Facing Expansion

[SmujnStar]

Ok, expansion....

We have been told to leave a gap in the floating subfloor to allow for expansion. Do we need to do the same with facing pieces? We are currently facing the boxes over our wheel wells, and planning on facing the walls of the bus soon. Do all wooden surfaces, even those screwed/nailed into framing, need the same expansion gap?

If so, does having a 3/8th gap in your walls allow water and debris to get back behind your walls?

[SmujnStar]

Image 1: Spacing on our subfloor (lego's are 3/8")

Image 2: Dry fitted wheel-well box, ready to be faced

[Jacob]

I wouldn't "wedge" any of the panels into place where you have pressure holding it in place. Or leave a large gap in between the panels. Most things I have read about plywood expansion say 1/8th of an inch on full sheets and this is probably a conservative number for worst case scenarios. My "opinion" is that as long as the sheets aren't butted against eachother tight and are attached well to the floor or wall you should be okay but if you can live with the gap and it makes you feel better about possible problems with expansion then by all means leave a gap!

[T-Bolt]

There in no need to leave any gap in the plywood subfloor. Plywood is dimensionally stable due the the fact that each layer of wood has the grain running in opposite directions. In building houses we use tongue and groove ply glued and screwed down. There is no movement.

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[Skipoffools]

You only need an expansion gap for hardwood floor.