Can You Put Metal Roof Over Asphalt Shingles?

Are you thinking about giving your roof a makeover? But can you put a new metal roof over your old asphalt shingles?

Yes, you can put a metal roof over asphalt shingles, a practice that offers several benefits, including cost savings on removal and disposal. However, it’s crucial to ensure the building’s structure can support the extra weight and to address ventilation issues to prevent moisture buildup.

A metal roof does more than just look good. It keeps your house safe and dry for a very long time. Plus, it can save you time and money. Want to learn more about how this works? Let’s dive into the world of roofing and find out.

Structural Considerations

When planning to install a metal roof over existing asphalt shingles, the strength and integrity of the existing roof structure are paramount. Here are 2 things to consider.

Assessing Roof Weight Capacity

• Ask your roof engineer or a certified contractor for the weight capacity of your roof.
• Factors like roof design, materials used, and overall age influence its weight tolerance.
• Metal roofs are lighter than traditional materials like slate or concrete tiles. But they still add weight compared to asphalt shingles.

Ensuring Structural Integrity

• Inspect the roof structure for any damage, sagging, or weakness. These could show problems. They need fixing before adding the weight of a metal roof.
• Rotting wood, damaged trusses, or compromised underlayment may not handle the extra stress of a metal roof.

Code Compliance

When considering placing a metal roof over asphalt shingles, ensuring code compliance is essential. Building codes can vary greatly depending on your location. Here are 2 things to remember –

Checking Local Building Regulations

• Contact your local building department. They know the rules for installing metal roofs over shingles in your area.
• In some regions, this practice may be banned. Others may have specific rules, such as limiting the number of shingle layers allowed.

Compliance For Metal Over Shingles

• Some metal roof makers may have guidelines for installing their products over shingles.
• These guidelines may cover factors like the most shingle layers allowed and the type of underlayment needed.

Existing Shingles Assessment

Before deciding to put a metal roof over asphalt shingles, assessing the existing shingles is important. This step is crucial for ensuring the success and longevity of the new metal roof. Here’s what you should focus on:

Inspecting Shingle Condition

First, you need to look at your old shingles closely. Here’s what to do:

• Look for Damage: Are there any shingles that are broken, missing, or look like they’re falling apart? This can indicate that your roof is only ready for a metal cover with some fixes first.
• Check for Moss or Mold: When you see green stuff or dark spots, that means water is getting trapped. It’s like when a sponge holds water; it can weaken the roof.
• See if Shingles are Flat: Your metal roof will sit nice and smooth if the shingles underneath are flat. 

Identifying Installation Suitability

After checking your shingles, you must decide if putting a metal roof on top is smart. It will help your asphalt roof last longer. Here’s how:

• Good Condition: You’re on the right track if most of your shingles look good. It means your roof is strong and can withstand the new metal roof.
• Even Surface: Your old roof needs to be pretty even. Adding metal on top could work well if it’s flat without big dips or bumps.
• No Major Issues: When you don’t find big problems like broken shingles or big areas with moss, your roof can be a good candidate for a metal upgrade. For this, you must take good care of and clean well the asphalt shingle roof.

Roof Surface Flatness

The flatness of the existing roof surface is a critical factor. A smooth, flat surface is essential for proper installation and long-term performance of metal roofing.

Confirming Surface Suitability

Before installing a new metal roof over old asphalt shingles, you must ensure the roof is even and ready for the metal. The metal roof won’t fit right if it has big bumps or dips. 

So, first, you look closely at your roof to see if it’s flat enough for a metal roof. When it looks mostly flat and even, you’re good to go. 

Preparing A Flat Substrate

Now, when your roof isn’t quite flat, don’t worry. You can still make it work. One way to do this is by laying down a thin layer of wood or special insulation over the old shingles.

This makes a new, flat surface for the metal roof. Think of it as putting a new drawing paper on top of a bumpy table. Now, you can draw smoothly.

FAQs

Conclusion

Putting a metal roof over asphalt shingles opens the door to enhancing your home’s durability and aesthetic appeal. Also, it provides a cost-effective solution. This approach simplifies installation and contributes to environmental sustainability by reducing landfill waste. 

However, consulting with a professional is essential to ensure your roof structure can support the additional weight and that the installation complies with local building codes.