# Can you put a metal roof over shingles?

Often you physically can, and frequently you should not. Model code limits a roof to two coverings before tear-off is required, so a single existing layer usually permits a recover. What it costs you is any knowledge of the deck underneath, and the deck is the part that fails silently.

## What does the code actually say?

Model code limits a roof to **two** roof coverings; a third requires tearing off to the deck first. It also requires that the existing covering be in a condition suitable to receive the new one, and that the deck be sound.

Adoption varies by state and often by county, and a recover normally still needs a permit and an inspection. Confirm with your building department before anyone orders material — the inspection is the one moment somebody independent looks at the assembly.

Some jurisdictions restrict recovers more tightly than model code, particularly in high-wind and hurricane regions.

## Why do roofers keep recommending against it?

Because a recover buys a cheaper job by declining to look at the expensive problem.

The deck is the part of a roof that rots quietly. Water that has been tracking around a chimney or a failed pipe boot for six years leaves sheathing that looks intact from the attic and fails under a boot. Tear-off is when that gets found and fixed. A recover paves over it.

You also inherit whatever is wrong with the old roof. Buckled shingles telegraph through metal panel as visible waves. Old flashing that was already marginal is now buried under a roof expected to last fifty years.

And it complicates the next job: the eventual tear-off is now two layers, and it costs accordingly.

## When is a recover actually defensible?

Three conditions, and all three have to hold.

**One existing layer, in flat condition.** Not curled, not buckled, not missing tabs. Anything the old roof does telegraphs through the new one.

**A deck that has been verified**, from the attic at minimum — no staining on the underside of the sheathing, no damp insulation, no rusted nail points, no soft spots.

**No leak history.** If the roof has ever leaked and the entry point was not definitively found and fixed, the water is still going somewhere and you are about to seal it in for fifty years.

If all three hold and the budget is genuinely the constraint, a recover over a purlin or batten system is a reasonable engineering decision. If any one of them is uncertain, the money saved is a deferred bill with interest.

## Does a recover affect the fire rating or the warranty?

Both, and people are routinely surprised by each.

**Fire class belongs to the assembly, not the panel.** A Class A metal panel over an existing asphalt layer over an unknown deck is not automatically a Class A roof. The rating comes from the tested assembly, and the tested assembly probably was not this one.

**Manufacturer warranties frequently restrict or exclude recover installations.** Many require installation over a solid deck to a specified detail, and deviating from the installation instructions is the standard way material warranties are voided. Get the manufacturer's own position in writing before, not after.

## What about ventilation and condensation?

This is the part that gets skipped and then causes damage.

Metal over asphalt with no ventilation gap creates a surface where warm moist attic air meets a cold metal underside and condenses. That water lands on the old shingles and the deck. Over years it does exactly what a leak does, without ever being a leak.

A recover done properly uses a batten or purlin system to create an air gap, an appropriate underlayment, and balanced intake and exhaust ventilation. Ask specifically how the assembly is being ventilated. "It'll be fine" is not an answer.

## What should this cost against a full tear-off?

A recover typically saves the tear-off and disposal — often a meaningful share of the job — but adds battens or furring where those are used.

Ask for **both** quotes from the same contractor: recover and full tear-off with a per-sheet decking allowance. Seeing the two side by side, with the decking allowance visible, is the honest way to make this decision. See [what a roof costs](/costs/).

## Common mistakes

- **Treating "code allows it" as "it is a good idea".** Code sets a floor, not a recommendation.
- **Recovering over a roof that has ever leaked.** The water is still going somewhere.
- **Assuming the fire class carries over.** It belongs to the tested assembly.
- **Skipping the ventilation gap.** Condensation on the underside of metal does the damage of a leak without being one.
- **Not asking the manufacturer about the warranty in writing.** Many restrict recovers, and the exclusion surfaces at claim time.