extension query re 40 square meter

delim9

I'm just wondering if someone could clarify something for me. I am currently building an extension within building regulations of 40 meter squared. When I measured it came out approx 2 meters more than what the builder has measured. The builder says this is to accommodate the roof as it has to have a 23 degree pitch to accommodate velux windows. All sounds ok but my boyfriend is very skeptical regarding this. I am completely clueless but would like to have some sort of idea either way before meeting the builder later. Any help/ advise would be greatly appreciated all getting a bit stressful and tense!

Calahonda52

Internal or external measurements for the 40?

based on your post, I don't buy the argument as presented?
Describe the roof: lean to, A roof or wha?

delim9

lean to roof. It's 40 square meters measured externally. they have poured the foundation concrete already

Gumbo

delim9 wrote: »

I'm just wondering if someone could clarify something for me. I am currently building an extension within building regulations of 40 meter squared. When I measured it came out approx 2 meters more than what the builder has measured. The builder says this is to accommodate the roof as it has to have a 23 degree pitch to accommodate velux windows. All sounds ok but my boyfriend is very skeptical regarding this. I am completely clueless but would like to have some sort of idea either way before meeting the builder later. Any help/ advise would be greatly appreciated all getting a bit stressful and tense!

delim9 wrote: »

lean to roof. It's 40 square meters measured externally. they have poured the foundation concrete already

What does the drawing show?
Usually you get the drawings and then the pitch of the roof has to match but in many cases, the pitch will be too steep or shallow for the velux to go in with driving rain, wind lift etc

Its very possible the builder had to move the back wall in/out to allow for a roof with adequate pitch but he should have confirmed this with you or your architect first.

The 40 Sq. M is an internal measurement too but there are other factors to consider such as distance to boundary, facing windows etc

Calahonda52

I don't see any magic number requiring 23 degrees here
http://www.velux.ie/~/media/marketing/uk/brochures/installer_handbook.pdf
I misread the first post, the 2m and the 40 are unrelated so time to sign off

Gumbo

Calahonda52 wrote: »

I don't see any magic number requiring 23 degrees here
http://www.velux.ie/~/media/marketing/uk/brochures/installer_handbook.pdf
I misread the first post, the 2m and the 40 are unrelated so time to sign off

I've always been told that the min pitch I should put a roof on to allow for velux installation is 18 degrees. Anything worse than this and the rain can blow In Under flashings etc

Is there any truth to this?

Charlie-Bravo

IIRC standard roof tiles need 22.5 degree pitch at 75mm lap (slating and tiling practice). This can be reduced by creating a longer lap under advisement of the tile manufacturer's recommendations. You can get tiles which will do 12.5 degrees (can't name brands as a recommendation on this forum). For the Velux windows, these can be pitched as low as 15 degrees. I would be very reluctant to have any roof below 17.5 degrees due to prevailing winds blowing rain back up under tiles or flashings.

delim9

He didn't provide any drawings. I asked but didn't receive so I've had to get an engineer involved now. He's agreed to come out to 37m squared with a hipped roof (cost of roof I will have to incur) now but is saying this will mean that the velux windows in the roof will have tunnels and won't be vaulted?? Another alternative is a flat roof perhaps. Also is saying that because of the boundary he might have to make the extension a bit narrow at the end.

Gumbo

delim9 wrote: »

He didn't provide any drawings. I asked but didn't receive so I've had to get an engineer involved now. He's agreed to come out to 37m squared with a hipped roof (cost of roof I will have to incur) now but is saying this will mean that the velux windows in the roof will have tunnels and won't be vaulted?? Another alternative is a flat roof perhaps. Also is saying that because of the boundary he might have to make the extension a bit narrow at the end.

It's not his job to have the drawings, that's your job as the home owner.
You should have had an engineer from the start too. Who else was going to design any structural elements?