Spray Foam and Insulation Foam Board

[danmerkel]

Very quickly, my layout is being built using 4" strips of 3/4" plywood to define the perimeter and 3" strips of 3/4" plywood on edge as inside bracing flush with the bottom of the 4" strips.  On the 3" strips, I add 1/4" luan paneling/plywood then top that off with 3/4" sheets of pink, blue or green sheets of foam insulation.  This brings the inside up to the same height of the outside perimeter boards.

As you might guess, I do have some gaps in the foam insulation sheets and would like to use low-expansion spray foam insulation to fill those gaps.  But I'm wondering if the spray foam would significantly "attack" the foam board.  I'm sure that you're thinking "try it and find out," but I'd rather not spend the $$$ for a can of the foam only to find out that it doesn't work.

Does anyone know/has anyone tried using spray foam with foam insulation sheets?

Thanks!

dlm

[JoeinPA]

Ken Patterson uses spray foam ( I think its called "Great Stuff")to glue sheets of foam together and to fill in gaps. You can see his work on his YouTube channel.

Joe

[mlehman]

Sounds OK then, I would've been wary also.

That said, spray foam is difficult to keep it where you want it, even the low expansion variety. If you just need to fill gaps, you might try Sculptamold. It's reasonably priced, sticks to foam, is easy to apply and cleanup, dries so it's light, and any excess is easy to store for later use. I use it as a base for my scenery, too, but it works great atfilling all kinds of gaps around and inside the layout.

[BigDaddy]

Ken Patterson shows his spray foam techniques in his Whats Neat Videos but you have to search for them.  There is a forum member that has a Youtube Channel called Ron's Trains N Stuff that did a recent video on using spray foam to fill the gaps.  that one would be easier to find.

It expands a lot.

[rrinker]

 No issue using the Great Stuff expanding foam with extruded foam board. As mentioned, Ken Patterson does this and shows it in his videos all the time. Of course it will expand and overflow the crack - you just slice it off and sand it smooth and level with the foam on either side. 

 I'm not too keen on Ken's using it to glue sheets of foam together, because it expands rather aggressively, but then if you watch his videos and see how much weight he stacks on top - that is probably the key. Uneven expansion could result in the bottom layer of foam being perfectly level but the top one glued on endign up tilted. Actually - I think he uses Gorilla Glue for laminating foam sheets, not the expanding spray foam. Gorilla Glue expands as well, but not anywhere near as much as the expanding foam stuff.

                      --Randy

 

[railandsail]

You might have a look at this blog from a fellow in Hawaii. I just happen across this particular foam subject of his.
http://model-railroad-hobbyist.com/comment/reply/26240/249683#comment-249683

[SouthPenn]

One thing to remember about spray foam, it's imposible to save a partially used can of the stuff. This makes it very expensive to use.

[Medina1128]

I fill the gaps in my foam with inexpensive acrylic caulk. You know those fake credit cards you get in the mail? I save and used them to smooth the caulk. When I'm done, I wipe them off with a paper towel and reuse them.