retro fitting Insulation to a flat roof

[jimAuk]

We have a small flat roof of size approx 2 x 4 m which is in good condition and not easy to convert to a pitched roof (like I am doing else where on the house)

But with the recent snow is was very evident of the lack of insulation, showing up the rafters as the snow melted.

Without bringing down the ceiling inside or taking the roof off outside, is it possible to insulate this roof be taking the front facia board off and inserting some type of insulation in?

My first thought was getting a cavity wall company to blow in the stuff they use in cavity walls.

Or just to take my time and push normal glass type wool down the cavities.

Thanks[/code]

 

[noseall]

It is not really practical to do as you describe as venting becomes difficult.

Your best bet would be to remove the ceiling and fill with celotex or kingspan, tape or foam all joints then replace the ceiling with foil backed boards.

Ideally, flat roofs are best constructed as a 'warm deck' i.e. fitting 97mm aerodeck to the joist (topside) then install the finished membrane straight to the aerodeck. You would also need to fit 25mm to the underside of the deck (to satisfy reg's), this is simply friction fitted from below and foil taped.

 

[jimAuk]

I spent a bit of time looking at the roof, taking some measurements and then drawing up and in a flash of inspiration I have managed to get round the problem of converting this roof to a pitched one.

The problem was there are two windows in the second story above the flat roof extension, one a bedroom one at 0.86m above the flat roof, the second a stair well window at only 0.4m above the flat roof.

Then I thought why not just replace the stair window with the same size (length wise) as the bedroom one!

This then allows a fairly simple roof to be added at 23 deg pitch.

Not the best pitch I know, but better than a flat roof, + ease of insulation during build + make front of house look better.

 

[noseall]

23 degrees is a lot better than flat.

Result!

 

[jimAuk]

The main house in clay pantiles, and we would want the same.

Is 23 Deg Ok for pan tiles (clay) or would man mande (concrete) be better?

What about saking boarding? and double felt/counter batterns?

Also is a breatherbale membrane now required as part of building regs?