Reroofing jobs are sometimes done without replacing flashings. However, installing new flashings, including special drip-edge flashings made for reroofing, will ensure a tight seal and a long life. Some roofers install a layer of waterproof shingle underlayment (WSU) over the existing shingles at the eave end, as would be done for a roof laid on bare sheathing. This provides added protection against ice dams. Asphalt shingles can be laid over cedar shakes or shingles, but this is a roofing project best left to the pros. Beveled wood pieces called “horsefeathers” must be laid along the thick edges of the shakes to make a fairly flat surface. Before you reshingle a roof, read our step-by-step guide for adding new shingles over old ones. Editor’s tip: If the existing roof has wavy horizontal lines, you can take out the waves by snapping a horizontal line a 1/2 inch below the shingle bottoms of one course. Install a course along the snapped line, then install succeeding courses using a guide or a snapped line. Editor’s Tip: The thicker the new shingle, the better it will hide any imperfections in the roofing underneath. It’s a good idea to use at least 40-year shingles; architectural shingles are an even better choice. Editor’s tip: In a reroof job, the starter course (or strip) is rip-cut so it butts up against the third course of the existing shingles. Its front edge is even with the front edge of the drip edge. The rest of the shingles are full width.
