should there be a void between celotex and plasterboard??

[fruitcake]

Hey up

as the title says. basically im going to use 25mm celotex sheets which are foil backed. Then plasterboard and skim.

So i was thinking of fixing 25mm deep laths onto the external wall and then putting/cutting the celotex between them and then screwing the plasterboards to the laths. But I read somewhere there should be a gap between the boards and celotex??? why should there be a gap? and if so how big should gap be.?

thanks

 

[warriorupnorth]

If the wall is fairly flat then just stick the sheets back with a temp fix then lath over the top of the sheets screwing into the brick/block behind , then screw boards to laths , easier , no cutting boards and no thermal breaks

 

[richie]

good way of doing it mr warrior

 

[fruitcake]

how thick should the laths be?

ta

 

[warriorupnorth]

how thick should the laths be?

ta

??? ??? ??? why don't you just send me the address i will go n do the job, and tell em just to send the money to you

 

[JohnnyChrist]

Just use 2x1 and watch, because quinntherm is thicker than 25mm so won't fit, so make sure too get celotex because its just right for 2x1

 

[warriorupnorth]

Just use tanalised slate lath

 

[richie]

have you got the job then warrior youth

 

[warriorupnorth]

Naah mate i was too dear : :

 

[richie]

;D

 

[fruitcake]

how thick should the laths be?

ta

??? ??? ??? why don't you just send me the address i will go n do the job, and tell em just to send the money to you

: : :i did ask the same question in my first post and it wasnt answered then either ?...

anyway i would send you but i heard your rough

 

[warriorupnorth]

how thick should the laths be?

ta

??? ??? ??? why don't you just send me the address i will go n do the job, and tell em just to send the money to you

: : :i did ask the same question in my first post and it wasnt answered then either ?...

anyway i would send you but i heard your rough

But fast ;D ;D

 

[Chris W]

why should there be a gap? and if so how big should gap be.?

thanks

the air gap acts as a low emmisivity break between the board and the cellotex, not essential as such but to achieve a 'u' value of about 3wm2k (ish if memory serves) on a single skin wall its included in the calculations...
youre missing the vapour barrier though (that stops warm moisture laden air permeating the insulation and condensing on a cold surface e.g. the single skin wall)
best way to do this is use warriors method and tape the joints with gaffer tape before you batten out, no need for duplex board, and any cables can be run in the void. Dry line boxes are used to mount sockets etc and the vapour barrier remains intact...

 

[Chris W]

p.s. your gonna need 50mil of cellotex to hit that target u value if theres regs on it, like if its a habitable room...

 

[warriorupnorth]

Yeah, yeah