Simple Rock-Solid Cantilever Desk
by jeff-o in Workshop > Furniture
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Simple Rock-Solid Cantilever Desk
With our kids moved upstairs, my wife finally got a room of her own on the main level. She needed a strong desk to support her sewing machine and especially two knitting machines - these things clamp to the desk and require a fair amount of force to operate! Any work surface that isn't attached to the wall or floor inevitably shifts back and forth as the carriage clatters on, row after row.
So, I built this simple desk for her. I'd done one just like it for myself a few years earlier, so I know it holds up well. The main criteria was that the desk didn't move, even a little bit, no matter how you yank and pull on it. However, cost and simplicity were also factors, and I know I nailed all three on this job! It is made of simple 2x4 lumber and a veneered plywood top - and lots of screws. The tool list is small, and the whole thing can be built in a weekend.
So, I built this simple desk for her. I'd done one just like it for myself a few years earlier, so I know it holds up well. The main criteria was that the desk didn't move, even a little bit, no matter how you yank and pull on it. However, cost and simplicity were also factors, and I know I nailed all three on this job! It is made of simple 2x4 lumber and a veneered plywood top - and lots of screws. The tool list is small, and the whole thing can be built in a weekend.
Tools and Materials
The amount of materials will naturally scale with the size of the desk to be built. The design for this room called for an L shaped desk attached to adjacent walls. The desk is only two feet deep to accommodate the knitting machines, but not stick out too far into the room. I used almost an entire 4x8 foot sheet of plywood. To build the desk as pictured in this instructable, you will need the following:
- One 4x8 foot sheet of 3/4" thick veneered plywood, either stain grade or paint grade ($50-$65)
- Six (and maybe one extra) pieces of 2x4x8 pine lumber. Make sure they're straight! (approx. $2.75 each)
- Eight to ten 2" L-brackets (less than $1 each)
- Two flat brackets
- 100-pack of flat head 5/8" long screws
- 3", 2.5" and 2" construction screws
- Paint (optional)
- 10" or larger compound miter saw
- Drill, with countersink bit and 2.25" hole saw bits
- screwdriver
- bubble level
- studfinder or magnet and plumb line/laser level
- Tape Measure
- Jigsaw or circular saw (optional, not required if you have the plywood cut at the store)
- Router with 1/4" roundover bit (optional, for rounding over edges)
- Random oscillation sander (optional, for sanding the surface)
- Impact driver (optional, for driving screws faster)
- paint brush (if painting)
The Basic Idea
Triangles! Aren't they just delightfully rigid? They are what make the desk so strong. That, and the dozens of screws holding the desk to the walls.
The desk surface is supported in two main ways; a 2x4 that runs along the wall itself, and evenly spaced "cantilever" supports that distribute the weight of the desk onto the wall. All of these are screwed into studs in the wall. Supports are placed approximately every 32", though they could be placed every 16" if you wanted to support the weight of a small car. Each cantilever easily supported my weight on its own (about 180 pounds), so three or four of these under the desk ought to be plenty. The desk surface is attached to the horizontal 2x4(s) and to the supports using screws and brackets.
Construction begins by identifying where the studs are hiding behind the walls, and deciding the size of the desk. The number of supports can then be determined. In my case, I needed six sets of supports.
The desk surface is supported in two main ways; a 2x4 that runs along the wall itself, and evenly spaced "cantilever" supports that distribute the weight of the desk onto the wall. All of these are screwed into studs in the wall. Supports are placed approximately every 32", though they could be placed every 16" if you wanted to support the weight of a small car. Each cantilever easily supported my weight on its own (about 180 pounds), so three or four of these under the desk ought to be plenty. The desk surface is attached to the horizontal 2x4(s) and to the supports using screws and brackets.
Construction begins by identifying where the studs are hiding behind the walls, and deciding the size of the desk. The number of supports can then be determined. In my case, I needed six sets of supports.
Studfinding
The easiest way to find the studs in a modern home is with a studfinder. Simply slide it along the wall until it beeps, and mark the location. You can also use a strong magnet; it will stick to the drywall screws in the wall, which are (for the most part) drilled into the studs. Mark the centers of the studs with pieces of masking tape. They should be spaced on 16" centers.
