From Newsgroup: uk.d-i-y

I'm leaning towards using rockwool insulation in my boat, I think it's
probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?
--
Chris Green
-+
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From Newsgroup: uk.d-i-y

On 26/04/2026 15:06, Chris Green wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

Hand saw or large knife, possibly guillotine if you have one.
Less nasty than PIR for dust but harder to get a straight edge.

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From Newsgroup: uk.d-i-y

Chris Green wrote:

I'm leaning towards using rockwool insulation in my boat [...]
So, how should one cut it and how nasty is the resulting dust?

Keep the roll tightly wound, preferably in its shrink-wrap covering and
use a handsaw.

I can't really say about the dust, it never seems to bother me
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From Newsgroup: uk.d-i-y

Nick Finnigan <nix@genie.co.uk> wrote:

On 26/04/2026 15:06, Chris Green wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

Hand saw or large knife, possibly guillotine if you have one.
Less nasty than PIR for dust but harder to get a straight edge.

Thanks. A knife sounds good from the point of view of not producing
too much dust. Does it need a serrated edge or is just plain sharp OK?
--
Chris Green
-+
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From Newsgroup: uk.d-i-y

Andy Burns <usenet@andyburns.uk> wrote:

Chris Green wrote:

I'm leaning towards using rockwool insulation in my boat [...]
So, how should one cut it and how nasty is the resulting dust?

Keep the roll tightly wound, preferably in its shrink-wrap covering and
use a handsaw.

It's not a roll, it's panels:-

https://www.leroymerlin.fr/produits/14-panneaux-de-laine-de-roche-rockwool-rockmur-kraft-ep-40mm-1-35x0-6m-94060938.html

I can't really say about the dust, it never seems to bother me

OK, I'm not particularly susceptible to dust etc. so that sounds as if
it should be ok.
--
Chris Green
-+
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From Newsgroup: uk.d-i-y

Chris Green wrote:

It's not a roll, it's panels:-

still use a handsaw, I used one for some of their acoustic slabs
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From Newsgroup: uk.d-i-y

Chris Green <cl@isbd.net> wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

I have used this for cutting PIR, it does say it is suitable for mineral
too

https://www.amazon.co.uk/Bahco-PC-22-INS-22-inch-Insulation-Saw/dp/B003Y3SJMG

Richard
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From Newsgroup: uk.d-i-y

On 26 Apr 2026 at 16:32:37 BST, Tricky Dicky wrote:

Chris Green <cl@isbd.net> wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's
probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

I have used this for cutting PIR, it does say it is suitable for mineral
too

https://www.amazon.co.uk/Bahco-PC-22-INS-22-inch-Insulation-Saw/dp/B003Y3SJMG

I've used one of those - pretty good but there's knack to it I've not quite mastered. Up to 50mm I still find deep score/snap (like plasterboard) works best for PIR. Not sure about the OP's slabs - I'd guess wood saw.

And really, use a decent dust mask. While the dust might not irritate short term you've no idea what lingering fibres might do.
--
Cheers, Rob
Sheffield, UK
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From Newsgroup: uk.d-i-y

Chris Green <cl@isbd.net> wrote:

Nick Finnigan <nix@genie.co.uk> wrote:

On 26/04/2026 15:06, Chris Green wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

Hand saw or large knife, possibly guillotine if you have one.
Less nasty than PIR for dust but harder to get a straight edge.

Thanks. A knife sounds good from the point of view of not producing
too much dust. Does it need a serrated edge or is just plain sharp OK?

For PIR I use a serrated knife, which I think should work here. I bought a pack of cheap 'steak knives' on Amazon which do the job, but a bread knife would probably work too and have a longer reach. The main thing is to have
a thin serrated blade - some knives have quite a thick blade and are more
work as a result, although probably not such a problem on wool which has
more give than PIR. (thin knives are also better at cutting bread, which
I'd guess has similar consistency as these wool slabs)

For actual sheep's wool, I use scissors.

Theo
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From Newsgroup: uk.d-i-y

On 26/04/2026 16:32, Tricky Dicky wrote:

Chris Green <cl@isbd.net> wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's
probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

I have used this for cutting PIR, it does say it is suitable for mineral
too

https://www.amazon.co.uk/Bahco-PC-22-INS-22-inch-Insulation-Saw/dp/B003Y3SJMG

I ran an angle grinder down either side of a worn wood cutting saw. You
need a blade length significantly longer than the roll width.


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From Newsgroup: uk.d-i-y

On 27/04/2026 11:05, Theo wrote:

Chris Green <cl@isbd.net> wrote:

Nick Finnigan <nix@genie.co.uk> wrote:

On 26/04/2026 15:06, Chris Green wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's >>>> probably bendy enough and it's non-flammable and it's reasonably cheap. >>>>
I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

Hand saw or large knife, possibly guillotine if you have one.
Less nasty than PIR for dust but harder to get a straight edge.

