Did you know that roof failures are the largest hurricane loss due to wind and water damage? Metal roofing is highly recommended for the locations that deal with hurricanes and high force winds as well as other weather conditions including hail, fire and ice. Metal roof panels from MBCI are designed to meet the unique needs of Florida home and business owners.
Able to resist and withstand the extreme environmental conditions that Florida is known for, MBCI’s metal wall panels and roofing systems offer better long-term cost benefits and lasting up to three times longer than asphalt shingles. With Miami-Dade County’s strict product approval and testing processes in place, you can have peace of mind that metal panels from MBCI meet requirements.
MBCI’s standing seam metal roof systems are one of the most durable and weathertight roof systems available in the industry.
Miami-Dade County Approvals
In order for your metal panels to be compliant for structures in Miami-Dade County, all panels for both roof and walls are tested to specific test standards. In addition to submitting an application, test reports are also required to move forward with the approval process. Third-party testing is required for verification.
Metal Building Panel Approval Process
Prior to submitting a metal building for approval, multiple steps must be taken to configure and test your panels. Each unique panel configuration requires its own testing.
Approval for a product is based on one profile, one gauge and several spans. The design pressures can be used in the field, corners and perimeters or interior and end zones. If a panel manufacturer offers the same panel profile in a thicker gauge, that material can be included in the approval, but they will be limited to the design pressure of the thinner gauge. Three samples of each configuration must be tested and differ no more than 20% when results are determined. The end goal of testing is to determine design loads for the panel system at a specific span.
There are separate requirements for the testing and approval of structural steel members and frames.
Why Install MBCI Metal Panels
UL 580 Class 90 Wind Uplift Resistance
Designed for Florida
UL Class 4 Hail Impact Resistant
Class A Fire Ratings
ENERGY STAR® Certified Colors
Miami-Dade County Approved
Insurance Discounts Available
Miami-Dade County Approved Panels
Florida has implemented stricter building codes to help prevent hurricanes and wind loss. Some of the toughest codes include Miami-Dade County and Florida Building Code. MBCI offers a wide selection of products that surpass the necessary ratings. Our Miami-Dade approved panels include PBR, 5V Crimp, Craftsman™ Series – Small Batten, DoubleLok®, CFR and most insulated metal panels. For more information on MBCI’s metal roofing and wall products, speak to your sales representative or visit our website at MBCI.com.
Performance-based building product testing and accreditation is a critical piece of just about every aspect of construction—affecting everyone from the manufacturer to the installer and ultimately to the owner and occupant. These certifications ensure real-world property loss will be prevented and provides protection when certified products are installed correctly.
With roofing being such a vital part of any building project, roofing manufacturers must take certifications for roofing products (in this case, metal roofing products) very seriously. Below, we’ll give a brief overview of the main certifications that we—and other metal roofing companies—test to and are audited for in order for the overseeing bodies to confirm that we’re producing what we’re testing it to. In the simplest terms, these specifications, such as UL or FM, will give the contractor peace of mind that he or she can provide what is spec’d.
At MBCI, we have several certifications through which we have ratings. These include:
1. UL (Underwriters Laboratories).
UL certifies roofing materials and roof assemblies for fire performance, hail resistance and/or resistance to wind uplift. Roof deck assemblies are investigated for performance under internal fire exposures and for uplift resistance. MBCI does a good deal of testing and we have UL constructions for many of our roofing products. We get the UL construction number, impact ratings and fire ratings. UL does quarterly audits in the manufacturing areas to make sure that we’re producing the panels the way we test.
2. IAS (International Accreditation Service) certification.
IAS accreditation programs are based on recognized national and international standards that ensure acceptance of its accreditations. To meet this standard, MBCI is “Part B” of the process, as we are responsible for the components. The auditor comes in to certify that we do what we say we do. Once IAS accreditation requirements are met, the company receives a certificate of accreditation.
3. FM (Factory Mutual) approvals.
MBCI has three roofing products that are FM approved for wind uplift standards, hail resistance, internal and external fire ratings. For each, we test the product and FM comes out yearly to do an audit.
This is an example of FM wind uplift testing.
