Every metal roof installation comes with an implied warranty: the roof shouldn’t leak. This is true even if your customer didn’t buy a “manufacturer’s weathertightness warranty.” It’s just the very basic expectation. Any details we send out, any materials, whatever the manufacturer supplies the installer…all go to that simple premise that you are buying a quality roof system from the get go.
Beyond that, though, a purchased manufacturer’s weathertightness warranty takes it a step further. It’s added insurance. In order to get the full value and peace of mind from a warranty, there are certain considerations the installer needs to keep in mind. Let’s take a look at five key installer responsibilities on projects with manufacturer weathertightness warranties—beyond, of course, putting down the roof correctly!
1. Understanding the weathertightness warranty type selected for the project.
MBCI sells two types of weathertightness warranties: Standard and Single Source. The approval process up front is the same for both but it is crucial to know the scope of the project’s warranty. With a standard warranty, the only real expectation is that the roof will remain watertight for 20 years. It is a very basic, very inexpensive warranty in which the manufacturer and the installer jointly warranty the roof for that period of time. The manufacturer covers all the materials and the details, and the installer is covering the installation.
The opposite end of that spectrum is the single source warranty, which is purchased when the customer wants not only the roof warrantied, but prefers everything associated with the roof—any accessories, anything else penetrating the roof—to be 100 percent covered by the manufacturer, if applicable. These warranties do cost more, require inspections, and require an installer to have completed the manufacturer’s certified installer training program.
It’s important for the installer to know what warranty was sold, particularly because he/she may not have been the one involved from the start. They may be coming in to bid the job as the installer only. Therefore, he/she needs to ask questions because they may or may not have the personnel on their crew that meets the requirements to install that roof for the weathertightness warranty purchased.
2. Obtaining/confirming building geometry approval for warranty.
Beyond the type of warranty, it is simultaneously necessary to investigate whether there are additional procedures related to the building geometry. Has everything been correctly noted so that the warranty itself will be valid? Is the manufacturer aware of transitions, edge conditions, roof penetrations, roof accessories (snow guards, solar, etc.)? It is extremely important to make sure that the geometry—or the conditions of the roof—are covered within a particular warranty.
MBCI, for instance, will review your roof plan and see the eave gutters, the ridge, the rake, etc. and we can survey what’s going on. Is that roof tying into something else? Will there be materials on that roof that aren’t provided by us or not being installed by the roof installer? As the manufacturer, we would be taking a cursory view to say, yes, we can warranty the roof or no, revisions are needed. If there is anything that we can’t warranty, we’re going to spell that out upfront. We will give as much direction as possible to get the project to a point it can be warranted.
That said, it’s the installer’s and customer’s responsibility to make sure that the manufacturer knows what’s happening. Think about it this way. Many times, there are other trades involved outside of the roofing contract. Along comes someone who says, “I need to run something through your roof,” or six months down the road the owner wants a satellite dish on the roof and the installer incorrectly penetrates the roof., causing a leak. Guess who they’re going to call? The installer/customer/owner needs to get that approved by the manufacturer. Otherwise, the warranty could be voided.
The main takeaways here: Do not make modifications to that roof without the manufacturer’s approval because the roof installer can end up inheriting the liability for that if they do. And, communicate the criteria or the requirements of the warranty to the customer. Don’t just hand them the paperwork. Make sure they understand what’s in it and their responsibilities as metal roof owners.
3. Ensure proper installer certification and training as required by the warranty type.
This sounds self-explanatory, but it goes back to the warranty type and the necessity to make sure the warranty selected is appropriate for the job. Verify whether or not the job requires a certified installer and if so, ensure certifications are current. If the installer is not certified, then they need to take the steps to get certified in order to meet that warranty requirement.
A common situation: A warranty gets sold by a general contractor and he/she subs it out to another roofing contractor. That sub comes in and says not to worry, “we know how to put the roof on. We’re certified.” Then, MBCI gets ready to issue the warranties or schedule inspections and finds out the subcontractor doesn’t know our system that well. And remember—for certain types of weathertightness warranties the installer needs to be certified via our training program.
