Teardrops n Tiny Travel Trailers

Good day all,

I was looking for some answer about gluing plywood to styrofoam but did not find anything on the forum.

I've seen a video on youtube about Glidden Gripper to glued foam together, but what about wood to foam?
Is it suppose to stick both together or there is something better?

Im from canada and they dont carry it at home depot, is there some other brand that will do the same?

Thanks

I have used the following to successfully glue blue XPS foam to wood:

TB2 (Titebond II wood glue)- The trick is to use the glue sparingly so that all of the moisture is absorbed and dissipated by the wood. The foam won't allow any of the moisture to escape, so if you use too much, or it is a broad surface, the moisture can get trapped and the glue won't set.

GG (Gorilla Glue, the original foaming polyurethane kind) - Works great but sands harder than the foam so you have to be careful. Also, you have to work really hard to clamp or fixture parts so they don't hydraulic out of position. For this reason, I never tried it on large surfaces, just butt joints and embedded blocking.

GS (Great Stuff spray foam) - Similar to GG but sands a little easier; still harder than the XPS. Keeping the applicator and nozzle clean can be a PIA, even when using acetone, so I never seem to be able to get all of it to come out of the can, and it becomes relatively expensive. Some like to spray it on a palette and knock the foaming action down real hard before smearing it on to the joint (making it act more like GG), stating that they get a finer bubble structure for more even sanding, and better manageability.

PL300 (Loctite adhesive in a caulking tube, blue colored) - This stuff behaves very much like window caulk and is intended to be used in big zig-zag patterns to stick foam boards to walls prior to fastening finished wall materials over it. When laminating larger panels I spread it with a notched trowel and ran into trouble when the edges sealed themselves up but the field did not cure (it is water based). It scrapes off of wood pretty easily and peels of the foam with minimal damage. My solution was to cut mini kerfs in the foam to act as air channels, and not to try and coat the whole surface; I just knocked the bigger zig-zag beads down with the notched trowel where they laid and did not try to spread the adhesive out widely. This can cause problems if you are making cutouts later, since you will likely cut across an area that is not fully bonded.

30NF 3M "Green" contact adhesive - This stuff is expensive, about $100/gal. It's water based so it won't eat the foam, but it wants a relatively high pressure to get the two surfaces to bond properly, and that gets tricky. I brushed and rolled it on, as opposed to spraying, so my usage was relatively high and it took a long time to flash over in humid weather, so I had to wait a long time before assembly.

Epoxy - I started using epoxy late in my build so most of my panel work and core assembly was complete by that time, but if I had to do it over I would have probably used epoxy a lot more. The biggest drawbacks are that it cures so much harder than foam, so sanding dissimilar areas can be a problem; it's relatively expensive; you have to mix it, so there are consumables associated with that (start saving mixing cups, I use cut down dunkinD's ice coffee cups); clean up is with acetone (wear rubber glove so the bad stuff doesn't get drawn into your system by the solvents... very bad); and you have to wear PPE (charcoal respirator, rubber gloves, and I like to wear Tyvek sleeves). On the other hand it does not expand, and it is a chemical cure, so as long as it isn't too cold, it will cure with or w/o air. I think it would work well for laminating larger areas if rolled on. I would also consider rolling on a thin coat just to protect the foam a little better during construction. The foam is so fragile it collects dents, dings, and chunks out easily; and is so easy to over sand, but with a little epoxy on it it becomes much more resilient (primer would probably have a similar effect).

I haven't tried using latex paint or primer as a glue, except for laminating canvas to foam in a test piece. The canvas breathes, so it cures no problem. For joints between foam and wood or foam and foam expect to see the same issues as other water based products. My guess is that small areas will dry fine because it is all close to an edge, but larger areas will trap moisture and might not set up. The mini kerf technique would probably work for laminating foam on foam, if the application allows for them. If rolled on sparingly when laminating to wood I expect it would work, but I haven't tried it personally.

One more thing, XPS foam under 1 inch in thickness usually comes with a plastic film on one side. This is to make it less fragile in handling. This film does not take glue well at all, so remember to peel it off before gluing. It is not a bad idea to scuff your foam and remove most of the extruding "glaze" before gluing. Some people feel the need to pounce holes as well, based on the theory that these spikes of glue somehow increase the bond strength. My thoughts are that this is somewhat subjective with different people describing different results, and after some testing I have never been compelled to do so on a large scale.

PL300 is what you want , all the big box stores carry it even Canadian Tire whatever is close to you .

PL300 is what you want , all the big box stores carry it even Canadian Tire whatever is close to you .

Actually, I was going to add that it really depends on the joint and what you are trying to do. The PL300 doesn't sand well at all because it dries into a rubbery state.

In my experience there is no one perfect answer. Each product has its own advantages and disadvantages, so you kind of have to pick and choose based on the task at hand.

Thank you guys for your help.

Where I live there is not to many material so I'll go like that for my wall.

1/4 Plywood, 1" foam or more, 1/4 plywood.

i dont know yet if I will paint or use aluminium skin for the exterior.

I dont want to use skeleton wall, It is cold over here and I prefer 100% insulation to be able to use it without condensation.

So I just need to sandwich 2 ply with a foam and I want to make sure it will hold together for long

The weak part is the foam itself. With a foam-core panel, the joint between the foam & the wood will be trying to work loose over time. 3M contact cement (Fastbond 30) would be good for what you're doing, but make sure your edge fastenings are all wood-to-wood solid joints, with glue & screws holding them in place.

You might look up SIP construction used in home building now. The difference between this type of construction & a trailer is the vibration & loading a trailer has to take over time. In a house it just has to sit there, a trailer is constantly moving & working as it bumps along down the road.

Zip panel R is a fiberglass faced osb with the foam already on it. You might see if it is available it will save a lot of steps.




I even plowed out the foam to make room for the wall studs ...

... and lined my pantry and closets with it

I make glue anchors into the foam by making a hole in the foam, then pumping the hole full of PLpremium, then applying a thin layer of PLpremium to the wood. Spread the PLp with a spatula.
PLp swells slightly as it cures, locking the glue into the foam panel hole.
viewtopic.php?f=55&t=64918&start=15#p1157227

Thank you all,

I'll check what I can find over here at the store and I will use your expertise