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So, you need a new roof. You may have shingles now, but are shingles your best choice for the years to come?

Maybe, but have you considered your other options? Metal roofing is one of the best types out there for any building, including all kinds of homes. Not only are they visually appealing, but they're also much more durable than shingles. If you're considering getting a metal roof, you may be wondering if you can install it over shingles. We're going to answer that question in this blog, so keep reading or give our Legacy Service team a call at 215-798-9790 if you're considering a metal roof replacement.

Two workers on roof at works with metal tile and roofing iron

Can Metal Roofs Be Installed Over Shingles?

In simplest terms: Yes, you can install a metal roof over shingles. However, you'll want to check with your local building department before you make any decisions. Building officials in some areas will only allow a re-roof over one layer of shingles, while officials in other places may allow you to place the roof over two layers of shingles. Fortunately, in most areas, it won't be an issue if you're only going over one layer.

Section 1511.3.1 of the 2018 International Building Code (International Code Council Series) 1st Edition states, "The installation of a new roof covering over an existing roof covering shall be permitted where any of the following conditions occur…2. Complete and separate roofing systems, such as standing-seam metal roof panel systems, that are designed to transmit the roof loads directly to the building's structural system and that do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings."

So, it's possible to have the installation of metal roofing over shingles, which is great news! But you might be wondering what the advantages and disadvantages are and what to keep in mind during installation. Keep reading to find out.

roof of the red metal and drops

Advantages of Metal Roofs Over Shingles

There's already plenty of advantages by choosing a metal roof, and there's even more when you decide to put a metal roof over shingles. They include:

Advantages of metal roofs in general:

Metal roofs have increasingly become a more popular option for homeowners due to their reputation for longevity and curb appeal.
They can last much longer than shingles. In fact, they can last for about 40-70 years depending on the material.
They can withstand almost any type of weather condition to keep your home safe, comfortable, and dry. Rain will quickly and easily drain, and snow will be able to melt slide off easily. They can also sustain wind gusts up to 140 mph.
Many of them also come with the ability to resist fire (whether it's a lightning strike or a wildfire) and withstand a hail storm without taking damage.
They can come in a wide variety of colors and finishes. These include the appearances of natural cedar shakes or stone.
They can improve your home's energy efficiency by reflecting solar radiant heat, which may even reduce cooling costs by 10-25%.

Advantages of metal roofs over shingles:

By placing metal roofing over shingles, you can save in the labor costs of ripping them off while also preventing them from being thrown into landfills.
Metal roofs over shingles will also provide an extra layer covering your home, helping to further insulate it.

Disadvantages of Metal Roofs

Like most other things, there are a few disadvantages of choosing metal roofs. Otherwise, they would be found everywhere! The disadvantages include:

Metal roofs can be much more expensive than shingles. Even with their durability, which helps increase value and balance over the expense over time, many homeowners simply can't afford to install metal.
They provide excellent protection against the elements, but in many cases, rain and hail sound very noisy under a metal roof. A layer of soundproof insulation can help, but it adds to the cost even more.

Installation of Metal Roofing Over Shingles

If you choose to install metal roofing over shingles, there are certain things you must keep in mind. We're going to break them down, so you know what to look out for. But first, here are a few precautions about the underlying material:

Address any existing roof leaks and replace rotten rafters or sheeting.
Look out for any signs of the previous roof weighing too much. Signs may include buckling tresses or sagging decking.

Also, make sure you acknowledge:

Manufacturer Specifications and Warranty

Even with the best warranties, it may be hard to track someone down after 40 or 50 years so they can assess your roof and write you a check for any damage. Depreciation may also significantly reduce the amount you'd receive. This is why it's good advice to purchase the best product you can afford, follow the specifications of the manufacturer, and have it installed properly. Then, you can pitch the warranty after about five years.

Fastener Application

When installing the roof, the screws should be applied as specified by the manufacturer (in the flat of the steel, not the rib), and in a way that the spacing creates an appealing view from the ground. Also, try not to use nails anymore because screws work much better. When adding the screws, they should be spaced between 24 and 30 inches and skip every other rib to create no more holes than necessary in your roof.

