Let’s face it—it’s easy to get water on the floor of your sink base cabinet. We’ll never understand why cabinetmakers use particleboard for the base, but they do. And once it starts swelling, your only option is to replace it. But you don’t have to cut out the entire bottom. Here’s an easier way to install a new sink base bottom.
Remove the drain lines (and garbage disposer, if there is one) to get maneuvering room. Then trace a cutting line about 3 in. in from all four edges. Then cut out the middle section of the swollen sink base with a jigsaw (Photo 1). Next, cut a piece of 1/2-in. plywood to the interior size of the sink base. Cut slots for the water supply tubes. Seal the edges and face of the plywood with urethane varnish. Then install the new plywood floor and fasten it to the old floor (Photo 2). Caulk around the edges and pipes to prevent water from seeping under the new floor. Finally, reattach the P-trap and garbage disposer.