Many homeowners considering a roofing upgrade are curious if they can put a metal roof over asphalt shingles.
The short answer is yes, under the right conditions, installing a metal roof over asphalt shingles is possible.
This can save time and money by eliminating the need for a full tear‑off, but it’s not always the best choice for every roof.
In this guide, we’ll explain when this method is appropriate, the benefits and limitations, and what you need to know if you’re planning to install metal roofing over existing shingles.
Can You Install a Metal Roof Over Asphalt Shingles?
Yes — you can install a metal roof over asphalt shingles in many cases, provided that:
- The existing shingles are in good condition
- The roof structure is strong enough for the added layers
- Local building codes allow it
This installation method is often chosen because it avoids the cost, labor, and waste associated with removing the old asphalt roof.
Benefits of Installing Metal Roofing Over Shingles
Here are some reasons homeowners choose this method:
1. Lower Immediate Cost
Installing metal roofing over asphalt shingles can reduce upfront labor and disposal costs. Removing an existing asphalt roof adds time and expense, so skipping that step can save money — especially if you’re trying to avoid a full asphalt roof replacement right away.
2. Faster Installation
Skipping the tear‑off process speeds up the project. Metal roofing panels can be installed directly over the old shingles, reducing downtime and disruption to your home.
3. Added Insulation Layer
The existing asphalt shingles act as an extra layer of insulation and can improve sound control, reducing noise from rain and hail.
4. Reduced Waste
By leaving the shingles in place, you reduce landfill waste and the environmental impact of your roofing project.
When You Should Not Install Metal Roofing Over Shingles
While it’s possible in many situations, installing a metal roof over existing shingles isn’t always recommended. Here’s when you shouldn’t proceed:
1. Roof Is Already Worn or Damaged
If your asphalt shingles are curling, cracked, missing granules, leaking, or otherwise compromised, it’s best to do an asphalt roof replacement before installing metal. Poor conditions below the new roof can lead to moisture issues and shorten the life of the metal roofing.
2. Too Many Existing Layers
Most building codes allow only one layer of roofing beneath a metal roof. If your home already has multiple layers of shingles, you’ll need a tear‑off.
3. Structural Concerns
Metal roofing adds weight, and although it’s lighter than some materials, you still need to confirm that your roof deck and framing can handle the combined load.
4. Warranty Considerations
Some metal roofing warranties may be voided if the manufacturer determines that improper installation over shingles contributed to future issues. Always check warranty details before moving forward.
How to Install Metal Roofing Over Shingles (Step by Step)
If your roof meets the requirements, here’s a simplified overview of how to install metal roofing over shingles:
1. Inspect the Existing Roof
A professional should ensure that shingles are secure, flat, and free of rot, mold, or structural damage. Any issues must be fixed before installing metal.
2. Install Roof Protection
Even with shingles in place, it’s best practice to install:
- A self‑adhering underlayment
- Roofing felt or synthetic underlayment for added moisture protection
3. Add Furring Strips or Purlins (If Needed)
To improve ventilation and provide a flat surface, many installers attach horizontal furring strips or purlins over the shingles. This raises the metal panels and allows airflow beneath the roofing, reducing heat and moisture buildup.
4. Mount the Metal Panels
Metal panels are installed according to manufacturer specifications. They are usually screwed through the metal into the furring strips or directly into the sheathing, depending on the system.
5. Flashing and Trims
Proper flashing is critical around chimneys, valleys, edges, and penetrations (vents, skylights). This ensures water doesn’t infiltrate beneath the roofing.
6. Final Inspection
A final walk‑through ensures that panels are secure, seals are tight, and the roof is weatherproof.
Pros and Cons of Metal Roof Over Shingles
| Pros | Cons |
| Lower upfront cost than full replacement | Not suitable for all roofs |
| Faster installation | Potential compatibility issues |
| Extra insulation layer | May affect warranty |
| Reduces tear‑off waste | Can trap moisture if improperly ventilated |
Metal Roof Lifespan vs Asphalt Roof
Metal roofing typically lasts 40–70+ years, far longer than most asphalt shingle roofs, which average 15–30 years. This long lifespan, combined with energy savings and durability, helps justify the investment.
However, installing over old shingles means you’re inheriting part of the shingle roof’s condition. If the underlying structure is aging or compromised, a full asphalt roof replacement before installing metal may offer better long‑term performance.
Do You Still Need a Roof Replacement Down the Road?
Yes, even if you install a metal roof over existing shingles, there may come a time when you need a roof replacement or structural refresh beneath it.
Metal panels can last for decades, but the shingles below may deteriorate with age if not properly ventilated and protected.
Final Thoughts: Is Installing Metal Roofing Over Shingles a Good Idea?
Installing a metal roof over asphalt shingles can be a smart, cost‑effective shortcut — but only when conditions are right. Good candidates for this approach have:
- A sound existing shingle roof
- Proper structural support
- Only one shingle layer remaining
- Good ventilation potential
If your roof doesn’t meet these conditions, consider a full asphalt roof replacement before upgrading to metal roofing.
When in doubt, consult a professional roofer to assess your specific situation and ensure you get a roof that performs well and lasts for decades.
