Extract through a flat roof ?

[40 watt spark]

Got a job on at the mo, ground floor single storey side extension consisting of bathroom, bedroom, & a 'kitchenette'/lounge.

Builder has just called to tell me that the owner has now specified an oven and hob in the kitchenette (previously only going to be a microwave, kettle & toaster). LABC have approved this, so the room now requires 60L/Sec extract to meet part F.

Now problem is, kitchenette area is in centre of the extension (6m to either end of building from extract point), the side (outside) wall would vent into next doors garden so thats a no no, and the build has a flat roof. Can't fit a ducted fan as no room (celotex insulation to meet part L) above ceiling, surface ducting would have to run against the joists, so even the thin stuff would look awful

Only option I can see is to go straight up through the flat roof..... now never had to do that before, has anyone had to do similar ? any suggestions ?

 

[RF Lighting]

It can be done, but you'll need a roofer to make sure the opening remains water tight.

Is the roof already on the extension yet?

 

[40 watt spark]

Yep roof is on, I'm just starting 1st fix. Adding the oven hob is fine that I can accomodate, its just this extract that has me worried.


Edited for spelin

 

[Lectrician]

It's done more often than you think.

The usual tack is to leave venting to the builders....

 

[Buzx1313]

when you buy a roof fan it will come with dimensions for an up stand which the fan will sit on, and the roofer can install his flashings.. if your using a roof fan that is

 

[40 watt spark]

LABC were out today to see the builder, had a quick chat and he's happy that the side external wall is within the boundary (by about 6") so he's happy with a wall mounted extract.

And who am I to disagree with the building inspector ! so no holes in the roof, yipee