What’s a good way to seal a flat concrete roof


My guess is that a long time ago there was a fire in part of our house and what was the top storey was capped and the floor replaced with thick slabs of concrete. This was then sealed over with bitumen and left as a flat roof, with traditional pitched roofs on either side.

Now, however, it seems something is failing and the roof has started to leak. It's always pooled water on the top to half an inch or so, but the last lot of heavy rain caused a stain on the ceiling underneath. That was easily redecorated, and I've made sure the drain to the gutter is properly free flowing now, but I don't want it to start again.

What's a good way to seal this roof so that doesn't happen again? I've used flash-band to patch up a couple of obvious cracks in the bitumen but I'd rather have something more permanent.

Best Answer

If you don't have a problem with water pooling any more, the real answer is probably to have a professional roofer look closely at the roof both on the inside and outside. The problem with a lot of roof leaks is that where the water shows up in the house isn't where it comes in. Water has an annoying tendency to run along internal beams and such, then come into the house far away. You can go over any edges with new tar and hope you catch it but in my experience this approach ends up being like playing whack-a-mole, you patch and wait for it to rain, then patch more and wait more, etc.

So I would say if you can do it yourself, look closely at the underside of the roof as well as the outside. If you don't find anything, a professional roofer is probably in order.