Partly in response to cold temperature and high-wind performance requirements, some manufacturers produce shingles derived from recent flat roof technology developments, with different base mat materials and configurations, as well as modified asphalt formulae. Malarkey makes a three-tab and laminated shingle that is warranted against material failure in up to 100 mph winds. Curled shingles can often be cemented back in place. Individual shingles that are badly damaged can be replaced by slipping a pry bar under the damaged shingle, removing the nails, sliding the shingle out, replacing the shingle, and applying roofing cement to the new nail heads and the bottom edge of the new shingle, and the one above. If a large number of shingles exhibit excessive drying out, curling, loss of protective granules, cracking, or other deterioration, or if there is evidence of significant leaks that are not due to faulty flashing, then a complete shingle replacement is likely to be required.
Repairs are easy to make and are cost-effective over small areas.
If large areas need replacement, or if serious leaks develop, postponing replacement may cause damage to the building's structural elements or finishes. A critical decision will be whether or not to remove the existing shingles or apply the new shingles over the existing layer. According to ARMA, in many cases it is not necessary to tear off the old shingles if the roof has only one layer of shingles, is laying flat and the decking is in good condition. In this instance, the existing asphalt shingles can provide a secondary moisture barrier and the cost of removing and disposing of the old shingles will be eliminated. If the roof does not look straight and feel solid, it should be inspected for structural adequacy by a professional engineer or architect.