25 years is common but most places allow 2 or 3 shingle overs that don't require a tearoff. They just slap a naked layer of new shingles over the old which is e

25 years is common but most places allow 2 or 3 shingle overs that don't require a tearoff. They just slap a naked layer of new shingles over the old which is even cheaper than the first roof/layer.