New extension leaking Velux windows help

[blake7]

Long time lurker in need of some input off you roofers please

I had a new extension built with two Velux windows put in with EDZ flashing kits. Prior to holes being cut for windows, with just felt and baton it was sound when it rained with only a little ingress due to the flashing not being done where it meets the house.

Since the windows were put in, I keep getting the same damp patches on the ceiling. They are always in the same place (in between joints on plasterboard) and dry out within a few hours. At first I wondered if it was condensation but I have had a camera up in the gap and all looks fine. We had 4 inches of snow last week which sat in the roof for 4 days with no damp patches at all, but as soon as it thawed they appeared.

It's random, in heavy rain it will be bone dry then in drizzle the patches appear. There's one patch about a foot down from the bottom of the windows bang in the middle of the two, another again in between about a foot down from the top and then another again about a foot from the top between one window and the end wall. The reveals are bone dry.

I'm at a loss as to why it is happening and I'm fed up of climbing on the roof to see if I work out what's going on

Pics below if anyone can offer any advice, it would be appreciated.
View media item 87956 View media item 87959 View media item 87958 View media item 87960 View media item 87961 View media item 87962 View media item 87963 View media item 87964 View media item 87965 View media item 87967 View media item 87968

 

[freddiemercurystwin]

What's the pitch?

 

[blake7]

I Think it is just about 20 degrees, but not sure how to measure it to be honest.

 

[freddiemercurystwin]

Hmm, looks like a tidy install, Using the brickwork as a guide I work the pitch out to be 15.2° which is bang on the limit for the tiles and the rooflights. So over to the roofers etc for their expert opinion!

 

[blake7]

Well the EDZ is for 20 degrees as min, so I'm wondering if the EDW should have been used as that goes down to 15 degrees.

I just can't work out how it is getting under the felt and onto the plasterboard. You would think it would be coming in the reveals if anywhere.

 

[freddiemercurystwin]

Gah! My bad, yes EDZ is only good for down to 20°. That's gotta be a suspect there.

 

[blake7]

I wonder what the difference between the two actually is? May ring Velux Monday and see what they say.

Thanks for your input matey.

 

[blake7]

Just used an app for my phone on the roof. Sat the phone on a long level and it gave 15.1 degrees.

 

[catlad]

What overlap has the tile been laid at it should be 100mm at that pitch.

 

[blake7]

Just measured it and it's 100mm

 

[terrypin]

It's unusual that the felt would let water penetrate in so many different places.

Check the lead under the window and along the brickwork.

 

[noseall]

I've got that roof at about 15 degrees too.

How are things at the top (high) end of the roof i.e. lead flashing etc?

 

[blake7]

All the lead work is sound, my dad is very much a belt and braces man. Felt is turned up under the lead etc so 100% certain it is not coming in there.

It's totally baffling why/how it is coming in, the only explanation I can think of it simply that it is the wrong velux flashing and it is getting under it somehow and then down onto the insulation below and then through the plasterboard.

Looking on the net, we did not use any extra felt around the cut out for the windows and I did not use the velux optional felt collar also.

Prior to cutting the felt for the windows, we had rain on the felt and baton and no water ingress at all.

I've been up there so many times to look and it really makes no sense. If it was an awful botched job I could understand it but it's not.

I'm thinking, remove ties around the windows, remove EDZ flashing kit, fit velux felt collar then fit the EDW flashing which is for 15 degrees, then re-fit the tiles and hope that the issue.

 

[blake7]

Looks like this chap had exactly same problem as me. Same tiles and he even used the EDW flashing but still had leaks.

//www.diynot.com/forums/roofing-guttering/velux-windows-leaking-after-installation.338104/

 

[yorkie1969]

I agree with my colleagues here, it does indeed look a tidy job. As a leadworker I sometimes find in cases like this that the lead does not go into the joint a full inch (25mm) which it needs to if it is going to prevent capillary action. Also worth checking that the side laps are adequate, they need to overlap by at least one full roll or a minimum of 4" (100mm).

Hope that helps.