4. Dade County roofing product approvals.
Miami-Dade and Broward Counties are classified as High Velocity Hurricane Zones (HVHZ), which are rated as 150 mph plus winds. It is Florida’s highest rating. An updated testing approval process has been instituted for building products and materials used in these counties. The purpose is to mitigate damage caused by wind-borne debris resulting from hurricane-force winds. MBCI does testing and this stringent certification is applicable for anything that ships into Dade County or Broward County in Florida. Product Notice of Acceptance can be located on the Miami-Dade website for roof and wall panel systems that are Dade County approved.
Safety and performance are the most important goals. All in all, these certifications ensure that we, the manufacturer, are doing our job and that customers are getting everything they’re paying for. For more information on MBCI’s product testing, please contact a sales representative.
Metal roof and wall panels have many test standards they must meet under certain environmental conditions. Test standards that are specified for metal panels in our industry are ASTM E283 (air leakage) and ASTM E331 (water penetration) for wall panels, and ASTM E1680 (air leakage) and ASTM E1646 (water penetration) for roof panels. While the corresponding tests are similar, the orientation of the panels is a little different for the wall and roof panels. Here we’ll take a brief look at these testing protocols and what they mean for the integrity of the metal panel system at hand.
For air leakage tests, the protocol has been to test at a specified pressure. It should be noted that some manufacturers have changed it from the standard as many in the market are testing at a higher pressure. And while it’s true that you are going to have air pass through, you want the air to be minimized. Air leakage is tested in terms of cubic feet per minute, with a lower number indicating a better, more efficient product. For water penetration testing, water is sprayed and is tested for the water getting through the seam or side lap of the panel system.
The purpose of air leakage and water penetration testing is to establish air and water infiltration rates on the referenced test specimen in accordance with ASTM E283 and ASTM E331.
Metal Wall Testing Standards
As indicated above, the wall test standards are: ASTM E283 (Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences Across the Specimen) and ASTM E331 (Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference).
The procedure for ASTM E283 is as follows: 1. Seal off test unit and measure air leakage (extraneous leakage); 2. Unseal test unit, then re-measure (total system); 3. Subtract extraneous air from total air = Performance.
According to ASTM, this test method is a “standard procedure for determining the air leakage characteristics under specified air pressure differences at ambient conditions.” Furthermore, the air pressure differences across a building envelope can have significant variation with numerous factors acting to affect air pressure differences relative to the particular building environment. For instance, the test method described is for tests with constant temperature and humidity across the specimen. These factors should be considered when specifying the test pressure differences to be used.
Additionally, rates of air leakage are sometimes used for comparison purposes but these comparisons would only be valid if the tested/compared components are of essentially the size, configuration, and design.
Using a Pass/Fail criteria, “Pass” results of this test indicated that water did not penetrate through control joints in the exterior wall envelope, joints at the perimeter of openings, or intersections of terminations.
The laboratory test procedure for ASTM E331 dictates that the test is conducted for a specified duration with water applied at 5.0 gal/ft 2 hr. at a specified pressure. The test has applied pressure and water spray for a period of 15 minutes.
According to ASTM, this test method is a “standard procedure for determining the resistance to water penetration under uniform static air pressure differences.” Furthermore, in applying the results of tests by this test method, ASTM points out that “the performance of a wall or its components, or both, may be a function of proper installation and adjustment. In service, the performance will also depend on the rigidity of supporting construction and on the resistance of components to deterioration by various causes, vibration, thermal expansion and contraction, etc.,” noting that exact simulation of real-world wetting conditions can be difficult (i.e., large wind-blown water drops, increasing water drop impact pressures with increasing wind velocity, and lateral or upward moving air and water) – and that it may depend to some degree on the design.
Metal Roof Test Standards
The Roof Test Standards are ASTM E1680 (Standard Test Method for Rate of Air Leakage Through Exterior Metal Roof Panel Systems) and ASTM E1646 (Standard Test Method for Water Penetration of Exterior Metal Roof Panel Systems by Uniform Static Air Pressure Difference).
