I have just finished dismantling my 5 year old. 4X8, “learning” layout. It is in an air conditioned and heated basement with controlled humidity. It had 2" extruded foam over 1/2" plywood. I used latex caulk spread out with a toothed blade. I weighted it down with lots of heavy books and let it stand for a week before removing them. Long story short, the foam was not stuck when I removed the cork roadbed and track. The plywood still feels damp after 5 years!
New shelf layout has 1/2" plywood so far. I am considering not using foam and just some cork as it is a switching layout in the prairies.
If I go with foam again, is there a better way to fasten it down?
You need to lay the adhesive with a caulking gun in a series of Ss. That way, air can get in from at least one direction to allow it to cure correctly. I can explain in more detail, but if you think about it like making a maze where there’s always a way out, then there will be a way for the air to get in.
BTW, are you talking about large area of plywood with foam bonded over the top? That does make it hard to run wiring, do switch machines etc. Better to build a good framework, then lay the foam on the crosspieces with a bead of adhesive to bond things.That’s a skinny area where air will get to the adhesive easily to cure it, too.
Or you can just leave the foam base loose and build your scenery as a series of liftouts, which is what I did on my Cascade Branch:
Bruce, a cheap caulking gun if you don’t already have one (although in fairness and in truth, based on my experience, I bit it and bought an industrial pro grade gun for my latest build, and don’t regret the extra cost), some PL 300, and a steel or plastic spreading spatula. As Mike says, lay a squiggly bead of it in four or five spaced squiggles, smear the goop thinly with your spatula, press the two surfaces together and weight the top one with stacks of magazines to spread the pressure widely. Wait 24 hours for a good solid cure, and you’ll never get it apart in one piece…not the foam, anyway.
Which brand of latex caulk did you end up using? If you didn’t use DOW Alex Plus Acrylic Latex caulk (plus silicone), I would highly recommend it. It begins setting up in ~45 minutes, which gives us plenty of time to make any necessary adjustments. Full cure is in 24 hours. Works GREAT and is only about $2.50/tube at your locale home improvement or hardware store.
Since it contains silicone, it cures using acetic acid (vinegar). Using an S-pattern when applying it over a large area is a good suggestion. I use it for affixing just about everything: foam → foam, foam → wood, foam → cork, cork → track, etc. It also stays flexible without sacrificing on holding ability.
I don’t know if this matters, but the 1/2" and 3/4" pink foam I bought locally this year has a very thin skin of plastic film on each side that I removed. It just peels back easily. Hard to tell it’s even there. I don’t know if removing it helps any air flow to the caulk for curing, but to the extent the caulk does cure, I’d think the adhesion would be better to the foam itself rather than the smooth film. I used Alex Plus to build some hills and it seemed to stick things (foam to plywood and foam to foam) together ok.
Just my [2c] If I were you on a ISL,I would use 1/2 ply,with Homasote 1/2 on top,hopefully you can get it where you are at,will hold most anything you put on it,nails screws,no wiring problem’s,I detest Foam,for a railroad layout topping,but that’s just me. Plus you won’t need any roadbed,use the foam for,mountains and rock out croppings,shear cliffs and the like.
Bruce, I never even thought about it, I just used Gorilla Glue. It is supposed to about glue anything big to anything big it seems?{?}. it seemed to work fine {not deteriorating the foam} and has held good and tight for a good 7 years now {since I built it}.
If you don’t know, be sure to put on in an “S” shape for about every 2 feet… That way any moisture can “escape” out the edges, or so they claim.
The way they advertise it , it will even bond into wetter and porous surfaces, so even if it “got wet” should hold tight.
I tried Gorilla Glue on an extruded styrofoam foam bridge abutment and the abutment began to dissolve.
BTW, I used the DAP Alex Plus with Silicone extensively on my latest build. The stuff that is white and dries white isn’t nearly as strong an adhesive as the stuff that goes on white but that dries clear. Dunno why, but thst has been my finding.
PL 300 is excellent, but nothing made of foam will survive the demolition process…it’s very sticky and hard when it cures. The PL 300 can also be used to fix tunnel portals and bridge piers into position…a good all-round adhesive that is safe when you need to use it on extruded foam.
Loctite makes an all purpose adhesive that will definitely to the job. They make one especially for foam board. But the all purpose label works well also
OK. maybe Crandell is right. I went looking in my “regular glue stash” for the trains…I found 3 bottles: Elmers GLUE ALL, Elmers Carpenter’s Wood Glue, and StyroGlue glue for foam.*
I USED ONE of those!! THE GLUE I used did NOT harm the extruded foam.
{I cannot find my Gorilla Glue any where nearby with my trains stuff, but Gorilla DOES say " BONDS: WOOD, STONE, METAL, CERAMICS, FOAM, GLASS & MORE!"…{now is that foam RUBBER or extruded foam?} so maybe I did use it. NOTE: Gorilla glue requires a “wetted” application, I do not recal doing that when I glued the foam to the wood. I used Gorilla somewhere and my biggest {meaning only} gluing jobs have been MRR related voer the last 6 years}
I do believe, and I may be wrong, as I may have been in my previous post, the StyroGlue was bought much much later than the initial table assembly. I bought it finding it after I glued the extruded foam to the wood and figured with LOTS of foam to glue for scenery, I shoud have it in my arsenal… It could also have been used?
*{I also have Super glue {CA, }plastic glue, and Woodland Scenics Scenery Glue but did NOT use those!}
Ah, now I recall…and you are right, G. I made the error. It was Goop, not Gorilla Glue, that dissolved my foam. I used the blue tube Goop Marine with acetic acid in it (I think?).
I now recall that the GG was what kept the end of the ME bridge in place on the foam.
That is OK, Crandell, I was fairly well SURE I used Gorilla Glue to glue the foam to the wood. I was going to test it out to see if you were right, but couldn’t find it in my “train glue stash” to do so. I could have been wrong.
Since my bottle of GG has disappeared to somewhere else than the “trains stash”, I wasn’t so sure {after you said you had it dissolve the foam}. GLAD to know you had something else dissolved the foam!
It has so many uses, the GG, That I am sure i have used it elsewhere and that is why it disappeared from the “trains stash”! I may have even used all of it. ANd the Maker DOES claim it is safe for FOAM.
Of course, once bonded, MAY NOT be removed without dammage, as GG claims to be “stronger bond than the wood it glues together”.
I use the Liquid Nails Heavy Duty Construction Adhesive for foam/ foam or foam/wood bonding. I had to tear some 2" extruded foam from a module framework and found that it took some convincing to break loose. In fact, there was a little skin of the foam left behind on the dried adhesive after it came off.
I also use the DAP adhesive caulk for bonding anything to the foam. Holds flat and tight, yet still comes loose easy enough if changes are needed. Don’t I know it… [:S]
The real test for me was when I needed to glue MDF to side of the the foam in one place as I had no wood to staple to on my high steel trestle area. Tried the Liquid Nails for projects (foam safe) but it failed miserably, Used the siliconized latex caulk, worked great and that is what I had been using for all the foam glue down. One must relize what one is trying to do to get the right performance. In the case of gluing to ply with ply being on the bottom we see that the foam will stay put without any glue help at all as long as nobody tries to move it so we really don’t need to worry at all about downward pressure and once all is said and done, very little about upward pressure. This leaves side pressure and since we have so many adhesion points, the caulk works great!
