concrete flat roof on a bay window

[simonsaysno]

Hi,

I have been spending hours trying to work out how best to tackle this problem and am looking for any advice.

I am tying to repair the ceiling of the bay window in my lounge. It is made of a slab of concrete which is tied into the house. There is then a layer of plaster which has crumbled away in the outside corners where water was entering. I am then only left with 25mm to play with before the windows. There were polystyrene tiles glued to the plaster previously.

When I first moved in I had it re felted to stop the water entering. Having read up on the issue I can see it would have been best to insulate on top of the concrete but I am loath to do this now.

I have read I need a layer of insulation followed by a vapour check such as foil backed plasterboard. Is it possible to get both of them on with the limited space I have? Plus how on earth do I go about fixing them? Could I use an adhesive and prop them up until it's set?

Any advice is much appreciated.

 

[catlad]

You can use insulated plaster board celotex pl4000 which has a vapour barrier built in to it.

 

[simonsaysno]

Thank you for your suggestion.

The thinnest celotex pl4000 I have been able to find to purchase online is the pl4025 25mm +12.5 plasterboard.

 

[catlad]

I thought you said you did not want to work from the out side. min plaster board is 9mm so you can chose that or similar but it will not give you much insulation.

 

[simonsaysno]

I have found Knauf Thermal Laminate Plus Tapered Edge 2400 x 1200 x 27mm which is an insulated plaster board like the celotex pl4000 you suggested.

I might be able to squeeze that in.