insulating a flat roof ceiling ??

[paulyoung666]

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:

 

[Alan.P]

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

 

[paulyoung666]

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

 

[mikethetile]

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

 

[Alan.P]

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

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.

 

[Ajax123]

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.........

 

[paulyoung666]

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 ...............

 

[Alan.P]

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 ...............

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 +/- ?

 

[paulyoung666]

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 +/- ?

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:

 

[mikethetile]

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

 

[Alan.P]

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:

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

 

[paulyoung666]

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

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

 

[mikethetile]

how are you going to board out your flat roof

 

[paulyoung666]

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

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

 

[paulyoung666]

how are you going to board out your flat roof

read post #14 for the answer

 

[Alan.P]

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

Starting to now, the gap above the joists is for air circulaion as stated by Ajax, I'm not clued up on any of that side so can't comment, I see what your wanting to do, whether it's acceptable or not ???????

 

[Alan.P]

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

we're getting there :lol:

forget that post up there

I now have no idea lol

So you have a ceiling, and have now put a false celing in ? and want to insultae that, can't see why you can't but like I said, I'm not clued up in that area .... sorry

 

[mikethetile]

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

now he tells us

yes you can, ensure theres an air gap above the insulation to allow free passage of air otherwise you will have condensation problems

 

[Tecnik2000]

Just sticking my nose in here, it makes little or no difference if you can go at 90 degrees to the joists & maybe better as there are no joins or cutting to achieve the insulation required with out jeopardising your uv values. I'm sure you can devise a way of supporting the insulation adequately using battens,strapping or just laying on your sus ceiling...

 

[chrisroe]

try

triso super 10

building control in my area recommend it

 

[paulyoung666]

now he tells us

yes you can, ensure theres an air gap above the insulation to allow free passage of air otherwise you will have condensation problems

thanks for that , with the joists i go then as i have condensation problems now , due i suspect because no insulation was put above the original ceiling :furious3:

 

[Scott]

I hope you get it sorted paul as that was probably the most confusing post i have read on here so far!

 

[White Room]

Why don't you use vapor check board, fix a board to right angles to the false ceiling then slide your insulation on top of the fixed board.

The one I done with flat roof (garage conversion)required 100mm of celotex insulation and building control checked it out as well.

 

[Diamond Pool Finishers]

im not with it here , i thought i did, but no :yikes:

 

[chrisroe]

sorry cant cope with this tonight need sleep then i might be able to help its to do with differant types of hot/cold roof systems

 

[mikethetile]

it is a warm roof construction which is why its essential that there is a freeflow of air in the roof space

 

[paulyoung666]

right , i am sorted now , apologies for the confusion , i was at the point of confusing myself :lol:

 

[faithhealer]

blimey Paul, read the forum on a morning to help get my head into gear, think I'll go back to bed after reading that lol

 

[paulyoung666]

:lol: :lol: :lol:

 

[chrisroe]

no still cant cope will try later after a couple of strong coffees