Velux windows on a 12 Degree Pitched Roof

owen2206 · 23 Apr 2009

We are currently doing an extension with drawings suggesting a normal Velux GGL Window.

The Builder and Architect have now said the strictly correct solution is to install the Velux flat Roof System, which we believe will be very unsightly particlarly from the upstairs windows.

I have been told there is little risk of problems (given the extension is four metres deep and south facing) and that Velux are being ultra cautious is recommending the 15 degree slope.

We are considering risking the GGL window as it is much more pleasing to the eye, internally and externally. We know this leaves the risk with us regarding the VElux guarantee, however opinions are extremely welcome.

freddiemercurystwin · 23 Apr 2009

Its a tricky one, it'll probably be ok, the shallower the pitch the more likely it is that wind driven rain can get blown up under the flashings, if the manufacturer is uncomfortable guaranteeing it below that pitch then you can't blame the builder/architect for recommending you use the flat roof versions. If we've got a job on site and the person paying for the build wants to do something quirky such as this that will invalidate a manufacturers warranty for example, we'd just write to them indemnifying us. That way if it goes tits up you can't complain. Your risk, your leak, your mess, your £££s!

Roofer · 23 Apr 2009

What pitch is your roof?

A GGL window can be installed in a 15 degree pitched roof.

If your roof is flat then the GGL is a definite no-no

freddiemercurystwin · 23 Apr 2009

Roofer said:
What pitch is your roof?

A GGL window can be installed in a 15 degree pitched roof.

If your roof is flat then the GGL is a definite no-no

Doh! His pitch is 12deg.

Roofer · 23 Apr 2009

Missed that

owen2206 · 23 Apr 2009

Thank you for the replies so far.

I know we would be taking the risk, with no comeback to the builder, architect or Velux, I was just wondering if anyone with experience has taken such a risk in the past and whether it paid off or not.

Thanks again

gaz116 · 24 Apr 2009

If any comeback would fall squarely on your shoulders, i would definitley go with velux`s specs.
If however the builder and architect are happy with you using it and want you to install it, let them know it`s wrong anyway before you fit it and explain you won`t be incurred with cost if it does leak.

I fitted a velux a year or 2 back into a very flat pitch roof (about 12 degrees if i remember) despite telling the builder it was wrong, and as of yet they have had no problems. But that certainly is no endorsement

jono_h · 28 Apr 2009

If you go for the Velux's make sure they are fitted as per the instructions.

You have to cut a hole in the felt to fit them, and then should fit a 'nappy' between the window and the felt. This maintains the secondary protection of the felt, so wind driven rain under the flashings will be caught.

The nappy stage isn't always done as it's a bit fiddly.

kjacko · 13 May 2009

Hi, my almost finished extension of 24sqm has a pitched roof of 12° and has 2 velux GGL windows in there measuring 1160x760.
Both have been fine since they were installed about 6 months ago, no leakage.
I would say that the flashing kit was a little more awkward to install due to the extra contouring involved at the bottom.
Both windows have survived some pretty fierce rain since installation.......with no issues at all. I know this because it was only recently that i actually boarded the ceiling, so nothing was 'hidden' so to speak.

Hope it helps.

Zebsport · 13 May 2009

We had exactly the same issue with our pitch at 13 degrees. We went ahead and fitted the velux anyway. Its been water tight for nearly 2 years, ours house is perched on the coast line and we get alot of wind driven rain and it still doesn't leak.
I spent an age fitting them carefully, and tiled in as tight as possible.
Hope this helps.

Fakroman · 18 May 2009

Hi - having senior moment and cannot remember if i already replied . worth looking at Fakro windows they can do a flashing for pitch from 10 degrees and have same sizes as velux .

edwardstock · 18 Apr 2012

why is it the diyers seem to think they know better then the manufacturer who has tested the product? !!
Get this, the rooflight will eventually leak if not installed in accordance with manufacturers requirements. The Building Control Surveyor will also not allow it as it would be a contravention of Building Regulations.

kjacko · 18 Apr 2012

deleted

catlad · 18 Apr 2012

I was offered three velux windows last week that had been taken out of a roof of an extension with a shallow pitch.

freddiemercurystwin · 18 Apr 2012

The threads' been dead for 2 years guys!

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Velux windows on a 12 Degree Pitched Roof

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