# Forum Home Renovation Structural Renovation  How do you cut polyester insulation batts?

## bcp

Tontine polyester insulation. Great stuff but a nightmare to cut. Tried: Razor knifeSaws = tenon saw, rip saw, hack sawRolling up into a tight roll and cuttingResulting in it still being a nightmare to cut.  Someone must know the easy way. 
(couldn't find which forum this belongs so put it here where there's lots of traffic :No: )

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## Bloss

Stanley knife new blade. use a straight edge - piece of timber underneath- kneel or press and draw knife along edge - same as for fibreglass batts and rockwool batts too.

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## Tools

If you want to cut across the width then just tear it and it will tear in a straight line. Length ways you will have to knife it. 
Tools

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## Bloss

> If you want to cut across the width then just tear it and it will tear in a straight line. Length ways you will have to knife it. 
> Tools

  Good quality brand name stuff yes - some of the cheaper chinese imports nope.

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## fubar

gday we cut heaps of this stuff using good quality serrated bread knife 
hold one end of the batt down with foot apply tension with one hand cut with other

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## stevoh741

I just hold it against the stud and cut through it along the length of the stud. Cuts perfect.

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## bcp

All this helps, but it's still very difficult. I'm using tontine sound insulation - perhap it's thicker or something, because you can't cut through it with a razor in 2-3 cuts or just draw the knife along - you literally have to saw down and down and down.

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## Armers

Kevlar Shears maybe? $$$ though... otherwise a good pair of felco secateurs.. (which i use for kevlar shears) 
Cheers

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## bcp

> I just hold it against the stud and cut through it along the length of the stud. Cuts perfect.

   This technique works pretty well! 
As does the tearing lengthways (thanks Tools)

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## fubar

is this  the grey coloured sound insulation? 2400x1200 sheets? comes in different grades and thicknesses?

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## bcp

> is this the grey coloured sound insulation? 2400x1200 sheets? comes in different grades and thicknesses?

  Yes, that's the stuff. It's 2.0 i think. (I'd hate to cut 5.0!)

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## fubar

I construct recording studios and have literally cut up tonnes of the stuff all gardes and thicknesses and there hasnt been an easy way so far but would love to find one .
Some sheets will tear after small cut but others have the fibres running in all directions and the serrated knife(very very sharp) seems the only way

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## Bloss

I though you meant the polyester insulating batts not acoustic panels. Sounds silly - but electric knife is the go - same to cut foams of various types too - styrofoam or bedding foam, cushion foams etc. Just a cheapie -$12-$18 anywhere. Brand name Sunbeam or Breville only $30 or so. Can cut you roast beef with it to . . .  :Smilie:

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## PhilT2

Did some soundproofing on a unit block a few years ago, around the lift well and common walls etc. Found out how difficult this stuff is to cut after putting in the quote..

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