Plywood grades explained: MR, BWR and BWP, and where each belongs

MR stands for moisture resistant, which in practice means it survives humidity and not water. It is interior-grade board for wardrobes, beds and anything in a dry room. It is also what gets substituted into a kitchen quote when nobody checks.

BWR is boiling water resistant, a phenolic glue that holds up to sustained damp. BWP — boiling water proof, sometimes sold as marine grade — is the same family taken further and is what belongs under a sink, in a bathroom vanity, and in the bottom run of any kitchen.

The grade only describes the adhesive between the plies. It says nothing about the timber, the number of plies, core gaps or whether the sheet is flat. A cheap BWP with a gappy core is worse than a good BWR. Lift the sheet, look at the edge, count the plies and check for voids.

Ask for the ISI mark and the batch stamp on the sheet itself rather than on a delivery note. Substitution happens between the showroom and the site more often than anyone admits, and the only place it is visible is the edge of the board after it has been cut.

The grade describes the glue. It says nothing about whether the core has voids.