Medicine cabinet makeover

Getting started

With the old thing removed, peek into the hole looking for obstructions: wood, wires or pipes within the wall that may restrict the overall size of the new installation. If the way is clear, make the new cabinet as large as you like. Typically, the only limiting factor in this equation is the width of the space between studs. This is usually 14 1/2", although not always, especially in older homes. Resist the temptation to cut studs to make a wider opening. While it's possible to reinforce wall frames to allow stud removal, it's better to leave structural wall members alone.

Next, carefully measure the width of the stud space you've created, with numbers noted from three places. These measurements ultimately determine the width of the melamine box, so be careful to get them right. In most cases I build inset cabinet boxes 1/4" to 1/2" smaller than the narrowest of the three measurements I find. This makes it possible to square the cabinet and position it just right during final installation.

Once you've determined the overall width and height of your melamine box, you're almost ready to make sawdust. But there's still the issue of cabinet depth to consider. The name of the game here is to maximize usable cabinet depth, given the wall cavity you have to work with. Walls framed with 2x4s offer a 3 1/2"-deep internal cavity, plus 1/2" for drywall. That works out to a 3 3/4" overall cabinet depth, allowing for a 1/8" cabinet back panel and some space. A 2x6 wall has room for a 5 3/4"-deep cabinet. If you're working on an exterior wall, see “Insulation Insights”.

Prepare the sides, top and bottom of your cabinet, including a series of holes drilled into the cabinet sides to accommodate adjustable shelf supports. I used 1/4"-dia. shelf supports, the kind you'll find at most hardware stores. A 1/4" brad-point drill bit and a drillpress make clean, square and accurate holes. Another option: a shop-built plywood drilling jig used after the box is assembled.

Join the sides, top and bottom of the cabinet with biscuits, dowels, pocket holes or particleboard screws. When all four sides are together, add a 1/8"-thick back. It strengthens the cabinet, but be sure all corners are square before nailing it on. Once the back is in place, nothing moves. The cabinet box is finished. Test-fit it into the opening before moving ahead.

Build the face frame

The three-inch wide face frame sits flush with the top edge of the cabinet bottom, so you can slide things out easily. The face frame sides and top are set in on the cabinet edges, creating a 1/4"-wide internal ledge that serves two purposes. First, it acts as a stop for the shelves, preventing them from accidentally being pulled out of the cabinet. Second, the inset allows for any variation from square in the cabinet or the face frame; in other words, the inset covers any building blunders you may have made so far. Join the face frame using glue and whatever method you like-dowels, pocket screws (my choice), biscuits or mortise-and-tenon joinery.

Now prepare the corbels, dentil moulding, three-inch-wide top and the header that sits above the dentil moulding. Take care with this last element, since it's so important to the overall look of the piece. The plans show how those end pieces of the dentil moulding that fit against the corbels are raised. Also, the three-inch-wide top needs to overhang the edges of the face frame by 1/2".

The cabinet door comes next, and although it might seem like the most difficult part of the project, it's actually quite simple. I built mine using a tenon- and-groove joint, a light-duty variation of the good old mortise-and-tenon that's more than adequate for this door. Start by cutting a 1/4"-wide x 1/2"-deep groove along the centre of the stile and rail edges, and matching tenons on the ends of the rails. You can use a dado blade in a tablesaw or a table-mounted router for the grooves. Multiple passes on a tablesaw is a good way to make tenons.

The tenon-and-groove joints should be snug, although you shouldn't need to hammer them together. Glue the door, clamp it square, then set aside to dry.

Next, convert the groove along the door edge into a back-facing rabbet to accommodate the mirror. I did this with a table-mounted router and a straight cutting bit. Set the router fence so the back edge of the groove is aligned with the bit, keeping the height of the bit the same depth as the previously cut stile and rail grooves. By milling away the back edge of the door groove like this, you'll get the rabbet you need. Square up the rounded corners left by the router and the door is done.

Down to details

Choose whatever method of securing the mirror you like-silicone caulking and mirror clips are two options. Secure the face frame on the cabinet and cut the shelves to fit. I used non-mortise-style door hinges for simplicity, available at most hardware stores. After the door is swinging, the last detail is to install a magnetic door catch and a doorknob.

If you have no choice but to install an inset cabinet in an exterior wall, be sure to include at least one inch of rigid foam insulation in the back. Also, seal the area around the cabinet with low-expansion foam during installation, to prevent indoor air from entering the wall cavity.

There are as many possible variations on this medicine cabinet theme as there are woodworkers. Pick one that matches your décor and, with all that increased space and style, you won't look at the lowly old medicine cabinet the same way again.

Insulation insight

If possible, avoid locating any inset cabinet within an exterior wall. There are two reasons why, one obvious and one not. When a cabinet steals space from the insulation used within exterior walls, it creates a cold spot that's prone to condensation in winter. I've even seen one that got so cold in the depths of February that the toothpaste was too stiff to squeeze out of the tube. A less obvious danger in exterior wall applications has to do with air sealing. Unless you're careful, warm indoor air can seep into exterior wall cavities around cabinet edges, causing internal condensation, mould and rot. -Steven Maxwell