4. The installer is responsible for correct installation per manufacturer’s details.
The onus is on the installer to follow the details and directions provided by the manufacturer. If you install the roof per those details, and then there’s a problem, the responsibility falls back on the manufacturer unless determined otherwise. If, however, the installer doesn’t follow the details provided and the manufacturer comes out to do a warranty claim or warranty inspection, then the installer is going to be responsible for correcting it. The installer can’t put it in wrong and just say, “oh, well, that’s covered by the warranty.” It’s not. A manufacturer’s warranty is not for covering a bad installation—particularly in the case of a standard warranty. If the installer does a poor install and the roof leaks, that’s not covered by the standard warranty; it falls back on the installer. Of note, this scenario can be different with a single source warranty, since the manufacturer will be out there doing ongoing inspections and ultimately can become responsible for the installation as well.
And, it goes without saying, the warranty doesn’t cover the interior contents of a building that may be damaged due to an installation issue.
5. Do not make adds or changes to an installed system once completed and the warranty has been issued without first getting manufacturer approval.
The warranty only covers the installed product per details, as mentioned. It does not cover additional materials added to the roof or any changes made, at least without the manufacturer’s prior approval—after the install is complete.
Some examples would be adding a mechanical unit to the roof, a plumbing vent added through the roof, or the satellite TV cable through the roof. Putting a penetration, fasteners, holes of any kind, into a previously installed roof system, unless approved by the manufacturer, will void the warranty in that location. If the manufacturer does not give approval, the installer, along with the customer, would need to make the decision—is it worth the risk to proceed knowing that if the roof leaks, that location would no longer by covered by the warranty.
Whether it is wind speed, sun exposure or the proximity to a coastline, these factors would be the major considerations when choosing metal roofing for a project in coastal areas. The good news is that metal panels can be used in just about any coastal area so long as you find the right product profile and finish that meets your specific requirements to maximize performance given the variables of the environment.
There are a number of special considerations given the environmental conditions inherent to a coastal area, including the impact to paint systems and certain unique maintenance requirements, wind ratings, hurricane conditions and certifications/regulatory product approvals that will limit the panels you can you use within specific coastal areas, for instance Dade County, the state of Florida, and the Texas Coast.
Finishes: The 1,500-Foot Rule
Metal components can be a great roofing choice, even in a coastal area, whether a bay, gulf, or ocean water. Key is how you manage the finish on the products and how close you are to the actual salt environment. Simply stated, if you’re outside of a 1,500-foot range from the coastline or salt water, then standard metal roofing would be suitable, but if you’re closer to the coastline there are special paint options or finishes you’d need for the product to withstand the coastal environment.
At MBCI, we use Flurothane Coastal coil coating system* as our standard solution to the challenge of salt spray and harsh coastal environments. This coating is a premium fluoropolymer (PVDF) system developed for use in the most extreme coastal environments. This system is unique in its use of an innovative thick film primer. The two-coat system has a total dry film thickness (DFT) of 1.7 to 2.0 mils.
Choosing an appropriate coastal finish can also affect your product’s warranty. If, for example, your project is within the 1,500-foot range and you don’t choose the required coastal finish, if the panels were to rust there would be no warranty offered and it could affect your warranty for weathertightness as well.
Suitable Panel Types and Additional Coastal Conditions
Overall, roof failures are the largest hurricane loss due to wind and water damage. For this reason, metal roofing is a highly recommended option for coastal regions where hurricanes and high force winds are prevalent. The appropriate metal panel type for these areas is mainly contingent upon what you want to accomplish. Because MBCI does have high wind ratings for most of our panels, whether it be a screw down (aka through-fastened) panel or a standing seam profile panel, selections should be determined by the complexity of the roof itself and the roof conditions. There are standing seam panels and through-fastened panels that can be approved for both roof and wall applications in many coastal areas.
