Roof-Over vs Tear-Off: Which One Fits Your Roof

You asked for a metal roof or new shingles and got two estimates. One includes removing the old shingles and hauling them away. The other goes over the existing roof and comes in lower. Both roofers sound confident. You are trying to work out whether the cheaper path is a reasonable shortcut or a problem you will pay for later.

Our residential metal roofing page says metal is able to be installed over an old roof, and that is true in many cases. It is also true that the building code puts limits on it, that panel manufacturers add their own, and that a roof-over means nobody sees the plywood under the old shingles. This guide lays out both sides so you can ask the right questions.

The older post of FAQs about reroofing mentions that some cities prohibit recovering and that a contractor may advise against it on a roof that has been covered before. The sections below put the actual code language behind those two warnings.

South Carolina enforces the 2021 International Residential Code with state modifications, in force for local jurisdictions since January 1, 2023, according to the SC Building Codes Council, which has set the 2024 editions to take effect January 1, 2027. The state's modification list does not change the reroofing section, so the 2021 text below is what applies to a house in the Upstate.

• Roof replacement (Section R908.3). A replacement means removing the existing layers of roof covering down to the roof deck. The one exception is an adhered ice barrier membrane, which may stay in place if it is covered by a new layer of underlayment.
• Roof recover (Section R908.3.1). A new covering may go over an existing covering where the new covering is installed per the manufacturer's approved instructions, or where the new roof is a complete and separate system, such as standing-seam metal, that carries roof loads directly to the building's structure and does not rely on the old roof for support.
• Recover not allowed (Section R908.3.1.1). No recover where the existing roof or covering is water-soaked or has deteriorated to the point that it is not an adequate base; where the existing covering is slate, clay, cement or asbestos-cement tile; or where the roof already has two or more applications of any type of roof covering.
• Reinstallation and flashings (Section R908.5). Flashings, edgings, outlets, vents and similar components must be replaced where rusted, damaged or deteriorated, even on a recover.
• Slope on a reroof (Section R908.1). A reroof does not have to meet the code's minimum design slope for roofs that already provide positive drainage.

The deck. A tear-off exposes the plywood or boards so the crew can find soft spots, rot around old leaks, loose sheathing and nails that missed the rafters. Our repair page describes cutting out rotted decking and replacing it, and the reroofing FAQ post lists basic carpentry as a standard step. On a roof-over, that step is skipped because the deck is never seen. If your attic shows stained or soft sheathing, a roof-over is the wrong choice.

Fastener holding power. Screws and nails have to pass through the old covering before they bite into the deck. Panel and shingle manufacturers specify fastener length and spacing for installation over an existing roof, and those instructions are part of what Section R908.3.1 requires. Ask to see them.

A flat, dry base. Old shingles that are curled, cupped or lumpy telegraph through new shingles and can leave gaps under metal panels. Some metal roofs over shingles go on battens or a new layer of underlayment to create a flat, ventilated plane; the panel manufacturer's instructions say whether either is required. Read roof underlayment basics for how the sheet under the panels changes on a roof-over.

Weight. A second layer adds load to the framing. The Metal Roofing Alliance states that metal roofing weighs half as much as asphalt, while a second layer of shingles adds the full weight of another shingle roof; exact figures depend on the products, and the manufacturer's data sheets give them. If the framing is undersized or already sagging, a roofer or an engineer should look before anything goes on.

Less labor, less debris and a shorter disruption. There is no dumpster full of shingles in the driveway and fewer nails in the lawn. The old roof stays in place as an extra layer under the new one, which some owners see as a benefit, though it is not underlayment and should not be counted as a water barrier.

A roof-over tends to make sense when the existing roof is a single layer of asphalt shingles that is dry, flat and well attached; when the attic shows no staining or soft decking; when the new roof is a standing-seam or other panel system whose manufacturer approves installation over shingles; and when the building department has no local rule against it. The post on safety tips before a roof replacement still applies: a roof-over is a smaller job but the house is still a work zone.

A roof-over does not fit a roof with two layers already on it, a roof that is leaking or has leaked for years, a roof with tile or slate, or any roof where the owner wants a sealed roof deck. IBHS's FORTIFIED program seals the seams of the sheathing itself, which is only possible with the deck exposed. Standing-seam metal over shingles is allowed by the code, but it cannot give you a sealed deck.

Both a replacement and a recover are alterations to the building, and the 2021 IRC's permit section (R105.1) covers an owner who intends to alter or repair a structure. The list of work exempt from a permit in Section R105.2 does not mention roofing. South Carolina leaves permit administration to each city and county, so whether a reroof permit is pulled and what gets inspected is a local question. Our guide to roofing permits in Anderson County and the City of Anderson has the official contacts.

Whichever path you choose, get it in writing. The estimate should say whether the old roof is removed or covered, how many layers exist now, what underlayment or battens go over the old roof if it stays, how rotten decking will be priced if found, and which manufacturer's instructions the installer is following. If you plan to file an insurance claim for storm damage, we can inspect and document the damage with photos and an itemized estimate; the claim itself is between you and your insurer.

Sometimes the right call is a repair. One damaged slope, a failed pipe boot or a bad valley does not require a new roof of either kind, and we will say so after an inspection. Sometimes the right call is to wait: if the deck is wet from an active leak, the leak gets fixed and the roof dries before anyone talks about covering it.

If you are ready to compare, ask each roofer the same questions: How many layers are on the roof now? Did you look in the attic? What do the manufacturer's instructions say about installing over shingles? What happens if the crew finds rot? Then read what happens on roof installation day so you know what to expect from either kind of job.

Start with our residential metal roofing or residential shingle roofing page, or request a free quote. We need to verify all measurements on site, which could adjust the price. Stay off the roof; a roofer can read the layer count from the edge, and the attic tells the rest.