I want to wedge some rockwool insulation between some joists that are only around one foot apart. The rockwool is on wide rolls, (paper backed on one side) and will need cutting. What is the best tool for the job? Knife, scissors, timber saw? Other? Someone said it is better to cut the stuff while it is still rolled up - any tips?
From experience when I take the wrapper off the roll it explodes like a coiled up spring, unrolling and puffing out very fat. I've never had to cut it before though.
Last time I needed to cut this stuff, I just used a timber saw, while it was still rolled up - seemed to work a treat!
Breadknife is one option - the serrated edge sort. Never tried cutting it while rolled up - but if you let it unroll you can then cut it flat on the floor using a piece of timber as a straightedge to cut against....
Watch out for stray fibres - it's not as bad as fibreglass - but can still get into places you'd never imagined
HTH Adrian
That's exactly what some builders did while they were insulating my next door neighbour's new extension. Each cut only took a couple of minutes or so.
Breadknife if uncoiled; panel saw if still rolled up.
I always cut it rolled if I have lots of similarly spaced joists; however as that's rarely the case it's usually the breadknife.
David
Ignore advice to unroll it, use a panel saw straight through the polythene packaging to slice the roll - some manufacturers even provide guide markings on the outer packaging for this.
I cut some Rockwool slabs with a very sharp kitchen devils 10" knife. One slice and it was a clean cut. I only cut a couple of packs so I have no idea how long the knife stays sharp and it is a very dangerous tool to have on site. I agree with cutting rolls before you unpack.. far easier while the plastic holds them.
Any old panel saw will give a clean cut
Thanks for the advice everyone, job now done. I used a panel saw as advised slicing straight through the rolls.
I wore a dust mask but wish I'd worn a long sleeved shirt too - my arms won't stop itching.
I did this myself recently with one of those double-width Wickes rolls - it had markings down the side for different joist spacings, which I just ignored since, as has been the case every single time I've done this job, the spacings were non-standard. So I cut it into slices like a Swiss roll whereupon it all went horribly wrong as apparently the rolls were already cut 2/3 of the way through at the pre-existing marks. I ended up doing the job with loads of lengths about 6" wide...!
David
Thanks for the warning. Now that the days are extending, I'm just getting motivated again and am thinking of the loft! It's a mid 80's house that could do with some additional/ replacement insulation.
I just got a 6 inch hand crafted Chinese made kitchen knife to cut the rockwool. Was wondering if it will be good enough
If that is what we used to call plasterboard, I just cut up two sheets with a Black & Decker Scorpion. Best to start it off with a fine handsaw so that there is a notch to position it in as the blades are inclined to wobble. Use a fine plade.
I would guess that it's 4 to 6 inch insulation material.
Plasterboard can be scored with a sharp blade and snapped - no need for a saw for the majority of cuts -
+1 although I would use an old saw as it seems to quickly blunt it and you don;t really need it to be sharp the blade profile seems to work just fine
I find a hand saw with the teeth removed and *rough* sharpened (coarse grit rather than oilstone) works well for insulation rolls.
Just buy a really cheap pair of large scissors and throw them away once you have finished.
Less dust, and fibres to inhale
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