I had to be a bit sneakier, however. In my house many of the walls are gypsum boards with plaster on top, and metal lathe! As you might imagine, the studfinder and magnet can't make heads or tails of where the studs are! The studfinder simply beeps randomly or fails to calibrate, and the magnet doesn't really stick to anything. Here's where the tricky part comes in - the baseboards. Old school carpenters almost always managed to nail the big, thick baseboards directly into the studs. I simply found the nails with a magnet, and used my laser level to indicate the center of the stud.
Either way, find the studs, because the supports must be screwed into them to achieve any semblance of strength. Mark all the centers you find in the space where the desk will be.
I had to be a bit sneakier, however. In my house many of the walls are gypsum boards with plaster on top, and metal lathe! As you might imagine, the studfinder and magnet can't make heads or tails of where the studs are! The studfinder simply beeps randomly or fails to calibrate, and the magnet doesn't really stick to anything. Here's where the tricky part comes in - the baseboards. Old school carpenters almost always managed to nail the big, thick baseboards directly into the studs. I simply found the nails with a magnet, and used my laser level to indicate the center of the stud.
Either way, find the studs, because the supports must be screwed into them to achieve any semblance of strength. Mark all the centers you find in the space where the desk will be.
Cut & Mount the Horizontal Support
First determine how high you'd like the desk to be. This may depend on the chair you're planning to sit on, the type of equipment being used or the work you're doing. And of course, your own height! Subtract the thickness of the plywood desk top, and you know how high the horizontal support should be. In my case, the height was 28.25", since my wife decided the top surface should be 29".
I first added a bit of a bevel to the ends of the supports with a miter saw. This isn't necessary, but it looks nice.
With the help of a friend, mount the support to the wall using a 3" screw, in the middle of the support. The support should now be able to pivot on this screw. Place the bubble level in the center of the support, and align it perfectly. Then, add screws to each end of the support, again to studs. I used two 3" screws at each intersection (ie. two screws every 16 inches).
If the desk is being build into a corner, clamp the second support onto the first to make sure they stay aligned where they meet. Screw in the second support piece just like the first.
I first added a bit of a bevel to the ends of the supports with a miter saw. This isn't necessary, but it looks nice.
With the help of a friend, mount the support to the wall using a 3" screw, in the middle of the support. The support should now be able to pivot on this screw. Place the bubble level in the center of the support, and align it perfectly. Then, add screws to each end of the support, again to studs. I used two 3" screws at each intersection (ie. two screws every 16 inches).
If the desk is being build into a corner, clamp the second support onto the first to make sure they stay aligned where they meet. Screw in the second support piece just like the first.
Calculate and Cut the Cantilever Supports
I knew the desk surface was 24" deep, and that I needed space around the edge to clamp things on. So, I set the maximum support length at 20". To keep things simple, I decided to make the supports perfect right triangles (90-45-45), so the section screwed onto the wall had to be 20" as well. But, that measure is only a guide.
The section (1) that runs along the underside is actually 18.5", due to the thickness (about 1.5") of the horizontal support already mounted to the wall. The section mounted directly to the wall (2) is only 16.5", due to the width of the 2x4 (about 3.5"). And of course the angled section (3) can be calculated from there. I chose a length of 21.5", a length that placed the angled section about 1" from the ends of the wall and desk sections.
A fourth piece (4) supports one end of the section that runs along the underside of the desk, and provides a convenient place to drive in more screws. It also joins the horizontal support to the wall section, adding additional redundancy.
So, how many supports do you need? Make sure there's one on each end of the desk for starters. In my case, one end of the desk was supported by the horizontal support screwed onto the wall, so one support was placed as close to the other end as the studs would allow. Then just place the supports 32" apart from there. Again, this will depend on how long the desk is. In total, I needed six sets of supports for desk top that is 8 feet on one side and seven on the other.
A miter saw is all you need to cut the 2x4 lumber into sections. Pieces 1, 2, and 4 were cut with a 90 degree cut on one end, and a 45 degree bevel on the other. The bevel looks nice for one thing, but also prevents bruised knees. Piece 3 was cut with a bevel on both ends, since it will be screwed on at an angle to the others. Cut one set to test for fit, then cut the rest.
