Building a small, gabled awning above an exterior doorway is a functional project that not only protects you when stepping out into a rainstorm, but adds a new visual dimension to your house. You'll also learn something about the construction process that goes into framing a gabled roof.
Remove the siding with a flat pry bar from the area above the doorway. It must extend at least 1 foot past the side of the door opening and at least 3 feet above the door. Do this cleanly, because part of the siding will have to be put back on the side of the house later.
Attach a level 2x4 board to the exterior side of the house, directly to the framing members. It should be level, about 6 to 12 inches above the door trim and extend 12 to 24 inches past the side of the door trim. The distance between the end of this board and the outside edge of the door should be equidistant. At least one end of the 2x4 should land on a stud.
Place two 2x4 boards above the one that you just installed to form an equilateral triangle. These three boards will form the shape of the roof of your awning. The triangle should be 1 to 2 feet high in the centre and nailed to the framing members with #16 galvanised framing nails. Cut each end of each piece at an angle to ensure a clean fit.
Make a second triangle to match the one that you just built on the side of the building. Use a pair of sawhorses and attach plywood cleats on one side to hold the piece together. The plywood scraps will have to be cut fit at the ends of the triangle and nailed with short galvanised box nails.
Decide on the distance that the awning will extend out from the side of the building (3 to 5 feet usually) and cut three pieces with square ends to that exact length.
Put the whole roof frame together. Nail the three boards you just cut into the side of the triangle that has the plywood brace, and then raise the whole unit. Attach it to the side of the frame you just installed on the side of the house, supported by temporary wooden braces.
Square off the unit and make sure it is level. As an alternative, assemble the whole unit, both triangular ends and the three connecting 2x4s on the ground, and lift the whole unit into place at once. You will still need the temporary braces once the roof frame is up.
Put in two concrete piers underneath the two corners of the roof frame. They should be at least 2 feet deep--they need to go past the frost line--and they can be poured or precast. Line these up so that they are both the same distance out from the house (3 to 5 feet) and located directly underneath the end of the 2x4 roof frame.
Set an anchor bolt or plate in the wet concrete. Align this plate just right, so that the 4x4 posts line up with the inside of the 2x4 frame. The post will extend upward and past the inside of the frame of the 2x4s. Attach the 2x4 gable frame to the side of the 4x4 post so that the frame is level and the post plumb in two directions.
Cut the post to length and attach it to the anchor. Nail the 2x4 frame to the side of the post--take an extra 3½ inches into account when you make your cut. The vertical post should be plumb. Use a 4-foot level to get this right, then nail the frame to the post.
Add one or two rafters on each side of the roof frame. They will get angled cuts on each end, which can be calculated with a bevel gauge.
Add three pieces of fascia to the wood frame. Use 1x6 pine or fir without knots and nail these down a ½-inch to an inch from the top of the 2x4 so the roof line continues on a straight line. Use # 6 or # 8 galvanised finish nails.
Put the roof on. The plywood goes on first and it needs to extend 1 inch over the sides and front. Then nail the drip edge and the felt paper on top of the plywood. Match the shingles with your main roof, using asphalt shingles and then cutting small pieces for the roof cap.
Frame in the 2x4s for the ceiling. On the underside, nail in place two or three 2x4s spaced equally apart.
Install the ceiling using beaded ceiling board or just plain 1x4 planking. The triangle section in the front should have siding put on that matches the rest of the house.
Paint the awning to match the side of the house.
Replace the siding on the house to make a watertight seal against the new roof.
Building the entire roof frame on the ground is a viable option. Use leftover siding that was removed from the main building to cover the front side of the awning.
You will need a helper for this project. Make sure the roof sheds water past the outside of any deck or stairs that are located outside the door opening.