Trim

When it comes to the cosmetics of your roof, the trim is the most important aspect. All of the edges must be wrapped with flashing, which improves the appearance and provides resistance against rain, snow, and wind. Also, consider ice guards even if you don't have gutters. If you're taking care of the trim yourself, make sure you have someone down on the ground to look up the trim for you.

Safety

This should be obvious, but make sure you wear gloves! It's an easy way to prevent cuts on your hands. Also, don't go up on the roof if it's windy. If it's slightly windy, keep the steel downwind from you, so a gust of wind doesn't knock you over.

Metal Roof Over Shingles Condensation

Metal roofs must be laid flat on a vapor barrier because steel will condensate if there's any air space underneath it. It doesn't matter if the air space is a half-inch or six inches because the condensation factor will remain the same. Put the steel down directly on a vapor barrier. You can either leave the shingles on or put down felt paper during new construction.

Is It Cheaper To Get a Metal Roof or Shingles?

You're probably wondering about the cost to install a metal roof over shingles. While it's cheaper to purchase shingles (which is why most homes have them), metal roofing may provide you with better value in the long-term. Not only do they look beautiful and unique, but they're also designed to last decades longer because of their durability. In fact, a metal roof that's built properly will be able to handle anything Mother Nature throws at it. You will most likely never have to purchase another roof again in your lifetime.

Frequently Asked Questions About Metal Roofing Over Shingles

Here are the questions our team is most frequently asked about installing a metal roof over shingles.

Can you put a metal roof over shingles?

Yes, it's possible to put metal roofing over shingles. Before you get started on your project, though, you will need to check with your local building department to see if they'll allow you to. Some areas will only allow re-roofing over one layer of shingles while others will allow over two layers. There are also some disadvantages to installing metal roofing over shingles that you'll want to know about before starting. Contact your local roofing company to learn more and see what they can do for you.

Do I need underlayment for a metal roof over shingles?

All roofs need an underlayment. If you're installing a metal roof over asphalt shingles, the shingles may be able to act as an underlayment for the roof. However, the shingles expanding and contracting can cause damage underneath the metal roof over time. For this reason, it's usually recommended that you remove the shingles on your home before installing a metal roof.

What is the best way to install a metal roof over shingles?

If you wish to install metal roofing over shingles, it's recommended to do it one of two ways. The first is to apply an approved underlayment over the old shingles. This is the fastest way to install but it doesn't provide the flattest surface for metal roofing installation. The second way is to install 1×4 purlins over the shingles. This is more expensive but will also be higher quality.

What is the advantage of a metal roof over shingles?

There are a couple of advantages when it comes to installing metal over shingles. The first is that it helps you save the labor costs of removing the shingles and prevents them from being thrown into landfills. The second is that the shingles provide an extra layer over your home, which helps insulate it further. Metal roofs over shingles also present a number of problems. Contact your local roofing company to learn more.

Can you put a metal roof over three layers of shingles?

If you research "how to install a metal roof over shingles," you'll find that you cannot put a metal roof over three layers of shingles in most cases. A majority of local building departments will allow one or two layers over of shingles, but not three. Check with yours before you make any decisions or start your project.

Can you put metal roofing over two layers of shingles?

You'll need to check with your local building department to see if you can install metal roofing over two layers of shingles. Many of them will allow one or two layers of shingles, but no more than that. If they allow you, contact your local roofing contractor to see what they can do for you.

How to install metal roofing over asphalt shingles

Whether you're looking to install a steel roof over shingles or another type of metal, it's a good idea to learn the know-how. Knowing how to install a metal roof over shingles is important for a homeowner whether they're looking to do it themselves or hire professionals. Remember that if you choose to install metal roofing over shingles, it's best to add an underlayment or purlins.

Roof detail house

Contact Legacy Service to Schedule an Appointment

At Legacy Service, we love just about everything about this type of roofing. When they are installed correctly using the right materials, they can withstand just about anything. And since it reflects heat from the sun, it can help you save significantly on energy costs. It's also 100% recyclable, making it eco-friendly. We have decades of experience when it comes to installing this type of roofing, and we can actually custom-make every panel for your project. We also offer a lifetime warranty, which makes for a sound investment. If you'd like to learn more about metal roof replacement, contact our Legacy Service team today to schedule an appointment.

Posted on Oct 19, 2019 in Roof