What Is Reroofing? Tear-Off vs Overlay and the Code Limits

What reroofing means

Reroofing is the code's word for any job that puts a new covering on an existing roof. It is not the same as building a roof on a new house.

The house, the rafters and the roof deck are already there. What changes is the outer layer that keeps the weather out, plus the underlayment and flashing that go with it.

The 2021 International Residential Code, or IRC, splits reroofing into two kinds ¹. A roof replacement removes the old roof covering.

The code says it "shall include the removal of existing layers of roof coverings down to the roof deck." Roofers call this a tear-off. A roof recover installs a new covering on top of the old one. Roofers call this an overlay, a layover or a roof-over.

The Asphalt Roofing Manufacturers Association, the trade group for shingle makers, uses the same two words.

It defines replacement as removing the old covering, repairing any damaged deck and installing a new covering, and recover as installing an extra covering on the existing one ².

When a roofer says "reroof," ask which of the two they mean. The words are often used loosely, and the two jobs are very different.

How each method works

In a tear-off, the crew strips the shingles, the underlayment and usually the old flashing and drip edge off the roof. That leaves the bare deck, the sheets of plywood or boards nailed to the rafters.

The crew checks the deck, replaces soft or broken pieces, and then builds the roof back up layer by layer: drip edge, underlayment, an ice barrier where the climate calls for one, flashing, and then the new shingles.

In an overlay, the old shingles stay. The crew cleans the roof, takes off the old ridge and hip caps, and nails new shingles over the top.

The nails have to be longer, because they must pass through both layers and still bite into the deck.

IKO, a shingle maker, says nails must be long enough for firm anchorage and that the new ridge caps need even longer ones ³.

One local building guide asks for nails that go all the way through the roofing and at least ¾ inch into the deck ⁴.

IKO describes two ways to lay an overlay ³. In nesting, each new shingle is fitted against the edge of an old one, so the old pattern is hidden.

In bridging, the new shingles span over the old courses, which can let the old layer show through as ridges. Which method works depends on the shingle sizes, so the crew should test-fit before starting.

The kinds of reroofing work

The code names these cases in Section R908 ¹:

On most houses with asphalt shingles, the real choice is the first two rows: tear-off or overlay.

Worked example: can this roof take an overlay?

Here is how the code test plays out on three made-up houses. Each one has an asphalt shingle roof that needs work.

House A also has to pass the other checks: the framing must carry the extra weight ¹, and many makers advise against laying new shingles over laminated (dimensional) shingles ². These are illustrative houses, not real jobs.

Where reroofing comes up

Most homeowners meet the word reroofing in three places. The first is the permit. Many building departments list "reroof" as its own permit type, separate from new building work.

The second is the roofing quote, where the line items often say "tear-off" with a count of layers, or "recover." The third is an insurance claim, where the adjuster's estimate may include tear-off and disposal of each existing layer.

The word also shows up when a house is sold. An inspector may count the layers at the roof edge and note that a second layer is already in place.

That matters, because under the 2021 IRC a roof with two layers cannot take a third ¹. The next reroof on that house must be a full tear-off.

Benefits of each method

• Tear-off: the crew sees the whole deck and can replace rotted wood before it is covered.
• Tear-off: new underlayment, ice barrier, drip edge and flashing go in, built to today's code.
• Tear-off: the roof carries one layer of weight, not two, and the next reroof is simpler.
• Overlay: less labor and less waste to haul away. ARMA notes the lower disposal cost ².
• Overlay: the old layer gives some extra backup protection, by ARMA's account ².
• Overlay: the house is open to weather for less time, since the deck is never bare.

Limits of an overlay

• It hides the deck. Rot, soft spots and old leaks stay under the new roof where no one can see them.
• It adds weight. The code requires the framing to carry the roof plus the loads during the work ¹.
• It can look lumpy. Curled or uneven old shingles show through the new layer.
• It is not allowed over slate, clay, cement or asbestos-cement tile, or over two existing layers ¹.
• It may change product ratings. ARMA notes impact-resistance ratings may be affected by a recover ².
• It uses up the last allowed layer, so the next job must be a full tear-off.

What drives the cost of a reroof

We do not list prices here, because they vary by place and by month. These are the things that move a quote up or down. For a figure for your house, use the roof cost calculator or the roof cost guide.

• Roof size, counted in roofing squares of 100 square feet each.
• Number of layers to remove. Each extra layer means more labor and more waste to haul.
• Deck repair. Rotted sheets found after the tear-off are often priced per sheet.
• Steepness. A steeper roof pitch is slower and needs more safety gear.
• Flashing and edge metal. Whether the old pieces are replaced or reused.
• Permit and disposal fees, which are set locally.
• Material. Shingle grade, metal or tile.

How a tear-off reroof usually goes

This is what you should see, not a do-it-yourself guide. The full project timeline is on how a roofing project works. Roof work is a fall risk.

Federal rules say workers on an edge 6 feet or more above a lower level must be protected by guardrails, nets or a personal fall arrest system ⁵.

1. The roofer inspects the roof and the attic and counts the layers.
2. The roofer or owner gets the reroof permit from the building department.
3. The crew tarps the yard and strips the old roofing down to the deck.
4. Soft, warped or cracked deck boards are repaired or replaced. Some towns inspect the deck at this point.
5. Drip edge, underlayment and, where required, an ice barrier go down.
6. Flashing is rebuilt and the new covering is installed.
7. The site is cleaned and the building department does a final roof inspection.

