wind design loads Archives

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.

Uplift resistance testing with UL 580 test platform.

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.

MBCI research and development team performs ASTM 1592 wind uplift tests. The wind pressure forces the panels to deflect, pushing the center of the panel above the seams.

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.

The concept of testing materials and assemblies in buildings has been around since the late 1800s, when John R. Freeman initiated Factory Mutual Laboratories (now known as FM Approvals) to test fire protection systems. Since then, the use of FM-approved building components and assemblies has become recognized as an accepted safety standard for insurance companies, building inspectors, design professionals, and building owners. In the case of roofing systems, FM is particularly well known for determining how roofing performs not only for fire, but also for high wind. In fact, it is unique among other testing laboratories in the way that it performs wind uplift testing – it uses full-scale roof sections measuring 12 feet by 24 feet to obtain an accurate view of expected real-world performance. Further, it tests not only individual products, but full assemblies. In the case of metal roofing, for example, that would include the metal roofing panels, the fasteners (e.g., screws), EPDM washers, seam sealant, and any insulation, all as attached to a specific roof deck or structure.

Is it Approved by FM?

To find out if a roofing product or assembly has been approved by FM based on its independent testing, the best place to look is on the FM roof navigation website, known as RoofNav. Registration is free and offers access to FM’s fully searchable, comprehensive database.

How to Use FM RoofNav

Here is a quick overview on using the website:

My Projects Tab: The opening page is on the “My Projects” tab, which welcomes the user to RoofNav and lets a registered user save and return to specific data searches.
Product Search Tab: The second tab at the top of the web page is labeled “Product Search,” and allows a user to enter information under search criteria based on a manufacturing company and/or a trade name, as well as selectable roofing categories (such as “cover”) and subcategories (such as “composite panel cover”). Clicking on the “search result” sub-tab will show all of the corresponding products tested, and their approved uses. If a specific manufacturer, such as MBCI, is entered in the search criteria, the results will show only for that manufacturer. Clicking on a particular result will open detailed specifications and information for that product.
System Search Tab: If a particular system is being sought, such as a fastening system or vapor retarder system, the “search criteria” portion under this tab can help narrow things down by name, type, and products.
Assembly Search Tab: Since the real performance of a roof is based not on a single product or system, but an entire assembly, it is possible to search either by “classifications,” using basic criteria, or by “specifications,” which allow a detailed roof assembly to be created. Either method will produce a list of “search results” that can be clicked on to get more details. This is likely the most useful tab when looking to determine if a total roof assembly will meet the wind uplift rating needed for a particular project, but it does require that the proper details are input.

The website also contains a number of very helpful ways to assist a user. A tab for a “ratings calculator” allows flexibility in the amount of information entered; a tab for “reference materials” provides drop-down assistance with tools such as a “quick-start guide.” Links for “help,” “support,” and “training” appear at the top of the page, along with a quick-search portal where a known FM assembly number can be entered and found directly.

The RoofNav tool is a great resource for anyone who wants to find out test-result information about any one or a series of roofing products, systems, or assemblies, and can be a go-to resource for contractors, designers, and specifiers of roofing systems of all types.

Tag: wind design loads

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