Will plywood swell in the monsoon? Grades explained

Many clients have had a kitchen cabinet swell or a bathroom vanity crumble in an earlier home, and they ask us whether that will happen again. It usually comes down to which plywood was used where.

Plywood is made of thin wood layers glued together. The glue decides how it handles water. MR, or moisture-resistant, plywood uses a urea-formaldehyde glue and handles humid air but not direct water. It is fine for bedroom wardrobes, bookshelves and living room units. BWR, or boiling water resistant, uses a stronger resin and suits most kitchen cabinets. BWP, or boiling water proof, uses phenolic resin and can take repeated wetting; it is what we use under the sink, in bathroom vanities and anywhere near a washing machine.

As a standard, we build all kitchen and bathroom carpentry in BWP and wardrobes in MR or BWR, depending on whether the wall is an outer wall. Outer walls in Ahmedabad often get damp during the monsoon from July to September, so we add a layer of aluminium foil or a laminate backing on the side that touches the wall and leave a small gap for air.

Edges matter as much as the grade. Water usually enters through an unsealed edge, not the face of the board. Every panel we make has its edges banded by machine, including the hidden ones. No plywood will survive a long-term leak. If you see a damp patch on a wall, have the plumbing or terrace waterproofing fixed before carpentry goes in. We check walls with a moisture meter at the site visit for this reason.