# Ridgid Foam to Concrete



## kevsprojects (Jul 8, 2011)

I am planning to insulate my crawlspace concrete walls with rigid foam board. Most of what I've read indicates to attach it directly to the walls. I agree with that but am curious about the exact method of attachment. I was thinking of using a #8 x 3" construction screw with 2" washers. I would probably use 2" foam board & figuring about 3/4" or so penetration of the screw into the concrete wall. The walls are solid not concrete block. I would need just enough penetration to hold the board in place. Does this sound like a viable method?

Thanks,
Kevin


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## UFoPilot (Apr 24, 2008)

I'd use glue.


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## packer_rich (Jan 16, 2011)

I've done the same project, and I used construction adhesive.


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## Lifeguardr (Dec 8, 2011)

Kevin, use Lepage PL 300 made for gluing foam board. Use the big one in your caulking gun and lay down a good healthy bead of glue either in an "S" pattern or 12" apart vertical lines. It'll be fine. Tuck tape the seams.


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## kevsprojects (Jul 8, 2011)

ok, I'll look into the glue, where can I get the PL 300 & will I need to "hold" the board in place with 2x4 struts or the like until it sets up?


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## Lifeguardr (Dec 8, 2011)

Almost any building centre like HD, Lowe's etc. will have PL300. It's pretty sticky stuff, so all you have to do is squeeze out the beads on the foam, then press it against the concrete - it'll stay. I used XPS stryospan 2"X2x8 shiplap edge and it was the best.


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## kevsprojects (Jul 8, 2011)

Great! sounds like a plan.

Thanks again


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## Gary in WA (Mar 11, 2009)

Keep in mind foamboard requires a positive attachment per Code requirements...... more than glue.

Pattern when gluing: http://joneakes.com/jons-fixit-database/743

Gary


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## kevsprojects (Jul 8, 2011)

That's a good site. I've researched topics from time to time on there. Maybe I missed something on that page via the link but, I didn't see anything about "code requirement" or "gluing pattern". I check the codes though to see if any red flags pop up.


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## Trucon01 (Jan 10, 2012)

Hey kevs... I'll be doing the same thing with my basement. We just started to tear down the drywall and the God awful painted paneling. Once I was down to the bare concrete, I was going to use Drylock Extreme to cover the walls (2 coats) and then glue that blue foam (either using 1 set of 2 inch foam or 2 sets of 1 inch foam, staggard seam). Then I was going to put up the framing around that.


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## kevsprojects (Jul 8, 2011)

yea trucon01, I was kinda wondering about the drylock for the walls before I insulate too. I'll be lookin at that too.


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## Beepster (Oct 19, 2009)

I am not so sure that the foamboard adhesives will adhere to drylock.

I am in the process of glueing the foamboards to my bare block walls. The only surprise that I am finding is that it takes a whole tube of adhesive per 4' x 8' sheet.

GBR, do you need positive attachment if you are going to 2x4 frame over the foamboard with the bottom plate being nailed to the floor and the top plate nailed to the joists?

B


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## concretemasonry (Oct 10, 2006)

Beepster -

I assume that GBR was referring to the fix-all, cure-all, prescriptive code requirement for foam requirement for universal administrative purposes. If there is a wood frame wall in front of the foam and not attached to the foam, a adhesive can be acceptable in the real world since the purpose of the foam is only to attach the foam to the concrete.

Use the proper adhesive for the type of "foam" you choose. The cheap EPS foams (expanded white beadboard) can be eaten by the better adhesives that are intended for use on XPS extruded foam.

Dick


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## Gary in WA (Mar 11, 2009)

Good point, Dick!

"GBR, do you need positive attachment if you are going to 2x4 frame over the foamboard with the bottom plate being nailed to the floor and the top plate nailed to the joists?" ----- no, but check locally with the AHJ.
Keep in mind the glue pattern provided on the site quoted will stop any air from getting to the colder concrete wall. Moisture will compromise it if left with a 1/32" air-gap....... So just tack-gluing a board then pushing a built frame wall tight next to it will *not *seal the board to the concrete. (The whole point of the glue pattern).

Remember to fire-stop every 10' along the wall as well; http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec002_par031.htm

Dryloc or other water-proofing, just directs the water to another, easier entry location, like the wall/footing/slab joint, where it will rot the framing easier. It localizes the moisture to do more damage in one area rather come through everywhere on the wall, a little at a time. UNLESS you have an interior drainage system; fig. #15: http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

Gary.


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## metal (Sep 8, 2011)

Glue for sure. It'll hold. It works a lot better as an insulator too. Go for it!


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