Discover when a metal roof overlay is a smart option. Learn the pros, cons, and key installation details for homes in Colorado and Georgia. Get expert insights from Roof Nuts.

Metal Roof Overlays: What Colorado and Georgia Homeowners Need to Know

Metal Roofing
August 23, 2025•3 min read

Metal Roof Overlays: Should You Install Over an Existing Roof?

Installing a metal roof over your existing roof—called a “metal roof overlay” or “metal-over” system—can be a great choice, but only if it’s done under the right conditions. If you're in Denver, Colorado Springs, Atlanta, or anywhere in between, here's what you need to know.

What Is a Metal Roof Overlay?

A metal roof overlay involves installing a new metal roof directly over your existing shingles. Rather than tearing off the old roof, metal panels are secured using furring strips or battens over the existing system.

When a Metal Roof Overlay Makes Sense

Overlay installations can save money and time, but they’re not for every roof. It’s a good fit when:

  • Your current asphalt roof has only one layer (per code in most areas).

  • The existing deck is solid and rot-free.

  • There are no major structural or ventilation issues.

  • You want to minimize landfill waste and cut labor costs.

Benefits of a Metal-Over-Metal or Metal-Over-Shingle Installation

  • Lower cost – No tear-off means less labor and debris.

  • Faster install – Overlay systems reduce project time.

  • Energy savings – Battens create an air gap for added ventilation.

  • Less disruption – Your home stays protected during install.

What Are the Downsides?

  • Traps problems underneath – If leaks or rot exist, they can go unnoticed.

  • Code limitations – Some cities may limit overlays to just one layer.

  • Weight load – Though metal is light, two roofing systems add load.

  • Reduced lifespan if done improperly – Moisture and ventilation problems shorten life.

Important Code Considerations in Colorado and Georgia

According to the International Residential Code (IRC) and local amendments, overlays are only allowed when:

  • The existing roof has no more than one layer of roofing material.

  • The sheathing and framing are structurally sound.

  • The deck must allow for proper attachment of the metal panels, with fastening that penetrates into solid wood or approved decking.

  • Ventilation must meet current code—often 1:150 ventilation ratio for attic space.

Key Installation Best Practices

  • Use vertical battens and horizontal purlins to elevate the panels and promote airflow.

  • Add ridge and eave vents to maintain attic ventilation.

  • Inspect and correct any sagging or moisture damage before installing.

  • Seal any roof penetrations (vents, chimneys) with approved flashing systems.

Frequently Asked Questions

Can you put a metal roof over two layers of shingles?
No. Building codes in Colorado and Georgia generally prohibit installing a roof over more than one existing layer.

Will a metal overlay last as long as a full tear-off installation?
Yes, but only if the deck is sound, ventilation is addressed, and proper fastening is used.

Is it cheaper to do a metal overlay?
Yes—on average, overlays save 10–20% in labor and disposal costs.

Get It Done Right with Roof Nuts

At Roof Nuts, we’ve installed hundreds of metal-over-shingle and metal-over-metal systems across Colorado and Georgia. We know the local codes, and we don’t cut corners.

Whether you're in Denver or Atlanta, call us today to schedule a free roof inspection:

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