How to Replace the Bottom of the Vanity That Has Been Wet and Ruined

Place a block of wood under the front of the vanity. There's an overhanging lip called a toe-kick where the front of the bottom shelf extends out over the frame. Place the block under the edge of the extended shelf. Insert the tip of a pry bar under the block and pry down to lift the front edge of the shelf above the cabinet face frame.

Insert a screwdriver under the front lip of the shelf to hold it there. Remove the prybar and insert it under the shelf. Pry the shelf up to loosen the nails or staples holding it in place. When you have enough room, use a jigsaw to cut the shelf in half from front to back. Pry and pull the two pieces out of the vanity. Wiggle them up and down if necessary to loosen them and pull until they come out.

Measure the two pieces. Use a table saw to cut two identical pieces of 3/4-inch fir plywood the same size. There are cleats or a solid bottom rail around the perimeter inside the vanity at the bottom where the shelf sits. Measure the distance from the floor inside the vanity, to the top of the cleats or rail where the shelf sits.

Cut a two-by-four-by-18-inch stud to the measurement width using the table saw. This is a brace to support the center joint for the two pieces of plywood shelf.

Insert one of the pieces of plywood into the vanity on one side. It should fit snug at the front and back and on one side. Apply glue to one edge of the stud brace. Insert it under the joint in the middle of the plywood, but leave one-half of the top edge of the stud exposed to support the second piece of plywood.

Insert the second piece of plywood into the vanity. It fits tight against the first piece, supported by the other half of the brace. Tap it down tight with a hammer if needed.

Shoot 1 1/4-inch pin nails around the perimeter of the two shelves spaced 8 inches apart. Shoot pin nails through both pieces at the joint to penetrate down into the top of the brace.