DIY Modifying the Height of a Vanity

Clear the top surface, pull out the drawers and empty the inside of the vanity. Spread a tarp or plastic sheet over the floor to protect it.

Turn off the water to the bathroom, either where the water pipes emerge from the wall inside the vanity or at the main water supply source. Open the faucet to drain remaining water.

Remove any knobs or handles on the plumbing inside the vanity. Use a wrench to disconnect the water supply lines and pull the P-trap pipe loose from the drain pipe exiting into the wall. Place a bowl or pan under the pipes to catch any escaping water.

Pry the backsplash slightly away from the wall to break the seal. Slip a thin sheet of plywood, a plastic cutting board or similar item between the wall and the vanity to protect the wall from pry bar damage. If the backsplash is separate from the counter, such as ceramic tile, wait until after the vanity is removed. Measure the current vanity height and add the inches you intend to raise the vanity. Cut the tile or backsplash material, using a tile cutter or appropriate tool, to the height needed. Pry the excess free and discard.

Remove any screws holding the vanity to the wall. These are driven from inside the cabinet into the wall studs behind the cabinetry. Mark the wall, well above the vanity top, to indicate where the studs are for the vanity reinstallation.

Insert the plywood or plastic between the vanity and wall, then slip in the pry bar and apply gentle force to break the vanity free. In some cases, installers glue the entire back of the vanity to the wall. If the vanity is glued to the wall, continue prying gently, moving the pry bar from section to section, until it comes free.

Use the protective plywood or plastic to protect the floor from the pry bar, and pry the vanity up from the floor, again working gently to avoid damaging the vanity or the floor. Lift or slide the vanity out of the area. In some cases, the floor covering doesn't extend underneath the vanity. Slide shims or plywood pieces underneath the edge to overcome the ridge. Lever and slide the vanity free.

Measure the length of the vanity, from side to side, and the depth, from the vanity face to the back. Run the tape measure from inside the toe kick to the back wall for accuracy. The platform will rest directly underneath the vanity walls, providing a built-in look.

Cut two boards to the length of the vanity toe kick. Cut two more measuring the vanity depth less the thickness of both length-wise boards. Cut a sheet of plywood to both the length and depth required. Use the board thickness desired according to how much you wish to raise the vanity and the plywood thickness needed for the boards used.

Drive nails through the ends of the lengthwise boards into the depth-wise boards, where the boards meet. Top with the sheet of plywood and nail in place. Set the vanity platform in place and attach it to the wall by nailing through the rear board, into the wall, where a stud is marked.

Replace the back of the vanity to eliminate large, ugly holes where the old plumbing lines were. Rip the old back off with a pry bar -- work carefully to avoid damaging the vanity walls. Cut a new back to size from 1/4-inch plywood. Spread a thin bead of construction adhesive along the back vanity frame. Press the new back in place and nail along the perimeter every 6 to 8 inches, using finishing nails.

Measure and mark the vanity back to show where plumbing holes are needed. Use the old back piece as a template to make the job easier. Raise the old piece the number of inches the vanity was raised above the new vanity bottom edge. Mark the plumbing holes and remove them with a hole saw or jig saw.

Set the vanity in place on top of the new vanity platform. Nail through the vanity back into the wall studs. Spread a bead of silicone caulk along the gap between the backsplash and the countertop if the backsplash is separate, or above the backsplash if it is one piece. Cover the exposed portions of the vanity platform with paint, stain, ceramic tile or any material desired.

Reattach the plumbing to the sink. You may need a longer drain piece, which generally slips in between the P-trap and the back drain pipe where it exits through the wall. Replace flexible water supply lines with longer pieces; soldered plumbing lines or PVC may require more extensive connection work. Consult a plumber if necessary. Replace the vanity drawers and contents, then turn the water back on.