A "re-roof" or "layover" installs new shingles directly over the old ones, skipping tear-off. It is legal in many places for exactly one additional layer — most building codes and shingle manufacturers cap a roof at two layers total, and many jurisdictions now require full tear-off. Some materials (metal over shingles, for instance) have their own rules.
Why we price tear-off as the default
- You can't inspect the deck. Rotten decking stays hidden under a layover — and fails later, under a newer roof.
- Shorter life. Shingles over shingles run hotter and typically age faster; manufacturer warranties may be reduced or voided.
- Weight. Each asphalt layer adds roughly 2.3–4 lb per square foot. Two layers plus a third material can exceed what older framing should carry.
- Resale. Home inspectors flag multi-layer roofs, and buyers price the eventual tear-off into their offers.
The math that usually settles it
A layover saves the tear-off line — roughly $50 per square for asphalt — today. A full tear-off later costs that same line per layer, so the two-layer roof of 2045 costs double to strip. On a 24-square roof, today's ~$1,200 saving becomes tomorrow's ~$2,400 extra. Layovers win when the deck is verified sound (from the attic) and the home will be sold before the next replacement; otherwise, tear-off is the honest default — and it is what every range on this site assumes.
Run your own numbers: the satellite estimator and the roof cost calculator are both free, and both use the published dataset on our methodology page.