I have a lot of tongue and groove, reversible shiplap / v-groove boards from a big box store. I would like to use them for a plank ceiling that is 25x8ft. It is unclear to me how these boards allow for expansion since they sit flush together with seemingly no expansion gap on the V-groove side (see image). If I use the shiplap side down, do I need to rip the tongue to allow for expansion?
I plan to treat the boards before installation. I live in an area that stay low humidity year round.
Best Answer
Barring very unusual circumstances, they are more likely to shrink from the "as installed" state than expand from it.
If they do expand, the small and sloped contact area works in your favor.