If you're comparing roof replacement quotes in Middle or East Tennessee, you may notice they aren't all describing the same job. Some roofers quote a tear off, where the old shingles are stripped down to the roof deck before the new roof goes on. Others quote a roof overlay (sometimes called a roof-over or re-cover), where new shingles go right on top of the old ones. An overlay usually costs less up front, but it can cost you more over the life of the roof. Here's how the two compare, and why we only do tear offs.
Tear off vs roof overlay at a glance
- What happens: a tear off removes the old shingles down to the deck; an overlay installs new shingles over the old layer.
- Up-front cost: a tear off costs more because it includes removal and disposal; an overlay costs less.
- Roof deck: a tear off exposes the deck so it can be inspected and repaired; an overlay keeps it hidden.
- Weight: a tear off adds no extra layer; an overlay leaves the old shingles on the roof, adding thousands of pounds on a typical house.
- Mold, mildew and rot: a tear off removes them with the old shingles; an overlay traps them under the new roof.
- Appearance: a tear off gives a flat, even surface; an overlay can telegraph the curls and dips of the old roof.
- Warranty: enhanced manufacturer warranties come with installation requirements, so ask in writing what coverage each option qualifies for.
Can you put new shingles over old ones?
Sometimes, legally. The International Residential Code, the model code many local building departments adopt, does not allow a re-cover where the existing roof already has two or more layers of roofing (section R908.3.1.1), and it also rules out a re-cover over a roof that is water-soaked or deteriorated. Your local codes office has the final word on what's allowed where you live.
Allowed doesn't mean wise. Any problem with the old shingles becomes a problem for the new ones, and the next roofer will have two layers to remove instead of one.
What a roof overlay hides
Added weight on the structure
A square of shingles (100 square feet) weighs about 200 pounds or more, depending on the product. On an average roof in our area, that's several thousand pounds of shingles. An overlay leaves all of it in place and adds a second full layer on top. Depending on how your home was built, plus any snow or ice, that extra load puts more stress on the rafters and decking.
Mold, mildew and rot
Any mildew, mold or algae on the old shingles stays there when the new layer goes on. Moisture trapped between the layers can rot the roof from the inside out, which drastically shortens the life of the new shingles.
A roof deck no one has seen
A spongy spot underfoot during an inspection points to a problem below the shingles, such as damaged or rotting decking. With a tear off, your roofer can see exactly what's wrong and how far it spreads, then repair it before the new roof goes on. With an overlay, that damage stays hidden under two layers of shingles. Our post on why you might need a new roof deck explains what we look for.
An uneven surface
New shingles need a flat surface. If the old roof has curled, bent, missing or misaligned shingles, those flaws show through the new layer. The result looks uneven and doesn't shed water as well as it should.
Does a roof overlay affect your warranty?
This is one of the biggest reasons to choose a tear off. GAF's enhanced warranties depend on how the roof is installed: they require qualifying GAF accessories installed with the shingles, and the top-tier Golden Pledge warranty is only available through GAF Master Elite contractors. Those accessories, such as leak barrier, roof deck protection and starter strips, are installed on a clean deck, which is part of why a complete tear off is the standard for a full system.
Before you sign, ask each roofer exactly which warranty you'll receive with their quote, and get the answer in writing. A cheaper overlay with weaker coverage may not be the bargain it looks like.
How to tell which one your quote includes
Look for a line item such as “tear off of existing roofing materials” or a charge for disposal of old roofing. Either is a good sign the quote includes a tear off. If the quote doesn't say clearly, ask before you sign. It's also fair to ask how the roofer handles decking that turns out to be bad once the old roof is off, and what that costs.
Why Mobley Brothers only does tear offs
As a GAF Master Elite residential contractor, we do a full tear off on every roof replacement and install a complete GAF roofing system, so your roof is eligible for GAF's enhanced warranties, including up to 50 years of coverage on qualifying new-roof installations, including up to 25 years of workmanship coverage, through the GAF Golden Pledge. Exact terms are in your written proposal.
- Your proposal states possible decking costs up front, so bad boards found after the tear off aren't a surprise.
- We protect the property around the house during the work, with the Catch-All system where required.
- We photograph what we find under the old roof and show you.
Learn more about our tear off roof replacement process and the architectural shingle roofing we install.
Get a free roof replacement estimate
We measure the roof from satellite imagery, send a written proposal, and look at the roof in person before install day, or sooner on request. Mobley Brothers Roofing & Renovation is licensed, insured and BBB accredited with an A+ rating. Call our Lebanon office at (615) 455-3131 or our Knoxville office at (865) 205-0800, or request your estimate online.
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