DIY: Lean-To Roof

Determine where you want to put your lean-to roof. Measure the length, width and how far out you want it to protrude. Decide how high you want the lowest edge of the roof to be.

Cut your posts to the length you want the lowest edge to be plus 3 feet, using the saw. This extra length will sit in the ground to give stability to the posts.

Dig holes for the posts 3 feet deep at the distance from the house that you want the lean-to roof to extend to, using a shovel. Usually you would place posts every 6 feet or so along the length of the lean-to. If you are building a small lean-to, place a post at each end of the roof.

Place the posts plumb in the holes (you should enlist a friend to hold them with a spirit level against them). Mix concrete with water in a bucket and pour the mixed concrete into the hole to a depth of approximately 1 1/2 feet. Allow the concrete to dry.

Fill in the holes with soil.

Install a timber header – a piece of timber to which you will affix the roof – to the house wall. Use a spirit level to ensure the header is true, and lag bolts to secure, ensuring that the header is at a level higher than the top of the posts you installed, so the lean-to roof slopes.

Install a timber header across the top of the posts. Use lag bolts to secure.

Mark where your rafters will extend from the header on the wall to the header on the posts. Typically these are placed 24 inches apart. Cut the ends so they fit flush with the headers and screw in place.

Place your plywood sheets across the rafters and screw into the rafters. Apply weatherproof finish to the plywood sheets.

Install a length of flashing – a piece of non-corrosive metal – along the edge where the lean-to roof meets the house wall to ensure the rain does not penetrate the join.