Craig,
Tight Bond works well for bonding foam to foam but not so much for other materials to foam.
I use a Polyurethane sealant like Vulkim Seal to bond wood or metal (beverage can corrugated metal) to the foam. it is a little messy and takes a while to set/cure but holds really well.
Have had it outside 24/7 for about 3 years on my mill buildings with no problem at all. It is flexible and has a very secure bond.
I’ve just been using silicone caulking to bond the cans to styrene and figured I’d use the same to bond the styrene to the foam, or on sections that didn’t have windows or other details the cans to the foam.
I’ve been experimenting a bit with some small pieces with CA to bond the cans to styrene. Not sure how long it will last but it’s just small sections so if I end up having to rebuild later it’s not tht big of a future issue.
We’ve had mixed results. We ended up going with gutter flashing sealant foro can-to-foam, and, even then, we had to drive some pins through the cans in places.
TiteBond III will work for wood-to-foam, if you go that route. We have used that on all of our foam core buildings to date. The wood will rot before the bond gives.
Eric
Quick question how do you seal the foam from the elements , or where there is ground contact with the foam. Or does it need it?
I was planning on building a frame foundation (wood)for the mill and placing everything on it. That way I can make sure everything is nice and level and is on the layout in the right place. But I’m guessing the foam would be okay in the dirt so to speak as folks use it for tunnels etc?
Thanks. Was looking at making a building out of it sometime soon. And do recall the process I read somewhere online, I think I have the GR stored somewhere
We don’t. There is some evidence of bugs beginning to bore into the foam after a couple of years in the ground, but that is it. I should note, however, we have no freeze-thaw issues out here! 
Eric
We have freeze warnings last night(30* when I got up) and about same tonight! First time since 2021
I might have an opening for plow service in a few days…
I did a couple small test pieces for this method. Much to my pleasure I discovered that the blue or pink insulation foam is polystyrene foam. MEK works well to stick styrene sheet materiel to the foam. But with one HUGE note of caution. MEK melts foam. Well it melts all styrene that’s why it works. But if very much at all is used it will severely comprise the foam. The best way so far I have found with my test panels was to paint the sheet with a liberal amount of MEK and get it tacky then lay it on the foam and apply evenly dispersed weight (I used a piece of plywood larger than my test Panels and then heavily weighted the plywood making a make shift press). A little touch up on the edges, and with a little effort I had a foam board backed with styrene sheet that then could be used to attach detail parts to.
I’ll have to give that a test. Thanks.
Got any updates on this thread?
Let’s see I just burned 30+ days on a related project…
So nope. Haven’t made any progress since the MIK build. Once I get the hay storage building done, I’ll get back to the main mill sections. I’m kinda stumped at the moment with the unloading shed and the visible roof trusses.