Insulation

[5125andrew]

I am rennovating an eaves bedroom, which has a lath and plast ceiling which is sagging/cracking in places. I've been advised it's easier to put new plasterboard over the top instead of removing. The other issue I am trying to address is insulation. The room is cold in winter and very hot in summer. How much insulation will another layer of plasterboard add. Would it be better to take down the ceiling and insulate between the rafters?

thanks

 

[jbonding]

why is is sagging? adding extra boards will add extra weight so it might be worth looking.is there any vents in the room?

 

[Mantamad]

An extra layer of plasterboard will not really provide any additional insulation, your best bet here is to put insulation between the rafters but you should leave a 50mm gap between the top of the insulation and underside of roof and install ventilation to the roof so air will flow through this 50mm gap.

 

[5125andrew]

why is is sagging? adding extra boards will add extra weight so it might be worth looking.is there any vents in the room?

It's not so much sagging as looks like the lath and plast has come away from the joists a bit. The whole thing is covered in woodchip paper and several layers of paints, but I'm pretty confident the roof is not sagging, it looks dead level from the outside. there are no vents as far as I am aware jbonding.

thanks for your advice.

Does anybody have any experience of insulating between joists with Celotex or Kingspan? Any tips?

 

[jbonding]

the ceiling is not connected to the roof that you could see from outside, i meant the joists. check the thickness of the joists , get up and have a look

 

[5125andrew]

When I say sagging a bit, I mean about 1mm, but enough for lines to be apparent in the plaster. I want it to be a completely smooth finish.

My email was a bit confusing, sorry. The ceiling is pitched and the lath and plast is fixed directly onto the rafters, which are 4 inches deep. I can't look behind it without taking it off.