Upgrading Your Roof with Metal Panels

In a recent blog post, we reviewed key considerations to help a building owner decide whether to repair or replace a damaged roof. In this post, we’ll address some ways metal roofing systems are an advantage when upgrading your roof and restoring your building to “like-new”, weathertight condition.

MBCI Blog: Upgrading Your Roof with Metal Panels

Installing Metal Panels Over Existing Roofing

Some owners are concerned about replacing a roof because they dread the cost of removing the existing roof. This concern is valid in many low-slope roofing situations because the new roofing membrane might not be compatible with the existing one, and could cause premature deterioration. There are, however, metal panels specifically designed to be installed directly over existing roofing. And, many of these retrofit systems can be installed over existing roofs made of metal or other materials. Avoiding removal of the old roof obviously saves on cost. However, it also saves considerable time when installing the new roof. As an exposed-fastener metal roofing system, this retrofit application also requires fewer construction components, further streamlining the installation process.

Retrofit metal panels typically feature a membrane treatment that prevents rust or contaminants from the old building materials from transferring to the new panels. This is a versatile solution for both low- and steep-slope roofs (minimum slope: ½:12). It is also very durable and can feature approvals for use in extreme weather locations, including Florida. Metal panels are available in a variety of colors that enhance the overall design of a building. Often, this “replacement metal over existing roofing” approach is the most cost-effective, even compared to some repairs. Additionally, new roofing is more likely be eligible for a warranty, while repairs rarely, if ever, are.

Upgrading Your Roof with Insulated Metal Panels

Energy conservation is on the mind of many building owners and building code enforcement officals. Therefore, adding insulation when upgrading your roof is often required to adhere to building codes. In this case, applying zee-shaped sub-purlins over the existing roof system helps support a new layer of metal roofing. In between the sub-purlins, insulation can be added to meet or exceed current energy code requirements. This system also eliminates the need to remove the existing roofing while providing an added layer (or more) of insulation to improve the overall energy performance of the building. Insulated metal panels (IMPs) like MBCI’s can help keep buildings cooler in summer and warmer in winter—conserving energy year-round.

Sub-purlin systems can fit any existing metal panel, support new panels, and be made to accommodate many types of insulation between the old and new roofs. They can also  support or incorporate a variety of solar energy systems where desired. Roof panel options include variety of profile shapes, textures and colors to suit aesthetic preferences.

Altering the Roof Slope

In some cases, upgrading your roof means changing the roof slope (i.e., turning a low-slope roof into a steeper-sloped roof). In these cases, metal roofing systems can be the most economical choice. Steel framing (16-ga. to 12-ga.) installed over the existing roof frame creates a sloped plane that can support new metal roofing panels. Note that the existing physical shape of the roof, the existing structural system and other rooftop conditions are usually the biggest factors in the geometry and shape of the new roof. Nonetheless, the beauty of the system is that it can dramatically improve the appearance and drainage of a building’s roof, regardless of whether the substrate is steel, wood or concrete.

Lower-slope applications (1/2: to 2:12) are typically driven by economy and designed to efficiently discharge rainwater from the roof. Higher-slope applications (greater than 2:12) often serve to improve and update the look of an existing building. They achieve this by showcasing the metal roof while also improving its drainage and durability. Once the framing is installed, standing-seam metal panels can be installed over the top, creating a ventilated attic space. This allows space for additional insulation , thus improving the energy performance of the building.

Working with Building Professionals

Any of these options are applicable over an existing metal roofing system. They cab also convert other types of roofing systems to longer-lasting metal roofing, or replace an existing roofing system altogether. Of course, engaging the services of a design professional (architect, engineer, etc.) is always appropriate when considering your options. They can help properly assess existing building conditions and recommend the best overall metal roofing solution from metal panel manufacturers.

To learn more about upgrading your roof system with more durable, longer-lasting, better-draining and easier-to-maintain metal roofing systems, contact your local MBCI representative.

Why Choose Retro-R® Panels?

