This is usually not advisable. Remember, shingles must be laid incredibly flat to be effective. Old shingles that are curled, lifted, or damaged may make a re-roof inadvisable. In addition to this, every 50 square feet of quality shingles can add 180 to 225 pounds of weight to a roof. A second re-roof may go over the weight limit of the rafters and void certain warranties on products. A tear-off allows us to inspect the decking and foundation of the roof, which may or may not be damaged. An inadvisable re-roof can lower your home evaluation by thousands of dollars when a realtor is advised by a home inspector’s report.