Can blown external render cause a roof leak?

BigT · Post by **BigT** » Wed Feb 19, 2020 4:53 pm

I have water running into my new conservatory on the wall adjoining the main house, the roof has been checked and is dry, so it looks like its from the outside wall of the main house. New flashing was installed when the new solid roof was fitted, but the supplier is now trying to blame blown render on the house wall, saying the water is between the render and the wall, but how can this be the cause?

dewaltdisney · Post by **dewaltdisney** » Wed Feb 19, 2020 5:15 pm

Water always find the easiest way down and it is possible to drip down behind render. The same happens in showers through broken grout where water gets behind the tiles and causes issues. Having said that, the water has to get in in the first place and I would have a good look over the wall in question, use binoculars if necessary. Have you any leaking or blocked gutters where rainwater is overflowing and running under the gutter? Is the caulk surrounding and under the windows intact and are they properly sealed? Is the new flashing actually sound and is the roof draining and not puddling? Have a look at those points first and see if you can make out how the water is getting in.

DWD

BigT · Post by **BigT** » Wed Feb 19, 2020 5:49 pm

Thanks, I'll do that in daylight tomorrow, but shouldn't the flashing be cut far enough into the wall to catch any water between the wall and render?

dewaltdisney · Post by **dewaltdisney** » Wed Feb 19, 2020 8:56 pm

Sometimes they use that stuck on flashing which does not always bond properly.

DWD

ayjay · Post by **ayjay** » Wed Feb 19, 2020 9:14 pm

If rain is getting through the render, it could end up way behind any flashing, just one dodgy perp joint will allow it to come down the cavity until it finds a way out into your new conservatory. I'm not saying that that's what's happening, but it could be, it's almost impossible to second-guess water correctly every time.

BigT · Post by **BigT** » Thu Feb 20, 2020 1:44 pm

Thanks guys, the flashing is cut into the wall but is several pieces, so ayjay may be right. I still think it hasn't been cut in far enough and for a new build I expected it to be watertight. They are coming again so have to wait and see their thoughts, but good info here to help my case.