Also, of note, different types of coastal areas may receive higher wind speeds. There is obviously a wide difference in wind speeds between the East Coast and the West Coast, for example, although both are coastal communities. In an area with higher wind speeds and/or hurricane conditions, you would want to consider panels that achieve higher wind ratings. Since there are many different panel options, and some may not be able to achieve as high wind ratings as others, you should look at what those values would be for wind and what testing has been done. MBCI’s metal wall panels and roofing systems are able to resist and withstand extreme environmental conditions, such as those in Florida or the Texas coast where strict product approval and testing processes are required.
MBCI has panels that meet requirements for Florida Approval, Dade County and Broward County for instance, where you need to have an NOA (Notice of Acceptance) for those county areas, as well as products that are TDI approved (Texas Department of Insurance), which is usually seen in the Texas coastal area.
Additionally, sun exposure and color can have an impact as far as solar reflectance, so that is another consideration. Somewhere like Florida gets a lot of sun yet a coastal area in Washington State would be mostly cloudy. If you are in an area that has more sun, then you may want to consider a panel with a higher solar reflectance value.
If you have metal roofing in a coastal area, you’re going to follow much of the same maintenance as you would on any metal roof, but you would want to inspect it for damage, especially after a wind event or storms. One of the main differences, though, especially if you’re within the 1,500-foot limit where you needed a special finish, is that you’re going to have to do a fresh water rinse regularly on the panels a couple of times a year. What this means is you are basically hosing it off with fresh water to get the potentially corrosive salt spray residue off of it.
For more on metal roof and wall panels and finishes for use in coastal areas, contact your local MBCI representative.
* (1) All substrates must be properly pretreated. (2) American Society for Testing and Materials. (3) Flurothane Coastal system is not designed to bridge cracks in the substrate. (4) Varies by color. (5) Flurothane Coastal system will generally meet the requirements for most post-painted fabrication processes. However, variations in metal quality, thickness or cleaning/pretreatment applications can lead to diminished flexibility.
SOURCE: Valspar Corporation
Cutting metal panels on site is an often-necessary part of installing metal roofing and wall panels. However, using the right tools and methods to ensure the panels remain damage-free is vital. Using the wrong tools can result in rust, rust stains, the voiding of warranties and diminished building service life. In this blog post, we’ll share several common field-cutting techniques and best practices that help ensure good results.
Maintaining Longevity When Cutting Metal Panels On Site
When metal panels are made in a manufacturing facility, the tools and methods used to cut the coated metal coil help protect the cut edge from deterioration like corrosion. When cutting metal panels on a jobsite or in the field, protecting any cut edges is just as important. To understand how to field-cut metal panels without sacrificing the quality and protection delivered from the manufacturing facility, you must first understand the what protects the panels. Most often, metal roof and wall panels are fabricated from Galvalume®-coated steel coil because of its proven longevity. Not only does the Galvalume coating protect the surface area of the metal panels, it has also been shown to be effective along the thin edges of the metal too, as long as those edges are cut properly.
During fabrication, the Galvalume metal panels are cut to length either by shearing while flat before entering the roll former, or by means of a profile shear as the panels exit the roll former. Either method tends to “wipe” the Galvalume coating across the cut edge of the metal panels. This provides superior cut-edge protection from corrosion.
Likewise, when panels arrive on site, any needed field cutting should address the same concerns of protecting the edge of the steel from corrosion. Of course, there are ways of doing the field cutting correctly. However, there are also poor strategies that can lead to real problems. The following are examples of common field cutting tools and the best practices for good results.
Common Tools and Methods for Cutting Metal Panels On Site:
Red and green aviation snips are a good choice for small cuts on metal panels, such as around pipe penetrations. These snips will wipe the Galvalume® coating in the same way as factory shears, making them a good choice.
Electric shears are optimal when making lengthier cuts along the steel, such as cutting a wall panel at a corner or at a door opening. These shears take a ¼” strip of metal out of the panel during the cutting process, which tends to leave both sides of the panel smooth and flat along the cut. Like the aviation snips and factory shears, electric shears will wipe the Galvalume coating and protect the edges.