The section (1) that runs along the underside is actually 18.5", due to the thickness (about 1.5") of the horizontal support already mounted to the wall. The section mounted directly to the wall (2) is only 16.5", due to the width of the 2x4 (about 3.5"). And of course the angled section (3) can be calculated from there. I chose a length of 21.5", a length that placed the angled section about 1" from the ends of the wall and desk sections.
A fourth piece (4) supports one end of the section that runs along the underside of the desk, and provides a convenient place to drive in more screws. It also joins the horizontal support to the wall section, adding additional redundancy.
I should note that being super-accurate here really isn't necessary. There will be no complex joinery here, and no piece relies on any other piece for a perfect fit. So don't beat yourself up about an eighth of an inch here or there.
So, how many supports do you need? Make sure there's one on each end of the desk for starters. In my case, one end of the desk was supported by the horizontal support screwed onto the wall, so one support was placed as close to the other end as the studs would allow. Then just place the supports 32" apart from there. Again, this will depend on how long the desk is. In total, I needed six sets of supports for desk top that is 8 feet on one side and seven on the other.
A miter saw is all you need to cut the 2x4 lumber into sections. Pieces 1, 2, and 4 were cut with a 90 degree cut on one end, and a 45 degree bevel on the other. The bevel looks nice for one thing, but also prevents bruised knees. Piece 3 was cut with a bevel on both ends, since it will be screwed on at an angle to the others. Cut one set to test for fit, then cut the rest.
Screw on the Cantilever Supports
Start by attaching the wall sections (piece 2). With the aid of your stud location marks, drive in at least two screws into each piece. The wood should be flat against the wall - if it isn't, back out the screw and drive it in again while applying pressure to the piece. The purpose of this wood is to distribute the weight of the wood evenly into the wall; it will wobble if it isn't flush.
Next, attach piece 3 using two pieces of scrap wood as a guide. Remember, piece 1 must fit in the space at the top. Attach piece 3 using four screws - two into the horizontal support, and two into piece 2. Again, make sure it sits as flush as possible.
Piece 1 is next. Hold it in place so it is flush with the horizontal support, and reasonably square with the wall. Drive in two screws through to piece 4. You may want to pre-drill the holes with a countersinking bit, to prevent the edge of the wood from splitting. Piece 1 may still be a bit wobbly - that's OK! just try not to bump into it.
Last is piece 4. This is the hard part. Set a level along piece 1, and clamp piece 4 into place so that the bubble is level. Pre-drill the holes with a countersinking bit, two screws at each end. Start the screws by hand with a screwdriver since the impact driver tends to rattle things out of alignment. Check for level again once all the screws are driven in.
At this point, the support should be able to handle an average adult's weight. Go ahead - sit on it! If it feels unstable, fix it now before it's too late...
Complete the other supports in this way, always measuring for level.
Next, attach piece 3 using two pieces of scrap wood as a guide. Remember, piece 1 must fit in the space at the top. Attach piece 3 using four screws - two into the horizontal support, and two into piece 2. Again, make sure it sits as flush as possible.
Piece 1 is next. Hold it in place so it is flush with the horizontal support, and reasonably square with the wall. Drive in two screws through to piece 4. You may want to pre-drill the holes with a countersinking bit, to prevent the edge of the wood from splitting. Piece 1 may still be a bit wobbly - that's OK! just try not to bump into it.
Last is piece 4. This is the hard part. Set a level along piece 1, and clamp piece 4 into place so that the bubble is level. Pre-drill the holes with a countersinking bit, two screws at each end. Start the screws by hand with a screwdriver since the impact driver tends to rattle things out of alignment. Check for level again once all the screws are driven in.
At this point, the support should be able to handle an average adult's weight. Go ahead - sit on it! If it feels unstable, fix it now before it's too late...
Complete the other supports in this way, always measuring for level.
