Building a deck on the cheap generally means not using a treated wood, and then to compensate for this, using a wood preservative instead. Some concessions can be made by doing this, as well as using deck screws instead of nails and sanded plywood for the top instead of individual boards, a deck made like this, although more labor intensive over its lifetime, can look and be just as beautiful as some of the finest looking decks made.
Lay out four corners where you want your deck to be. Measure diagonally from corner to corner and get exact measurements. Use the tape measure for this step. You may need a partner to help with the measurements and hold the end of the tape measure.
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Dig four post holes at the corners, approximately 24 inches deep. Do not dig when the weather is cold or wet, as it can make digging very difficult.
Plant the 4 x 4's in corner holes. There isn't a shortcut here; they must be treated because they are coming in contact with the ground and will rot if they are not. You can buy treated boards, so that you do not have to do it yourself.
Make sure that the 4 x 4's are level and solidly planted. Level off the board in each hole. Fill the rest of the hole with dirt, and tamp down snug. Do this for all four of the corner holes.
Attach all corners together on the outside with the 2 x 6 boards. Make sure to level each one. It is your choice to go as low as the ground, or as high as is comfortable. If you are making this deck attached to a patio, the attachment boards should be ½" lower than the doorway.
Complete your deck frame. Attach 2 x 6 boards to the inside of the corner posts. Use at least two nails for each end of each board. Trim the corner 4 x 4 posts flush with the connecting 2 x 6's.
Soak or roller on wood preservative on all of your 2 x 6 boards. Standard-grade lumber costs less than half of treated lumber, so it's now up to you to waterproof your wood. You will save money to be sure, but you will have a little more work to do too.
Position your joists. This is very important. Depending on which way you want the grain of your plywood to run, the joists that support them must be attached in the opposite direction. Every 24 inches, attach a joist holder to the frame and then attach a joist inside the joist holder, using your hammer and deck nails to secure them.
Attach the plywood base. Lay out your plywood sheets, sanded side up, on the top of the joists. Nail them into position and continue nailing down your sheets until the entire surface is covered.
Finish the edges. If there is any overhang, cut the boards flush with your circular saw. You will now see your new, inexpensive deck take shape.
Preserve your deck. Roller on wood preservative to the top of the sanded plywood. Then, use an oil based stain over that. The sanded plywood will have an attractive grain showing once the stain is applied, but you'll have to roller on a wood preservative year after year to make this deck last.
The basic plans are the same for building a regular deck, but these instructions include shortcuts and other tips to cut costs. For additional support, add another upright supporting 4x4 along the connecting 2 x 6 boards at 24- or 36-inch intervals. The same can be done for the interior of the deck to better support the joists.
Things You'll Need
Treated 4x4 boards
Standard-grade 2x6 boards
Sanded 1/2” plywood
This deck is cheap to build, but you will have to put in a little more work on maintenance. If you neglect to sufficiently seal and preserve it, it will rot much faster than a conventional deck.