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HomeExclusiveHow To Install Metal Roofing Over Asphalt Shingles

How To Install Metal Roofing Over Asphalt Shingles

Metal Roofs Are Not Just A Novelty

Standing-Seam Metal-Shingled Roof Installation

Once, metal roofing was found only on high-end, architect-designed homes. That’s no longer true. Metal roofing is increasingly found in conventional houses, thanks to increasing availability and improved manufacturing processes. According to industry statistics published in 2017, market share for metal roofing increased at a rate of roughly 3 percent each year for a few years and about 15 percent of all roofing installations used metal roofing materials. At the same time, the market share for asphalt shingle roofing fell, and accounted for about 59 percent of the total roofing installed.

What Is The Best Color Metal Roof For Energy Savings

White is the most energy-efficient if you are only considering color. There are pigments used with the darker colors that help them reflect a part of the heat they usually would not, though. Even then, a very dark roof wont get near the heat reflectability of white.

A well-ventilated roof is less of an issue. A well-insulated roof and attic may also seal out some of the heat. In this case, the color will be less critical.

There is also the possibility that you live far enough north that most of the year is cooler, and you would rather be collecting the extra heat instead of reflecting it. In a colder climate, it may be beneficial to have a dark roof because of this.

Overall, metal roofs are already more energy-efficient than asphalt shingles, so whatever color you choose is an improvement over them.

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People have been installing metal roofs over layers of asphalt shingles for decades in fact, it used to be common practice and likely would have been considered wasteful in terms of time and energy not to do it. This practice is done less and less with asphalt on asphalt shingles, yet many people still find it acceptable to bury a shingle roof under a metal roof.

There are pros and cons to most methods for home improvements, and roof-overlays are no exception. On the positive side, not tearing off the old asphalt shingle roof when installing metal roofing can save time and money. It can also arguably increase the R-value of the roof and act as an increased sound barrier. On the flip side, not tearing off the additional layers of the current roof increases the load of the roof, void or reduce manufacturer warranties, may impact the aesthetics of the new metal roof, and keep serious construction issues hidden.

Here are the benefits and disadvantages of installing a metal roof over an asphalt shingles roof, along with things you might not have considered and, ultimately, whether you should do it or not.

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Why Should I Install A Metal Roof

Although shingles and most other types of roofing materials maybe a little less expensive, they require more maintenance, and theres always a need to repair or replace some portion. Its also quite unfortunate that shingles cannot be recycled. Most shingles usually end up in landfills and waste disposal companies that charge nearly exorbitant fees before accepting them.

But with metal roofing, you need not worry about its disposal as it is 100% recyclable. You will indeed have to pay more to get these materials than with shingles. It, however, pays off in the long run. Metal roofing comes with lesser maintenance and repair needs, and it can last for up to 50 years.

Metal roofing adds more appeal to the entire structure, thanks to its numerous styles and colors. Aside from its aesthetic appeal and longevity, corrugated metal roofs are highly energy-efficient. Most metal roofing sheets are treated with a special paint that helps it reflect a huge amount of UV rays, helping to maintain a reasonable temperature within your home during hot days and saving good bucks on utility bills.

How To Install Metal Roofing

Can you install a metal roof over shingles? Absolutely ...

If you choose to overlay a single layer of asphalt shingles there are quite a few things youll have to do to prep your existing roof properly.

Prepare Your Old Roof

Any portion of your existing roof that is already metal, which means valley tin, gutters, roof jacks, and chimney flashing, should come off. You can overlay the valleys and gutters, but youre asking for future problems if you do.

Cut back the shingles along the valley or gutter apron about two inches beyond the width of the metal. Pull the nails and metal off the roof. Remove all the roof jacks and any chimney flashing. You may be able to use the chimney flashing again if its not badly damaged.

Start With The Gutters

Following the manufacturers instructions, start with the new metal roof. If youre going through a layer of shingles, youll want self-taping sheet metal screws a little longer than the standard 1 5/8 screws used on new metal roof installations. The zip screws for the overlapping seams will still work fine.

Set the valleys/gutters in place with the roofing material provided in your metal roofing package. Make sure you dont screw or nail anything into the valley pan, the business end of the valleys. If water runs down it and it hits a screw, the water will find a path inside if you have an errant fastener in your valley/gutter assembly.

Lay Down The Roof In Complete Sheets

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How To Install A Metal Shingles Roof Diy Guide

If you are the type of homeowner who wants to embark on the installation of a new roof, a metal shingles roofing system will be the easiest to install.

Most metal shingle systems feature a four-way interlocking design, and the panels are usually small enough to be easily installed without using any complicated tools.