Mechanical shears are an add-on tool that fit onto a battery-operated impact or screw gun. These shears do not take any metal out of the panel and will leave a slightly wavy edge. Mechanical shears are an excellent choice for bevel cutting standing-seam panels at hips and valleys, since they too wipe the Galvalume coating over the cut edges to offer protection.
A nibbler is a great tool for cutting across corrugations in wall panels to create openings for windows, doors and similar structural additions. A good nibbler typically costs $500-$700 (currently), but is well worth it if you often cut corrugated metal panels. The punch and die in the nibbler tends to wipe the Galvalume across the cut edge as it punches out small, half-moon shaped pieces of panel. However, because these little metal pieces will fall away from the cut, it’s important to contain them so no one walks on them. Otherwise, they can embed in the soles of installer’s shoes and create scratches in roof panels when they walk on the roof.
Skill saws are an ideal tool for cutting metal panels because of their versatility. This tool can cut either across or parallel to corrugations, whether straight or at an angle. When using a skill saw, it is critical to use a saw blade that cuts cool. Otherwise, the Galvalume coating can melt along the cut edge and become ineffective. In particular, do not use an abrasive blade, which will generate heat and damage the coating.
Additionally, its vital to avoid cutting panels on the roof or above other panels. A skill saw blade will throw considerable amounts of steel debris into the air and down onto any panels below. This debris, called swarf, will quickly rust and ultimately cause rust spots in the panels. If enough swarf gathers in one spot, it can rust through the panel.
Steel swarf, like this collected at the ridge will rust through the panel.
Which Tools Should To Avoid When Cutting Metal Panels On Site:
Tools that should never be used include:
- Cut-off saws
- Reciprocating saws
All of these tools will melt the Galvalume® coating, causing edge rust just like an abrasive blade would. These tools also throw a lot of steel debris (swarf) onto the panels they cut. This debris will be hot and will embed into the panel coating. This can cause rust spots and bigger problems down the road.
In conclusion, using the right tools and following metal panel manufacturer recommendations when cutting metal on site will help ensure that the panels remain damage-free and the final installation will be a fairly seamless process. Using the wrong tools can result in rust, rust stains, and the voiding of warranties. For more on best practices and recommendations for on-site cutting and installation of metal panels contact your local MBCI representative.
Many large, commercial, low-rise buildings often don’t benefit from steeply-sloped roofs the way residences and small commercial buildings might. This is because a steep roof slope would add unwanted height and unnecessary construction cost. Buildings like warehouses, retail stores, etc. are more appropriately built with low-slope roofing, commonly known as “flat roofs”. The National Roofing Contractors Association (NRCA) defines low-slope roofs as those with “a slope at or less than 3:12″. Anything steeper qualifies as a “high-slope roof”. With this in mind, let’s look at some key points to consider when designing and constructing a low-slope roof.
Low-Slope Roofing Materials
When it comes to selecting low-slope roofing products, there are generally three fundamental choices:
- Asphalt/ Bituminuous Products: The traditional commercial roofing norm for many years, the use of asphalt/bituminous products has dwindled as newer, more appealing options have emerged.
- Flexible Membrane Roofing: This roofing material can be made from a variety of types of plastic/polymer-based materials (commonly known as EPDM, TPO, PVC, etc.). Rolls of the chosen membrane are laid out on the roof structure and secured in place either with mechanical fasteners (screws with large washers) or with a continuous layer of adhesive.
- Metal Roofing: Sometimes overlooked, metal roofing is suitable for different roof slopes. Many metal roofs that use standing-seam systems are rated for use with a pitch as low as ½:12.
When considering which type of roofing material to use for a building project, there are a number of significant differences that illustrate why metal roofing is often the ideal choice.
Engineered For Superior Performance
Standing-seam metal roofing is made specifically for use on low-slope roofs as it meets a number of performance requirements:
- Water resistance: Precipitation doesn’t penetrate through metal or through the standing seams where the metal panels join together. This is why they can tolerate such low slopes, allowing the water to drain away slowly and predictably without leakage.
