Although a roof looks like just shingles, there are other materials used to keep your home free from leaks and your roof in good condition. A metal drip edge is one of those items. It is installed along the edge of the decking to prevent water from either blowing or wicking up under the shingles. It is very easy to install if you are comfortable with heights. When you do it from the roof, the time involved is not long, depending on the size of your roof.
Clean and sweep the roof decking, if needed, removing all debris.
Measure lengths for drip edge pieces one at a time. Cut your first piece, if necessary. You should measure each piece after the previous one is installed.
Lay the first piece, starting on the front lower edge of the roof from one corner to the next, and nail it in. Use 1 1/4-inch galvanised roofing nails to attach the drip edge metal strip. To make a butt joint, overlap the drip edge ends and force the two pieces together. Complete the front and back lower edges of the roof.
Place the drip edge on the rake or sloping outer edges. The piece of drip edge on the slope should overlap the piece of drip edge on the lower section of the roof to prevent water from dripping behind it. Cover all sloped edges up to the bridge. All edges of the roof should be covered.
If the roof was installed originally without drip edge and the end or the roof does not overhang the gutter, the water can run behind the gutter and cause problems. You can lift the first row of shingles and install drip edge along the front and back edge to extend it to overhang the gutter, Just cut to length, place along the edge and nail up high under the shingles. If you cannot get the drip edge up high under the shingles, use a continuous bead of roofing cement all along the top of the drip edge and press down on the shingles.