Warp resistance of plywood vs solid SPF lumber

Question

I need to fabricate a small wooden masking platform that will serve to reduce the gaps between radiator pipe holes in the floor and the floor itself. Basically, the gaps are more than what pleases the eye and, now that I know exactly where the pipes are going, I can stencil out a hole projection on a piece of wood that is about 1" x 10" x 10" so that, when it goes on the floor, it closes some of the gap between the pipes and the holes. Basically, I am doing the same thing that an escutcheon would do but I can't use escutcheons because the pipes are too close to one another.

Since this wooden plate will be nailed to the floor and there will be presence of heat nearby, what is the best choice of wood-like material to cut this piece? The clear choices are SPF lumber (cut a piece out of a 1x12) and smooth plywood. I would prefer to not use OSB as it has a rough surface. The most critical aspect is the material's warping resistance, obviously I would like something that will not warp under the presence of heat over time.

Answer 1

Plywood is inherently more stable than solid wood due to having been constructed in layers with grain at alternating right angles. Specifically, plywood with many thin layers will be more stable, and hardwoods will typically move less than softwoods.

I'd consider BC grade (commonly found at lumber suppliers) to be a minimum standard of quality for this purpose. You could look to a specialty supplier for thin-veneer hardwood plywood for maximum stability.