The first step is the preparation of the roof deck. In a new construction, metal shingle roofing can be installed over any type of solid sheeting such as plywood or wooden planks / boards that do not have spaces in between them.

Alternatively, a metal shingles roof can be installed over the old asphalt shingles, if you do not want to tear it off, provided there is only one layer of existing shingles on the roof.

Installing Underlayment:

The next step in preparing your roof deck is to use a special product called roofing underlayment. It is made out of breathable synthetic material and designed to provide an additional level of protection from condensation, as well as to allow the roof deck to breeze in order to prevent any rotting of the wood.

When installing the underlayment, you will always want to have about half an inch of the membrane over the eaves and gable of the roof deck. First, the membrane gets secured at one side/end of the roof, it is then rolled out horizontally until it reaches another side of the roof where it also gets secured with special nails that have colored plastic caps.

Installing Metal Flashing and Trim Details


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 youd receive. This is why its 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.

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Putting A Metal Roof Over Shingles

Its absolutely fine to install a metal roof over shingles. People are accustomed to thinking of metal roofs as being heavy or cumbersome. In fact, metal roofs are so beneficial because theyre very light. Theyre fast to install, and they come in large sheets rather than individual tiles.

When you install a metal roof over shingles, you actually get additional protection from the shingle roof as well as additional insulation. And having shingles under the metal roof can reduce some of the sounds that can transfer from a metal roof, though modern metal roofs have countered this problem very effectively.

Average Cost To Install Metal Roof Over Shingles

Asphalt Roof Shingles Installation

Metal roofing costs vary depending on the type of material. Metal roofing ranges between $1.50 and $2 a square foot, depending on the brand of the roofing. This compares to asphalt shingles which cost around $1.50 per square foot.

Installing a metal roof yourself can save a significant amount of money. The cost of installing metal roofing costs between $7 and $14 a square foot for standing seam roofing and from $8 to $10 per square foot for metal panels or shingles.

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Detail : Ventingthe Ridge

Cool outside air travels under the shingles to the vented ridge, pulling out moisture and heat.

A steel roof is a lifetime investment, lasting 50 years or more if its a good one. Asphalt roofs typically last 20 to 30 years, depending on the installation and shingle quality. So, the investment might be worth it, but the range of choices makes shopping for a steel roofing system more complicated than you might think.

If you want to install steel over asphalt, your best choice for installing metal roofing is to use a steel shingle system like the one shown instead of the more common standing seam steel. In a standing seam roof, long, single panels run vertically all the way from the eave to the ridge. In contrast, steel shingles are small panels installed in horizontal rows much like other shingles.

Better steel shingle systems, like the one shown, install over a framework of 2x2s. This framework has three big advantages. First, because the frame is screwed directly to the rafters and the interlocked shingles are screwed to the frame, the roof can withstand winds of up to 120 mph without damage. Second, the frame creates a flat and straight surface even when the shingles are badly curled or the roof ridge is bowed.

Putting Metal Roof On Top Of Shingles

by Mountaintop Metal Roofing | Jun 30, 2020 | Residential

Metal roofing can be seen almost anywhere. Covering bus stops in the city, covering barns in the countryside, or covering undercover play areas. Metal roofs are often used in these cases because of their longevity, easy maintenance, and simple aesthetic.

During the last two decades, however, metal roofing has been growing in popularity for residential homes. The industrial-looking corrugated roof or simple standing seam metal roofing has been replaced by metal roofing systems made to look like slate, cedar shingles, and more. While its gaining in popularity, finding an experienced professional to install this type of roof can be a challenge.

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Can You Put Metal Roofing Directly Over Shingles

Yes. In fact, here are some of the benefits of installing a metal roofing system over a shingle roof:

Convenience Installing a metal roof over shingles is convenient because there is no tear-off mess or disposal of old/used roofing material.

Cost-Effective You save on both labor and material. There is no tear-off and disposal cost, and the roofing systems substrate is already in place.

Sound Reduction Metal roofing systems can be very noisy. A shingle roofing system under a metal roof acts as an excellent sound reducer.

Better Insulation Having a shingle roofing system under a metal roof significantly improves the structures insulation.

Increased Water Resistance Effectively, your roof will have twice the protection when a metal roof is installed over shingles, significantly reducing the chances of leaks.

Wind Resistant A well-installed metal roof over a shingle roof can withstand severe winds up to 120 mph.

Practicality While shingles are a relatively inexpensive roofing material, they require more frequent maintenance and shingle replacement. Well-installed metal roofing not only minimizes the need for maintenance. It eliminates the constant need for damaged shingle replacement.

Value A metal roofing system can also add curb appeal to a structure since they come in a wide variety of sizes, styles, and colors.