According to ASTM, test method E1680 covers the determination of the resistance of exterior metal roof panel systems to air infiltration resulting from either positive or negative air pressure differences. The test method described is for tests with constant temperature and humidity across the specimen. (This test method is a specialized adaption of Test Method E283.)
ASTM literature explains that variables such as the slope of the roof and other factors can affect air pressure differences and, therefore, affect the implications of the resulting air leakage relative to the environment within buildings. Just as with wall panels discussed earlier, these factors need to be taken into consideration when specifying the test pressure difference to be used.
ASTM describes its E1646 test method as a “standard procedure for determining the resistance to water penetration under uniform positive static air pressure differences, and simulates win driven rain imposed on sidelaps and rain that is free to drain while building a water head as it flows.” For this test method, the slope of the roof is a significant factor.
According to ASTM, this test method covers the determination of the resistance of exterior metal roof panel systems to water penetration when water is applied to the outdoor face simultaneously with a static air pressure at the outdoor face higher than the pressure at the indoor face, that is, positive pressure. (This test method is a specialized adaption of Test Method E331.)
To learn more about MBCI wall and roof panels, please visit www.mbci.com.
Are you involved with a building project along the Gulf Coast of Texas in which metal roofing or siding is involved? If so, obtaining a building permit may be subject to compliance with the Texas Department of Insurance (TDI) Windstorm Inspection Program. Here is some information that can help.
What is the TDI Windstorm Inspection Program?
In 1987, the Texas Legislature enacted HB 2012 with a requirement to mitigate losses to structures due to hurricanes along the Texas Gulf Coast. On January 1, 1988, the Texas Department of Insurance (TDI) began administrating the Windstorm Inspection Program in support of this legislation. The program is centered in Austin, with four other field offices also located along the Gulf Coast.
Where does the TDI Windstorm Inspection Program apply?
The Windstorm Inspection Program applies to all commercial and residential structures located primarily along the Gulf Coast of Texas. TDI has designated specific areas as catastrophe areas, also known as Texas’ First Tier Countries. The affected countries include Aransas, Brazoria, Calhoun, Cameron, Chambers, Galveston, Jefferson, Kenedy, Kleberg, Matagorda, Nueces, Refugio, San Patricio, Willacy and certain cities east of State Highway 146 in Harris County (La Porte, Morgan’s Point, Pasadena, Seabrook, Shoreacres).
Designated Catastrophe Areas
What is the Texas Windstorm Insurance Association?
The designated catastrophe areas often use Texas Windstorm Insurance Association (TWIA) as the insurer of last resort for the wind and hail portion of their building insurance. To qualify for wind and hail insurance through TWIA, all new structures plus any alterations, additions, or repairs to existing structures (including re-roofs or roof repairs) located in the designated catastrophe areas must be constructed and inspected according to the building specifications adopted by TDI.
How are Building Permits Affected?
All building work needs to meet the requirements of the adopted building codes in Texas (currently the 2006 version of the International Building Code and the International Residential Code). However, in addition to the codes, the TDI requirements must also be complied with in the designated countries. This is similar to other parts of the country that experience severe weather events (e.g., Dade County, Florida) where additional requirements above the code have been instituted for safety reasons. At the time of building permit application, evidence will need to be shown of TDI compliance in design documents; therefore, many times the local TDI office is contracted first and an application is submitted (Form WPI-1). Then, during construction, a TDI certified inspector (usually an engineer) will inspect the work, as will the regular building inspectors. Compliance will need to be shown with the TDI requirements (Form WPI-8) in order to obtain final sign off and a Certificate of Occupancy.
What Building Products are Approved for Use?
In order to be compliant with TDI standards, building products must be independently tested and shown to be able to withstand different levels of severe weather. For products like metal roofing and siding, the testing needs to include the method of attachment and the substrate type (metal, wood, etc.). Product evaluations are available by product type (such as “Exterior Coverings” for metal siding or “Roof Coverings” for metal roofing) and then by manufacturer all by either contacting a local TDI field office or on TDI’s website: www.texas.gov/wind/prod/index
Metal building panels, whether for roofing or walls, are manufactured with a long-lasting and durable finish of different types and in many colors, allowing the panels to hold up and look great for decades. However, once they get to the building they may need to be cut to fit a field condition, or they may need to be cleaned either during or after installation for any number of reasons. Innocently doing either, without understanding that doing it the wrong way could compromise the integrity of the finish, can be disconcerting at best or warranty-buster at worst. Here are a few tips for the proper cutting and cleaning of metal panels.
