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Roof Membrane Wind Uplift Testing
A meticulously designed and installed standing seam metal roof system provides the building owner with long-term dependability against harsh weather conditions. To do so, manufacturers must conduct a series of extreme weather or wind uplift test requirements for durability and protection against various weather situations involving high winds.
Roof Uplifting Standards
- Underwriters Laboratories (UL) 580
- Underwriters Laboratories (UL) 1897
- Factory Mutual (FM) Global Standard 4471
- American Society for Testing and Materials (ASTM) E 1592
In the most severe weather conditions, metal roofs that have not been rigorously tested will succumb to wind pressure that can force panels to deflect. Causing seams to open and the panels to shift into failure mode at the corners and edge zones. Manufacturers will conduct roof uplift testing to ensure the typical corner and edge zone failure is passed.
The most reliable standing seam roof uplift test is the ASTM E 1592. It is the standard wind uplift test method for the structural performance of sheet metal roof and siding systems by uniform static air pressure differences. Below is a list of critical roof uplift standards we meet to provide our clients with the optimal metal roof design.
Underwriters Laboratories (UL) 580 Roof Uplift Test Method
The UL 580 rating determines the uplift resistance of roof assemblies. The wind uplift test evaluates the roof panel, panel clips, fasteners, and substrate.
- To test, a 10-foot by 10-foot sample of roofing material is installed onto a test platform. The edges are then sealed with closely spaced fasteners and two purlins in the interior.
- Next, the sample is subjected to a static uplift pressure for a 5-minute period and an oscillating pressure in 10-second intervals over a 60-minute period.
Underwriters Laboratories (UL) 580 Roof Uplift Test Considerations
- UL 580 is a pass/fail test and does not specifically determine the wind resistance of the panel assembly.
- It only tests over a specific substrate at a certain clip/fastener spacing.
- The test standard will not indicate how strong the panel assembly is under load.
- Most importantly, the test does not simulate real conditions.
Underwriters Laboratories (UL) 1897 Roof Uplift Standards Test Method
The UL 1897 wind uplift test is a continuation of UL 580 and is the standard for uplift tests for the roof covering systems. The purpose of this roof uplift standards test is to gain uplift resistance data for the panel assembly and evaluate the attachment of the roof covering systems to the roof decks.
- Utilizing a test chamber, this test is conducted by either pulling a vacuum above the assembly or by pressurizing an air bag placed loosely between the deck and the roof covering.
- The test is run to failure, and the results are reported as the highest uplift pressure achieved prior to failure (in psf).
Underwriters Laboratories (UL) 1897 Considerations
- UL 1897 does not consider the strength of the roof deck.
- The method does not necessarily simulate the actual dynamic uplift pressures encountered by roofing systems.
Factory Manual (FM) Global Standard 4471 Test Method
FM 4471, Approval Standard for Class 1 Panel Roofs, states the requirements for meeting the criteria for fire, wind, foot traffic, and hail damage resistance.
This roof uplift standards test sets performance requirements for panel roofs, which includes all components necessary for installation of the panel roof assembly. This includes the potential for fire spread on the underside and exterior of the roof panel. It also measures the ability to resist simulated wind uplift resistance while maintaining adequate strength and durability.
- FM 4471 utilizes a 12-foot by 24-foot section, including the connecting fasteners and clips used in the field. The panels are subjected to increased wind pressures until the assembly fails.
- The ratings are stated as 1-60, 1-90, 1-120, and so on, referring to wind pressure in pounds per square foot (psf).
- This rating is used to apply a classification to roof panels. Class 1 roof panels are rated at 1-90. A safety factor of 2 means the maximum allowable design load is 45 psf.
- FM Global is a non-profit scientific research and testing organization that deals with commercial and industrial property insurance.
- For roofing projects where FM insurance is required, project designers should work closely with the roofing manufacturer to ensure the roofing system complies with FM requirements.
American Society for Testing and Materials (ASTM) E 1592 Test Method
This roof uplift test method provides a standard for structural performance under uniform static air pressure differences and is run to failure to find the ultimate uplift load capacity. This roof uplift standards test measures both panels and anchors. ASTM E 1592 is not a pass/fail test; it merely shows how a roof performs under uniform static load.
Test Method
- A 5-panel-wide sample (10 feet) by 25-foot length is subjected to pressure from underneath to imitate wind load. The sample has intermediate purlin support at varied intervals and covers several spans.
- The pressure is applied to identify slowly developing failures such as seam separations, and to determine the ultimate failure load of the standing seam roof system.
Roof Uplift Standard Testing for Reliable Design
ASTM E 1592 was developed to account for the many complexities of evaluating uplift properties of metal roofing. The test method “provides a standard procedure to evaluate or confirm structural performance under uniform static air pressure difference. This procedure is intended to represent the effects of uniform loads on exterior building surface elements.” (https://www.astm.org/Standards/E1592.htm)
In conclusion, while all the standardized test protocols mentioned above were established to determine the uplift capacities of roof assemblies, only the ASTM E 1592 test is reliable enough for the design of standing seam roof panels. Among its key differentiators, the test considers the roof’s flexibility and changes in shape occurring under air pressure, and it measures both metal panels and their anchors.
