This blog post accompanies my youtube video about building a 2x4 workbench. If you didn't come here from there you should check it out.
A 2x4 workbench is super easy to build, and super sturdy, well assuming you use quality lumber to build it. What I love about this design is that there are no complicated cuts, and only three or four different lengths you need to cut your lumber too.
Each color represents a specific size that you need. Here are the sizes I used, but of course you can modify sizes to fit you space and liking.
The BLUE cross members are eight feet, and don't need to be cut. This is also the overall width of the workbench, so if you have a smaller space adjust accordingly.
The RED legs are three feet tall. The workbench top sits on top of these, so the work surface will be a little higher, adjust accordingly. If you aren't planning on putting a back on your workbench, cut four this length
The Green cross members are twenty-seven inches deep. There will be two 2x4s width added to that, so I have a thirty inch deep workbench.
The Tan rear legs are six feet tall. The size on these only needs to be taller than the front legs, it all depends on how tall the pegboard you are using will be.
Depending on what you are using for a table top and shelf you may need more or fewer cross members. I was using half inch OSB so I wanted to make sure I had plenty of support, a sturdier material would allow you to use fewer cross members.
All the boards are cut and joined at ninety degree angles, unless you are adding the pegboard all cuts can be made with a chop saw.
The corners are joined in this fashion, the leg goes on the outside and the cross member on the inside. You can use whatever combination of screws, bolts, nails, glue etc you want. I just used some construction screws, and it holds my body weight, so it should be plenty strong.
If you are putting a pegboard on the back I'd advice putting the table top in place before installing the lower support 2x4 as it can just sit right on top of the tabletop and give you a solid backstop. The support brackets I made are less than perfect but they get the job done. They're just 1x2s with notches cut off of the ends to slip between the 2x4s. The size of these will be completely determined by the size of the pegboard you are going to use. I made mine as tall as the overall distance spanned by the top and bottom support 2x4s and then cut out a notch that width of a 2x4, and cut in about halfway to the 1x2. Pre-drilling is a must for these, as they will certainly split on you if you don't have a hole for the screws.
The spacing on these parts is completely up to you. I lined them up with the holes in the pegboard so I could put screws right through those holes, but you could put them behind the board where holes aren't to keep all of the holes open to hooks. You could also use little standoff dodads to allow hooks to be placed where the supports are, though this will let the board warp and wiggle a bit. If you really wanted you could even apply a bead of glue to the supports and glue the pegboard in addition to screwing it in place.
Once completed you'll have an amazing desk that will probably cost about 20-30 dollars, depending on where you source your materials and what you can find already laying around your home.