If you want to protect your car from the elements without the expense of adding a garage, building a carport is a practical solution. This is not an unrealistic goal for the average do-it-yourself enthusiast. The instructions below are for a carport that is 10 feet wide x 20 feet long, but you can easily make the necessary changes to create a carport that better fits your needs.
There are three ways you can install the posts. The first is to dig the post holes and put the posts directly into the holes and fill the holes with concrete. The second method is to fill the post holes with concrete and set galvanized post brackets into the concrete before it hardens. The third method is to fix the brackets to the concrete slab using masonry bolts or anchors.
Now it's time to trim the posts, making sure that the rear posts are 7 & 1/2 feet higher than the ground or the slab. Make sure that the posts are all level with one another. You can use a spirit level to get the straight edges right. Make sure to measure the front posts approximately 4 inches higher than the back posts
Attach the beams, taking two beams 20 feet in length cut a 45-degree angle in each of the ends and place them in such a way that the tops of the beams are flush with the tops of the post. Clamp them down and affix them in place.
Cut the rafters with 45-degree angles at each of the ends that were previously cut to length. Make sure that they are nailed flush alongside the beams and are reinforced using galvanized brackets. Cut 6 more rafters and affix them to the beams using joist hangers placed about 3 feet apart from one another.
To evenly space any number of joists, stanchions, or the like, within a specific space simply divide the length of the space by the number of openings the materials will create inside that space, not the number of posts.
Next, you will need to brace the posts if they were not cemented into the ground. Take a few of the lengths of wood, bracing them diagonally between one post and another in order to create greater support on all sides.
Now you can attach the roof properly. This simply involves nailing down the roofing material that you chose. You are going to want to insert a few well-placed screws, meaning that weaker areas should have screws attached to keep them in place and create more strength.