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What are the Problems With Installing a Metal Roof Over Shingles?

September , 2023 | 8 min. read

By Joe Martinez

Roofer tearing off a metal roof over shingles

Ready to join the metal roofing revolution? We know the feeling! Investing in a new metal roof is a big decision. You want to make sure you're getting the best roof for your money. But with so much information out there, it can be tough to separate the roofing myths from the facts.

Fear not, roofing wizards! RoofCrafters has been in the metal roofing game for three decades, and we've seen it all. We're also certified by the top metal roofing manufacturers in the US, so you know we've got the goods. But with our experience, we've also seen some less-than-stellar roofing practices out there. 

rusted flashing at a brick chimney coming through a metal roof

With all the information out here, you’ve probably heard some conflicting stories too.

So, in this article, we'll tell you about the problems that can happen when putting a metal roof over shingles. By the end, you'll know how to pick the best metal roofing company for your upcoming project.

 Let's get started!

What are the Problems With Installing a Metal Roof Over Shingles?


Hold on to your shingles folks, we're about to dive into the world of metal roofing woes! You may have heard that putting a metal roof over shingles is a good idea. Yet, it's not as great as it seems. Don't worry. We'll guide you through the storm and tell you about problems when mixing shingles and metal.

Screws backing out a metal roof

Potential pitfalls when installing a metal roof over old shingles:

1. Building Code Violations

Before putting on a new metal roof, you often have to take off the old shingles because of building codes. If you don't follow these codes, your installation may not meet the requirements. Later, you could have legal problems.

2. Installation Issues

Due to the lack of exposing the wood decking. The installer may install your new metal roof over bad or rotten decking. Because of that, people consider this method of installation to be poor.

3. Reduced Longevity

Installing metal over shingles can trap heat and moisture. Which can lead to premature failure of the metal roof.

4. Lack of Proper Ventilation

When you install a metal roof over shingles, it can block the air from flowing properly in the attic. This can lead to moisture buildup and mold growth.

5. Insulation Issues 

Installing a metal roof over shingles can make it difficult to properly vent the roof. This can cause higher energy bills and make it harder to control the temperature in the attic.

6. Warranty Issues

Many metal roofing manufacturers will void their warranty. Which can leave you without protection in case of any issues or defects.

7. Compatibility Issues 

Some shingles and metal roofing materials may not be compatible. They can cause issues such as warping, curling, or buckling of the shingles.

8. Aesthetics Problems

Installing a metal roof over shingles can lead to a bad appearance. This is due to the visible lines and ridges of the old shingles showing through the new metal roof.

9. Extra Costs 

Installing metal over shingles can add extra costs. Costs associated with extra labor and materials making repairs.

In some cases, you may install a metal roof over shingles. Make sure to have a metal roofing contractor check if they can do the installation. 

recommended reading

It's worth saying that installing metal over shingles is not recommended. By most roofing experts or metal manufacturers. To ensure your installation meets building codes, consult a metal contractor. As well as maintain its warranty.

Will I Void My Metal Warranty Installing Metal Over Shingles?


Oh, the age-old question of warranties and roofing. Will installing a metal roof over shingles void your warranty? The answer, as with most things in life, depends. Some metal roofing companies don't let you install their materials on top of shingles, which cancels the warranty. Others, might not mention anything about it in their warranty.

Are you covered after the work is done

So, what's a homeowner to do? Well, it's simple. Call the company that made your metal roof and ask about their warranty. Also, remember to confirm if removing the old shingles is necessary for the warranty.

Remember, it's always better to be safe than sorry. Before you install a metal roof over shingles, make sure you do some research. This will help you protect your warranty and meet building codes. Everyone does not want to hold the shingle bag!

Why Most Experts Don't Recommend Installing a Metal Roof Over Shingles?


Well, buckle up folks, because this is where things get serious. Most experts will tell you that installing a metal roof over shingles is a big no-no, and here's why:

Picture yourself at the doctor's office, complaining of a headache. Instead of prescribing medicine, they apply a band-aid to your head. That's what it's like trying to install a metal roof over shingles. To know if the plywood is good, take off the shingles to check underneath. And let's be honest, who wants to take on that headache?

roofer tearing off a roof with rotten plywood decking

But don't worry, some red flags can help you determine if the plywood is in trouble. Keep reading, and you'll be a metal roofing expert in no time!

Signs that can show that there may be problems with the plywood:

  1. Sagging or uneven roof deck: If the roof deck is sagging or uneven. It can be a sign that the plywood underneath is rotting or has become waterlogged.
  2. Visible water damage: If you can see water stains or discoloration. Either on the underside of the roof deck or the ceilings of the attic. It's a sign that water has likely been leaking through the roof and may have damaged the plywood.
  3. If the roof deck feels soft or spongy when walked on: it might mean the plywood is rotting.
  4. You can tell if the roof deck is rotting by looking at the plywood: It might be dark, discolored, or moldy.

Some of the above signs may not become visible until we install the metal roofing. A good metal roofer knows that underlayment and wood decking are very important for a new metal roof's quality. So most will stay away from these installation methods. 

Can I Save Money Installing a Metal Roof Over Old Shingles?


Well, it depends on how you look at it! You can save money on labor costs and dumping fees by installing a metal roof over old shingles. But, it's not always the most frugal solution in the long run.

torn up roof caused by a roof leak

It's like trying to patch up a ripped pair of jeans. Although it may appear as a simple solution, the holes will enlarge over time. Thus, the ripped jeans will need replacement. The same goes for installing a metal roof over old shingles. It may seem like a budget-friendly option, but it could lead to bigger problems down the line.

And let's not forget about the cost of removing those old shingles. On average, it can run you between $1,000 and $1,600 to say goodbye to your shingles and hello to a clean slate. So, think twice before jumping on the metal roof over the shingles bandwagon!

How Much Does a Metal Roof Cost?


Now that you know the issue with putting metal roofing on top of old shingles. You’re probably ready to see the cost of having a metal roof installed the right way. We recommend that you get 2 to 3 roof replacement estimates before hiring a roofer.  Feel free to use our pricing calculator to get a good idea of how much a new metal roof will run you.

Image call to action, use the pricing calculator to estimate the cost of your roof replacement

For 30 years, RoofCrafters has been teaching homeowners about metal roofs. We have put metal roofs on many homes and businesses in the Southeast. If you live in our service areas, you can schedule an onsite inspection to see if we're a good fit to work together. 

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Joe Martinez

At RoofCrafters, our mission is to provide job opportunities for others to thrive and grow while making a meaningful impact within our communities.