Roof leaking below Velux

[Happyunited]

I had an extension completed in August 2020 and not long after that a damp patch occurred inside under the velux. The builder came round and applied some silicone under the flashing as apparently, these can blow up in the wind (his words, not mine). A few weeks past and the problem is still there so he comes back. He starts lifting some tiles and noticed 3 tiles were broken (they were being overlapped so couldn't see them when looking from ground level. He blamed me for standing on them to clean the velux glass but everyone knows you can clean velux from the inside which I did. I don't have a window cleaner either.

Few months pass and I'm not noticing the problem getting any better but thought maybe I was being paranoid. This recent heavy rain has shown that the problem is still there as the damp bath has got even worse inside. I contacted the builder whos first reply was "someone has been walking on it again, I've already fixed it once". I told him that was nonsense, no one had been up there. Said if he finds broken tiles he will charge me blah blah I said what if there is no broken tiles (there won't be)? I got the whole "I've been fitting these for 20 years and I've never had one leak" the amount of first times on this job meant he must have been really unlucky.

Anyway he hasn't come back yet but I want to know where I stand. Personally, I think it's a velux install issue but I'm no roofer and he will struggle to admit that. Luckily I still owe him a small amount from the build so if he doesn't sort I'll get someone to sort it and deduct from the balance.

Thoughts?

thank you.

 

[noseall]

Thoughts?

What is the pitch of the roof?

 

[Happyunited]

Thoughts?

What is the pitch of the roof?

Pitch is 16.5 deg, thanks.

 

[noseall]

Pitch is 16.5 deg, thanks.

Not brill but ok. Has he put 100mm head-lap on those tiles and is there at least 100mm cover on the bottom Velux flashing?

 

[Happyunited]

Not brill but ok. Has he put 100mm head-lap on those tiles and is there at least 100mm cover on the bottom Velux flashing?

I honestly don't know and not quite sure. Is there a way for me to check this? will any more photos show this or is this only seen by lifting tiles?

I just want to be prepared if he tries to fob me off with some story. He fitted both these yet only this one is leaking, I guess they were both fitted the same way.

 

[noseall]

Is there a way for me to check this?

Have a look on the verge. Failing that measure how much tile is showing and subtract that from the length of a full tile.

You should be able to tease the bottom flashing up and see how much lap is on those tiles.

Its a stab in the dark though as I have seen those tiles work with very little lap, albeit with steeper pitches than 16.5 degrees. Smooth Marley Modern tiles will only go down to 17.5 degrees with 100mm head-lap as will Grampians. He's used the wrong tiles.

 

[Happyunited]

Is there a way for me to check this?

Have a look on the verge. Failing that measure how much tile is showing and subtract that from the length of a full tile.

You should be able to tease the bottom flashing up and see how much lap is on those tiles.

Its a stab in the dark though as I have seen those tiles work with very little lap, albeit with steeper pitches than 16.5 degrees. Smooth Marley Modern tiles will only go down to 17.5 degrees with 100mm head-lap as will Grampians. He's used the wrong tiles.

That’s the same tile used throughout on the 2 story side extension and small porch roof at the front.

I’ve just measured and the tile length is 420mm and between 310 and 325mm is showing so I guess that has the overlap.

I can’t touch the flashing until he looks at it as he will accuse me of tampering with it and causing the problem.

Does this still point towards a problem with the velux install?

Thanks for your help.

 

[noseall]

That’s the same tile used throughout on the 2 story side extension and small porch roof at the front.

Whilst using a tile that is rated minimum pitch 17.5 degrees on a 16.5 degree pitch is unlikely to be a problem, it does however void your roof in terms of manufacturer and Building Control aspects.

Does this still point towards a problem with the Velux install?

No not really. Everything looks ok.

 

[Happyunited]

That’s the same tile used throughout on the 2 story side extension and small porch roof at the front.

Whilst using a tile that is rated minimum pitch 17.5 degrees on a 16.5 degree pitch is unlikely to be a problem, it does however void your roof in terms of manufacturer and Building Control aspects.

Does this still point towards a problem with the Velux install?

No not really. Everything looks ok.

Building control have done their final inspection and I’m just waiting on the certs as I’m waiting on the elec certs for the job. They said it’s all approved. Thinking back now she did question something about the tile but said she would speak to the builder, she later said she spoke to the builder and everything was fine.

Should I query the tile used for the pitch of the roof? Excuse my ignorance but how does this cause the leak? Taking away the minimum 17.5 deg water should just run off one tile to the next and downwards and even if it gets between/under the tile the membrane is there as a backup.

 

[noseall]

water should just run off one tile to the next and downwards and even if it gets between/under the tile the membrane is there as a backup.

Correct.

Unlikely its a pitch problem but still a bit naughty.

Yes the membrane should do its job. We take a bit of extra care when dealing with a Velux roof in that the membrane should still be watertight even if water can get past the tiles, especially the zone directly above the Velux.

I have not seen how yours has been constructed, sorry.

 

[Laurieo]

Does the lead flashing under the toilet window overlap the tile much .It doesn't look long enough but could just be photos?. Should be like this so rain cant get blown back .

 

[Alastairreid]

Bottom left of the channel is all gunked up and the tile looks cracked.

 

[noseall]

Does the lead flashing under the toilet window overlap the tile much .It doesn't look long enough but could just be photos?. Should be like this so rain cant get blown back .

Whist in principle you are correct, showing an example of plain tiles (as in your image) v's concrete interlocking can be a wee bit confusing.

However, it is still the head-lap which is important, whether that be from the lead or from the tile above. I'm just not convinced that it's a lap issue although the shallow pitch and unsuitable tile is not a good starting place. Neither is the fact that the roof tiles and the felt membrane are BOTH failing.

 

[Happyunited]

Does the lead flashing under the toilet window overlap the tile much .It doesn't look long enough but could just be photos?. Should be like this so rain cant get blown back .

It sits 160mm on the tile all the way along.

 

[Happyunited]

Bottom left of the channel is all gunked up and the tile looks cracked.

The gunked up bit is where he put silicone on the first ‘fix’. Sorry what tile looks cracked?