If you are looking for a low-cost retrofit solution and want to cover your roof with a lightweight, through-fastened panel, MBCI’s Retro-R® Panel installed over your existing roof could be the answer. Retro-R® panels provide a host of advantages for the retrofit roof project, including allowing the existing roof to stay in place during installation, thereby eliminating business downtime; time and labor cost savings; minimizing the possibility for water entry into the building; and providing a safer working environment—all with energy-efficient, versatile options. Here’s a quick rundown of some specific benefits of Retro-R® panels.

MBCI's Retro-R® panel can be installed directly over an exiting R panel.
MBCI’s Retro-R® panel can be installed directly over an exiting R panel.

Cost and Time Savings

There are a number of potential cost saving scenarios afforded by choosing the Retro-R® panel solution. First and foremost, this panel entirely eliminates the roof or wall removal process as it is installed directly over an existing R panel. This allows the facility to remain open so there’s no interruption to business operations, minimizing the loss of revenue.

Also, by not having to remove the roof or wall, installers save time (which also equates to lower labor costs). Not only does installation of Retro-R® panels save time in the project schedule and maintaining operations, this exposed fastening system requires fewer installation accessories, thereby keeping costs down while still providing a new look and long product life.

Additionally, existing rooftop equipment, vents or light transmitting panels can all be accommodated by the Retro-R® system, again providing significant cost savings when compared to installing a new roof system.

Installers may also be able to reuse all the trim from the original building when utilizing Retro-R® panels for a retrofit. They may not have to remove certain roof elements, such as the rake, gutter or down spouts; in fact, they may not even have to disassemble them. On one recent Retro-R® retrofit project, for example, Texas-based Benny’s Transmission, installers only took the ridge vents up in order to lay the panels flush, and were able to reuse them once the roof was installed, adding up to large material and labor savings for the building owner.

With a seamless solution to their 41-year-old roof in mind, Benny's Transmission selected MBCI's Retro-R® panel to be installed over their existing roof.
With a seamless solution to their 41-year-old roof in mind, Benny’s Transmission selected MBCI’s Retro-R® panel to be installed over their existing roof.

Site Safety

Any time installation time and required manpower are reduced, jobsite risks are also reduced. Additionally, it is more likely an installer could fall through if the original roof is not in place. With Retro-R® panels, if tied off at the eave, that risk is minimized as well. Generally speaking, inspecting and evaluating the existing roof panel and structure to determine if they will support the new panels and any live loads on the roof during installation is a key safety guideline.

Long Lifespan and Rust Prevention

The Retro-R® panel has a Drip Stop membrane to prevent rust from the old roof or wall from transferring to the new panel, which helps contribute to a longer lifespan.

Coatings, Color Choices, and Energy Efficiency

With availability in both 26- and 29-gauge Galvalume Plus® and Signature 200 color options, MBCI’s Retro-R® roofing system is a great option for retrofitting projects. On the Benny’s Transmission project, for example, the color chosen was Galvalume Plus®, which comes with a 20-year Galvalume warranty through MBCI. Although there was no extra insulation added, the high reflectivity of the Galvalume roof increased the building’s energy efficiency.

All in all, Retro-R® panel systems can be a cost-saving, efficient, versatile solution for your next retrofit project.

To find out more about Retro-R® panelscontact your local MBCI representative or stop by MBCI’s booth #2245 at the International Roofing Expo 2019 in February to see this panel installed live. Can’t make it to IRE? Tune in to our Facebook page on Tuesday, February 12th to watch our demos live!

Why Upgrade a Roof to Metal Panels?

Have you considered using metal panels in building and roofing upgrades? Metal roofing panels from MBCI offer significant advantages over traditional roofing material, including the ability to be integrated with the existing structural system. For buildings that need to comply with strict code requirements, our huge selection of metal roofing can meet your needs.

Save Money with Metal Roofing

Using metal instead of asphalt shingles for roofing provides several cost-saving benefits, including:

  • 60-year lifespan: The strength and durability of metal is unparalleled compared to traditional asphalt shingles, and weathers the elements for a much longer period of time.
  • Sustainability: Our cool roof coatings are extremely energy-efficient, saving you cost associated with heating and cooling your building. With strict requirements in place for buildings today, reducing energy and maintenance costs is top-of-mind, and metal roofing is a simple solution that offers both. MBCI also works with LEED project documentation and has EPDs using LCA results for core panels.
  • Higher Quality Material: From insulated to standing seam and exposed fastening roof panels, our selection of panels are available in gauges ranging from 22 to 29, with a variety of finishes and coatings to ensure your metal roof stands the test of time.
  • Extensive Warranties: MBCI’s signature panels each come with their own unique warranty, with coverage for features including film integrity, chalk and fade, and more depending on the product.

