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Internal PIR vs offcuts


BartW

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Hi,

we are nearly ready to install internal PIR in our timber frame walls. 
 

The trouble is that out screed to ceiling joist height is 35mm higher than full sheet of PIR. 
 

Would it be best to:

 

a) lift boards 20mm off the ground and foam up with expandable foam later? There would be tiles and adhesive later so I guess it would be ok? Then remaining 15mm on top, do the same thing because there will be a plasterboard applied?

 

b) fully plant it on the floor tight to screed and foam up the top?

 

c) install a row of pir boards horizontally, and do 650mm pir cuts from a vertical board, and generate a lot of cutting and waste?

 

what would a self-build-hubber do?

 

thanks!

 

bart

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Aren't there noggins in that would stop a full board length being installed?

 

I would install a full board then a 35mm slither off cut, expand foam any gaps, then alu tape over joints

 

Edit: it was my assumption that your insulation is going in the cavity, however it sound like it may be on the inside of the timber.

Edited by Moonshine
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Thanks guys, both good suggestions. 
 

I will probably end up cutting 35mm slivers to top in order to keep alu faces back and front rather than top and bottom  

 

thanks!

 

 

oh, and would it be good to have horizontal battens top and bottom of the wall to give the plasterboard better bedding or would it be counterproductive?

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