- Rigidity: The rigid nature of metal means that there is less opportunity for ponding (standing water). This is not always the case with asphalt/bituminous or membrane roofing systems.
- Drainage: Metal roofs carry water to the building’s edge toward gutters and downspouts that carry it away from the building. Other roofing systems rely on drainage piped inside the building. This takes up space and has the potential to leak water inside the building and cause damage.
- Wind Resistance: Standardized uplift testing shows that metal roofing performs as well or better in extreme weather than mechanically-fastened or fully-adhered membrane systems.
- Durability: The most cited advantage of metal roofing is its long-term strength and durability. Engineered design and use of high-quality coatings ensures a longer lifespan—50 years or more. In contrast, other roofing types typically feature lifespan ratings of 20 or 30 years.
- Puncture Resistance: Low-slope metal roofing is more puncture-resistant than asphalt/bituminous or membrane roofing. This makes it better able to tolerate foot traffic, hail and other puncture-inducing hazards.
- Construction/ Installation Ease: Metal roofing panels are custom-made to suit specific building sizes and end uses. This customization typically means it takes less time to place and install metal roofing in the field. Further, metal panels can tolerate a wide range of temperatures and weather conditions and still install and perform as intended. Low-slope roofs are also safer to walk on with less risk of slips, falls and other hazards.
Using metal roofing on low-slope roofing systems can be cost effective in a number of ways:
- Fewer labor hours as a result of the ease of installation saves money during construction.
- Competitive material costs, particularly if the metal roofing is part of a total metal building package from a single manufacturer.
- Minimal maintenance requirements and aversion to rusting, mold growth and decay that save the building owner money over time.
This all adds up to a very favorable life-cycle cost.
The performance, cost-effectiveness and life-cycle benefits of metal roofing panels make them a viable option for low-slope roofing systems. Manufacturers like MBCI can help you select the right metal roofing products and provide information and resources to help ensure proper installation.
It would seem logical that the most important field installation process for a standing-seam metal roof is the actual process of creating the weathertight seams that connect the metal panels together and ensures the structural integrity of the roof. Perhaps for many different reasons, however, this critical seaming process is not always given the proper attention it deserves, nor are installers given the proper training required to ensure installation runs smoothly. This approach can cause some serious issues, not the least of which is the voiding of a manufacturers warranty or the discovery of roof leaks and the resulting damage.
To help, here are some best practices for readily and successfully carrying out the metal roofing seaming process:
Because of the critical nature of seaming metal roofs, the crew members doing this work should be properly trained. Team members who will be performing this work should not perform the seaming without having participated in the appropriate installation training required to ensure the seaming process is appropriately managed. Most roofing manufacturers offer installation training that many installers take advantage of—and this training opportunity should be taken advantage of by the staff who will be doing the seaming.
It is very important that the seaming equipment being used is matched to the specific roof panel system being installed. Manufacturers routinely rent out this equipment in order to be sure that the metal panel profiles are installed properly and are not compromised through the use of generic equipment or that of another manufacturer. Using the wrong equipment can end up being costly for everyone if panels and seams are ruined in the process.
As metal panels are set in place, they are often secured with metal clips, spaced according to engineering and construction needs. Hand crimpers are used to form the seams around the clips as well as any end laps. This process must not be overlooked as improper hand tooling is the number one cause of faulty seaming. To ensure costly mistakes aren’t made, follow the process described in the “Field Seaming Tool Manual”. This manual should be provided with the equipment and reviewed in training.
The next step will involve the use of an electric seamer which obviously needs a source of electricity to operate. However, not just any electrical power source will do. Almost all professional seamers have an AC/DC motor that will require 10 or 15 amps and 120 volts. A dedicated electrical circuit—preferably from a temporary electrical pole or an existing building electrical panel—is the best and most reliable way to go. A generator with 15 amp capacity dedicated to be used only for the seamer (in order to avoid power surging) may be acceptable as well. In either case, the power line to the seamer needs to be 10-gauge (minimum) cord. It should also be no more than 200 feet long (to avoid power drop).