Watch this video about metal roof installation over shingles.

Work With Experience Professionals


Remember that with any roofing or re-roofing project, the materials are only as good as those who install it. We believe our metal roofing is the best on the market. But if incorrectly installed, it will still lead to the same leaks and damages common with other products.

Our crew has more than 20 years of experience installing metal roofs. We understand the little differences and nuances of metal roofing to ensure you and your roof gets the best results. Interested in pursuing metal roofing over your existing roofing system? Request a roof quote today and find out how we can help.

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Determine The Measurement Of Your Roof

The measurement of your roof will help you know the number of materials you need for your project. As you take your measurement you must consider the chimneys, dormers, and valleys of your roof. Accurate measurement of your roof is preferred to an estimate thus you could engage a professional to do it for you to ensure precision.

Pros & Cons Of Metal Vs Asphalt Shingle Roofs

When it comes to these two materials, there are categories in which one or the other is clearly the best choice. But, there are also categories in which the choice comes down to preference.

The following guide addresses the advantages and disadvantages of metal roofing in general versus three-tab asphalt shingles. This chart outlines the best options for major considerations and uses.

Which is Better: Metal or Shingle Roof?

Metal is best for
  • Most builders stick with standard colors, textures and shades because they are widely available and low-cost.


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Directly On Top Of Shingles No Underlayment

If the roof is relatively level and in sturdy condition, you can install directly on top of shingles without underlayment, but it is not recommended. Problems may arise when doing this.

You cant be certain what condition the roof under the asphalt shingles is in unless you tear away the old shingles to get a good look. There may be weak or rotting boards, which may not hold the screws for the metal roofing.

The main, most important reason not to install directly on top of asphalt shingles with no underlayment is that the asphalt shingles will wear away the back of the metal roofing. This can expose bare metal, allowing it to rust. Expansion and contraction from heat cycling can cause the metal to slide back and forth against the asphalt shingles. When this happens, the rock on the shingles acts like sandpaper against the metal.

How Does Installing Metal Roofing Over Shingles Work

Installing the Metal Roof

Before even starting the process of installing metal roofing over shingles, you need to contact local building officials to ensure it can be done. The majority of areas allow for a re-roof over one layer of shingles, while some do allow for a re-roof over two layers of shingles.

Youll want to get this sorted out immediately before you invest in researching a new roofer or worse yet, investing money into a roof you cant have installed on your home.

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Step : Lay Down Roofing Felt Over The Entire Roof

Your goal with the roofing felt is to make sure everything is as straight and as square as possible. To do this, you might need to put wood strips in place as well.

Also, keep in mind that flashing will need to be installed for dormers, chimneys or any possible seam where you are especially concerned about water. The key here is that you are aiming for a very square, symmetrical look without the risk of water damage later.

Can You Put Metal Roofing Over Asphalt

The first thing many people face in choosing a metal roof is the question of whether they can overlay their existing shingles with it. The Uniform Building Code only allows two layers of shingles on a roof. Shingles are heavy and more than two layers affect the carrying capacity of roof trusses and supporting members. Metal roofing is substantially lighter than asphalt shingles, but it is still heavy. So the answer to this is yes, you can put metal roofing over your asphalt shingles so long as you only have one layer of shingles.

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Metal Roofing Can Work On Roofs With Low Slopes

It’s often believed that metal roofing is suitable only for roofs with a steep slope, but standing-seam metal roofing can work fine on gently pitched roofs. This type of roofing is installed in large sheets with seams that are raised and sealed tightly together to resist water. While some slope is necessary to ensure water run-off, most homes can accept metal roofing.

Installing A Metal Roof Over Shingles

Can You Put Steel Roofing Over Shingles

Shingle roofing systems have a typical lifespan of 20 to 30 years when properly installed with good quality materials. Metal roofing, however, can last upwards of 50 years or more, making it a worthwhile investment. There are several Metal Roofing Advantages and Disadvantages, so consider the following when installing a metal roof:

Installation Metal shingle systems are installed over a framework made of 2x2s. Such framework offers three significant advantages:

  • The framework/rafters is/are fastened directly to the deck , then standing seam sheets , or interlocking shingles/R-panels are fastened to the framework.
  • The framework creates a flat and straight surface even when shingles are curled, or the roof ridge is warped.
  • The framework also creates a ventilation gap helping prevent ice dams during winter months and works to cool the roof during summer months.

Ventilation holes are cut in the old roof above the soffit. This pulls air through the soffit vents , helping remove moisture and heat from the roof.

Note: You may find metal roofing options somewhat overwhelming. From sizes to colors, selecting the roofing style and appearance may be more complicated than the actual installation.

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