CAN YOU INSTALL METAL ROOFING OVER EXISTING SHINGLES?
Image Credit: McElroy Metal
Yes - It’s technically possible
Installing a metal roof over one existing layer of asphalt shingles is allowed under most building codes, including in Vermont as long as the shingles are in reasonably flat condition and the roof structure can handle the added weight (which, with metal, is usually not an issue since metal is actually lighter than most people expect).
When done correctly with proper underlayment and battens, a metal-over-shingles installation can perform well and save you the cost of a full tear-off as it reduces labor costs and waste.
Here's an honest breakdown of when installing metal over existing shingles makes sense, and when it doesn't.
Good candidates for metal-over-shingles
✅ Only one existing layer of shingles
✅ Shingles are flat, not severely curled or buckled
✅ No signs of rot, moisture damage, or soft spots in the decking
✅ Roof structure is solid and in good shape
When a tear-off is the better call
❎ Two or more existing shingle layers already present
❎ Shingles are heavily curled, blistered, or uneven
❎ Evidence of water damage, rot, or mold underneath
❎ You want the longest possible lifespan from your new roof
Our honest take
The key is having an experienced roofer assess the condition of your current roof before making that call. Installing metal over damaged or uneven shingles can trap moisture, create an irregular surface that shortens the life of your new roof, and hide problems that will only get worse over time. If there's any question about what's underneath, it's better to find out now than after your new metal roof is installed.
If your existing shingles are in good shape and you're working with a tight timeline or budget, a well-executed metal-over installation is a legitimate option.