Re-doing upvc cladding - help with insulation Information, help, tips and advice on cavity walls, ceilings and lofts etc....

[Superslim007]

Hi I'm looking for a little advice, I moved to this new (to me) house and replaced all the doors/windows and want the cladding replacing, I had a quote of £6k and I think they thought I was daft, I priced up the materials for fibre cement board and celotex etc and there isn't £2k worth of material so £4k for 2 days work, nah.
I am very handy but at 52 thought I'd pay someone else but there having a laugh so I'm going to do it myself. The existing is batons onto breeze block then wooden cladding with poor foam insulation between, then very cheap UPVC clad over that, my plan is to rip it all off, re-baton and put in some celotex 50/100mm ?? then vapour barrier and clad with cement fibre board cladding, I think I get my head around it but am unsure of what thickness celotex to use, can anyone advice and just confirm my plan is sound - so - strip off all the upvc, then all the wooden cladding, remove all the poor foam insulation, strip off the batons, take back to the breeze block, then new batons, fasten celotex direct to the breeze blocks the same thickness as the batons, then vapor barrier, then say 1" batons on top of that to to fasten the fibre board to with a mesh vent on the top and bottom, I do need the gap between the celotex and cladding don't I ? if that's correct is there any stipulation on how thick the celotex should be or is it the more the merrier ? I would greatly appreciate any advice so I don't stuff it up

[stoneyboy]

Hi superslim007,
If the wall behind the cladding is a cavity wall with ventilated cavity there is little point in insulating the outer skin.
If the wall is solid you will need to start with a vapour barrier, vertical battens with insulation between, horizontal battens with insulation between, breathable felt and then cladding.
Finer detail will depend on the existing construction.
Regards S

[Superslim007]

Thanks for the advice, the wall behind is solid breeze block, it has no brick, it’s like when the house was built it was cheaper to clad the front rather than cavity and brick it, so does the vapour barrier go directly over the breeze block first then the insulation? I have seen some jobs where the vb goes on after the insulation

[stoneyboy]

Hi superslim007,
You need to prevent damp getting into the insulation where is would condense. So vapour barrier first.
Regards S

[Superslim007]

Hi superslim007,
You need to prevent damp getting into the insulation where is would condense. So vapour barrier first.
Regards S

Thanks for taking the time to comment I really appreciate it, forgive me if I sound stupid I just want to be 100% you said the vb up against the breeze block before the batons go on ? that wont stop the celotex getting condensation on it ? I have attached a crude pic can you confirm which is the best way to do it, I don't know if there should be a gap between the celotex and cladding or can it go straight over the celotex ??

[stoneyboy]

Hi superslim007,
It’s the lower of your drawings - but the vapour barrier goes against the blocks, suggest you fit horizontal battens with insulation between, vertical battens with insulation between, breathable membrane and then cladding.
The depth of insulation you can use will be dictated by how much your cladding can stick out beyond the return walls.
Go for a PIR insulation board which will give you a good u value without spending silly money.
Regards S