We’ve had 3 new velux installed in our new extension.
Our builder used ggu mk04 velux with standard flashing. 2 of them are leaking constantly, from between the bottom opening and the frame, even when it’s not raining there is water trickling through the opening and frame and running down the wall. There doesn’t seem to be anything coming from between the wall and frame. One only seems to leak when it’s raining with the wind blowing in a particular direction.
When I’ve done some research I’ve found out that these windows should only be fitted on 15 degree or more pitch roofs. I’ve measured ours and it’s 13.8 degrees.
I’ve looked into the velux flashing for low pitch roofs, is this our only option?
I’m going to go back to our builder and he’s going to have to change it, but as he didn’t put the right ones in the first place I’d like some more opinions please!
Thanks
Thanks for everyone’s responses. We’re getting a roofer to come and have a look and then we will speak to our builder. He’s used Redland regent tiles so he must have noted the low pitch.
I’m so annoyed by it. We said to him before he started we could move the upstairs window up a few bricks to get a steeper pitch if required and he said no. Or if he’d said we needed a rubber roof we’d have had it gladly if it meant we were completely watertight! The extension was finished off just before Christmas, I’m so fed up the velux etc may need to come out!
Are you a tradesperson and able to answer this question?
You can’t get a flashing to go down that low unfortunately it’s either lose the windows and hope you don’t get further leaks else where or treat the roof as a “flat roof” and change the hole roof to a flat roof covering like rubber or fibreglass or 3 layer high performance torch of felt etc and install velux flat to pitch roof window adapter to get the window to the correct pitch so it doesn’t leak this way you keep the existing window frames and just need to buy a new flashing and the adapter works out cheaper slightly not much though.
I’d be interested to know what tiles his used for the extension roof as a hole as I can’t think of many that go as low as 13.8 degrees your most likely relying on your breathable membrane to keep the water out not the tiles.
Your probably find in 2/3 years time when your breathable membrane loses its effectiveness your have multi leaks all over the extension this is why you would get specialist in for each section of the build so you know it’s done correctly.
I never advise having a pitched roof below 15 degrees ideally 18/20 degrees is the lowest but sometimes you have to go lower due to windows etc.
it just causes issues the lower you go even if you use tiles that go down to 15 degrees your really pushing it on that tile limitations and I won’t personally guarantee a roof under 18 degrees too much risk to factor into.
I hope you get sorted
Not the sort of news you wanna hear this time of year.
Regards
Frankie
BT Roofing Services
Most definitely a combination of all, we are certified velux installers and come across this issue all the time, problem is its very difficult for the customer to accept. Most definitely the pitch and/or the installation is incorrect, stick to what the minimum pitch (roof degree) is for the product, ensure the flashing kit is correct for the type of tiles being fitted, ensure window is sitting level, If the pitch of the roof is too shallow for instance 15° then really you will have problems with all the elements. Your builder really should have checked the pitch prior to proceeding.
Velux windows arent to be used on any less than 16° pitch roof nor any tile or slate as the rain water cant get a fast enough run off then the problems arise you cud alter the velux opening raise the higher side by 4" and that will change the velux window pitch and dress around with a lead flashing but wont solve any leaking issues where the roof pitch itself is 13.8°.... it may be a case of remove all tiles, batons fit plywood and torch on felt it but still need to have the top end if velux raised to give you a higher pitch.. hopefully this is of help to you...
Jimmy @ oaklands joinery services
One thing you haven’t mentioned is which tile has been used on the roof. We have this problem over and over with single storey extensions. Yes velux rooflights are only guaranteed to 15 degrees but you could also have the wrong tile too. Sometimes its not always the builder/roofer its the architects design fault. Check the tile used would be your next move 👍🏻