Electrical power sources that are NOT acceptable include outlets from a powered man lift or a generator that is not dedicated to only the seamer. (This includes a generator that is part of a welding machine.) Check the manufacturer’s requirements for any other restrictions that can damage the seamer. Skipping this step can place the responsibility for repair or replacement onto the installer.
Once all panels are in place, the hand crimping is done and the power source is set. Then, electric seaming takes care of finishing the roofing system. Again, consult the seamer manual for proper procedures, including which direction the seaming should be done. (Seaming can either be done up or down the roof depending on direction of roof installation.) The electric seamer includes a switch for the operator to control the starting and stopping of the process.
On low-slope roofs, the operator should walk alongside the seamer to be sure nothing is in its path and that the seam is done properly. While stopping and re-starting is fine, the seamer should never be removed in the middle of a seam. Doing this makes it very difficult to set it back in exactly the same spot again. If something appears to be wrong with the seamer or the seams being produced, then don’t keep using it. There is no point in damaging multiple roof panels if any one panel indicates that things aren’t going right. In this case, contact the manufacturer right away for assistance or replacement of the seamer.
Electrical seamers are heavy and—if not used and secured properly—can cause harm or injury. Therefore, they should always be tied off with a safety line—the same type used for workers—not a common rope and definitely not the electrical cord. The safety line should be properly secured to the seamer and then attached to something rigid on the building. Never attach this to a person who could be pulled off of a roof by it.
Before use each day, check the electric seamer and remove any oils, debris or dirt. Make sure the seamer is unplugged from the electrical power source before you begin cleaning. Also, check the grease level in the machine daily and only add a little bit (2-3 pumps from a grease gun) as needed. Too much will cause the grease to leak out onto the roofing.
Following these pointers should help assure the safe and efficient use of the right seaming equipment when installing roofing panels. To find out more about proper seaming or to schedule training, contact your local MBCI representative.
Standing seam roof (SSR) systems are built to move, designed to account for necessary—and often substantial—expansion and contraction due to thermal conditions. In fact, for many builders, this fact is one of the main reasons SSRs are such an attractive option.
Even with this expectation baked into the mix, many contractors and installers may still make a wrong turn when tying the SSR into adjacent structures and other building edge conditions. By not allowing for that same expansion and contraction on trims and transitions, problems can ensue.
Fixed and Floating Clips
One main consideration in planning for this movement is the clip type used. Standing seam metal panel clips are designed specifically to interact with their corresponding roof panels in order to allow movement (both interior and exterior) caused by thermal changes. The clips, which are part of the concealed fastening system used with SSRs, provide improved aesthetics in addition to durability and protection from the elements.
The two main options are fixed clips (one-piece) and floating/sliding clips (two-piece). Fixed clips are limited by and dependent on the substrate’s ability to expand and contract with the roof system, whereas floating/sliding clips permit the panels to expand and contract within the clip itself. These clips will allow for greater thermal movement of the panel, which is independent of the substrate while still ensuring the panel remains secured. Regardless of which clip is utilized, you are not going to stop the expansion and contraction. You can, however, have some control of the direction of movement, and, therefore, can address or compensate for the degree of this movement when tied into adjacent structures.
Standing seam roofs with floating/sliding clips require one end of the panel run to be “pinned” and the other end to be “moveable” in order to permit expansion and contraction. The “pinned” point of the system is typically the low eave, although it doesn’t have to be. There will be instances when it becomes beneficial to “pin” the roof at the complicated transition or tie-in point and design the roof system to expand/contract outward from this location. This can eliminate potentially “troublesome” areas from the equation on having to deal with the roof movement, and in turn can make them easier to install and have greater weathertightness success.
With all this in mind, it is important to always check with the manufacturer to determine the best clip and design layout to use with any given SSR system and be aware of how much and in what direction the expansion and contraction is going to occur.
