Whilst searching the internet to learn about celotex for my other post about floors and ceilings, I came across a web site that said a house built today would need 100mm of celotex in its cavity. It also said that houses built before 1975 had much smaller cavities, so to get to today's standards of insulation, you would have to add 50mm of celotex to the walls. I am told that my house was built in the 1930s. I haven't yet removed a brick to see what insulation, if any, I have. I suppose I should do this.
As it happens, another job I'm about to get round to, is redoing the bathroom. It's only a small room but it does have two external walls. I think I could add 25mm celotex to the walls without problems. I know that's only half what the web site recommends, but it's better than nothing.
I could use 50mm but I might need to move the door frame across, as it is close to the external wall. I do wonder whether all this work is worth it, but I suppose I have not lived through a winter here yet to see how cold it is, and it would mean I would use my heating less, so I suppose it would save fuel in the long term. I guess I will have to do the calculations again and see what the savings are with both thicknesses.
Would it be best to put battens on the wall at 600mm centres and insulate between those, or would it be better to have no wood and glue the insulation to the wall with some sort of "no more nails" product. The advantage with the latter being there would be no gaps in the insulation? I suppose battens would allow me to get the wall straight if it was not already.
I have an irrational fear of the wall falling down if I glue it; I'm thinking I would be gluing plasterboard with tiles on to celotex to the wall. But I suppose that's only because I am used to mechanical fixings and have not glued before.
I would need to fix a radiator to the wall and a toilet cistern. What would be the best way to do this? Use long fixings into the masonry wall behind the celotex or should I cut out the celotex behind these and fit a wooden batten to the wall and screw into that?