Wood carports protect your car from the elements and create shelter between your vehicle and a home-entry door. You might want to pour a slab of concrete under the shelter later, but having a slab is not a requirement for building a wood carport attached to your house. Typically, a carport will measure around 3 m x 6 m (10 feet x 20 feet), but you can adjust the length and quantity of materials to increase the size.
Set aside four of the 5 cm x 20 cm (2 x 8 inch) boards. Mark 85-degree angles on one end of each of the remaining 5 cm x 20 cm (2 x 8 inch) boards. Cut the marked ends of the boards. Placing the "point" side up against the wall will provide 30 cm (1 foot) fall in the roof slope, and match the rafters to the height of the outside posts.
Mark a starting location on the wall where one end of the carport will be attached. Use the tape to measure 6 m (20 feet) along the side of the house and make a small mark with your pencil. Hold the tip of the tape measure against the wall and measure 3 m (10 feet) perpendicular to the wall, marking the ground.
Go to the first mark and affix the end of a string at the mark. Measure 90 cm (3 feet) toward the second wall mark, and place a small dot on the wall. Have an assistant hold the end of the tape measure on this new location. stretch the string out to exactly 3 m (10 feet), and pull it taut. Move the string line in or out until the 1.5 m (5 foot) mark on the tape measure lines up with the string exactly 1.2 m (4 feet) from the wall along the string length. Push a nail into the ground at the 3 m (10 foot) measurement on the string. The 3-4-5 formula is an ancient method of determining a true 90-degree angle.
Repeat this process for the opposite end of the carport. Use the same 3 (along the wall) 4 (along the string) 5 (measured between the other two marks) method, Pushing a nail into the ground as before. Measure between the two nails and verify that you have them spaced 6 m (20 feet) apart.
Dig the post holes. Go down to a depth of 60 cm (2 feet) for each pole. Place the corner posts so that the outside of the post is at 3 m (10 feet) from the wall, and next to a line pulled between the wall and the nail. Install the final post halfway between the corners, with the outside edge 3 m (10 feet) from the home wall.
Install two of the uncut 5 cm x 20 cm (2 x 8 inch) boards as the attaching supports along the home wall using 16d nails spaced in pairs along the length of the lumber. Using the level and tape measure, measure straight up from the first mark to a height of 3 m (10 feet) above ground. Put the carpenter's level on the top edge of the board and use it to keep the lumber aligned levelly. Butt the second board against the end of the first one and nail it in place.
Install a cross member at the front of the carport by placing the wide side against the end of the supporting board. Space two 16d nails, driving them through the board and into the end of the mounted one. Attach the end of the board directly to the corner post with two nails. Line the end of the board up so that it is aligned with the top of the 10 cm x 10 cm (4 x 4 inch) post. Repeat for the other end of the carport.
Install one of the angled-cut boards at each end of the carport, with the cut end toward the wall and the long end toward the top. Put the final two uncut pieces in place, butted end against end and flush with the outside edge of a corner post. Use two 16d nails to fasten it.
Nail rafters inside the frame, spaced 40 cm (16 inches) from the centre of one rafter to the centre of the next. Attach rafters with two nails driven through the outside support lumber, and toenailed top and bottom to the support board on the home.
Begin at one of the wall-side corners, and align the plywood sheet flush with the outside edge. Use 6d nails to drive through the plywood and into the supports and rafters. Space nails approximately 20 cm (8 inches) apart, and along every rafter. Repeat for all of the full sheets.
Rip-cut three sheets of plywood down the middle, lengthwise. With the factory side facing the other roof sheets, mount one of the half sheets at each corner of the carport. Measure the remaining opening, and cut one of the half-sheets to fit that length.
Begin on the lower, outside edge of the carport and roll out the rolled roofing along the edge. Attach the top edge with tabbed roofing tacks spaced 15 cm (6 inches) apart. Do not attach the lower edge.
Place the next row of rolled roofing so that it overlaps the first by 15 cm (6 inches). Tack the roofing along the top edge only. Repeat this process until the final row of sheeting is butted against the wall of the home.
Place the flashing along the wall of the building with the bottom turned down along the surface of the rolled roofing. Use roofing tacks to attach the flashing along the wall of the building.
Check the building codes for your area. Many locales require you to get planning permission for any structures that are attached to your home. Instead of rolled roofing, you can use plastic, tin, or vinyl roofing sheets. To help with visualising this and other construction projects, begin by drawing them on paper, and sketching the materials in place.