It is important to note that when working with older buildings, there is a possibility of degradation of the subsurface as well as pre-existing structural issues such as overloading the structure.

MBCI's metal roofing panels are a durable and energy-efficient alternative to standard roofing products.
MBCI’s metal roofing panels are a durable and energy-efficient alternative to standard roofing products.

Panels & Systems for Every Application

  • Standing Seam Panels: Commonly used for a variety of commercial, residential, and recreational applications, these are some of the most durable and versatile systems available. We offer everything from mechanically field-seamed panels to curved and snap-together options. No matter what your building is used for, these systems withstand the elements and have fire and impact resistance ratings.
  • Lightweight Panels: MBCI’s product line features lightweight panels that can be used as framing and sheeting materials. For example, the BattenLok® HS is a high strength standing seam roof systems that can be installed directly over the purlins or bar joints. The type of metal paneling chosen for your roofing systems allows for additional customization by being able to choose your color with our extensive color chart. The experts at MBCI have years of experience matching the retrofit roof panels to the new roof membrane.
  • Exposed Fastening: With 9 different styles to choose from, MBCI’s vast selection of exposed fastener roof panels are sure to exceed your expectations. Cost-effective and easy to install, these panels are often used in commercial and agricultural buildings, and are designed for both vertical and horizontal installation.
  • Retrofit Systems: Selecting the correct roofing system is critical in the retrofitting process. MBCI’s NuRoof® retrofit system has the capability to “stick-frame” the current supporting structure. The new retrofit system allows for redistribution of loads while increasing the energy-efficiency of the building. If you prefer installing new panels over existing roofing, the Retro-R® Panel can enable you to skip the removal of the existing roof entirely. This is a great option for saving time and cost related to installation, and can keep your operation up and running with no downtime. The Retro-R® Panel’s Drip Stop membrane prevents rust from old roofs from interfering with new panels, providing a new look with a long life span. With availability in both 26 and 29 gauge Galvalume Plus® and 200 color options, the Retro-R® roofing system is a great option for retrofitting.

To find out more about which metal roofing panel is ideal for your new project or existing building, contact your local MBCI representative.

 

Standard Testing for Metal Roofing – Part 1: Structural Performance and Uplift Resistance

When selecting a metal roofing product, there is an expectation that it will perform as intended over the life of the building. But what assures building owners, code officials, or design professionals that a product will in fact perform as promised? This question often comes up in building product discussions and the accepted way to answer it is to subject the products to physical testing. The type of testing is usually very specific to the product based on protocols and procedures developed by independent agencies such as Underwriters Laboratories (UL), ASTM International, or others. Manufacturers typically submit their products to independent testing labs who follow these standard test procedures. Once testing has concluded, they report the results back to the manufacturer. These results then show whether the product meets stated performance criteria or not. If not, the manufacturer can re-design and re-test until it does and then make the final results available to the public.

For metal roofing, a series of relevant and important tests are typically performed. In this blog, we will look at two of them related to structural performance and wind uplift.

ASTM E1592

The structural integrity of metal roofing is crucial given the various natural forces that can be imposed on the materials. Effects from wind, snow, or other conditions can compromise its integrity. Accordingly, the ASTM Committee E06 on Performance of Buildings (including sub-committee E06.57 on Performance of Metal Roof Systems) has developed ASTM E1592 “Standard Test Method for Structural Performance of Sheet Metal Roof and Siding Systems by Uniform Static Air Pressure Difference”. While the standard acknowledges the use of computation (i.e. calculations) to determine the basic structural capacity of most metal products, it also points out that some conditions are outside of the scope of computational analysis and hence need to be tested.

