yep! run down to your local DIY store/home depot or such and grab a small bucket of multi-purpose plaster and a spare paint brush!
cardboard and foamboard have a bad habbit of getting beaten-up fairly easily! to prevent this, and also to add some cool texture to your buildings, take some plaster and water it down a little bit.
by coating your entire building in a light layer of plaster, you'll really strenghen it and help it surviv the rigours of general gaming!
this is what we did at the canadian hq with *all* of our cadian display tables! (and our helms deep table too!)
plaster coating is also a must if you're building with foamcore as it seals it and thus allows you to spray primer your terrain! (handy when you've got a dozen or so 8'x4' tables to paint!
)
cheers!