Preparing the Desk Top
I bought the 4x8 sheet of plywood and cut it myself, since I needed a shape they couldn't (or wouldn't?) easily cut for me at the store. But by all means; if all you need is an 8x3 section (or whatever) definitely have the store cut it for you - they typically have either a large table saw or panel saw and will do a small number of cuts on the spot for free.
Measure out the cut lines using a tape measure and straight edge. I cut the plywood using a jigsaw and got pretty good results - you could also use a circular saw. For lack of a better place to do the work, I simply laid some scrap 2x4s in the driveway and cut right on the ground. Before you do this, make sure the blade height is set so that it won't touch the ground!!
After cutting, I drilled several cable access holes using a 2.25" hole saw. Before drilling these holes, make sure you measure out where the cantilever supports are. Otherwise, you may end up with a hole right over a support! Also make sure the edge of the hole is at least 1.5" from the edge of the desk top, to avoid overlapping the horizontal support beam. Drill as many holes as you think you'll need - then add an extra just in case.
There are a few ways of finishing the edge of the table. You could give it a quick sand to remove any splinters, or you could apply some wood trim or a strip of veneer. I knew my wife would be working with textiles, which tend to snag on sharp corners. So, I decided to round over the edges with a router. I used a 1/4" roundover bit on both the top and bottom of the table on all the outer edges, as well as the cable access holes.
The last step is to sand the desk top. The veneered surface will likely be very smooth already; it may not need sanding at all! But you will probably want to sand the cut edges a bit to remove and splinters or burrs. I started by sanding the edges with a small handheld random orbit sander. I sanded the cable access holes by hand. Finally, I sanded the desk surface itself with a 5" random orbit sander.
If you like, you may paint or stain the table surface now. If you're using a particularly smelly stain, or have any other reason why it would be better to paint the table top outside of the room it will eventually be in, by all means do so at this point!
Measure out the cut lines using a tape measure and straight edge. I cut the plywood using a jigsaw and got pretty good results - you could also use a circular saw. For lack of a better place to do the work, I simply laid some scrap 2x4s in the driveway and cut right on the ground. Before you do this, make sure the blade height is set so that it won't touch the ground!!
After cutting, I drilled several cable access holes using a 2.25" hole saw. Before drilling these holes, make sure you measure out where the cantilever supports are. Otherwise, you may end up with a hole right over a support! Also make sure the edge of the hole is at least 1.5" from the edge of the desk top, to avoid overlapping the horizontal support beam. Drill as many holes as you think you'll need - then add an extra just in case.
There are a few ways of finishing the edge of the table. You could give it a quick sand to remove any splinters, or you could apply some wood trim or a strip of veneer. I knew my wife would be working with textiles, which tend to snag on sharp corners. So, I decided to round over the edges with a router. I used a 1/4" roundover bit on both the top and bottom of the table on all the outer edges, as well as the cable access holes.
The last step is to sand the desk top. The veneered surface will likely be very smooth already; it may not need sanding at all! But you will probably want to sand the cut edges a bit to remove and splinters or burrs. I started by sanding the edges with a small handheld random orbit sander. I sanded the cable access holes by hand. Finally, I sanded the desk surface itself with a 5" random orbit sander.
If you like, you may paint or stain the table surface now. If you're using a particularly smelly stain, or have any other reason why it would be better to paint the table top outside of the room it will eventually be in, by all means do so at this point!
Paint the Supports
It is much, much easier to paint the supports before the table top is mounted. Of course, painting the supports is completely optional. If you used nicer wood than construction-grade lumber, or if you like the look, or don't really care either way, you can skip this step.
To paint the supports, I used inexpensive "self-priming" door & trim paint. The colour (uhhh... white) was chosen to match the existing trim. This part is fiddly, and watch out for paint drips! There are lots of corners and recesses where the paint can pool and drip. Add as many coats as you like until you achieve the finish you want. Two coats should be enough in almost all cases.
To paint the supports, I used inexpensive "self-priming" door & trim paint. The colour (uhhh... white) was chosen to match the existing trim. This part is fiddly, and watch out for paint drips! There are lots of corners and recesses where the paint can pool and drip. Add as many coats as you like until you achieve the finish you want. Two coats should be enough in almost all cases.