The standard describes a test method with “optional apparatus and procedures for use in evaluating the structural performance of a given (metal) system for a range of support spacings or for confirming the structural performance of a specific installation”. As such, it is very specific both to metal roofing and its installation. This test method uses imposed air pressure not to look at air leakage but simply to determine structural reactions. It consists of three steps:

1. Sealing the test specimen into or against one face of a test chamber

2. Supplying air to, or exhausting air from, the chamber at the rate required to maintain the test pressure difference across the specimen

3. Observing, measuring, and recording the deflection, deformations, and nature of any failures of principal or critical elements of the panel profile or members of the anchor system

The test needs to be performed with enough variation to produce a load deformation curve of the metal and account for typical edge restraint (fastening) representative of field conditions.

Manufacturers need to submit different products that are tested at least once at two different span lengths between supports. Standing seam roof panels are typically tested at a 5’-0” and 1’-0” span. Spans between the two tested spans can be interpolated. The result is a table of tested loading results that can be compared to code required or engineered design loading to then determine if the selected material and spacing are adequate for the project needs or if another product or spacing is needed.

MBCI's metal roofing products undergo a series of tests to ensure maximum resistance and performance.
MBCI’s metal roofing products undergo a series of tests to ensure maximum resistance and performance.

UL 580

The ASTM E1592 test is focused on the structural integrity of metal panels. It also uses positive and negative air pressure in a static (i.e. non-moving) condition to determine performance. There is also a separate concern about how metal roofing will perform in a dynamic condition as would be expected in a windy condition where wind gusts can ebb and flow erratically. In that regard, a separate test developed jointly between Underwriters Laboratories (UL) and the American National Standards Institute (ANSI) looks at the ability of roofing to resist being blown off a building due to wind. Known as ANSI/UL 580 “Standard for Tests for Uplift Resistance of Roof Assemblies”, it has become the recognized means to identify and classify the suitability of roofing for different wind conditions – low to high.

This test is also specific in its scope and intent stating that it “evaluates the roof deck, its attachment to supports, and roof covering materials”. It also points out that it is not intended to test special roof conditions, main or secondary structural supports, or deterioration of roofing. The standard prescribes in considerable detail the type of test chamber that needs to be constructed and used for the testing which includes three sections: “a top section to create a uniform vacuum, a center section in which the roof assembly (i.e. deck, attachment, and roofing) is constructed, and a bottom section to create uniform positive pressure”. The test procedure is then based on placing the roof assembly into the test chamber and subjecting it to a prescribed sequence of 5 phases of oscillating positive and negative pressure cycles (simulating dynamic wind conditions) over 80 minutes of total testing.

There are four wind uplift classifications obtainable for a tested assembly based on the test assembly retaining its attachment, integrity and without any permanent damage. These include Class 15, Class 30, Class 60, and Class 90. Each class has its own requirements for test pressures with increasing pressure as the class number increases. Higher class numbers indicate increasing levels of wind uplift resistance. Note, that to obtain a Class 60 rating, the tested assembly must pass the Class 30 test then be immediately subjected to the Class 60 test sequence. Similarly, to obtain a Class 90 rating, the tested assembly must first pass both the Class 30 and 60 tests. Metal roofing manufacturers who want their roofing products tested and classified under UL 580 must pair them with standard roof deck and fastening materials. Hence most have many different tests performed and results reported accordingly.

When reviewing metal roofing options, it is comforting to know that most manufacturers have tested their products and designed them to meet or exceed minimum requirements. To find out more about tested results of products you may be considering, contact your local MBCI representative or see the MBCI website and select the “testing” tab under a selected product.

The Importance of Roof Installer Training and Certification

Many metal roofing installers may think that their years of experience on the job is enough. But even for those who have been putting up metal roofs for a long time, the truth is that if they haven’t put up a particular brand’s roof before, they need to go through that manufacturer’s installer training and get certified. There are several reasons for this.

  • More and more, architects are starting to specify that an installer must be certified by the manufacturer of the product being installed.
  • For many manufacturers, including MBCI, in order to get a Standard III warranty with no dollar limit—or any Day One warrantytraining and certification are required.
  • Installers need to know the proper technique and protocols—for a particular manufacturer’s product! After all, you don’t make any money by going back and fixing leaks.

