Roof tear-off vs overlay

When replacing an asphalt shingle roof, two main approaches are possible.

Tear-off: Remove all existing shingles down to the roof deck, inspect and repair any deck damage, install new underlayment, then install new shingles. The complete approach. Slightly higher labor and disposal cost; significantly better long-term results.

Overlay (or 'reroof'): Install new shingles directly over the existing first layer of shingles. Avoids tear-off labor and disposal costs. Building code typically allows one overlay (two total layers) on most residential roofs; some jurisdictions don't allow overlays at all. Overlay may also void shingle manufacturer warranties.

The trade-offs: overlay saves $1,500-$4,000 on a typical residential roof but compounds problems. Existing damage is hidden; second layer adds significant weight (potentially exceeding structural design); installation quality suffers (shingles can't be precisely aligned over existing); ventilation suffers (vents may be partially or fully blocked); future tear-off is more expensive (two layers to remove).

For roofing operators, the recommended approach is tear-off in nearly all cases. Overlay is appropriate only in narrow circumstances: customer financial constraint with first roof in good underlying condition, single-layer roof less than 15 years old, no visible damage. Honest customer communication about the long-term cost difference (tear-off lasts 20-30 years; overlay lasts 12-18 years) builds trust.