Can you put a metal roof over shingles?
Short answer. Often, yes. The International Residential Code generally allows a new roof covering over one existing layer of asphalt shingles as long as the old roof is not water-soaked or deteriorated, and metal panels are one of the most common recover choices. Whether you should depends on the deck underneath, ventilation, local rules and the metal manufacturer's requirements, and many roofers still recommend tear-off.
When code allows it
The code bars a recover when the existing roof is water-soaked or too deteriorated to serve as a base, when it is slate or tile, or when there are already two or more layers. Georgia adopts the IRC with state amendments, and local building departments may add requirements, so check before you sign. A permit is typically needed either way.
How it is done right
- A synthetic underlayment over the old shingles as a separation and secondary water barrier.
- Often wood strapping or purlins over the shingles to create a flat plane, which also helps the panels lie straight.
- Fasteners long enough to reach solid deck or framing through the old layer.
- New eave and rake trim, flashing at walls and chimneys, and proper ridge ventilation.
Pros
No tear-off labor or disposal, less mess, and a faster job.
Cons
- Nobody sees the deck, so rot and soft spots stay buried.
- Old shingles can hold moisture under the new roof.
- Thin panels laid directly on shingles may show the bumps beneath.
- Some metal manufacturers restrict or set conditions on recovers.
- Insurers and future buyers may ask how many layers the roof has.
When tear-off is smarter
If the roof leaks, the deck feels soft, the shingles are badly curled, or there are already two layers, tear it off. See roofing over existing shingles and metal roofing in Georgia for the full trade-off.