Talk With A Metal Roof Expert
Call (615) 649-5002.jpg)
No, you should not install metal roofing over shingles in Nashville or anywhere in Tennessee. You can install metal over shingles in limited situations, but it is usually a shortcut that compromises the very reasons people choose metal in the first place: long service life, clean appearance, and predictable performance.
Homeowners ask this because it sounds logical. Why pay for tear-off, dumpster fees, and extra labor if you are covering the roof anyway? On paper, a metal-over-shingles overlay feels like it should save time and money.
In reality, overlaying metal on top of shingles stacks risk into the assembly. It hides the roof deck, hides existing problems, makes detailing harder, and often produces a less professional finished look. In Middle Tennessee, where you get long hot summers, humidity, and wind-driven rain events, those weaknesses tend to show up sooner.
So the answer is “no” in the sense that it is not the right way to do a metal roof on a home you care about long-term.
Most homeowners do not care about code language until something goes wrong. But the code is the starting point for understanding why overlays exist at all.
The International Residential Code language is clear on the definition of “roof replacement.” It states that roof replacement includes removing existing layers down to the roof deck, with a narrow exception related to certain adhered ice barrier membranes. (gptx.org)
The same section also describes when a “roof re-cover” can be permitted. It allows installing a new roof covering over an existing one if the new covering is installed per manufacturer instructions. It also notes that “complete and separate” systems, such as standing-seam metal roof systems designed to transmit loads directly to the structure, may not require removal of existing coverings.
Then it tightens the rules. A roof re-cover is not permitted if the existing roof is water soaked or deteriorated to the point it is not an adequate base, or if there are two or more existing roof-cover applications.
That is the general framework.
Now here is why Nashville matters: Davidson County’s adopted codes can differ from state minimums and from nearby counties. Metro Nashville’s adopted codes list includes the 2024 International Residential Code with local amendments. (Nashville.gov) Metro’s public notice also states the 2024 International Codes were adopted via BL2025-898 and applies to plans and applications submitted after the effective date in July 2025. (Nashville.gov)
At the state level, Tennessee’s State Fire Marshal office lists the currently adopted IRC as the 2018 edition with amendments. (tn.gov)
Practical takeaway: even if an overlay can be allowed under the IRC framework, you still need to meet local enforcement expectations in Nashville and your specific jurisdiction, and you need the installation to be manufacturer-compliant. Code allowance does not make an overlay a good idea.
This is the number one practical reason. A metal roof is only as good as what it is fastened to. Shingles hide soft decking, edge rot, sagging sheathing, old leak stains, and bad repair patches. If you cover shingles, you are accepting the deck as-is without truly seeing it.
That is a bad trade in Middle Tennessee because roofs here take heavy rain loads and repeated heat cycles. Small deck issues become movement issues. Movement becomes flashing stress. Flashing stress becomes leaks. Those leaks get blamed on the metal, even though the real failure was a hidden deck condition that should have been corrected on day one.
If you are investing in metal to avoid doing another roof later, it makes no sense to gamble the foundation.
A big reason homeowners pick metal in Nashville is appearance. Clean lines. Straight seams. Crisp edges. A premium look.
Shingles are not a flat substrate. They have ridges, thickness changes at laps, uneven spots from age and heat, and sometimes multiple repair layers. Overlaying metal over that surface can telegraph unevenness into the finished roof. You end up with subtle humps at transitions and waviness where you wanted clean geometry.
This is especially important for standing seam aesthetics. If someone is paying for a roof to look intentional and architectural, the substrate should be flat and correct. Tear-off helps you get that.
Nashville and Middle Tennessee are humid. Moisture control is already a key part of residential roof performance, especially in attics.
Overlaying changes how the assembly dries. It adds an extra layer that can trap heat and slow drying when there is incidental moisture. That does not guarantee condensation, but it increases the odds that a marginal attic becomes a problem attic. If your ventilation or air sealing is not perfect, overlaying makes it easier to end up with hidden moisture issues that are hard to diagnose because the shingle layer is buried.
A clean deck install gives you a chance to reset the system correctly. You can address ventilation strategy, underlayment selection, and flashing details in one coordinated plan.
Metal moves. It expands and contracts daily. A properly designed metal system accounts for movement with the right fastening strategy, correct spacing, and correct transitions. That is harder to do when you are fastening into a layered, compressible surface.
Overlaying can also make installers tempted to take shortcuts. Some crews screw through the shingles into decking and call it a day. That is not a thoughtful assembly. It increases the chance of uneven torque, compression, and fastener stress. It also makes it harder to achieve consistent fastening patterns that match manufacturer requirements.
If the system is supposed to transmit loads directly to the structure, it needs to be built like a structural system, not like a cover-up.
Most leaks do not come from the middle of panels. They come from the details. Chimneys. sidewalls. headwalls. valleys. skylights. pipe penetrations. Every one of these is a transition that requires correct rebuilding for a metal roof.
The IRC guidance on reroofing details is not subtle about flashings. It says flashings must be reconstructed in accordance with manufacturer instructions.
Overlay jobs often pressure installers to reuse parts of the old system, or to “tie into” existing flashings rather than fully rebuilding them. That is where you get persistent leaks that are blamed on metal as a concept, when the real issue is improper flashing scope.
If the goal is a long-life roof, you rebuild the details the right way.
A layered roof assembly is harder to diagnose. If there is a leak later, you have to determine whether the water is traveling between layers, whether the underlayment is compromised, whether a hidden deck seam is opening, or whether a penetration detail is failing.
With a clean deck install, diagnosis is straightforward. With an overlay, it becomes a layered mystery. That increases service time and often increases the cost of repairs, even when the repair itself is not complicated.
Skipping tear-off can save some labor and disposal cost. But relative to the overall cost of a residential metal roof in Nashville, the savings often do not justify the downside.
If you are spending premium dollars for metal, it makes little sense to cut corners on the part of the job that gives you certainty: a visible deck, corrected substrate, and rebuilt details.
If you want the “do it once” version of a metal roof, the best practice is simple: tear off the shingles and start with a clean deck.
A quality Tennessee metal roof scope typically includes:
That is how you get the clean finish, predictable performance, and long service life homeowners expect when they choose metal.
Only in narrow situations, and even then, it is a compromise.
If a homeowner insists on overlaying, the minimum conditions should look like this:
Even then, it is still usually not the best approach for a homeowner who wants a true long-term roof.
No, you should not install metal roofing over shingles in Nashville, TN. You can sometimes do it, and the IRC framework describes when a re-cover may be permitted, including for certain standing seam systems, but it is still a compromise that commonly trades short-term convenience for long-term uncertainty.
If you are in Nashville, Franklin, Brentwood, Hendersonville, Murfreesboro, or anywhere in Middle Tennessee, the best recommendation for a metal roof that is meant to last is the same: tear off the shingles, inspect the deck, rebuild the details, and install the metal system correctly from the substrate up.
