Opinion on timber ceiling in dormer house

rustynutz

I am in the middle of decorating upstairs in my dormer house, I am also trying to upgrade insulation as I go. My biggest concern is I don't think there is enough insulation on the sloped part of the ceilings, at the moment there is 4" fibreglass between the rafters and it is finished with ordinary plasterboard. In an ideal world I would fix a 50mm or thicker insulated slab to the underside of the existing slab and reskim it but the thoughts of skimming and the mess that goes along with it does not appeal ( I'm living in the house for past 5 years) so as an alternative I was thinking of doing the following:
Fit 50mm xthratherm board to underside of sloped side of ceiling
Fit battons and finish with red deal 100mm wide t & g board
Finish under side of flat ceiling the same way

I'd love to hear from anyone who has done this in a dormer house or has seen it done
Would it be too much timber in one room?
Has anyone any other suggestions how I could up the insulation under the rafters without doing anything drastic like taking the slates off the house? !

BryanF

rustynutz wrote: »

I am in the middle of decorating upstairs in my dormer house, I am also trying to upgrade insulation as I go. My biggest concern is I don't think there is enough insulation on the sloped part of the ceilings, at the moment there is 4" fibreglass between the rafters and it is finished with ordinary plasterboard. In an ideal world I would fix a 50mm or thicker insulated slab to the underside of the existing slab and reskim it but the thoughts of skimming and the mess that goes along with it does not appeal ( I'm living in the house for past 5 years) so as an alternative I was thinking of doing the following:
Fit 50mm xthratherm board to underside of sloped side of ceiling
Fit battons and finish with red deal 100mm wide t & g board
Finish under side of flat ceiling the same way

I'd love to hear from anyone who has done this in a dormer house or has seen it done
Would it be too much timber in one room?
Has anyone any other suggestions how I could up the insulation under the rafters without doing anything drastic like taking the slates off the house? !

don't forget moisture barrier (intello membrane or similar) on room side of the insulation.. also go with more insulation if you can.. and watch out that you retain adequate ventilation, both in the room and in the structure (two separate things)

rustynutz

BryanF wrote: »

don't forget moisture barrier (intello membrane or similar) on room side of the insulation.. also go with more insulation if you can.. and watch out that you retain adequate ventilation, both in the room and in the structure (two separate things)

Thanks for your response, would Xtratherm with foil both sides have this membrane built in? By structural ventilation do you mean allowing 50mm air gap between roofing felt and insulation? That gap is there alright

BryanF

rustynutz wrote: »

would Xtratherm with foil both sides have this membrane built in?

no

rustynutz wrote: »

By structural ventilation do you mean allowing 50mm air gap between roofing felt and insulation?

yes

One shot on kill

you cant use xtratherm and fibre glass over or under it it will sweat like mad id take out the fibre glass and put in 100 mm xtrstherm or kingspan i personaly would slab and skim it far nicer in my opinion trough the fibre glass on top of the other fiber glass on the ceiling of the down stairs for more insulation

rustynutz

One shot on kill wrote: »

you cant use xtratherm and fibre glass over or under it it will sweat like mad id take out the fibre glass and put in 100 mm xtrstherm or kingspan i personaly would slab and skim it far nicer in my opinion trough the fibre glass on top of the other fiber glass on the ceiling of the down stairs for more insulation

I am looking for the easiest way to insulate, I don't want to start ripping out plasterboard and insulation at this stage. What do you mean when you say you can't use fibreglass over or under xtratherm? What would sweat like mad?

rustynutz

Ok, rang Xtratherm today and got advice on what board to use, they say their XTPR 60mm board would bring me up to current regs (taking the 4" fiberglass between rafters into account), they say the foil back on this product acts as a moisture barrier once all joints are taped with a foil tape.
Anyone have any advice on the red deal ceiling, have never seen it done, is it a nice finish etc?

dathi

did they say any thing about covering the x therm with plaster boards before you put on the timber t and g boards other wise you have a fire hazard ,ie the xtherm is flammable and it has no protection without the plasterboard on the room side of it.

rustynutz

dathi wrote: »

did they say any thing about covering the x therm with plaster boards before you put on the timber t and g boards other wise you have a fire hazard ,ie the xtherm is flammable and it has no protection without the plasterboard on the room side of it.

He never mentioned that, good point though, I wouldn't have thought it was flammable. I thought insulation was fire resistant.

One shot on kill

when you have two differant types of insulation you will end up with one tempature on the inside one between the two insulations and one temp on the out side so there for when inside and out side meet in the middle it will sweat because of thefoil on it

when you say the easyest way is there insulation behind the plaster board now or is there plaster board there at the min or what

rustynutz

One shot on kill wrote: »

when you have two differant types of insulation you will end up with one tempature on the inside one between the two insulations and one temp on the out side so there for when inside and out side meet in the middle it will sweat because of thefoil on it

when you say the easyest way is there insulation behind the plaster board now or is there plaster board there at the min or what

There is 4" fibreglass between rafters and slabbed & skimmed, the house was built in 2004. After the comments above about it being a fire hazard I think I may go back to the original plan of insulated plasterboard over the existing plasterboard and re skim, it's just the thoughts of skimming and the mess that goes with it is putting me off.

BryanF

rustynutz wrote: »

There is 4" fibreglass between rafters and slabbed & skimmed, the house was built in 2004. After the comments above about it being a fire hazard I think I may go back to the original plan of insulated plasterboard over the existing plasterboard and re skim, it's just the thoughts of skimming and the mess that goes with it is putting me off.

whats to stop the inner plasterboard turning to mush as moisture builds up on it?

rustynutz

BryanF wrote: »

rustynutz wrote: »

There is 4" fibreglass between rafters and slabbed & skimmed, the house was built in 2004. After the comments above about it being a fire hazard I think I may go back to the original plan of insulated plasterboard over the existing plasterboard and re skim, it's just the thoughts of skimming and the mess that goes with it is putting me off.

whats to stop the inner plasterboard turning to mush as moisture builds up on it?

They didn't seem concerned about moisture build up when I contacted xtratherm