insulating a flat roof ceiling ??

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paulyoung666

• Mar 16, 2010

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• #1 of 32

put the insulation between the joists or at 90 degress to it , i have space and to do either , just wondering what would be the best way , i was thinking at 90 degrees to the joists but am i right :yikes:

 

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Alan.P

• Mar 16, 2010

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• #2 of 32

Nah Paul, go with the joist, easier that way, make some form of wedge, wood / plastic ..other to keep it up, bobs ya uncle.

 

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paulyoung666

• Mar 16, 2010

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• #3 of 32

would it be considered wrong to go the other way though ?

 

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mikethetile

• Mar 16, 2010

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• #4 of 32

No it wouldnt , sometimes its easier to keep them up as gravity doesnt take over

its not done like that because its time consuming cutting each bit to length

 

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Alan.P

• Mar 16, 2010

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• #5 of 32

mikethetile said:

No it wouldnt , sometimes its easier to keep them up as gravity doesnt take over

its not done like that because its time consuming cutting each bit to length

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Exactly, not wrong just time, it might be easier for you that way if your working on your own, then wedge them in, otherwise, some sort of retainer might be needed.

 

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Ajax123

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Lincolnshire

• Mar 16, 2010

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• #6 of 32

I just got some advice on this from building control. They said if it is unvented then go in between the joists but leave an air gap then place a vapour barrier on the warm side before plasterboarding (or what ever)

If it is a vented roof then there are actually regs covering the size of air gap and the depth of insulation and you would probably have to go with a rigid board insulation rather than a mineral wool. You still go with the joists. For added insulation I was told to place a further 25mm of polyurethane (cellotex) board on the underside of the joists. Tape the joints and this acts as the vapour barrier. The plasterboard as normal.

I of course am ignoring all of this advice and doing my own thing.........

 

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paulyoung666

• Mar 16, 2010

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• #7 of 32

the reason i was thinking of going across the joists is that the rolls of insulation are in a bag to avoid all the nastiness associated with fibreglass and they are 5 metre rolls , the room is 5 metres long ...............

 

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Alan.P

• Mar 16, 2010

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• #8 of 32

paulyoung666 said:

the reason i was thinking of going across the joists is that the rolls of insulation are in a bag to avoid all the nastiness associated with fibreglass and they are 5 metre rolls , the room is 5 metres long ...............

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Lost me there Paul, are you saying ypu want to follow inbetween the joists ie follow the full 5 m with the 5m roll or cut into strips of 300mm +/- ?

 

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paulyoung666

• Mar 16, 2010

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• #9 of 32

Alan.P said:

Lost me there Paul, are you saying ypu want to follow inbetween the joists ie follow the full 5 m with the 5m roll or cut into strips of 300mm +/- ?

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it is joisted narrow , i want to use the 5 metre roll across the joists along the length of the room if that makes sense :lol:

 

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mikethetile

• Mar 16, 2010

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• #10 of 32

the insulation needs to go between the joists otherwise you cant fix your boards to the underside of the joists

 

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Alan.P

• Mar 16, 2010

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• #11 of 32

paulyoung666 said:

it is joisted narrow , i want to use the 5 metre roll across the joists along the length of the room if that makes sense :lol:

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Nope, I'm having a blond moment, like this ???

 

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paulyoung666

• Mar 16, 2010

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• #12 of 32

mikethetile said:

the insulation needs to go between the joists otherwise you cant fix your boards to the underside of the joists

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i was going to put the insulation above the joists and the boards below the joists if that makes sense

 

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mikethetile

• Mar 16, 2010

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• #13 of 32

how are you going to board out your flat roof

 

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paulyoung666

• Mar 16, 2010

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• #14 of 32

Alan.P said:

Nope, I'm having a blond moment, like this ???

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not you , it is me , it is a false ceiling below a ceiling !!! :mad2: :mad2: :mad2:

 

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paulyoung666

• Mar 16, 2010

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• #15 of 32

mikethetile said:

how are you going to board out your flat roof

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read post #14 for the answer