Velux leak, 12 degree roof

[Ross Morrin]

3 years after building an extension planned with a 16deg roof, we got leaks through the wood at the bottom end of two of our velux windows.

I spoke to velux, and sent them photos, and they said all looked in order. Before they came out they asked me to check the roof pitch - 12 degrees.

Builder is now out of business, so I'm shafted there.

Velux wouldn't specifically tell me why my window would leak below 15 degrees, does anyone know?

 

[freddiemercurystwin]

Because in the thousands of tests Velux have done they've found that they leak below 15°.

 

[Ross Morrin]

Thanks Freddie. What I really meant was where / how do they leak?

 

[freddiemercurystwin]

Water will be able to seep through the seals/gaps of the flashing components in particular weather conditions at such a low pitch compared to 15°, capillary action will probably play its part, I dare say the test engineers at Velux know but the bods in the tech department at Velux are not privy to said information - they don't really need to know.

 

[garyo]

If there's that much moss on the tiles then there may well be moss on the drain channels that'll be down either side of the velux just underneath the tile overhangs. It's worth getting a ladder under the velux, sticking your head/shoulders out, and give it all a once over for any obvious obstructions.

If you're keen you could even get a hose pipe and soak localised areas to establish which part of the window design is struggling at 12 degrees, and assess whether you can do anything about it - i.e. a choice bead of silicone to help direct the water in a particular direction, or a judicious adjustment of some flashing.

 

[datarebal]

Firstly open the velux and check all screws are fitted. (seen It)
Looks like a cut tile is fitted which cant be helped. Make sure these are not fixed through the side flashings
clear any moss,

 

[catlad]

Velux flashing kits are not all 15° some are 20° some are 25°
The one you have looks like 20°

 

[noseall]

3 years after building an extension planned with a 16deg roof,

Builder is now out of business

Did the builder just arbitrarily decide on a 12 degree pitch or did the constraints of the job mean he had no choice? Why was it designed this way? Why were Velux even fitted?

 

[Ross Morrin]

Just poor builders workmanship I think, was designed to be 16 degrees.

Think I've identified the route in. The water is appearing from the rubber seal between the wooden frame and the glazing.

When I was outside I notice a slight pounding of water at the bottom end of the window, where the side trims are, and open ends in the trims. These open ends were filled with moss. I'm guessing this was my problem. Don't know why this was open ended?

 

[noseall]

Just poor builders workmanship I think, was designed to be 16 degrees.

I'm finding it difficult to understand why any builder would opt for a shallower pitch when almost every GF extension is pushed as far out as possible to gain as much space as possible and consequently is screaming at the builder to pinch as much pitch as possible.
Is it possible to see a picture of the roof abutment against the house?