Things You'll Need:
- Saw, tape measure, string line, speed square.
- 4x4 post's, 2x8's, 1x3's
- bags of cement
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Step 1
Building a Pergola on a concrete slab will require cutting the concrete to run the 4x4 posts into the ground, or, drilling holes in the concrete and attaching a metal POST MOUNT hanger on the concrete. Both of these methods will work, however, running the posts into the ground will be the strongest way. To install it through the concrete slab, just cut 12"x12" square out where every post goes. Dig the hole anywhere from 12" to 42"(depending on your local building codes). Next, place the post in the ground and level it(both ways), then back fill it with concrete untill flush will the old slab. If you are using a POST MOUNT, just use a hammerdrill and concrete screws to attach the 4x4's to the slab in the appropriate locations.
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Step 2
After the posts are set, you will need to build the main BOX HEADER that attaches to the top of the 4x4 posts. [the size of your 2 x's, & the distance you're spanning, will determine the size joists and header material you will need] Check your local lumber yard for a chart showing spans. Standard lumber used for the header would be 2 x 8's. Start with building the outside box, then fill in the center with joists that are the same size lumber as the header, every 16 inches on center. Depending on the size of the Pergola, joist hangers may be required. [You could check your towns requirements for joist hanger codes, or use hangers on any joist span 8' or more to play it safe]
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Step 3
To complete, using the same size lumber used to build the header, cut 12" boards with the design preferred, for the "false" joist tails. Then run 1x3's across all the joists to connect the joist tails, flush to the header.
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Step 4
This picture detail gives you a close up on the hangers used to build a Pergola.
