What to do with the seams between foamboards?

[videobruce]

Not really a "design" question, but using 1/2" rigid foamboard over 3/8" plywood with seams staggered so they are not in line with the plywood seams.

Can/should the seams between the foamboards be covered over like drywall seams? If not, isn't movement a issue and the resulting cracks?

 

[Motley]

Just use latex caulk in between the seems. Thats what I did. The caulk is flexible enough not to crack.

 

[videobruce]

Interesting.

 

[D&J RailRoad]

I would think that using an adhesive between the foam boards would keep them from shifting from each other. Subsequent layers of scenery on top of the joints would coceal them.

 

[Ken Portner]

Dry wall tape. Apply drywall mud (spackle). Sand it down and no more seams.

 

[Beachbum]

I use latex caulk.

 

[joed2323]

caulk is the way to go. caulk - spread even with putty knife and done

 

[Selector]

Depending on what is going to appear on the uneven or gapped surface, you can just place a single spanning layer of the green painter's tape over the gap, spray glue, and sprinkle ground foam, or use smallish clusters of ground foam to make a hedge row. You could place styrene slabs atop the gaps to act as roadway.

When I need embankments, gaps filled, or hills, I mix a batch of Plaster of Paris, Portland cement, fine-ground vermiculite, a dash of powdered masonry dye, and when it is hydrated I trowel it into place. The stuff is great for anchoring trees and utility poles.

The caulk would work, too, but it is much harder to drill it out so that poles can be stuck into it.

 

[videobruce]

How about a narrow sheet of cardboard?