Useful Tool: FM Wind Ratings RoofNav

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.

Best Applications for Water Barrier Standing Seam Metal Roof Panels

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.Water barrier SSR

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.

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