Finishing the Underside of Furniture

Sealing and finishing table tops on both faces helps prevent seasonal warping and cupping. January 18, 2011

There is a debate in our shop about whether to seal the underside of tables, due to breatheability. Should we?

Forum Responses
(Finishing Forum)
From contributor B:
I always seal the underside. Cabinetmakers tell me it helps stop the top from warping, and I think it looks more professional.

From contributor J:
We always lay a good coat(s) of sealer under solid wood tops. Veneered tops we seal outside of the aprons.

From contributor P:
I always seal the underside, especially on veneer tops. It traps whatever moisture is in the top, thus avoid warping.

From contributor L:
Always finish the underside of a tabletop. It will balance the slab. If you only spray the top, the moisture will be absorbed through the bottom and trapped in the slab unable to escape through the top. When this happens the top will become concave. In the winter the opposite will happen. If both surfaces are sprayed equally, then the moisture will travel through the slab at an equilibrium, stabilizing the slab.

From contributor G:
Not to mention keeping odors from permeating the wood.