Care after a reroof

• Keep the permit, final inspection record and the list of layers removed. Buyers and insurers may ask.
• Ask for photos of the bare deck and any repairs made before they were covered.
• Check the attic after the first heavy rain for drips or stains near vents and chimneys.
• Keep gutters clear so water leaves the new roof edge.
• Look at the roof from the ground after big storms for lifted or missing shingles.
• Write down whether the roof is one layer or two. It decides what the next reroof can be.

Risks to watch for

• Hidden rot under an overlay. A soft deck holds nails poorly, and ARMA says the deck must allow good fastener hold ².
• Too much weight. ARMA lists sagging along the ridge or between trusses as a reason to tear off ².
• Reused flashing that fails. The code says rusted, damaged or worn flashing, vents and edging must be replaced ¹.
• A layer count above the limit. A third layer can fail inspection and may need to be torn off.
• Trapped moisture. IKO says the roof should be fully dry before an overlay ³.
• Poor ventilation. ARMA and IKO both say to check attic airflow during a reroof ^{2 3}.

What the code says about reroofing

These rules are from Section R908 of the 2021 International Residential Code, read in the Maryland adoption ¹. States and cities adopt the IRC on their own schedule and can amend it.

Sources: [1]

Tear-off vs overlay vs repair

Not sure whether you need a repair or a new roof? See repair or replace.

Common misconceptions

Myth You can always add another layer.

Reality The 2021 IRC bans a recover over two or more existing layers, so a third layer is not allowed ¹.

Myth An overlay is a full new roof.

Reality It is a new top layer. The old shingles, underlayment and deck stay in place, unseen.

Myth Reroofing and roof replacement mean the same thing.

Reality Replacement is one kind of reroofing. A recover is the other kind.

Myth Old flashing is always fine to reuse.

Reality The code requires rusted, damaged or worn flashing and vents to be replaced ¹.

Myth Any roof can take an overlay.

Reality Slate, clay, cement and asbestos-cement tile roofs cannot be recovered under R908.3.1.1 ¹.

Myth Two layers are always legal everywhere.

Reality Two is the limit in many places, but local rules can be stricter. Some towns require a full tear-off.

Local rules for reroofing

The rules on this page come from the 2021 IRC. Your state or city may use an older or newer edition, and may amend it. That is why the same overlay can be fine in one town and turned down in the next.

Local building guides show how this plays out.

The East Point, Georgia, reroof guide, based on the 2018 IRC, says a permit is needed, that "no more than two (2) layers are allowed upon completion of installation," that the owner must call for a final roof inspection, and that a mid-roof inspection may be required ⁴.

It also says warped, cracked or split deck boards must be repaired or replaced on a full tear-off, and that worn or rusted roof jacks and vents must be replaced.

In cold areas the code also calls for an ice barrier at the eaves, and on a tear-off that is put in fresh. Ask your building department, or your roofer, which code edition applies, whether a reroof permit is needed, and which inspections they do.

How to choose: tear-off or overlay

• Count the layers first. Two or more means tear-off, with no choice.
• Is the roof slate or tile? Then it cannot be recovered. It is a tear-off or a relay of sound units.
• Any soft spots, sagging, leaks or stained deck in the attic? ARMA says remove the old roof ².
• Are the old shingles curled or badly uneven? An overlay will show it. IKO says avoid an overlay over curling shingles ³.
• Is the old roof laminated shingles? Many makers do not recommend an overlay over them ².
• Does the new shingle maker's instructions allow an overlay, and does the warranty still apply? Ask in writing.
• If all of that checks out, an overlay may be allowed. Otherwise, plan a roof replacement.

The guide shows that the code settles most cases; only the last row is a real choice.

Keep going

• Roof inspectionCount layers and check the deck first
• Roof life calculatorHow much life the old roof has left
• Choosing a rooferQuestions to ask before you sign
• Ice and water shieldThe eave membrane added on a tear-off
• Roof plannerSee roof options for your house in a few steps

Related terms

Roof Replacement

Removing the old roof covering (or recovering it, where allowed) and installing a new one over the whole roof.

Roof Sheathing

Roof sheathing is the layer of plywood, OSB or wood boards nailed across the rafters or trusses.

Roof Flashing

Roof flashing is thin, water-shedding material, usually bent metal, installed at the joints of a roof where shingles alone cannot keep water out: along walls, around chimneys and pipes, in valleys and at the roof edges.

Roof Underlayment

Roof underlayment is a sheet laid over the whole roof deck before the shingles or other roof covering go on.

Drip Edge

Drip edge is a strip of bent metal flashing installed along a roof's eaves and rake edges that carries water off the edge of the roof and away from the fascia and the deck beneath.

Ice and Water Shield

Ice and water shield is a self-adhering, rubberized asphalt membrane laid directly on the roof deck under the roof covering, where it seals around nails and blocks water that ice dams or wind-driven rain push back under the shingles.

Roofing Square

A roofing square is a unit of area equal to 100 square feet of roof surface, a 10-by-10-foot patch, and it is the unit in which shingles are sold and most roofing quotes are priced.

Asphalt Shingles

Asphalt shingles are roofing pieces made from a fiberglass mat coated with asphalt and topped with mineral granules, laid in overlapping rows so water runs off the roof.

Also referenced from: Roofing System, Roof Sheathing, Low-Slope Roof, Asphalt Shingles, Architectural Shingles, Standing Seam Metal Roof, Roof Truss, Roof Underlayment, Drip Edge, Step Flashing, Valley Flashing, Chimney Flashing, Kickout Flashing, Pipe Flashing, Ridge Vent, Soffit Vent, Roof Wind Uplift, Hurricane Roofing, Roof Moisture Inspection, Roof Certification, Roof Life Expectancy, Roofing Square, Roof Estimate