Foamboard to Plywood glue

[Mark Gibney]

I plan on using rigid foamboard to make large floating shelves torsion box style.
They will be 2 1/2" x 12" x 80", so I plan on using 1 1/2" rigid foam with a skin top and bottom of 1/2" Baltic birch plywood.

Right now I can only source rigid foam with a foil surface.
Does anyone know if I can glue plywood successfully to this foil?
Is the foil in danger of de-laminating?

I am looking at getting the Formular sheets (no foil) but they are on backorder until April here in SoCal.

Don't want call-backs on this job! Thank you

[John TenEyck]

Mark I posted about doing the same thing a little while ago: https://sawmillcreek.org/showthread.php?290227-A-Quick-Stress-Panel-Approach I used 1-1/2" Owens Corning foam panels and ran them through my drum sander to calibrate the thickness prior to adding the 1/4" plywood skins. I used Gorilla Glue to glue the plywood to the foam.

I suspect GG will stick to foil, too, but I wouldn't do it because you can't calibrate the thickness. Can't you buy OC foam panels out there?

John

[Jim Becker]

Polyurethane (Gorilla or any other brand) works well for this application.

[Mark Gibney]

Thanks John and Jim. I spoke with a rep for the company that sells thru Home Depot out here and he said there is no issue with gluing plywood onto the plastic coating on their rigid foam boards, so that's the way I'll go.
I'll get some foam and do a test with Gorilla glue.

[Mark Gibney]

John I forgot to answer your question about Owens Corning. AFAIK they sell 4x8 sheets under the brand name Foamular (exactly what you used in the shelves you made), which I cannot get here in time for the job. There are other brands of rigid foam available that are probably very similar so I think they'll work out.

By the way you did a great job with the shelves for your friend, they look great!

[Dave Sabo]

North Hollywood says they have over 50 on hand
https://www.homedepot.com/p/R-Tech-1-1-2-in-x-4-ft-x-8-ft-R-5-78-Rigid-Foam-Insulation-320817/202532855

even if it’s inaccurate , they should have one or two lying about.

[Mark Gibney]

Dave that's the product I'll be using. I had my eye on the Owens Corning pink foam which I don't think has a sheathing on the surface, but I think this R-Max / R-Tech product will work fine too.