un insulated bay window.

vic_sf49

Yes I agree, if putting a bay in, do it properly with bricks, then you can benefit from the extra floorspace, or at least not have a heat-waster as a window/winsowsill. It seems to be the fashion around this area to have these daft bay windows!

My bay is not identical to the one in the link I posted; I also have nothing substantial over the top of it - some flashing and hopefully something underneath that. If I was going to get any work done on it, I'd just do away with it altogether which would involve a new window, and a little bit of 'building' work. It might cost a bit more, but it seems like the most logical solution to me, and wouldn't involve trying to match any decorative stone that forms that part of the wall.

lstar337

What a stupid design! Faux bay windows??? :rotfl:

I would probably get a sheet of Kingspan (or similar) and cut it to shape and fit it under, then box it in with wood battens and sheet over with some waterproof Ply or something.

Go for 50mm foam sheet, or polystyrene sheet if funds are an issue.

Based on your posts above I think its all within your capability.

chappers

Ah now I understand, Yes as Istar says fix celotex underneath and then box it all in.
Absolutely pointless design.
I would construct something like this;
fix 50mm battens to the underside and wedge fit 50mm celotex in between then underdraw the whole lot with 12 mm celotex, to prevent cold bridging, followed by thin ply or masterboard fixed through the insulation into the battens. with a fascia fitted around the perimeter.
The whole lot would be stepped back in 15-20mm with the fascia protruding 10mm down below the whole construction. You could pretty it up with some decorative moulding if you wanted.
You may want to remove the gallows brackets and refit to prevent further cold bridging.
However BC let them get away with that is beyond me, a while ago we created an Oriel window in an extension and BC insisted we used the same amount of insulation as for a flat roof.

spongybobby

Is 50mm thick enough? I was thinking of using 100mm foam board?

With regards to the 'support' things (gallows) they will probably be removed and reduced in size then refitted under tge new box section.

Ectophile

tonyh66 wrote: »

Can't understand the designers head when they put these bay type windows into a normal opening without creating the extra floorspace
under it. You could I suppose get a bricky to build a wall under it and fill the newly created void with rockwool.

I was going to suggest that, but you beat me to it. It's just what my brother did with a rather manky bay window.

chappers

100mm would be better if you don't mind the aesthetics of a deeper box, but would have thought 50mm with 12mm under draw would be sufficient. Your not trying to prevent heat escaping so much as preventing the cold conducting through the bay material. But as you say the more the merrier.

spongybobby

I would get a builder to extent out but it would not be easy with my house.

Chappers, what do you mean by the 12mm underdraw?

chappers

If you use battens and insulate between them then I would then cover the whole lot with 12 or even 25 mm celotex, which would prevent cold bridging through the battens.

lstar337

chappers wrote: »

If you use battens and insulate between them then I would then cover the whole lot with 12 or even 25 mm celotex, which would prevent cold bridging through the battens.

I would be tempted to just get a big sheet and cut it to shape, that way you only have a single piece with no thermal bridge.

If battens are used across the space, then covering the whole lot is the best idea.

spongybobby

Chappers. I was going to do what Istar suggested and use one large sheet cut to size.
Fit this to the underside then 'box' the foam in with some wood?