Cutting Metal Panels:
Field cutting of panels is certainly allowed and acceptable to manufacturers and is common, particularly at framed openings. However, there are two things to pay attention to here:
Cutting Method: If field cutting is required, the panels must be cut with nibblers, snips or shears to prevent edge rusting. Do not cut the metal panels with saws, abrasive blades, grinders or torches. Abrasive saw blades, grinders and torches can leave irregular or rough edges that are no longer coated or finished, thus causing rust and corrosion.
Corrosion on this panel edge is due to an abrasive saw blade cut.
Cutting Location: All cutting of metal will produce fine particles, or swarf, that will fall from the cut. If this swarf falls on the roof, it can cause permanent staining and, if enough of it accumulates in one place, it could rust completely through the metal roof panel. Therefore, never cut metal panels on the roof or over other metal panels. It is best to cut the panel down on the ground where the swarf can be captured and disposed of.
Accumulated swarf from cutting is staining this metal panel.
Cleaning Metal Panels:
Metal panel manufacturers will usually provide information and directions for cleaning. A typical set of cleaning recommendation follows, based on a progression of cleaning levels—start with number 1 and work your way down the list for tougher jobs.
For simple cleaning, water and mild detergent will often be all that is needed. However, bleach should never be used, since it can change the finish color or interact disastrously with certain metals.
For water-soluble dirt or other deposits requiring more complete cleaning, a solution of hot or cold water mixed with detergent is appropriate. In a container of water, use a 5 percent solution of commonly used commercial (non-industrial, non-bleach) mild detergent, so as not to have any deleterious effect on the painted metal surface. Use a cloth or a soft-bristle brush for application of the cleaning solution, followed by an adequate rinse with clean water. Alternatively, pressure-washing with a 40° tip is also an option.
For non-water-soluble deposits such as tar, grease, oil and adhesives, a solvent or alcohol-based cleaner may be required. In this case, since most organic solvents are flammable and/or toxic, they must be handled accordingly. Generally, keep them away from open flames, sparks and electrical motors. Use adequate ventilation, protective clothing and goggles, and read the manufacturer’s Material Safety Data Sheet (MSDS) of any solvent used for any other specific safety details. The following are among the cleaners recognized by manufacturers for this type of non-water-soluble cleaning:
Alcohols
Denatured alcohol (ethanol)
Isopropyl (rubbing alcohol)
Solvents
VM&P naptha
Mineral Spirits
Kerosene
Turpentine (wood or gum spirits)
Regardless of the level of cleaning required, never use wire brushes, abrasives, or similar tools that will abrade the surface coating and leave scratches or other finish damage and lead to corrosion. Further, keep in mind that any misuse or abuse of any of the acceptable cleaning agents will automatically void any manufacturer’s warranty for the affected surfaces.
By using the tips above to properly cut and clean metal panels, installers can avoid the problems of corrosion, staining or other surface damage. Thus, the integrity and beauty of the finish is maintained without any impact on the warranty. To learn more about metal panel finishes, cutting, cleaning and warranties, contact your MBCI representative.
While metal roofing is often used because of its resiliency, strength and longevity, there are circumstances under which corrosion and other reactions can become real issues, to the great detriment of the system’s performance and life cycle. Some basic knowledge and awareness of common causes of galvanic corrosion (also called “electrolytic corrosion”) from the use of certain dissimilar metals, can go a long way in mitigating potential problems.
Lead and Copper with Metal Roofing
Lead from pipe penetrations can deteriorate the metal.
Lead and Copper are the biggest culprits when it comes to shortening the service life of metal roofing due to corrosion. It almost goes without saying to make sure these metals don’t come into contact with the roof, specifically roofs with Galvalume Plus products. Here we’ll take a brief look at some of the common problems that can arise.
Due to the high probability of corrosion, it is not advisable to use lead roofing products, such as lead roof jacks for pipe penetrations.
