Is B-B plywood (oil-impregnated construction grade plywood) suitable for use in casting architectural concrete?
If used it should first be made impervious to moisture absorption by applying two coats of a suitable coating or wood sealer. Even then it should not be used until tested to ensure that the coated or sealed plywood will produce an acceptable concrete surface. B-B grade plywood is nonuniform in its absorption and unless effectively treated it will not produce a satisfactory architectural surface. Furthermore, grade B-B commonly used for formwork has both faces of B-grade veneer, which is a smoothly sanded solid-surface sheet with circular repair plugs and tight knots permitted. Impressions from the plugs and knots could appear in the final concrete surface.