There are many other standing seams that are very similar to those that MBCI sells, and while they may look similar, there will be a number of small differences, such as the way panels are notched or the way sealants are put in. Even the way companies test panels can be different. For instance, if you have a Florida or Dade County approval or an FM approval, that’s all tied into the way the roof system is tested. So, if someone has a project where one of those things is required, it is imperative to make sure the installer is using that brand’s system of doing things, down to every last detail. These are some of the things covered in certification courses.

Certification Courses and Installer TrainingInstaller Training

At MBCI, we offer a three-day course that covers all of our standing seam panels, and have a separate two-day course for insulated metal panels, which provides advanced installer training in metal roof installation through classroom lecture and hands-on application in a variety of MBCI’s products, assembling roof systems on a mockup to reinforce what was learned from the presentations. Courses take place once a quarter in different locations throughout the United States.

In terms of who should attend certification courses, generally speaking, it’s the person from the company who will be doing the actual work since a certified installer needs to be on the roof any time any work is being done on the roof. He or she is the one we train. And that installer is tied back to the company in order for them to receive certification. That company has to have workman’s comp and general liability insurance. If the certified person leaves the company to go elsewhere, the first company needs to certify someone else.

The Bottom Line of Certification

From a bottom line perspective, it’s important for companies to be proactive in making sure there is always someone on their team who is a certified installer for the products they use—or might use. Not only will they learn tips and tricks for proper installation, but it will also avoid a situation where you have a job, the panels are being delivered the next week and you realize you need someone to be certified. Maybe it’s three weeks until the next certification opportunity. You’ll want to have all that settled before you need it.

Just because you’ve been installing roofing for 30 years, doesn’t mean installer training and certification isn’t necessary. Our best advice is to come to the class and learn all the little idiosyncrasies about whatever manufacturer’s roofing panels you’ll be installing. This is a case where even a little knowledge goes a long way.

Knowing When to Call the Metal Manufacturer: Part 2

As stated in Part 1 of this series, the success of a metal roof or metal wall project can rest on the installer knowing when something isn’t working or just doesn’t seem right. When that happens, a call to the manufacturer is not just suggested but is really imperative to ensure any potential problem is averted before it’s too late. In addition to the previously discussed scenarios, such as damage to the physical panel or problems with the fasteners, let’s take a closer look at a few other common circumstances under which MBCI recommends immediately reaching out to the manufacturer:

Alignment and Substrate Issues

It is the installer’s responsibility to verify the substrate and check for proper alignment before attaching any sheeting materials. If the installer notices any issues of this sort (either before installation or once they start putting on the sheeting), they should stop and address them immediately. This might include oil canning or other irregularity in appearance of the panel. The installer should investigate the source. If unable to identify and properly remedy the situation on their own, then a call to the manufacturer’s support team is recommended. They may be able to suggest items to check to help locate the source of the problem—whether it be installation or manufacturing—and from there make suggestions as to the best possible means to address the situation.

Accessories

When physically getting ready to modify a panel system by adding things to the roof (such as snow guards or mechanical curbs) or to walls by installing doors, windows and louvers, these penetrations can have an impact on the system and its weather-tightness and appearance. Oftentimes, other trades—who may or may not have knowledge of the sheeting system—are coming onto the job to perform the accessory installation. It’s wise to visit with manufacturer prior to installation and/or alert the non-metal panel installer of precautions to take when adding accessories.

bad roof jack installation - part #2 ACCESSORIES SECTION
The pipe penetration shown here is not the correct type of piping for metal roofing, and not the correct installation. This can lead to issues with roof performance, including leaking and water damage.

Coordination regarding material types of accessories, fasteners and placement is critical. There are materials that can react negatively with the installed system and lead to damage as well as void manufacturers warranties. Accessories should always be discussed prior to installation. Read more about different types of roof accessories and penetrations in MBCI’s blog article, Roof Penetrations Made By Non-Roofing Contractors.

Panel Engagement

Panel systems have an engineered means by which the panels attach and engage one another as shown in the manufacturer’s installation manuals and project drawings. If at any point the panel will not engage as depicted in the details, installation should be halted and reviewed to determine the cause. This can require a call to the manufacturer to help determine if the matter is site and substrate related or potentially a manufacturing issue.

