are roof drains, and what looks like mastic just put everywhere, no doubt trying to find the leaks in the past without success. The client did say roofers have come in over and over again to try to fix this issue. It seemed like mastic was put over every part of the roof details, like the skylight and drain sections.

There was standing water in that section, so we asked the homeowner if they were getting any water in the home, which they said they weren’t, only during heavy rains. So we kept looking for another section. It wasn’t the chimney either as the volume of water was too great to come from there.

We ended up finding the detail, it was where you have a sloped roof tied into a flat roof. This is always a very tough detail to water proof, you have a lot of different angles, corners and materials coming together in the one spot. We removed the metal flashing details, and noticed a lot of wet wood around the section. We also noticed that the cap sheet was no longer well adhered, so when water comes down the tiling during rain, it runs right off into the sections where the membrane has come away. It was all very wet and deteriorated, which is a huge sign that water is a big issue there. We were looking for an open flat roof seam the whole time, and I think we hit the jackpot.

We are going to fix that detail. We aren’t going to tear the whole thing apart, we are going to clean the area up, and use alsas with a dual application, and then put all the metal flashing back in place, caulk the sections and create an area where water sheds away from that area and out of the home! We are also going to do some seam sealing work on the siding to keep water out, as even though its under the overhang water is still quite active around the whole wall section.

You can see the repair we completed. We also put another layer of mastic over the area, as we weren’t sure how well of a job the previous roofing contractor did, how well they terminated the membrane seals, so for good measure we added another layer of protection. We don’t always use mastic, but wanted to be doubly sure.

We removed one panel of the soffit. We could see that there was staining, so water is running down the underside of the soffit. We wanted to remove that one panel so that water wouldn’t go all the way to that seam and cause any further issues. It also helps us see how water is behaving up inside the roof, as the clay tiles may be leaking.

The homeowner definitely needs some roof work done at some point, but we were just trying to keep them dry until then.