As with almost any carpentry project the first step is to decide what design you will use. Are you looking for a typical picnic table with attached benches, or do you prefer separate benches and table? Whatever your taste, ready-made plans are available for purchase and some free plans can be found online.
Expert carpenter? Then make your own plans, here are a few considerations. How many people will your table typically seat? Allow 18 to 24 inches of bench space for each person. Will it be mostly adults, or children, or a combination of the two?
You should at least have basic dimensions, know what material you plan to use and decide whether you will be fastening your joints with nails, screws or bolts or a combination of the three before going to purchase your materials.
Whether you need a simple list of pieces to cut or a full blown blueprint, it is best to have a plan before you begin cutting. The most common type of picnic table is an A frame with angled legs that also support the bench. Typical table height is about 30 inches, while bench and chair tops average out around 17 inches. Lay your legs out so that the table height is correct while allowing at least 12 inches between the front of your bench and the edge of the table for seating. Spreading your legs too far will weaken the table, while placing them too upright will not leave enough room for seating.
Separate benches and table require more material and planning but can be more versatile. Again, observe typical table and seat height to provide maximum comfort.
Make sure to provide braces for A-frame legs; with careful placement these can also support your bench top. With separate benches make sure you have adequate reinforcements to make the legs strong.
Write a list of dimensions and number of parts required and, if needed, make a drawing showing where each piece fits and how it will be joined to the table. Be as detailed as possible, it will save time and material.
Now you must decide whether you will assemble your table with nails, screws or bolts. Nails are easy, inexpensive and quick, but will not last as long as either screws or bolts. Screws require a drill, preferably cordless, and screw tip, take a little more skill and time but provide more strength and will last twice as long as nails. Bolts require careful planning of each joint, will need to be pre-drilled and are the most expensive. They will provide the strongest, longest lasting table, and your parts will then be replaceable if a leg or bench should break.
Once you have chosen your style and drawn up a plan, it is time to choose materials. Picnic tables in the U.S. have traditionally been built of long-lasting, lightweight, redwood lumber, however, environmental and cost concerns may make this impractical. There are treated lumber options that will last almost as long, but will not provide the same beauty. Another naturally pest and weather resistant option that may be more cost efficient is red cedar. Whatever material you choose should be at least 2 by 6 inches, straight, smooth and free from large cracks and loose knots. Make sure you purchase enough to cover any cutting mistake or breakage. Usually 10 percent extra is enough.
Using your plans as a guide, layout all your pieces and mark your lumber carefully. Be sure to layout longer pieces first to make best use of your materials. Remember this old adage: measure twice, cut once.
When cutting your pieces, make sure to start with the largest pieces first to make best use of your material. Cut as close to your marks as possible. Remember to make allowance for the thickness of your saw blade (kerf) to avoid ill-fitting pieces. It is best to cut everything before beginning assembly. Mark similar pieces to avoid confusion.
Once all pieces are cut to length, mark and pre-drill any screw or bolt holes required. Measure each joint and mark carefully to avoid boring extra holes. If you are using bolts, be sure to countersink the outside of each piece to allow for bolt heads and nuts/washers.
Before attaching anything, break your parts down into groups. Place bench parts together, top parts together and leg parts together. This will save time and frustration.
Assemble frame elements first, then add bench tops and table top. Leave joints a little loose until all parts are in place to make things a little easier. It is usually best to start from the ground up. Once all pieces are assembled, double check and tighten each joint.
Finally, before that big family picnic, give the table a good sanding to avoid splinters and sharp edges. Pay special attention to seat and table tops.