Metal Roof Over Shingles: Can You Do It in San Antonio?

It’s a tempting pitch. Skip the tear off, skip the dumpster, skip the disposal fee, and put a metal roof straight over the shingles you already have. Some contractors around here will quote it that way, and it does save real money up front.

The honest answer is that it’s sometimes allowed and often a bad idea, and the difference comes down to three things: what the code says about your specific roof, whether anyone can still inspect your decking afterward, and how the assembly handles heat and moisture once it’s sealed up.

Here’s how to tell whether your roof is a candidate, and what you give up if you go that route.

Can you legally put a metal roof over shingles?

Sometimes. The residential code permits a roof recover, meaning a new covering installed over the old one, but it bans it outright in three situations. Your roof has to clear all three before the conversation goes any further.

The code language is specific. A roof recover is not permitted where the existing roof or covering is water soaked or has deteriorated to the point that it isn’t an adequate base for additional roofing, where the existing covering is slate, clay, cement, or asbestos cement tile, or where the existing roof already has two or more applications of any type of roof covering.

That third one catches a lot of local homes. If somebody already went over the original roof once, you’re done. The only compliant path is a full tear off.

Permitting is handled locally, so confirm with the city before anyone starts. A contractor who waves off the permit question is telling you something.

The problem nobody mentions in the quote

Cover the shingles and you also cover the decking. Nobody sees the wood again until the next roof comes off, which could be forty years.

That matters because decking damage is exactly what a tear off exists to find. Look at how our crews actually work a repair. On a roof repair in 78248 the crew took the area down to the deck first and replaced damaged and rotted decking before anything new went on. On a roof and gutter repair in 78254 they did the same thing, confirmed the surface underneath was solid, and swapped decking where it needed it.

Neither of those problems is visible from on top of the shingles. A recover installs over whatever is under there, sound or not.

So the real question isn’t just whether the code allows it. It’s whether you’re comfortable never looking. If the roof has ever leaked, that answer should be no.

What about heat and condensation?

Metal over shingles traps a layer of hot, dark asphalt directly under the panels, and that changes how the assembly behaves. Most systems address it by installing over furring strips or a batten system, which creates an air gap and a drainage plane rather than laying metal flat on shingle granules.

Laying panels straight onto old shingles causes two problems. The granules are abrasive and work against the panel’s underside as it expands and contracts, and there’s nowhere for condensation to go if it forms.

Metal moves a lot in our climate. That’s normal and it’s designed for, but it needs the room to do it. Our guide to how long metal roofs last in Texas covers what actually drives lifespan here, and installation method is near the top of that list.

Does it actually save money?

Less than the pitch suggests. You save the tear off labor and the disposal fee, which are real line items, but you add furring strips or a batten system and you inherit whatever is wrong underneath.

You also lose leverage on the biggest variable in any roofing quote. When a crew opens a roof and finds soft decking, that’s a known cost handled once. When nobody opens it, that cost doesn’t disappear. It just waits, and it compounds, because water reaching bad decking under a sealed metal roof takes far longer to show up inside.

For what a metal roof runs here on its own terms, our standing seam metal roof cost guide has the real numbers.

When does it actually make sense?

A recover is reasonable on a single layer roof with sound decking, no leak history, and a documented inspection confirming it. Structures where a tear off is genuinely disruptive, like a workshop or an outbuilding, are also fair candidates.

On a primary residence with any leak history, we’d tear off. Not because a recover can’t work, but because the inspection you skip is the one that finds the expensive problem while it’s still small.

Here’s a straightforward test. Ask the contractor how they’ll confirm the decking is sound without removing the shingles. If the answer is vague, that’s your answer.

What a metal roof done properly looks like

On a metal roof replacement near the Medical Center in 78229, we installed McElroy Metal panels in a Galvalume finish. The Galvalume coating fights corrosion, which is what you want on a roof meant to outlast a couple of shingle roofs back to back.

It costs more up front. The payoff is longevity and a roof that stops being a recurring decision. That’s the actual case for metal in this climate, and it holds whether or not you tear off first.

If you’re weighing materials rather than methods, our comparison of metal shingles against asphalt shingles lays out the tradeoffs.

What to do next

Three things worth remembering. The code bans a recover outright if your roof is water soaked or deteriorated, if it’s slate, clay, cement or asbestos cement tile, or if it already carries two or more layers. Covering shingles means covering the decking, and decking is what a tear off exists to inspect. And the savings are smaller than the pitch implies once furring or battens go in.

If someone has quoted you metal over shingles, get a second opinion before you sign. Our free 27-point roof inspection includes photos and a written report, and it will tell you how many layers you actually have and what shape the roof is in. Call (210) 267-9029 or talk to us about a metal roof.