To build a detached patio cover, put post anchors into 12-inch holes in patio corners, and fill the holes with cement. Attach posts to all anchors using 1/2-inch bolts. Attach post caps to each post using 1/2-inch bolts. Attach a post to two post caps on the opposite sides of the patio using 1/2-inch bolts, and do the same for the other side. Attach rafter boards on the center using 16-penny nails, and use lap plywood to cover the rafters.
To build a regular patio cover, determine the height and size of the patio cover, set the post base, and nail posts to it. To create the support beam, place double 2-inch by 12-inch boards into the roofline, determine where the rafters are going to be, and install them. Make three 1 1/2-inch holes in each third rafter. Make sure to put blocks in between rafter tails before doing this.
Attach pieces of metal screening to each block, and set the roof decking in place. Locate the intersection of the patio roofline and the existing roofline, and install flashing there. Attach the tarp paper to the roof. Make sure to leave an overlap of at least 6 inches. After that, install shingles and the roof jack. Attach sheathing to the inside of the roof, and place some boards close to the posts.