Time: 4-5 hours
Cost: $35-$65 (depending on if you already have hardware, stain, poly, etc.)
Tools: Table and/or circular saw, hammer, drill, paint brush, level, yardstick or measuring tape, bolt cutters, stud finder
Optional Tools: Biscuit joiner, Kreg jig, nail gun, driver
Size: 34 1/2" x 15" x 3" total including the trim pieces. The length was determined by the spacing of studs in our wall (16" x 2 plus a little extra) and the depth was chosen to allow a laptop to be used comfortably without hanging off the edge.
Background: We were looking for a small desk for the bedroom that wouldn't take up too much space but still looked nice and matched the other furniture in the room. All in all, this ended up being a fairly easy build with only a few items to purchase and not a lot of tools needed. You can pick from a variety of wood and finishes to match the surrounding decor as needed.
Step 1: Purchase and Cut Lumber
Shopping List: 2x White Pine Stair Treads (48"x11.5"), 1x White Pine Select 1"x3"x6' board, 2x L-Brackets, 1x Pack of 2" Finish Nails, 1x Vinyl Coated 1/8"x30' Steel Wire Kit (included Clamps and Loops), 2x Rope Loops (Brackets that attach to wall), 1/2pt can of Polycrylic, 1/2pt can of Stain (I used Minwax Dark Walnut oil-based Stain), 1x pack of #8 x 2" wood screws
Shopping Trip: Step 1 is to take a trip to the store and by all of the materials. The list above contains everything used to build the desk shown in the pictures and everything was purchased at HD. I had leftovers of the stain, poly, nails, and screws, so that cut down on cost, but you should be able to buy everything new for $65 or so if needed. I used 1" thick stair treads because they are typically sturdier, flatter, and have a better finish than longer pieces of lumber sold at the big box stores. The type of wood purchased should depend on end use. Pine is soft (easier to scratch), but is inexpensive and easy to stain. Oak will cost a little more and is slightly harder than the Pine, so you will get slightly more durability. HD sells stair treads in both pine and oak.
Cutting Lumber: The stair treads were cut to 33" x 7 1/8" each. I left an extra 1/8" or so on the first cut of each and then finish cut both sides after joining to get a smoother edge. The side trim pieces are each 7 1/4" long and the front trim is 34 1/2" long.
Step 2: Join Wood and Add Trim
Joining Wood: To join the wood, I used a biscuit joiner for better top surface alignment and then applied wood glue liberally between the stair tread pieces. MAKE SURE THERE IS NO GLUE THAT HAS OOZED ONTO THE TOP SURFACE OF THE DESK. Wipe up anything that squeezes out on top or else you will be kicking yourself later during staining. If you don't have a biscuit joiner, just use a very flat surface when joining the pieces. The stair treads are typically very straight and smooth so you should get a good enough surface either way. Because I am an engineer, I added some pocket screws with a Kreg jig for that warm and fuzzy feeling on strength, but these really should not be needed since the trim pieces will actually offload the majority of buckling load. Once the wood is joined the glue is dry, finish cut the side(s) as needed to create smooth edges with a total length of 33"
Adding Trim: Add the trim to the sides and front with glue and nail in place. The underside doesn't matter much since it can't be seen. In addition to nailing the trim pieces to the stair tread pieces, also nail the trim pieces together by adding 2 nails towards each end of the front trim.
Step 3: Sand and Finish
Drilling: You can now add the two holes for the steel wire to pass through the top of the desk. They should be 14" from the back edge of the desk and 32" apart (assuming your wall studs have the same spacing as mine). Use a drill bit that is just barely larger than the steel wire to eliminate slop and make sure things stay as rigid as possible. I drilled my holes after finishing (forgot about them...), so they aren't shown yet in the picture above.
Sanding: Once everything is joined, nailed, and dried, you can start sanding everything down. Start with a rougher piece of sandpaper (80-120) and work your way up to very fine (220). Run your hand over the seams to make sure you have them as smooth as possible.
Finish: I applied 1 coat of Dark Walnut Minwax Oil-Based Stain using a rag (you can use a brush if you want). Make sure you wipe up any excess stain to avoid pooling on the wood. After the stain fully dries, apply several coats of Polycrylic or Polyurethane, sanding with 220 in between each coat.
Step 4: Mount Wall Hardware
Mount L-Brackets: First, determine the desired height of your desk and mark the bottom surface of the stair treads on the wall using a pencil. Install the L-Brackets on your wall studs (typical spaced every 16" so Brackets are 32" apart) with the top surface of the L-Brackets in-line with the mark on the wall (use a level).
Mount Top Brackets: Before mounting the top brackets, add the Wire Loops (came with Steel Wire Kit), since it isn't easy to add these on once the brackets are screwed in. Measure up 15" from the tops of the L-Brackets and install the Rope Loops (Brackets) with their centers at the 15" mark up, spaced 32" apart. Use a level to make sure everything is in line prior to screwing things down. Pre-drill holes with a very small bit to help with alignment and make sure you are actually hitting your studs.
Step 5: Mount Desk and Add Steel Wire
To install the Desk, have someone hold the front edge while you screw the L-Brackets up into the bottom of the Desk with the provided screws. Next loop the steel wire through one of the brackets and clamp in place with a few inches extending past the first clamp. Run the steel wire through the first hole, along the underside of the desk, up through the other hole, through two clamps, around the loop, and back down through the two clamps. Cut the steel wire to the desired length using bolt cutters.
The tricky part is trying to tension the wire. This step takes a little bit of trial and error, but my best recommendation is to get one side as tight as possible without bending the L-Brackets (use a level), and then work on the other side by tightening the clamps just enough where you can still pull through with some force. In the end, you should have some tension in your wire so that they are offloading some of the force of the desk and everything isn't going through the Brackets. Use a level to make sure everything looks good and finally, enjoy your handiwork.