FM Approvals Provides Free Access to RoofNav®

Feb. 19, 2007

By Richard L. Fricklas

This headline assumes a great deal. First, it assumes that you know who (or what) FM Approvals is. Secondly, it assumes that you know what RoofNav is (and why were they charging for it in the first place).

You are probably aware of a property insurance organization called FM Global. In 1999, FM Global was formed through the merger of Factory Mutual and several commercial property insurance companies, and became one new company. FM Approvals is a business unit of insurer FM Global. As a Nationally Recognized Testing Laboratory (NRTL), it tests, certifies, and approves products and services for property conservation. FM Approvals’ work helps support FM Global’s focus on helping its policyholders prevent property losses or reduce their impact.

Class 1
Over the years, FM Approvals has been the accepted leader in the testing and approval of commercial roofing systems, especially when installed over steel roof decks. For certain tests of roofing materials, FM Approvals uses a calorimeter (a fire-test device that determines fire performance of the roof assembly when a building suffered from an under-deck, interior fire exposure).

Successful steel deck roofing assemblies are rated Class 1, which indicates that if the roof was constructed as tested and approved by FM Approvals, it is an acceptable insurance risk from an internal-fire viewpoint.

Because the calorimeter tests are reasonably priced and correlate well with real building fires, Class 1 became a benchmark for commercial roofing. Within the industry, the term “FM Approved” became synonymous with "the Good-Housekeeping Seal of Approval."

Wind Rating?
Wind loss can be especially catastrophic for the building owner, as well as an insurance company, because when the roof fails due to a windstorm, the interior of the building is exposed to the elements. Interior damage and inventory loss (combined with business interruption) are major disasters indeed.

Based on studies of roof failures at FM Global-insured locations, FM Approvals developed a pressure test to predict wind-uplift resistance. It was a fairly straightforward test machine measuring 5 feet by 9 feet, in which the roof assembly was subjected to positive air pressure from the bottom (interior) side. Tests were conducted in steps; the minimum requirement was that the assembly would resist 60 pounds per square foot (psf) for 60 seconds. If it did, FM Approvals would rate it as 1-60, with the 1 representing the fire resistance (Class 1) and the 60 indicating 60 psf resistance under the test conditions. In keeping with good engineering practice, FM Approvals applies a safety factor of 2 to the tested value, indicating the system would be recommended for use on buildings with an actual field of roof pressure of 30 psf or less. Systems that passed the test requirement of 60 psf could continue to be tested stepwise to 75, 90, and higher. The 1-90 classification was adopted by the roofing industry as being quite prestigious and heavily promoted because, originally, it was the highest rating available from FM Approvals.

Analysis of wind losses indicated that blow-off almost always started at corners and perimeters of buildings. Wind tunnel modeling and instrumentation of real buildings verified that corners could be subject to 2.6-times as great an uplift force as the interior of a roof area, and perimeters were roughly 70-percent higher.

FM Global reacted to these observations by implementing a series of recommendations requiring higher wind resistance in both the corners and perimeters. More recently, FM Global also acknowledged that blow-off of perimeter edge metal was a major contributor to roof failure. This information was added to some of FM Global’s roofing-related Property Loss Prevention Data Sheets, which provide users with engineering guidelines to prevent or reduce the likelihood of property damage. While FM Approvals’ ratings were primarily intended to help guide FM Global’s insured clients, the lack of other independent information on fire and wind led to the practice of designers inserting the phrase “shall meet the requirements of FM Class 1-90” in their design requirements - even though the building may have not been insured by FM Global.

Over the years, FM Approvals has kept pace with developments in roofing technology. While the 5- by 9-foot wind tester was adequate for fully adhered systems and 2- by 4-foot insulation boards, it was not suitable for the more newly developed mechanically fastened systems and certain other assemblies especially where the fasteners might be widely spaced. FM Approvals designed and implemented a larger 12- by 24-foot device for these systems.

FM Approvals also adopted a sequence of pull tests to evaluate the effects of wind forces on roof perimeter flashing. Impact tests have been introduced, with ratings for Moderate Hail (MH) and Severe Hail (SH).

What Does All This Mean, and Where Does RoofNav Fit in?
FM Approvals requirements not only provided excellent design data - there was a lot of it. FM Approvals claims that their approvals cover over 6,000 roofing products and 180,000 possible roofing assemblies. In addition, each assembly contains many options, such as different insulations or fasteners. The performance criteria consider not only fire and wind, but hail, edge performance, and much more. Add to that variables such as type of roof deck, use of vapor or air retarders, type and number of possible thermal insulations and thermal barrier boards, cover boards, methods of attachment, roof membranes, and surfacings, and it is easy to understand why it was difficult in a paper environment to find an FM Approved system that met the needs of a roof designer.

RoofNav is FM Approvals’ online roofing tool that simplifies the configuration and assembly of roofs, and provides users with the most up-to-date details FM Approved roofing products and assemblies. RoofNav was previously available via subscription.

The decision was made to offer RoofNav free of charge to better support the needs of the roofing industry - specifically, to take the guesswork out of configuring an FM Approved roof without cost being a barrier, and to help prevent roofing-related property loss due to human error.

How Does RoofNav Help?
RoofNav helps:

  • Roof designers select the right equipment and materials to address property threats and protect facilities by putting at their fingertips engineering and technical information on more than 6,000 FM Approved roofing products and 180,000 roofing assemblies.
  • Reduce the likelihood of property loss due to fire, weather conditions, and equipment breakdown by making available FM Global’s 15 Property Loss Prevention Data Sheets most often used by the roofing industry. The data sheets comprise hundreds of pages of engineering guidelines based on 170 years of FM Global property protection research.
  • Determine the proper roof classifications for fire, hail, and wind uplift using a ratings calculator.
  • Easily develop one document for contractors - at the click of a button - that contains all the information they need to assemble a roof that meets the approval criteria of FM Approvals.

What is unique about RoofNav is its straightforward approach to determining what is needed and how to accomplish it. For example, once size, height of building, and location are entered, RoofNav will determine what the wind requirements will be. Type in the planned roof deck, the thermal insulation, underlayments (or overlayments planned), method of attachment, and roof system, and RoofNav will present only those systems that meet all of FM Approvals’ requirements. Construction numbers are provided, and by narrowing your search by manufacturer, only systems by that manufacturer that are FM Approved will appear on your screen.

Now that RoofNav is free and online 24/7, readers are encouraged to visit the site, plug in data on a hypothetical building (or one that has been recently installed), and take a test run. To gain free access and view prerecorded online training sessions, register at ( ). For background information on FM Global or FM Approvals, visit ( or (

To obtain the 15 roofing-related FM Global Property Loss Prevention Data Sheets that complement RoofNav, visit (, and click on “data sheets.” (These are free downloads - a significant value, considering that hard copies sell for $25 each.)

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