Tear-off or overlay
An overlay — a second layer of shingles installed over the existing one — is cheaper on the day, because nobody pays for removal or disposal. It is also, in most circumstances, the wrong decision, and it is worth understanding why rather than taking that on faith.
Three reasons. First, an overlay conceals the sheathing, which means the one opportunity to find and replace deteriorated decking is thrown away, and any soft spot is simply covered over. Second, the new layer follows the contour of the old one; every cupped, lifted or uneven shingle underneath telegraphs through, and those irregularities become points where the new layer cannot lie flat or seal. Third, the assembly runs hotter, because there are now two layers of asphalt holding heat against the deck, and heat is what ages a shingle.
There is also a code dimension. Most jurisdictions cap roof coverings at two layers, so an overlay on an existing second layer is not permissible and an overlay on a first layer forecloses the option next time. And the added dead load matters on older framing.
We will quote an overlay where the existing roof is a single flat-lying layer in genuinely sound condition, the framing carries it comfortably, and the budget requires it. We will say plainly that it is a compromise, and what is being given up.
The decking is the part nobody quotes
Sheathing condition cannot be known until the old roof is off. That is not a hedge; it is a physical fact, and any quote implying otherwise is either padded or incomplete. What separates an honest proposal from a bad surprise is how the unknown is handled in writing before work starts.
Our proposals state a per-sheet rate for sheathing replacement and how many sheets, if any, are included in the base price. Every sheet we replace is photographed in place before it comes out. You get the count and the evidence, so the extra is auditable rather than asserted.
What we are looking for once it is open: delamination, soft or spongy areas around penetrations and along the eave, sheathing that has been repeatedly wetted at a valley, boards spaced too widely for the covering being installed, and any framing damage that the roof covering has been hiding. Occasionally a rafter tail or a section of fascia has to be dealt with too, and that is better found now than in three years.
Choosing the covering
| Covering | Typical service life | Suits | Watch for |
|---|---|---|---|
| Architectural asphalt shingle | Roughly 25–30 years, exposure dependent | The default for most residential replacement — good wind ratings, wide colour range, repairable in future. | Ratings assume correct nailing and adequate ventilation. Both are commonly wrong on production work. |
| Three-tab asphalt shingle | Roughly 15–20 years | Budget-constrained replacement and matching an existing roof on a secondary structure. | Lower wind resistance and less forgiving of an uneven deck. Rarely worth the saving over architectural. |
| Impact-resistant asphalt shingle | Similar to architectural, better hail survival | Properties in hail-frequent exposure, where many insurers offer a premium reduction that offsets part of the cost. | Confirm the specific class with your insurer before ordering. Not every product qualifies for a discount. |
| Synthetic composite slate or shake | Roughly 40–50 years | Owners wanting the appearance of slate or cedar without the weight or the maintenance profile. | Cost per square is substantially higher, and installation quality varies more because fewer crews work with it regularly. |
| Concrete or clay tile | 50 years or more for the tile itself | Structures already framed for the load, in high-UV exposure where asphalt ages quickly. | The underlayment fails long before the tile does — budget for a re-underlayment at roughly half the tile’s life. |
Metal and other premium systems are quoted case by case rather than offered from a standard menu, because the framing, the substrate and the detailing all have to be assessed first.
Ventilation, while the roof is open
A replacement is the only convenient moment to correct attic ventilation, and it is worth spending the money. Under-ventilated attics hold heat against the underside of the sheathing, which ages the shingle from below and can take years off a roof rated for decades. In cold climates the same problem drives ice damming, because a warm roof deck melts snow that then refreezes over the cold overhang.
The principle is balance: intake at the eaves and exhaust at or near the ridge, roughly matched in net free area, with intake never less than exhaust. The two failures we find most often are soffit vents blocked solid by insulation pushed into the eave, and multiple exhaust types on the same attic — ridge vent plus box vents plus a powered fan — which lets the exhaust pull air from the nearest opening instead of from the soffits, so the far end of the attic never ventilates at all.
We assess intake and exhaust before quoting and include whatever correction is needed in the scope, itemised rather than buried.
Disposal, protection and the site
A tear-off generates a remarkable amount of debris, and how a crew handles that is a fair proxy for how they handle everything else. Ours protect landscaping and hard surfaces with plywood and tarps before the first shingle comes off, keep the debris contained rather than letting it accumulate wherever it lands, and sweep the site with a rolling magnet at the end of every working day rather than only at the end of the job. Fasteners in a driveway are the single most common post-replacement complaint in this trade and they are entirely avoidable.
Old roofing goes to a facility that will take it, and asphalt shingles are recyclable in many areas into road material. Where that option exists we use it.
What to expect during the work
- Duration. Most single-family replacements run one to three working days. Complex rooflines, steep pitch, multiple layers or extensive decking replacement extend that.
- Noise and vibration. Tear-off is loud and the structure transmits it. Take pictures off walls and secure anything hanging or fragile, particularly in an attic or garage.
- Access. The crew needs the driveway and clear ground around the perimeter. Park elsewhere and move vehicles out the night before.
- Weather. No responsible crew opens more roof than it can dry in before the day ends. A forecast change can pause a job mid-course, and that is the correct call rather than a delay tactic.
- Permits and inspection. Most jurisdictions require a permit for a full replacement. We pull it, and the municipal inspection happens before final payment.
Get the ventilation calculation in writing. Ask any contractor quoting a replacement to state the net free ventilation area being provided at intake and at exhaust, and how it compares to the attic floor area. A contractor who has done that calculation will hand it over. A contractor who has not will change the subject, and the shortfall will quietly shorten the life of the roof you just paid for.
If a full replacement turns out not to be necessary, we would rather find that at the inspection stage — see roof repair and roof inspection for how that assessment works. USA Roofing Contractor Pros quotes the replacement only after the case for it is documented.