Thanks. A knife sounds good from the point of view of not producing
too much dust. Does it need a serrated edge or is just plain sharp OK?

For PIR I use a serrated knife, which I think should work here. I bought a pack of cheap 'steak knives' on Amazon which do the job, but a bread knife would probably work too and have a longer reach. The main thing is to have
a thin serrated blade - some knives have quite a thick blade and are more work as a result, although probably not such a problem on wool which has
more give than PIR. (thin knives are also better at cutting bread, which
I'd guess has similar consistency as these wool slabs)

For actual sheep's wool, I use scissors.

Theo

I use wallpaper scissors to cut the floppy rockwool, and a stanley
knife to cut the hard compressed rockwool batts that Wickes used to
sell for sound-proofing purposes (but they don't seem to stock it
now).

Even the floppy stuff can be cut with stanley knife. Just compress
it flat on a hard surface with a length of 4x1 or similar and
cut along the wood edge.
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From Newsgroup: uk.d-i-y

On 26/04/2026 16:01, Chris Green wrote:

Andy Burns <usenet@andyburns.uk> wrote:

Chris Green wrote:

I'm leaning towards using rockwool insulation in my boat [...]
So, how should one cut it and how nasty is the resulting dust?

Keep the roll tightly wound, preferably in its shrink-wrap covering and
use a handsaw.

It's not a roll, it's panels:-

https://www.leroymerlin.fr/produits/14-panneaux-de-laine-de-roche-rockwool-rockmur-kraft-ep-40mm-1-35x0-6m-94060938.html

They blocked me, but then allowed me to see the item anyway !

It's very similar to what Wickes used to sell.

Just use a Stanley knife with the blade at its elongated setting,
Or use an angle grinder to put a sharp edge on the back of a
hacksaw blade if you need a longer cutter. Then make up a handle
to suit.

There are also Bosch 100mm cutter blades for jigsaw cutters -

https://its.co.uk/pd/bosch-pro-t-313-aw-special-for-soft-material-jigsaw-blades-pack-of-3-_bos2608635187.htm?gclsrc=aw.ds&gad_source=1&gad_campaignid=19638158635&gbraid=0AAAAAD_BUEtZjX7WjKEh2m99vKcu1X4wr&gclid=EAIaIQobChMI6_y3za6OlAMVyqNQBh03Lwv9EAQYAiABEgJ07fD_BwE

I can't really say about the dust, it never seems to bother me

OK, I'm not particularly susceptible to dust etc. so that sounds as if
it should be ok.

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From Newsgroup: uk.d-i-y

On 26/04/2026 15:46, Andy Burns wrote:

I can't really say about the dust, it never seems to bother me

Wear a mask, some sort of gloves, and overalls. Fibreglass can leave you feeling quite hitchy, if it gets to the skin.
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From Newsgroup: uk.d-i-y

On 27/04/2026 16:43, Harry Bloomfield Esq wrote:

On 26/04/2026 15:46, Andy Burns wrote:

I can't really say about the dust, it never seems to bother me

Wear a mask, some sort of gloves, and overalls. Fibreglass can leave you feeling quite hitchy, if it gets to the skin.

I ended up with a bloody great pus filled swelling on the side of my
neck the size of a pigeon egg.

That was in Johannesburg, though.

Lanced washed daily and fed on antibiotics for 10 days.

I hate the stuff with a passion.
--
"And if the blind lead the blind, both shall fall into the ditch".

Gospel of St. Mathew 15:14


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From Newsgroup: uk.d-i-y

On 27/04/2026 16:42, Andrew wrote:

Just use a Stanley knife with the blade at its elongated setting,
Or use an angle grinder to put a sharp edge on the back of a
hacksaw blade if you need a longer cutter. Then make up a handle
to suit.

Full marks for mentioning an angle grinder! This has been sadly lacking around here for some time.
--
Sam Plusnet
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From Newsgroup: uk.d-i-y

On Sun, 26 Apr 2026 15:06:37 +0100, Chris Green <cl@isbd.net> wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's >probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

A really sharp bread knife with at least an 8" blade, serrated or
plain. Or perhaps a pair of really sharp garden shears?
--

Chris
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From Newsgroup: uk.d-i-y

On 28/04/2026 10:12, Chris Hogg wrote:

On Sun, 26 Apr 2026 15:06:37 +0100, Chris Green <cl@isbd.net> wrote:

I'm leaning towards using rockwool insulation in my boat, I think it's
probably bendy enough and it's non-flammable and it's reasonably cheap.

I've read lots of (boring) instructions on how to use it but I can't
find anywhere that tells me how to cut it.

So, how should one cut it and how nasty is the resulting dust?

A really sharp bread knife with at least an 8" blade, serrated or
plain.

+1.

Or perhaps a pair of really sharp garden shears?

I've never encountered those, ever
--
"In our post-modern world, climate science is not powerful because it is
true: it is true because it is powerful."

Lucas Bergkamp

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