Do not continue to install the system if the laps are not nesting properly, clips are not engaging as detailed, panel modularity cannot be controlled or if the overall panel is not “resting” on the substrate such that there is excessive bowing and stress in the panel. This is the time to call the manufacturer, as once the material is completely installed, it is much more difficult to determine the cause of a problem and is potentially more expensive to remedy. Additionally, in many cases, full installation constitutes acceptance of the product and the manufacturer’s hands could be tied or extremely limited in being able to assist in remedying after the fact.

By knowing when to be proactive with a call to the manufacturer, installers can mitigate many types of potential pitfalls. And if you’re just not sure, it’s best to call.

For more information on metal roof and wall products and training, MBCI offers courses through its Metal Institute. These courses are available for general training purposes or for those seeking installer certification. To learn more, visit mbci.com/metalinstitute.

Fastener Compatibility with Metal Roof and Wall Panels

The installation of a new metal roof or wall panel on a residential home, business or commercial building takes care, precision and—of course—the right tools. Regardless of the structure, you’ll likely find that choosing the correct mechanical fastener plays a key role in the long-term performance, durability and efficacy of the project.

Many metal roof and wall panels, in fact, rely upon the use of quality mechanical fasteners to secure components to a structure. In order to guarantee a resilient and weather-tight attachment, it behooves the user to select an appropriately compatible fastener type for the specific metal construction, thereby ensuring expected benefits, such as energy efficiency, extended life cycle, and even lowering insurance bills for the owner. In other words, once the decision has been made to use metal building materials for your roof or wall project, the next step is figuring out how to hold it all together.

Know Your Fastener Options

Before selecting fasteners for the project, it is important for the designer or installer to understand the various materials and options available. Typically, this involves the following considerations:

  • What type of material and coating is appropriate?
  • What type of head do I need? Does it need to be painted?
  • Do I need a washer? If so, what material should I use?
  • Should I use self-tapping or self-drilling screws?
  • What thread count should I specify?
  • How long does the fastener need to be?
Many Types of Fasteners
The MCA provides a summary of the different types of fasteners in their technical bulletin, Fastener Compatibility with Profiled Metal Roof and Wall Panels.

Select a Fastener on the Basis of Material

Most fasteners are made from coated metal but both the type of metal and coating must be chosen on the basis of the materials the fastener is bringing together. Galvanic action between dissimilar metals can cause premature fastener failure and lead to leakage. Even stainless steel screws will corrode severely under the right (or actually wrong) conditions. In extreme exposure, sometimes the best option is to use galvanized screws and plan on replacing them at a later date with a larger screw once the zinc has been depleted.

Considerations for Self-Drilling Screws

Self-drilling screws have a drill bit built in and don’t require a pre-drilled hole. Although self-drillers save the installer the step of drilling a hole, they are not always a good idea. The available space between the back of the hole and the next physical restriction must be at least as big as the bit itself or the threads will not engage. Also, drilling a hole allows a quick inspection to ensure the hole is in the correct location and plies are aligned and parallel. Generally, self-drillers are used when going through thin gauge steel into thicker gauge steel and self-tappers are used when fastening two thin gauge plies.

Washers

Fasteners may be used with or without washers. While plastic washers help prevent leaks, they are not required on purely structural connections. When using washers, it is important to visually inspect the screw after installation to be sure they are properly compressed and not kinked. Exposed plastics generally degrade when exposed to ultraviolet light. Furthermore, use of neoprene washers may be prevented by restricted material lists, or “red lists.” Fastener heads themselves may be made of different materials than the rest of the screw, long-life ZAC heads being the most common example.

Fastener Profiles

Fasteners have different profiles. Flat or “pancake” screws are used when low profile installation is necessary and may have Philips, hex, or Torx sockets. Which socket to use is usually an installer’s preference based on accessibility restrictions. Another common feature is an over-sized dome beneath the head to encompass a larger washer. Also called shoulder screws, these screws are useful when thermal movement might distort the holes.

Colored Fasteners for Metal Roofs
Fasteners can also be colored to match the roof or wall panel.

