Tuesday, April 10, 2007

Custom wooden light soffit construction

To build the custom light soffit that will hang above my upstairs bathroom sink, I’m using architectural trimwork from my local Home Depot. The box will be constructed out of pine rabbetted stool, that’s typically used for a window stool. Once the box is build, I’ll attach a piece of trim to the two front edges to add some visual appeal to the box (the left and back sides of the box will be flush against walls).

For more on the two pieces of moulding I’m using, read my Custom wooden light soffit post.

While the rabbetted stool is designed to be laid flat when used as a window stool, I’m standing it up on edge and using it as the sides of my soffit box. The box is simply made my cutting the four sides with bevels on each end. The photo to the right shows one of the sides with the bevel cut on a compound miter saw.

Once the four sides were cut to length, I used my router table to cut a channel -- or “dado” -- in the inside bottom edge of the rabbetted stool. This dado with hold the 1/8" plywood that will serve as the bottom of the box, and the light fixtures will be installed in the plywood. The photo to the right shows the rabbetted stool. The red arrow shows where the dado was cut.

Cutting the dado on my router table was tricky because the inside of the rabbetted stool isn’t flat. If you enlarge the image above you’ll notice there’s a bevel that moves inward from the top edge down to the area by the red arrow. When I laid that side of the rabbetted stool face down on my router table, it wouldn’t lay flat.

The solution to this problem was tapping one of my steel rulers down to my router table, parallel to the router bit. As the photo to the right shows, the ruler lifted the beveled side of the rabbetted stool and meant I could safely cut the dado.

I used a straight router bit that matched the thickness of my plywood to cut the dado in the rabbetted stool. Next, I cut the plywood to fit the box and then determined where I wanted the light fixture “cans” to be placed within the plywood. Once the position of the cans were marked (using a template provided with the lights), I cut the holes in the plywood with my jig saw.

Now the box is ready for assembly. Assembling a box with four sides and a bottom can be tricky. Since I wasn’t in a big hurry, I glued the front of the box to the two sides and let it dry over night. By doing so, I only had to worry about two joints (where the back of the box met the two sides) and the plywood bottom during final glue-up. It also meant I didn’t have to use long pipe clamps to hold the box along its length. I used small, and much more manageable, hand clamps during the initial glue-up to hold the corners together with a 90-degree square while the glue dried.

To finish assembly of the soffit box, I slid the plywood into the dados on the sides of the box and in to the dado in the box’s front, then applied glue to the bevels of the box’s back piece. I secured the back of the box to the sides with a couple of brad nails. To drive those nails, I used my Porter-Cable BN200A Brad Nailer, a great tool to own for situations like this where you want to quickly secure something into place.

Next time I’ll show how I installed this wooden light soffit into place above my sink.