# How to cut and seal insulation



## Mijotter (Nov 14, 2012)

I was wondering what you guys thought the best way to cut 2" xps rigid foam board. Tools I have at my disposal are a table saw, circular saw, jigsaw, and simple knife. Can it be scored and snapped. I just want it to be a nice clean cut no matter what it is. 

Also, they are 4x8 pieces so what would be the best way to seal them together? Simply joist tape? Thank you.


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## Trucon01 (Jan 10, 2012)

I would imagine the circular saw would give you the best cut. You certainly wouldn't be able to cut a 4x8 board on a table saw...

I used Tyvek tape when I put my boards together along with PL 300 adhesive on the walls.


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## Mijotter (Nov 14, 2012)

Yeah i realized after i typed that, that it might be abit too big for the table saw lol. Yeah I bought the PL 300 as well. How much did you use per board?


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## jklingel (Dec 21, 2008)

saws make a lot of "dust" which blows everywhere, and static makes them a PITA to clean up. a hand saw is the best in that regard. i find that if i cut them w/ a knife on both sides, sheets snap pretty nicely & w/ little dust.


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## joecaption (Nov 30, 2011)

I also perfure using a knife to cut it.
Just use some spray foam to fill any gaps or flaws once it's all up.
I use a cheap throw away plastic putty knife to smooth off the foam.

One other way that I did many years ago was install the blade backwards in a jig saw. It sort of melted it's way through and made almost no dust.
I've only done it that way once, and that was 10 years ago but it worked.


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## Mijotter (Nov 14, 2012)

The dust I can deal with, just looking for which option will give me the smoothest cut.


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## Windows on Wash (Aug 30, 2011)

Utility knife with a sharp blade works well.


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## Mijotter (Nov 14, 2012)

Good call. I went out and got a drywall blade for my utility knife and it scored and snapped like a charm. Thanks everyone. Now for the next part. Does anyone know the cure time for PL 300 adhesive?


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## Mijotter (Nov 14, 2012)

Actually I finally found it. 20 minutes to set and 7 days to cure...what the. Does it have to be braced against the wall for those 7 days? sheesh.


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## Beepster (Oct 19, 2009)

I braced mine overnight. Never had a problem. Shoot out a little dab and see how hard it gets in 24 hrs. My sheets were wedged snug between the joists and floor.

B


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## Mijotter (Nov 14, 2012)

So I cut, glued and placed the xps boards on 1 wall tonight. They're being braced by whatever I could find around the house lol. Should 24 hours be enough to take the braces down? 

Also, How do i go about sealing the xps at the corner. I have 1 side that is cornered to concrete, it's a small indent coming in about 5 inches from the main wall(only finishing half the basement) and another corner that will take more xps on the perpendicular wall. Thanks.


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## Windows on Wash (Aug 30, 2011)

The glue should be dry by then. Whether it holds very well is another story.


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## Mijotter (Nov 14, 2012)

Ok good. So does anyone know how best to seal those corners in my above post?


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## Mijotter (Nov 14, 2012)

Would just sealing it with the PL-300 caulk be adequate for the floor and corners?


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## Mijotter (Nov 14, 2012)

Anyone?


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## Windows on Wash (Aug 30, 2011)

Use a foam compatible sealant. PL might melt the foam.


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## Mijotter (Nov 14, 2012)

Actually pl300 is made specifically for adhering to xps just need to know if it will give me the proper seal at the seams and the concrete floor as well.


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## Windows on Wash (Aug 30, 2011)

Just make sure the concrete is clean and it should work.


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## rebelranger (Aug 1, 2012)

Screws and Nails! If the glue doesn't work.


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## jpc (Dec 11, 2010)

Hey don't rule the table saw idea out just yet, if you havent already completed this project. Depending on whether you have enough outfeed and side feed support around your saw, and its rip capacity, we use 2"xps all the time at work and unless it's a random small peice or doesnt break on one of the joints we used the table saw for any repetitive cuts. Nice clean edge for tight fit. It does make a pink mess.Im just speaking from personal experience, not sure if its right or wrong but it does yield good results. Good luck with your project


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## Gary in WA (Mar 11, 2009)

Check with your local AHJ as the f.b. may require positive fastening per Code.The adhesive pattern is important, no air to concrete; http://joneakes.com/jons-fixit-database/743

Use the waste on the rims; http://www.buildingscience.com/docu...joist/files/bscinfo_408_critical_seal_rev.pdf

Use canned foam under them and between joints or mastic/tape because it may shrink later; http://www.buildingscience.com/documents/published-articles/pa-foam-shrinks

Gary


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## Mijotter (Nov 14, 2012)

Ok so everywhere I look people are suggesting this Great Stuff...stuff. However I cannot find any information if it's compatible with xps rigid foam foam or not. And is this Great Stuff truly safe as far as vapors and coming in contact with moisture/condensation goes? If there a caulk or sealant alternative out there? Please help and thank you.


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