Not only does the building move, but anything it ties into has to be able to permit that movement, e.g., the edges or perimeter of the buildings. Manufacturers can provide both longitudinal and transverse transitions that allow for thermal movement so that when they tie into an adjacent structure it doesn’t restrict the panel from moving. Not adequately compensating for or preventing that movement entirely can lead to potential pitfalls, such as oil canning. It could also lead to fasteners backing out and slotting of holes. Bottom line, any time that we try to confine or restrict the roof from doing what it was meant to do (move!), we inevitably run the risk of damaging the panel not just aesthetically but more importantly, from a weathertightness standpoint.
The Role of Expansion
Issues can arise not just when tying panels into adjacent structures. Because of the roof’s size and magnitude of potential movement, you may/will have to implement expansion/contraction capability of various degrees into the perimeter of the roofing system itself. In these cases, this is why manufacturers offer roof accessories as ridge expansions, edge trim expansions, panel expansions, gutter expansions and other details to account for not only the roof movement but the perimeter trims that are secured from the roof system to the wall system.
Know Your Details
The key takeaway here is to remember that if you’re considering a standing seam roof for a project, then you need to make sure that the designer looks at every detail from the manufacturer and accounts for movement of the roof panel, such as how it ties into adjacent structures or simply how the edge or perimeter of the building is terminating to make sure they permit that expansion and contraction. Know what you’re buying and understand that if the roof you’re purchasing is meant to expand and contract, everything that ties into it has to be able to expand and contract as well.
To find out more about how to correctly install your standing seam roof, contact your local MBCI representative.
Insulated metal panels (IMPs) are “lightweight, composite exterior wall and roof panels with metal skins and an insulating foam core” as defined by the Metal Construction Association (MCA). The outer skin serves as either metal wall siding or metal roofing using standard profiles, while the inner face serves as a metal interior finish or liner. The rigid insulation between the metal skins gives the panels their superior energy conservation properties and also provides a rigid core for extensive spanning capabilities across structural members.
With this basic make-up in mind, here are a few things you should know about using IMPs in a metal building project:
Virtually any building being designed as a metal building should consider the use of IMPs. This includes all types of commercial, industrial, institutional, recreational and government buildings. More specifically, IMPs have been used very successfully on manufacturing facilities, schools, retail centers, offices, warehouses, power plants and many other building types.
Insulated Roofing and Walls Assemblies
IMPs serve as a complete wall or roof assembly. That means they can provide cladding, insulation, a water-resistant barrier, an air barrier, and finished surfaces all in one panelized product – essentially everything but the building structure upon which they are installed. These characteristics are true for conventional buildings as well as for specialty construction types such as the climate controlled processing, storage, or distribution of perishable food or other items. With panel thicknesses commonly available from 3 inches to 6 inches, walls and roofs can be designed to meet the specific thermal performance requirements of virtually any building need.
IMPs are available in a wide variety of colors, widths, profiles and finishes, enabling virtually any aesthetic desired for walls and roofs. Further, architectural IMPs provide the freedom to address building-specific or unique circumstances with options such as custom shapes and widths, special custom colors and finishes, custom fabrication including, but not limited to bent corners, curved panels, and trimless ends. Architectural IMPs also offer options to integrate with windows, louvers, sunshades or other similar products to offer total building envelope solutions.
Most IMPs are fabricated with the intention of working together as a complete system. That means attention has been paid to the design of the edges so the panels can interlock and be sealed to form a continuous joint that is water tight and air tight. In some cases panels may need to overlap, such as on long roof runs over 50 feet, but manufacturers have worked out those details to help assure the roof or wall performs as intended. Based on this, properly-installed IMP systems generally come with a very long warranty period.
Ease of Installation
The fact that IMPs are a single, finished, rigid panel, makes them quicker to install than other multi-product and multi-step assemblies. This translates to obvious labor savings and some material cost savings compared to other systems. Further, the simplified installation process has been shown to limit exposure to accidents, helping create a safer, more efficient work flow. It can also mean that construction time schedules are easier to meet or even beat.
With the great variety on the market, one of the main questions we, as metal roof panel manufacturers, get from customers is “How do I select the right panel for my project?” The answer can generally be found by examining a number of criteria, including the properties of the roof, the region and climate, geometry, slope, warranty type…among other key factors.
