Cutting Styrofoam

[rburke65]

I am planning on erecting a shop in the near future and a buddy called with some free 2 1/2 " 4'x8' sheets of styrofoam. I got 225 sheets. My problem is now I have to make a Hot Knife to cut these to fit the stud cavity. Anyone have any experence with this or been down this road before......don't want to re-invent the wheel here. As always, Thanks of your response.

 

[nate379]

Drywall knife, straight edge and your knee.

 

[e-tek]

Nate's right - he means scoring it with DW (razor) knife, then snapping it. Should take seconds per piece. Nice score BTW!!

 

[rieferman]

someone told me (I think on this forum? I can't remember now) that a circular saw with the blade installed backwards cruises right through this material like butter - not verified by me though. But try score and snap first because that'll be much faster and easier if it works.

edit: +1 on the "nice score" comment by e-tek..

 

[Jeffksf]

Electric turkey carving knife has been known to work good on foam, maybe worth a try with styrofoam.

 

[Bull]

I am the proponent of the reversed saw blade in a circular saw...only way to go IMO. I tried the score and snap method. Blades dull quickly on the thicker foam, and you have to use a lot of force to penetrate the stuff far enough to get a clean snap (again, more an issue on the thicker sheets.)

I used a small 14.4 volt battery saw with the blade backwards...like butter, as they say.

 

[walrus]

I used a small 14.4 volt battery saw with the blade backwards...like butter, as they say.

Got to try this, when I did the addition on my home I used a circular saw with the blade in right. I was cutting polyurethene foam. It made a mess but worked well. I only cut outside

 

[rjohnson]

Get an old Lionel train transformer and connect a wire, it'll cut like butter!

 

[Bull]

Got to try this, when I did the addition on my home I used a circular saw with the blade in right. I was cutting polyurethene foam. It made a mess but worked well. I only cut outside

There will still be a mess in the form of styrofoam "sawdust." But having the blade backwards makes for a cleaner, more smooth cut.

 

[tab2]

I have done it with the blade in normally with a circular saw and was doing it with the foam already on a vertical wall. It cut extremely easily but the "sawdust," as Bull called it, are hot little pieces of foam that land on your arms and face that then cool on your skin which isn't exactly pleasant.

Good luck!

 

[nate379]

Score and snap works great on 2" foam, I haven't worked with 2.5" but I would imagine it's not much hardly to do. I would try that first and see how it is. If it works ok it will be much much faster than cutting it with a saw, hot knife, etc.

I used a sawzall when I had to notch stuff as well. Makes a mess but I just did it outside.

 

[Dragster Racer]

I used a table saw for thinner stuff. Set it up for the width I needed most, and went to town. Two people on the saw makes quick work of a pile.

 

[Falcon67]

someone told me (I think on this forum? I can't remember now) that a circular saw with the blade installed backwards cruises right through this material like butter - not verified by me though. But try score and snap first because that'll be much faster and easier if it works.

edit: +1 on the "nice score" comment by e-tek..

Also works on corrugated tin material. Foam - Slice and snap like sheet rock, stock up on box cutter blades.

 

[tcianci]

I used the train transformer and wire set up myself. I scored piles of 18 inch square by 6 inch thick blocks so I sliced them down to 1 1/2 and ran them over the outside of my foundation held on with roof coating before I backfilled.

 

[kbs2244]

All I have ever seen on jobsites is a razor knife with the blade extended all the way.
One guy was useing what looked like a kitchen paring knife.
A deep score and it snaps just fine.

If you have a lot to do all the same a jig set up on a 4x8 on some saw horses with a 2x4 screwed to it as a snap block under the sheet and useing an 8 foot drywall square as a score guide will work well.