Metal Roof Skylight Benefits
The beauty of metal roof system skylights can be a real benefit to the aesthetic value of a metal building project. Beyond looks, though, the proven benefits of daylighting are many: building occupant satisfaction from natural lighting, mold, mildew growth prevention, and, of course, energy savings, to name a few. In fact, once the decision has been made to go with metal for the roofing material, a skylight is often a natural tie-in when it comes to sustainable design—for both form and function. To make the most of the design choice, there are a few key considerations to bear in mind during the specification and pre-installation phases of the process.
Types of Metal Roof System Skylights
Common metal roofing skylight installation involves one of two types of skylights, Light Transmitting Panels (LTPs) and Curb Mount Skylights. Both metal roof system skylights supply natural light into the building and provide similar benefits.
LTPs, which are formed from a translucent material and come in many different panel profiles can be used not only in metal roofs but as an accessory for metal wall panels, too. One of the key benefits of LTPs is that the panel is formed so that it matches the configuration and characteristics of the system into which it is installed, and therefore can work seamlessly with specific metal roof systems.
Curbed (curb mount) skylights include a raised structure (“curb”) formed around the roof opening where the skylight will be attached. Curb skylights come in many shapes and styles.
In addition to the general “type” of the skylight, another consideration is selecting the best orientation for the skylight—which we will look at next.
Skylight installation Metal Roof Placement, Orientation, and Climate Factor
Placement and orientation are some of the most crucial factors in getting the maximum benefit from metal roof system skylights. During the planning phase, determine the best location to achieve optimal light and avoid obstructions (such as HVAC, plumbing, electrical, and vent pipes) below the skylight. In terms of getting the most out of the skylight from an energy-savings standpoint, climate, and exposure are also key factors. For example, with southern exposure, skylights provide an excellent level of passive solar heat during the colder winter months, while keeping cooling costs down during the summer heat. On the other hand, a skylight with western exposure will increase cooling costs if the structure is in a warm climate.
Installation Planning and Timing
Metal roof skylight installation can be installed during or after the roof has been installed, but it is in the best interest of the project to plan for a skylight from the initial stages of the design phase to best accommodate and prepare for the addition of the skylight.
Safety Concerns, Responsibility, and Compliance
Skylights and LTPs should be guarded to protect from fall through the metal railing, nets or some other protection method. Last but certainly not least, it must be stated that it is the user’s responsibility to ensure that the installation and use of all light transmitting panels comply with State, Federal and OSHA regulations and laws, including, but not limited to, guarding all light transmitting panels with screens, fixed standard railings, or other acceptable safety controls that prevent fall-through.
For additional information about skylights for metal roofs, please contact MBCI at (877) 713-6224.
Substrates for Metal Roofing Systems Explained
The substrate or substructure is a key part of the metal roofing system, which rests underneath the metal roof panels. The two types of substrates used with metal roofing systems are open framing and solid substrates (composite or plywood). Its two main functions are:
- It acts as a base to which the metal roof material is attached-securing the fasteners and clips used to hold the panel. (Note: fasteners and clips would be attached to the substructure.)
- It serves as a structural member, transferring the weight of both live (ex: wind, snow, rain) and dead (ex: HVAC units, roof materials, etc.) loads to the supporting joists or purlins.
How to choose the correct Substrates for Metal Roofs?
Substrates for metal roofing system considerations include the assurance of a structurally sound metal roofing base, knowing the type of underlayment required, and how that required support can vary depending upon the type of metal roofing product being utilized.
In its most basic terms, metal standing seam roof (SSR) and through-fastened roof panel systems can be supported on either open framing or solid substrates. The choice will often depend on the type of construction and the purpose of the building, including residential, commercial, industrial, and agricultural applications.
Types of Substrates for Metal Roofing Systems
The two main types of substrates used with metal roofing systems are open framing and solid substrates (composite or plywood).
Open Framing Substrates for Metal Roofing Systems
The open frame substrate uses wood or metal framing members (such as bar joists or min. 16-gauge purlins) to secure the metal roof panels. These members may be individual pieces of wood, formed steel, or truss-like members built from multiple individual pieces. Open-frame substrates for metal roofing systems should be used with structural-style panels in which the design can support the weight and can also span the dimensions of open areas.
Solid Decking Substrates
A solid deck substrate may consist of panels, solid sheets, or closely spaced deck members (made of wood, metal or composite materials) to which the roof membrane is applied.
- Solid decking should be used with non-structural style panels, such as MBCI’s Craftsman™ Series – Small Batten panels. (Note: While structural panels do not require a solid deck, they may be installed over one, depending on preference.)
- Composite deck roof designs may or may not include rigid board insulation as part of the installation.
- Plywood, oriented stranded board (OSB), and individual wood planks can all be used for the construction of a solid roof deck.
Other Considerations
It goes without saying that installers must follow OSHA practices and make sure to follow installation details of the manufacturer. Beyond this common-sense advice, there are other considerations to look at when matching substrate to a metal roof system, such as moisture control and acoustics. For instance, if you’re going over a plywood deck, you would always want to be sure you have a moisture barrier between the wood and the panel; metal decks should have a vapor barrier, and sound transfer through certain substrates could be an issue. It’s always wise to do your research–confirm with the manufacturer, check installation manuals, etc.
The main takeaway here is an awareness that depending on your project’s panel profile, you need to take steps to ensure you have the appropriate substrate. For detailed information on MBCI roof panels and substrates, view MBCI’s standing seam panels.