How do I handle a roof with three layers of shingles?

The best thing to do in a case where there are three layers of shingles is to tear them off and start a new layer directly on the roof deck.

The best thing to do in a case where there are three layers of shingles is to tear them off and start a new layer directly on the roof deck. Most shingle manufacturers recommend always to do a tear-off before re-roofing, however, they will allow a second layer if necessary. Three layers have extreme potential for blow-off and each extra layer of shingles will decrease the life of the new shingle.