Additionally, graphite, which is the primary material in the common pencil, is extremely corrosive to aluminum and aluminum alloys. Therefore, it is not advisable to write on a metal panel with a graphite pencil. In time, the element will eat through the coating and it will rust out. Eventually, you’ll actually be able to see whatever you wrote on there (that’s not what you want!). Instead, using a Sharpie or a grease pencil will solve the problem with little to no effort.
Chemical damage caused by corrosion and other reactions.
Copper is another metal that does not react well with galvanized metal panels used in many metal roofing systems. Contact between copper parts and metal roofing can greatly increase the likelihood of corrosion. Some specifics to keep in mind:
Don’t use treated lumber, which has copper in it. Sometimes, an installer will set some type of treated lumber post and place something on top of it.
Copper in condensation can eat through metal, damaging the structure.
Over the course of a year or even a few months, the panel will face deterioration at that spot since once moisture invades it will corrode the panel due to chemical reaction. A possible solution to avoid this scenario if treated lumber or a lightning system with a cable is needed is to ensure the cable has aluminum instead of copper.
Another situation where copper can be an issue is with an AC unit on the roof. The AC unit may have copper in the coils, and when condensation drips out on to the roof with copper in the water, those drips onto the metal roof will cause corrosion. The solution in this case would be to install PVC piping all the way up the roof so the copper does not make contact.
Conclusion
An understanding of these and other potential corrosion pitfalls that exist from using dissimilar metals and knowing the basics behind galvanic reactions will provide a solid basis for the smart, proper selection of roofing installation metals. With this knowledge in hand, problems can be eliminated before they occur, which in turn can save time, money, and resources, not to mention meeting the all-important goal of extending the life of the metal roof.
If you’re reading this article, then you are probably already aware that metal roofing can provide many benefits, including longevity, durability and water shedding—not to mention the aesthetic features of today’s metal roof products. When specifying a metal roof system, choosing the correct panel is a key factor. Roof slope is critical in determining that choice. Let’s take a look at some of the main things to consider when choosing a metal roof panel with regard to roof slope, including building codes, minimum slope requirements and typical applications.
Building Codes
Building codes are perhaps the most important driving force dictating the roof slope to choose. Different types of roofs have distinct specifications for installation. According to the 2012 International Building Code (1507.4.2 Deck slope), minimum slopes for roof panels need to comply with the following:
The minimum slope for lapped, non-soldered seam metal roofs without applied lap sealant shall be three units vertical in 12 units horizontal (25-percent slope).
The minimum slope for lapped, non-soldered seam metal roofs with applied lap sealant shall be one-half unit vertical in 12 units horizontal (4-percent slope). Lap sealants shall be applied in accordance with the approved manufacturer’s installation instructions.
The minimum slope for standing seam of roof systems shall be one-quarter unit vertical in 12 units horizontal (2-percent slope).
Minimum Roof Slope Requirements
Depending on the roof profile, there are minimum roof slope requirements for each panel, which need to be considered. The profile refers to the shape the metal sheets take when they bend to form panels. Metal roof slope is expressed by a ratio indicating the roof pitch, which notes the vertical rise of the roof (in inches) for every 12 inches the roof runs horizontally—in other words, dividing the vertical rise and its horizontal span. The most common slopes are: 3:12, 1/2:12 and 1/4:12. When looking at metal roofing panel, you will need to consult with the manufacturer to ensure that the metal panel you selected will work for your application.
Applications: Low Slope or Steep Slope
Commercial Application– Low Slope Roofs
A low-slope roof is one whose slope is less than 3:12. Low slope roofs have several benefits. They have simpler geometry that is often much less expensive to construct and low slope metal roofs require fewer materials than a steep slope, which reduce material costs. Metal roofing panels are excellent solutions for roofs with low slopes. Commercial roofs are typically low slope (less than a 3:12 slope), and larger than residential roofs. This is due to low slope metal roofs being a bit easier to build on large structures.
Cecilia Junior High in Cecilia, Louisiana uses 7,180 sq. ft. of MBCI’s SuperLok®. This panel requires a minimum slope of 1/2:12.
