How to Roof a House Over an Existing Roof

Walk all over the roof to inspect the existing shingles for damage. Replace damaged shingles, and pound nails in that are sticking up out of the roof. Sweep off any debris that is on the roof.

Remove the existing ridge caps from the roof for an easier installation process. Remove fixtures on the roof, such as pipe flashings and air vents that you'll need to shingle around.

Install drip edge flashing strips along the edges of the roof. These metal strips hold down the edges and provide protection. Nail in the strips along the eaves and then along the other sides of the roof.

Nail on the starter strip along the bottom edges of the roof. Line up the bottom of the starter strip with the bottom edge of the old shingles. The starter strip is essentially a shingle without the tabs and helps protect the roof along the edges.

Center the first shingle right in the middle of the bottom edge of the roof. Nail it in with four roofing nails. Finish the first row by nailing down each shingle, butting it up to the one next to it.

Center the second row of shingles so the middles of the shingles land at the joint of two shingles in the first row for an offset appearance. Continue working up the roof, offsetting each row from the last.

Cut shingle strips as needed to shingle around vents and chimneys. Install step flashing along a chimney before nailing down the shingle.

Position the new ridge cap shingles so that equal amounts of the shingle are on either side of the roof. Nail the ridge caps in place along the entire ridge of the roof.