Thread Count per Inch

Thread count per inch, or TPI, must also be considered. Most commonly, fasteners are installed through the thinner ply first and grip in the thicker ply, pulling the plies together. Therefore, TPI selection is usually driven by the thickness of the thicker ply. Generally, the TPI is close to the gauge of the metal for gauge steel and higher for plate and sheet.

Length

The fastener must also be long enough to fully engage all plies of material, plus the length of the drill bit in the case of self-drillers. Generally, this is rounded up to the next half or quarter inch. However, the longer the screw, the more torsional strain is produced during driving and in the case of very long fasteners, this can break the fastener or introduce wobble, leading to poor installation. Therefore, stainless steel with over-sized washers is often used for long screws for added strength and protection.

For More Information on Fastener Compatibility

To learn more about fasteners and their compatibility with different types of metal roof or wall panels, check out Metal Construction Association’s recently published technical bulletin, Fastener Compatibility with Profiled Metal Roof and Wall Panels.

Installing Metal Roofing Over Asphalt Shingles

Can Metal Roofing Be Installed Over Shingles?

When an asphalt shingle roof wears out, one of the most long-lasting solutions is to retrofit the roof with metal panels, and not remove the asphalt shingles.  While it’s a change of appearance, the metal roofing panels will provide a greater durability and longer service life.

UCI
UCI Retrofit Corporate Office installed 7.2 roof panels over the existing asphalt shingle roof

Installing Metal Roof Panels Over Asphalt Shingles

There are a number of considerations when installing metal panels over an existing asphalt shingle roof.  First, the building codes allow metal over shingles if there is only one layer of asphalt shingles.  A third roof is not allowed, so there must only be one shingle roof in place.

If you’re considering installing metal roofing over asphalt shingles, contact us today to learn more about MBCI’s panel systems.

Choosing the Correct Retrofit Metal Roofing System

Fastener choice is important for wind resistance.  As is the pull-out resistance of the deck. The panel thickness (e.g., 24 gauge), panel width, height of the standing seam, spacing between clips, and clip strength all help determine the overall wind resistance of a metal panel recover installation.  Wind design loads are specific to geographic location and height of the building; work with the metal panel manufacturer to determine the design specifications.  Importantly, use fasteners that are long enough to penetrate through the asphalt shingles and the deck by at least ½” to ensure proper strength.UCI_2

 

Because metal panels run from eave to ridge, the flatness of the existing roof can affect the appearance—the waviness—of the metal panels.  Three tab shingles are quite flat versus laminated dimensional shingles.  Consider installing a base sheet or a #30 underlayment over the shingles before installing the re-cover metal panels.  The uneven surface of the asphalt shingles can be telegraphed to the metal panels, leading to an uneven or wavy surface of the new metal panels.  And, like oil canning, it’s not a performance issue, but homeowners don’t want an unsightly roof.  Spending a few dollars on a heavy base sheet/underlayment is cheap insurance to ensure an aesthetically pleasing roof, and that means a satisfied homeowner who is willing to pay for the new roof!

Benefits of Installing Metal Roofing Over Shingles

There’s a sustainable advantage to installing metal over existing asphalt shingles.  Not removing the asphalt shingles not only saves money but also reduces the amount of waste sent to a landfill.  Roofing tear-off is one of the largest contributors to landfill waste in the U.S. And, while there’s a lot of discussion about the reuse of asphalt shingles (i.e., downcycling) in asphalt roads and bike paths, the reality is that much of the shingle tear-off is not actually reused.  For example, the Colorado Department of Public Health and Environment no longer considers asphalt shingle waste to be a recyclable material.  Not because it’s not recyclable, but because there is no significant market for its use.  These ideas will influence some homeowners, so use them when selling the idea of recovering with metal.

Installing metal panels over existing asphalt shingles is a smart choice.  Design it right, and the new metal roof could last the life of the house.

Contact us today to learn more about how our panels can be installed over asphalt shingles.

Reroofing with Steep-slope Metal Panel Roof System Over an Existing Low-slope Roof: Part 2

Let’s continue the discussion about converting low-slope roofs to steep-slope metal roofs. Part 1 discussed attachment of framing, the new attic space, ventilation and condensation issues, and drainage.