Residential Application– Steep Slope Roofs
A steep slope roof 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. When it comes to residential construction, your roof is a visible part of the structure. Choosing a metal roof for residential construction involves choosing a panel profile that will be aesthetically pleasing.
It is common to use steep slopes in residential applications, such as this home in Guntersville, Alabama that utilizes MBCI’s LokSeam® (requiring a minimum slope of 3:12).
Conclusion
Regardless of whether you’re choosing metal panels for a commercial or residential structure, slope matters. Following common standards, doing your research and paying attention to manufacturer guidelines regarding minimum slope will ensure you’re reaping the full benefit of your metal panel selection.
With building code compliance and sustainable building envelopes at the forefront in today’s marketplace, spray polyurethane foam insulation (SPF) applied to single skin metal roof and wall panels is an alternative to insulated metal panels with a manufacture-applied polyurethane foam core. SPF insulation improves a building’s energy efficiency and provides thermal, air and vapor barrier capabilities.
What Is Spray Polyurethane Foam (SPF) Insulation?
SPF insulation consists of isocyanate and polyol resin that is chemically combined and applied to surfaces using a spray gun. SPF insulation can be open cell or closed cell. Open-cell foam provides insulation and air sealing for a building, but is water and vapor permeable. Closed-cell foam provides better insulation than open cell and also functions as an air barrier. Closed-cell foam differs from open cell in that it prevents water entry, minimizes moisture vapor permeability and decreases air leakage, making it the preferred insulation to apply to metal panels.
Spray Polyurethane Foam Insulation with Metal Panels. Image courtesy of Spray Polyurethane Foam Alliance
SPF insulation is well suited for use as interior insulation for metal wall and through-fastened metal roof panels. The traditional thermal insulation layer—one or two layers of batt insulation with a facer—has its intricacies; for example, compressed areas and difficulty taping seams at edges and penetrations for air barrier performance. But because of SPF’s inherent physical characteristics and spray application method, SPF overcomes many obstacles.
8 Application and Safety Tips for SPF
Using SPF to fully insulate and seal a building with metal panels can have unintended consequences if the material characteristics and project parameters are not well thought out. The Metal Construction Association (MCA) recently conducted research with the Spray Polyurethane Foam Alliance (SPFA) and published their findings in a technical bulletin. It includes the following best practices and considerations for installing SPF.
Image courtesy of Spray Polyurethane Foam Alliance
Utilize a certified foam spray technician to ensure the insulation meets the desired thickness, density and adhesion.
Only apply SPF to clean, dry areas.
SPF should not be used on standing seam metal roof panels because it may restrict the thermal movement of the panels, causing distortion.
Follow a “picture frame” application technique, further detailed here, to prevent SPF from getting between girts and metal panels, causing deformation.
Notify other contractors, including HVAC and electrical, to ensure necessary precautions are made.
Follow building code requirements for fire protection because in some instances SPF may meet thermal barrier requirements.
Prevent SPF chemicals from being drawn into a building’s ventilation system during and after installation. There may be a mandated wait time before other occupants can reenter the space.
Consult with your metal panel manufacturer before applying SPF.
Among the most important factors to account for when specifying a standing seam metal roof are wind control and wind uplift. It is imperative to take the necessary measures to ensure the safety and efficacy of the metal roof. The wind clamp—an extruded piece of aluminum that is placed on the panel seams at clip locations—is one accessory that can be used to improve wind uplift characteristics on metal roofs, delivering substantial time and cost savings as these devices help mitigate risk of wind uplift and improve overall wind design.
Standing Seam Panel Deflection as a Result of Wind Uplift
Why Use a Wind Clamp
A typical failure mode of a standing seam metal roof panel is the clip top pulling out of the panel seam when the panels are subjected to high winds. With a standard install of a standing seam panel, the seams just fold into each other. With enough pressure, wind will force seams to come apart—be it a vertical failure, horizontal movement of the seam or from clip disengagement. The clip top can then pull out of the panel seam.
The wind clamp resists the panel seam being opened, allowing for higher uplift loads. The purpose of wind clamps, in fact, is to prevent failures at the seam openings due to any deflection of the panel. The wind clamps provide more strength, thereby dramatically improving wind uplift performance.