Mount the Desk Top
Once the paint on the supports is dry, the table top can be mounted!
Drag in those big pieces of plywood and dry-fit them to make sure everything lines up OK. If your desk top is in multiple pieces, attach the largest piece first. Line it up flush against the wall. If possible, clamp it down to keep it from shifting while you work (or inevitably smack your head as you crawl underneath).
The L-brackets are used to attach the desk top to the horizontal support beam. I spaced them between the cantilever supports. Start in the middle and work outward; first attaching the bracket to the support beam and then to the table top. You may want to use a center-punch to mark the holes and give the screw a nice little hole to dig into.
Once the L-brackets are in place, drive 2" screws through the cantilever support beam and into the desk top. Again, it's probably a good idea to pre-drill these holes with a countersink bit. I used two screws per support beam; one near the outside edge of the desk top and one near the wall.
The L-shaped desk that I built was made in two pieces. Unfortunately the two pieces were out of vertical alignment by about a quarter-inch. After attaching the two pieces to their individual support beams, I clamped them together to bring them into alignment. I then screwed on a pair of flat support braces to permanently hold the pieces together.
Well! Nearly done. The desk should easily support the weight of an adult or two. I proudly jumped up and down on the desk to prove it. So did my kids. I hope they don't think they're allowed to do this all the time...
Drag in those big pieces of plywood and dry-fit them to make sure everything lines up OK. If your desk top is in multiple pieces, attach the largest piece first. Line it up flush against the wall. If possible, clamp it down to keep it from shifting while you work (or inevitably smack your head as you crawl underneath).
Tip: If you have clamps whose jaws can be removed, you can run the bar through a cable access hole and reattach the jaw on the other side of the desk surface. Then, clamp the desk top to the support beam!
The L-brackets are used to attach the desk top to the horizontal support beam. I spaced them between the cantilever supports. Start in the middle and work outward; first attaching the bracket to the support beam and then to the table top. You may want to use a center-punch to mark the holes and give the screw a nice little hole to dig into.
Once the L-brackets are in place, drive 2" screws through the cantilever support beam and into the desk top. Again, it's probably a good idea to pre-drill these holes with a countersink bit. I used two screws per support beam; one near the outside edge of the desk top and one near the wall.
The L-shaped desk that I built was made in two pieces. Unfortunately the two pieces were out of vertical alignment by about a quarter-inch. After attaching the two pieces to their individual support beams, I clamped them together to bring them into alignment. I then screwed on a pair of flat support braces to permanently hold the pieces together.
Well! Nearly done. The desk should easily support the weight of an adult or two. I proudly jumped up and down on the desk to prove it. So did my kids. I hope they don't think they're allowed to do this all the time...
Paint the Desk Top
If you've already painted the desk top, skip this step. You're done! Go and put stuff on it and enjoy your new desk.
I decided to paint the desk top after mounting it. I first masked along the wall to prevent paint from getting where it shouldn't be (ie. the freshly painted walls.) Then I applied two coats of the finest door and trim paint they had at the hardware store. Apparently it's enhanced with urethane or something. As long as it's sturdy and can resist wear I'm happy!
Wait a while before putting anything on the desk. Often the paint feels dry to the touch, but is still wet underneath. Setting something heavy on the paint before it is dry may result in permanent marks.
Well that's pretty much it! The entire construction of the desk as pictured took about two days of work (16 hours), including painting. It's solid as a rock, supports a ton of weight, and ended up costing only about $120 including the paint.
I decided to paint the desk top after mounting it. I first masked along the wall to prevent paint from getting where it shouldn't be (ie. the freshly painted walls.) Then I applied two coats of the finest door and trim paint they had at the hardware store. Apparently it's enhanced with urethane or something. As long as it's sturdy and can resist wear I'm happy!
Wait a while before putting anything on the desk. Often the paint feels dry to the touch, but is still wet underneath. Setting something heavy on the paint before it is dry may result in permanent marks.
Well that's pretty much it! The entire construction of the desk as pictured took about two days of work (16 hours), including painting. It's solid as a rock, supports a ton of weight, and ended up costing only about $120 including the paint.