Before After Retrofit

Reroofing Code Requirements 

Converting a rooftop is a specialized type of reroofing.  The codes specifically allow this via an exception that says “complete and separate roof 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.”

To meet this code requirement—and to not have to remove the existing roof system—the loads must bypass the existing roofing system. This is critical to create a load path from the new structure to the existing structure for dead loads, snow loads, rain loads, and uplift (e.g., wind) loads.

Structural Loads & Wind Resistance

IBC’s Chapter 16, Structural Design, includes all the required information and design methods to determine the dead, snow, wind, and rain loads acting on the building.  The new framing members and their connections, as well as the new metal panels and their attachments to the new framing, must be able to resist the loads acting on the building.  The resistance must exceed the loads.  Most often, wind resistance loads control the design.  Manufacturers and structural engineers should be consulted for material specifics and fastener requirements.

Fire Resistance

Fire resistance for a converted roof needs to meet the requirements of the model codes.  Check with manufacturers for fire classification of the system installed, and ensure it meets the minimum class (A, B, or C) required in the project location.  See the blog “Fire resistance of metal panel roof systems” for more information.

Insulation

For all types of reroofing, the most recent insulation requirements need to be met.  In most cases, additional insulation will be necessary.  Insulation can be placed at the attic floor (i.e., on top of the existing low-slope roof) or directly under the new metal panels.  Where the new roof meets the wall is very important for continuity of the overall building envelop insulation; lack of continuity is energy inefficient and may be a point of condensation.  The location of the new insulation needs to be coordinated with the ventilation plan and condensation potential should be considered. See Part I for more information.

While reroofing with metal can be an aesthetic improvement and solve leak issues, structural loads and wind resistance, fire resistance, and insulation requirements are necessary considerations when converting from a low-slope roof to a steep-slope metal panel roof system.  Don’t overlook the basic code requirements, or the need to deal with heat, air, and moisture issues of the new attic space.

Reroofing and the Building Code

Reroofing is and always will be the predominant project type in the roofing industry.  Roughly 70-90% of all roofing projects (depending on the year) are performed on existing buildings.  Understanding the reroofing requirements in the building code is critical to proper design and construction.  And fortunately, the reroofing requirements are not all that complicated.International Building Code

The 2015 International Building Code, Section 1511, Reroofing provides the building code requirements when reroofing.  Reroofing projects are divided into two types: recovering and replacement (which includes full removal of the existing roof).

Metal panel reroofing projects must meet the same fire, wind, and impact requirements for roof systems for new construction; however, they do not need to meet the minimum slope requirements (¼:12 for standing seam; ½:12 for lapped, nonsoldered and sealed seams; 3:12 for lapped, nonsoldered, non-sealed seams) if there is positive drainage.  Also, reroofing projects do not need to meet the secondary drainage requirements (i.e., installation of emergency overflow systems is not required).

The requirements for metal panel and metal shingle roof coverings are in Section 1507.4, Metal roof panels and Section 1507.5, Metal roof shingles of the 2015 IBC.  These apply for new construction and reroofing, and include information about decks, deck slope, materials, attachment, underlayment and high wind, ice barriers, and flashing.  The 2012 IBC has the same requirements; the 2015 IBC added new language about deck slope and attachment requirements for metal roof panels.  Nothing was changed for metal roof shingles.

In general, recovering is only allowed if there is one existing roof in place, except if a recover metal panel roof system transmits loads directly to the structural system (bypassing the existing roof system).  This provides a great advantage for metal panel roofs!  The existing roofs do not need to be removed, but new supports need to be attached through the existing roof (typically a metal panel roof) directly into existing purlins.

If metal panels or metal shingles are installed over a wood shake roof, creating a combustible concealed space, a layer of gypsum, mineral fiber, glass fiber, or other approved material is required to be installed between the wood roof and the recover metal roof system.

Good roofing practice is codified in the reroofing section of the IBC; contractors who design and install a recover or replacement metal roof are legally required to follow locally adopted code requirements.  And, of course, all metal roofs must be installed according to the manufacturer’s approved instructions.

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