Standard bathroom sink cabinets are without drawers or shelves to accommodate plumbing. Bathroom sink cabinets are generally shorter and narrower than kitchen cabinets. A typical bathroom vanity cabinet will measure approximately 30 inches tall, 30 inches wide and 22 inches deep. There are two doors for access to the plumbing and one shelf forming the bottom of the cabinet. The front of the cabinet will have a 3-by-4-inch toe-kick notch cut out on the bottom where your toes slide underneath when you are using the sink.
Cut a 3-by-4-inch notch out of the two 20 1/4-by-29 1/4 matching pieces of birch plywood on the front corners. Balance them on their backs with the toe-kick notch facing up.
Glue the edge, then insert the 20 1/4-by-27 3/4-inch piece of plywood in between the two jambs for the bottom of the cabinet. Line the front edge of the bottom up with the toe-kick notch, leaving a 4-inch recess between the floor and the bottom of the cabinet. Nail through the jambs into the bottom edge of the shelf with the pin nailer.
Tip the cabinet up toward you on its jambs. Insert one piece of pine between the back corners of the jambs where the cabinet will screw to the wall. Nail it through the side of the jambs with the pin nailer.
Build the face frame by laying two 26 1/4-inch pieces out on a flat surface parallel to each other for the vertical styles of the face frame. Place the other two 25 1/4-inch pieces of alder between them at the top and bottom for the horizontal rails forming a square. Insert the 22 1/4-inch piece of alder in the centre vertically in the square as a divider. Glue all the points of contact. Hammer one corrugated nail into each joint creating a face frame with a centre divider.
Lay the cabinet on its back, run a bead of glue along the top edge and lay the face frame onto the cabinet, face side up. Flush the sides, the top and the bottom with the top edge of the toe-kick. Nail the face frame to the cabinet using the pin nailer. Insert the other piece of pine between the jambs in front for the face of the toe-kick, and nail it through the sides of the jambs. Putty all the holes.
Sand the cabinet and doors with a sanding block with 100 grit sandpaper.
Measure down from the top 2 inches and up from the bottom 2 inches on both pieces of the 22 1/2-by-12-inch plywood and make a mark. Mount the hinges on the mark. Lay the doors on the cabinet face frame, square them up and finish by screwing the doors to the cabinet through the hinges. Stain and lacquer the cabinet.
A prefabricated one-piece integrated sink and top works well for this cabinet. Measure for plumbing, make the appropriate cuts, screw to the wall and drop the sink-top combo on. Fasteners are attached to the bottom of the one-piece sink-top. Screw the top on to the jambs by reaching into the cabinet through the door openings.
Always wear safety glasses when working with power tools or wood.