standing seam roof system 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.

We discussed water shedding standing seam metal roofs in my last post, and the fact that despite their water shedding properties, you still really must guard against water infiltration. Today I’ll discuss water barrier roof systems, which are structural standing seam roofing systems. These panels can withstand temporary water immersion over the panel seams and end laps. They normally have factory applied mastic in the seams to insure weather integrity. End laps, when needed, are installed using high quality tape and/or bead sealant supplied by the manufacturer. The trim designs used with these systems are much more water resistant as well.

The advantage these water barrier SSRS systems offer:

They require no deck. This is a tremendous savings on the in-place roof cost.
Many systems can be installed on roof slopes as low as ¼:12. This allows greater design flexibility and can also save on the in-place roof cost.
Because they are the only thing between the interior of a building and the weather, these are the most tested metal roof systems available. Manufacturers spend a lot of time and money testing these systems for air and water intrusion, dead load, wind uplift and fire.

Water barrier SSRSs can be further divided by seam type—trapezoidal or vertical rib.

Trapezoidal systems usually have a rib height of 3 inches. The most common panel width is 24 inches, although some manufacturers offer them in other widths as well. Trapezoidal systems are traditionally thought of as commercial or industrial standing seam systems. They are used on warehouses, factories and buildings where the roof is not meant to be seen from the ground. However, some designers have taken these systems and incorporated them into architectural applications with stunning results.

But be careful. Trapezoidal rib systems are much harder to seal at hips and valleys than vertical rib systems. The outside closures at the hip must be cut on a compound bevel with a trapezoidal system. At a valley, the panels are harder to seal because they require an inside closure; the vertical rib panels do not.

Vertical rib systems have traditionally been thought of as non-structural. However, there are now many vertical rib systems available that can span purlins or joists. These systems are available in a wide variety of panel widths, ranging from as little as 10 inches to as much as 18 inches wide. Rib heights vary from 1 foot to 3 feet.

Vertical rib systems are usually easier to install than the trapezoidals. There are fewer parts to the typical vertical seam system, which makes for a simpler, quicker installation. Because there are no inside closures, valleys are much easier to seal and quicker to install. Hips are easier to seal because the outside closures can be cut quickly and simply from a stock length of zee closure.

For these reasons, the vertical rib systems are often a better choice for applications on high-end architectural roofs. Ask just about any metal roof installer, and he will tell you that he prefers the vertical rib system over the trapezoidal system in this application.

Bottom line, when selecting a roof system, choose function first, then aesthetics. When you use the wrong roof system for a given function, the installation process becomes complicated, and results less than ideal. With so many great metal roof options, don’t make life more complicated and uncertain than it need be.

And to make things simple, safe and sound, choose from MBCI’s array of metal roofing system products. Find out more.

Tag: standing seam roof system

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