Here we will provide a brief overview of the various factors that should be considered when narrowing down the choices.
1. Slope— Slope is the first consideration as just this one aspect will eliminate certain panels, making it easier to narrow down options right from the start. The two types of roof slopes are low slope and steep slope.
- A low-slope roof, commonly found in commercial applications, is one whose slope is less than 3:12. The benefits include a simpler geometry that is often much less expensive to construct, and the requirement of fewer materials than a steep slope, thereby reducing material costs.
- A steep slope roof, more common in residential construction, is one whose slope is greater than 3:12. Steeper slopes are ideal for areas that have higher snow loads and will also prevent the possibility of ponding water on the roof. Since the roof is a visible part of the structure, choosing a metal roof for residential construction often skews more toward aesthetic considerations.
2. Location/Climate— The location and climate of the project is a factor, specifically when looking at certifications/regulatory product approvals, which will limit the panels you can you use within specific regions. This is most relevant to Dade County, the state of Florida, and the Texas Coast, as well as certain snow regions.
3. Specified test standards—Often times, you may need to specify UL 580 or Factory Mutual Insurance Design.
4. Engineering Design—Due to the roof pressure acting on the buildings, engineering design factors eliminate some products because they’re simply not strong enough. This is an area that needs true technical expertise. For that reason, make sure to get a professional engineer to design the roof system in order to determine the correct panel for the project. Also, check with the manufacturer to determine if they have panels that have been tested to certain test standards. If they do not have the testing on a product, that in itself can exclude a particular panel.
5. Geometry—In its most basic terms, roof geometry is an overview of what the finished roof will look like, including special conditions, such as hips, valleys and ridges. The various conditions that go along with specific roof types will determine if a roof geometry is simple or complicated—which will affect the type of panel that can—and can’t—be used. For instance, a Double-Lok® roof panel can be used on a low slope roof—it can go down to 1/4:12. However, if a low roof slope condition has a valley, you may want to avoid a Double-Lok® panel since this product is more difficult to use in a valley situation.
6. Panel type— Panel types can be broken out into two main types: standing seam and through-fastened. The choice of specific product within these general categories depends on a number of considerations, including aesthetics and weathertightness warranties. If your project calls for either standing seam OR through-fastened, that will eliminate about half the types right off the bat.
- Standing Seam Roof Systems
In basic terms, there are four unique styles of metal standing seam panels: Double lock seam, symmetrical seam, one-piece snap-lock interlock and two-piece snap-lock interlock. These styles can be further delineated by seam shape or profile, i.e. trapezoidal rib, vertical rib, square rib and tee rib.
- Through-Fastened Roof Systems
Exposed, or through-fastened panels, are available in a variety of widths, usually from two to three feet wide. They also come in various rib shapes, heights and spacings. Typical gauges are 29 and 26, but they also come in 24 and 22 gauge. There are also structural and non-structural through-fastened panels. Structural panels are capable of spanning across purlins or other secondary framing members such as joists or beams. Non-structural panels must be installed over a solid deck. Through-fastened roofs are best suited to small- and medium-sized metal buildings and residential applications. In both instances, the panel runs are limited to shorter lengths where thermal movement is typically not a problem.
7. Substrate— Examples of substrates are open framing, plywood, and metal deck. Some panels can’t be attached, for instance, to open framing but almost every type of panel can attach to plywood.
8. Required Weathertightness Warranties— If a weathertightness warranty is a requirement, your options are down to the only panels offered with that guarantee—eliminating all the through-fastened panels.
Looking to the Manufacturer for Help
While specifiers need to take that initial look at all the determining factors, the choices can still feel overwhelming. Once you’ve eliminated the panels that surely won’t work, you will still likely be left with many strong choices. The metal panel manufacturer can guide you to that decision. We encourage you to contact the MBCI team of experts to help further narrow down the choices in order to finalize what is the best metal roof panel for your project. For more guidance on finding the right roof panel for your project, stay tuned for our white paper coming soon.
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.
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.
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.