How to Roof Over Existing Shingles
Is your roof in disrepair? You might be able to lay new shingles over existing shingles and avoid the cost of tear-off.
If conditions are right, new shingles laid over old shingles can be just as attractive and durable as shingles laid on bare sheathing. Installation is easier than for a tear-off job because you can use the existing shingles as guides for laying the new ones. But you must take care to install shingles correctly so they lie flat. And a good job involves installing new flashings rather than relying on the existing ones.
Reroof 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, however, this is a roofing project best left to 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.