The clamp is installed over the panel seam at clip locations, in the edge and corner zones of the roof. This allows the roof to resist the higher wind pressures in these zones, usually eliminating the need for additional purlins or joists. On large roofs, the savings can be substantial.
Another benefit is shorter installation time. Since additional purlins or joists are typically not required at the edge or corner zones of the roof, the building can be erected faster.
Choosing Wind Clamps
When choosing the type of wind clamp, it is important to consider the type of panel and the special features of the clamps. MBCI, for example, uses S-5!’s patented wind clamps, which work for two panel types—Ultra-Dek® and Double-Lok®. The S-5! wind clamps do not penetrate the steel, thereby eliminating the risks of corrosion and water leakage that can be introduced by a hole in the steel. Since the screws are hidden from the weather elements, it helps to maintain waterproofing.
Quantitative Difference with Wind Clamps
One of the biggest benefits of using wind clamps in the edge and corner zones is that usage minimizes the quantity of purlins needed, resulting in substantial cost savings. For example, let’s look at a comparison using MBCI’s Double-Lok 24” – 24 ga. panels with and without wind clamps.
In this example:
The use of wind clamps in the edge and corner zones eliminated 3,800 linear feet of purlins.
Assuming 8” x 2-1/2” Zee 14 ga. purlins were used, there would be a cost savings of $10,400.
Conclusion
Utilizing wind clamps to protect the investment of a standing seam metal roof can increase strength, make installation faster and lower overall cost.
One of the most important requirements for metal roof installation is ensuring that a roof stays in place when the wind blows. The core concept is that the roof’s wind resistance needs to be greater than the wind loads acting on a building’s roof. Wind resistance is most commonly determined by a physical test; wind loads are calculated.
Calculating Wind Loads
Wind loads are based on the design wind speed (which is based on the geographic location of the building), height of the roof, exposure category, roof type, enclosure classification and risk category. The height of the roof, and exposure and risk categories are factors that are used to convert design wind speed to an uplift pressure. Wind speed maps and the rules to calculate wind pressures are found in Section 1609, Wind Loads, in the 2012 or 2015 IBC. The information is based on an engineering standard written by The American Society of Civil Engineers, “ASCE 7-10, Minimum Design Loads for Buildings and Other Structures.”
Defining Exposure Risk Category
Exposure categories relate to the characteristics of the ground, such as urban and suburban areas or open terrain with some obstructions or flat areas like open water. There are 4 risk categories. Category I is low risk to humans, such as agricultural facilities. Category III includes, for example, buildings for public assembly, colleges and universities, and water treatment facilities. Category IV includes essential facilities like hospitals and police stations. Category II is everything else—most roofs are Category II. A building shall be classified as enclosed, open or partially enclosed. The enclosure classification is used to determine the internal pressure coefficients used to calculate design roof pressures.
Determining Wind Pressures
Contractors should work with a structural engineer or the metal panel manufacturer to determine the wind pressures for each roofing project. Wind pressures are determined for the field of the roof, the perimeters and the corners, where loads are largest. Only after determining the design pressures can the appropriate metal panel roof system and attachment requirements be designed.
Testing Uplift Resistance
Physical tests are the most common method to determine uplift resistance. Panel width and profile, metal type and thickness, clip type and frequency, type and number of fasteners, and the roof deck contribute to the uplift resistance of every metal panel roof system. Metal panel roof systems installed over solid substrates (with concealed clips or through-fastened) can be designed using the following test standards: FM 4471, ASTM E 1592, UL 580, or UL 1897. Metal panels installed over open framing can be designed using either ASTM E 1592 or FM 4471. Manufacturers run these tests; uplift resistance data is available for most metal panel roof systems. Installers can get this data directly from manufacturers or from web-based listing services provided by FM and UL.
Designing a Legal Metal Roof System
Wind loads and wind resistance information is necessary to verify code compliance. Get it for every project you install! Using systems that not only have been tested to the correct tests, but using systems that have uplift resistance greater than the design loads is key to a successful installation, and quite frankly, key to installing legal roof systems.
