In my loft I have a section of loft boards that runs the length of the loft (roughly 7m x 2m) with ~1.5m glass wool on either side. These sit on top of 70mm high joists (which are ~300mm apart) which have glass wool between them (presumable compressed 100mm). This is clearly nowhere good enough, so I want to add more underneath the boards. Being pretty crap at DIY I've tried to find someone to do this for me but it seems the job is too small.
So I'll have to give it a go myself. My plan is to place 120mm PIR boards (once shipping is taken into account they work out roughly the same as 100mm) underneath the loft boards which I'll screw into the PIR boards.
I think my main issue will be getting the boards up since the loft hatch is ~60cm, so I suspect I'll have to saw each board into quarters as cutting simply down the middle alone will be too unwieldy to saw.
So with that in mind I would appreciate some advice on details:
1) I've seen mention of using aluminium foil tape to join the top of PIR sections together. Is this necessary?
2) Is it necessary to screw the PIR boards into the underlying joists or can they just float on top? Or perhaps use battens or angle brackets to keep them in place?
3) Will a normal handsaw be good enough for sawing the PIR boards? Any common gotchas sawing PIR boards?
4) The area around the loft hatch will be tricky for me since there is a ladder there so I intend to leave that for the time being. How badly will this impact the overall insulation? Is it case of the insulation only being as good as its weakest point?
5) Have I missed anything or not taking something into account?
and finally
6) Is this a reasonable plan?
Appreciate any opinions on all this.
So I'll have to give it a go myself. My plan is to place 120mm PIR boards (once shipping is taken into account they work out roughly the same as 100mm) underneath the loft boards which I'll screw into the PIR boards.
I think my main issue will be getting the boards up since the loft hatch is ~60cm, so I suspect I'll have to saw each board into quarters as cutting simply down the middle alone will be too unwieldy to saw.
So with that in mind I would appreciate some advice on details:
1) I've seen mention of using aluminium foil tape to join the top of PIR sections together. Is this necessary?
2) Is it necessary to screw the PIR boards into the underlying joists or can they just float on top? Or perhaps use battens or angle brackets to keep them in place?
3) Will a normal handsaw be good enough for sawing the PIR boards? Any common gotchas sawing PIR boards?
4) The area around the loft hatch will be tricky for me since there is a ladder there so I intend to leave that for the time being. How badly will this impact the overall insulation? Is it case of the insulation only being as good as its weakest point?
5) Have I missed anything or not taking something into account?
and finally
6) Is this a reasonable plan?
Appreciate any opinions on all this.
