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Problems With Installing a Metal Roof Over Shingles

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Psst… We see you over there, searching the internet to see if you can get away with installing a metal roof over an existing shingle roof to try and save a few bucks. 🫣

Hey, we don’t blame you. It’s a worthwhile question! And as a homeowner, repairs and maintenance can get overwhelming, so it makes sense why you’d be looking to save money right now.

Unfortunately, there are many problems with installing a metal roof over shingles. And one of them is that it’ll end up costing you way more money in the long run! By the end of reading the rest of the issues that can occur, we’ll help you schedule the proper metal roof replacement you need.

Issue #1: Problems From the Old Roof Will Still Be There

Unfortunately, you can’t stick a bandaid on a failing roof in hopes that the problems will disappear. Even if your old roof is out of sight and out of mind, it can still cause issues for your home.

Especially if you’ve covered up an asphalt shingle roof at the end of its lifespan, you’ll quickly run into the same problems you experienced before covering it.

metal roof over shingles problems country home

Issue #2: Can’t Replace Rotten Roof Decking

One of the biggest reasons professional roofing companies perform a complete tear-off during a roof replacement is actually the structure underneath your shingles. Roof decking is the wood boards that act as the foundation of your entire roofing system.

Normally, roofing contractors tear off your roof down to the decking during a replacement. This allows them to carefully inspect your roof deck and look for signs of rot. A rotten roof deck is an urgent issue that can lead to sagging decking or even a total roof collapse, and it must be fixed immediately.

If your roof deck hasn’t been inspected for 10+ years, and you simply cover up your old asphalt roof with metal, then there’s a good chance you have a rotten roof deck that’s getting worse and worse over time.

Without a proper inspection, you won’t know that you have an urgent issue until it’s too late.

Issue #3: You Won’t Have the Proper Underlayment + Other Components

Speaking of roof decking, it’s not the only important aspect of a complete roofing system! Your roof also needs:

  • An ice and water shield (underlayment)
  • Flashing
  • Vents
  • Gutters

These components don’t last forever. So, if you put a metal roof on top of your existing shingles, you won’t get the opportunity to lay the proper metal-specific underlayment or replace any damaged flashing or vents.

Issue #4: You Add Too Much Extra Weight ⚖️

Your home is tough, but it isn’t indestructible. Metal roofs are a little heavier than asphalt shingles. While metal roofs aren’t too heavy on their own, adding a second roof to your home adds a significant amount of weight that your home’s structure may not be able to support in the long run.

This extra weight can cause major issues if you have rotten roof decking underneath all the other materials. The weakened decking can’t support the additional weight, and it will eventually result in major, expensive structural damage.

Issue #5: Leaks Become Difficult to Repair 🛠️

It takes a lot of skill for a roofing contractor to be able to locate, track, and repair a roof leak. Roof leaks are tricky enough when you only have one roof on your home. The water rarely drips directly under the source; instead, it slowly spreads out across your ceiling and walls before making an appearance.

If you install metal roofing on top of old asphalt shingles, locating and fixing a roof leak can be next to impossible. In this case, it’s probable that the leak is stemming from the asphalt shingles, so your roofing contractor will need to cut through the metal roofing in order to get to the shingles underneath.

This is an incredibly tedious, difficult repair to make, and it will cost you a pretty penny.

metal roof over shingles problems brown metal roof

Issue #6: Shortening Your Roof’s Lifespan

Did you know that a properly installed metal roof can last 40-70 years? There’s no denying that metal roofing is a fantastic investment for its durability alone. Plus, it has other benefits, such as being:

  • Fire-resistant
  • Environmentally-friendly
  • Aesthetically-pleasing
  • Affordable
  • Low-maintenance

However, the keywords here are properly installed. Installing a metal roof over existing asphalt shingles disqualifies the metal roof from being correctly installed. All of the aging materials underneath the metal roofing panels shorten your roof’s lifespan tremendously.

Needing to replace your roof much sooner defeats the purpose of trying to save money by installing a new roof overtop of an old one.

Issue #7: Breaking Building Codes 📋

Every state and local municipality has strict building codes that residential and commercial properties must adhere to. Some states allow an additional layer on top of an existing roof, but most do not.

If you move forward with installing metal panels over an existing shingle roof, you’re likely violating local building codes. Doing so can result in you paying hefty fines to your local government. Plus, you’d likely be required to replace your roof anyway.

Issue #8: Voided Warranty or No Warranty to Begin With

In order to receive a warranty on a roof installation, it must be installed to the manufacturer’s standards. If you place a metal roof over an asphalt roof, you automatically void any warranty that existed with the asphalt shingle roof.

Additionally, in this situation, the metal roof on top would not come with a material or labor warranty since it was improperly installed. This situation is unfortunate because the second any issues arise that need repairing (and it will happen quickly), you won’t have any protection. You’ll need to pay for any repairs completely out of pocket.

(It’s also worth noting that you would not be eligible for insurance coverage after a storm because your roof was not properly installed.)

Issue #9: Mold Growth From Trapped Moisture 🌱

Installing metal roofing over shingles traps water vapor and moisture between the two layers of roofing materials. This excess moisture quickly causes mold growth that eats away at the roofing materials and can even make its way into your home.

Exposure to mold can cause symptoms like:

  • Red or itchy eyes
  • Wheezing
  • Stuffy nose
  • Irritated skin

Plus, people with athsma and respiratory allergies can experience increased issues and adverse health effects. Don’t put your health at risk by compromising your home’s structure!

metal roof over shingles problems black metal roofing

What Should You Do Instead?

You’re probably thinking, “Okay, okay… it’s clear that I shouldn’t install a new roof over my old one.” But what should you do instead? If you’re looking to reap the benefits of durable metal roofing (we don’t blame you!), the best thing you can do is schedule an inspection with a trusted local roofing company.

Often, these inspections are free of charge. The roofing contractor will take a thorough look at your roof and write you a detailed quote for the repairs or replacement the recommend. Alternatively, they may find that your roof is still in good condition and you may not need immediate service.

If your current roof is found to be nearing the end of its lifespan, be sure to ask the contractor what materials they offer. If you’re interested in a metal roof, you may need to shop around for a roofing company that offers metal roof installation.

  • Once you’ve found a roofing contractor you trust, schedule a metal roof replacement with them.
  • On the day of your replacement, the roofing crew will completely tear off and dispose of your old roof.
  • If there are any issues with your roof decking, they’ll replace it accordingly.
  • Then, they’ll lay all the necessary components of your new roofing system, complete with durable metal panels on top.

And there you have it! When a new metal roof is installed correctly, it can last between 40-70 years! Talk about money savings— you’ll likely never have to replace your roof again. Plus, metal roofs are great selling points if you ever decide to sell your home.

Need a Reliable Metal Roofing Team in Minnesota?

As we mentioned earlier, not every roofing company has the skills or experience to install a high-performing metal roof. But thankfully, the team at Level Edge Construction & Roofing knows metal roofing like the back of our hands.

If you’re ready to say goodbye to short-term relationships with your roof and opt for a long-term relationship with metal roofing, Level Edge is the team to call. We’ve been serving Minnesota and Western Wisconsin for over 20 years, and we’re looking forward to helping you out, too.Reach out today for a free metal roofing estimate!

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