My observations of FM GlobalDick Baxter
Editor's note: The following article represents the
experiences of the author, not necessarily those of NRCA or
Professional Roofing magazine.
The old Factory Mutual (FM) system that transformed itself into
FM Global has long been proactive in developing criteria for roof
system evaluation through its research division, now called FM
Research. FM Research started out as a nonprofit arm of the FM
system to evaluate the performances of many construction materials
and systems, including roof systems and roof components, and assist
FM's underwriters in adjusting insurance rates for its
insureds.
With the transformation to FM Global came some other changes. FM
Property Loss Prevention Data Sheets became FM Global
Property Loss Prevention Data Sheets, and the FM Approval
Guide now is published by FM Global Technologies LLC. Although
the original intent was to provide in-house information to the FM
system, FM recommendations have permeated every nook and cranny in
the roofing industry and indirectly affect every roofing contractor
who deals with FM Global insureds and anyone who subscribes to FM
Research recommendations. The yet-to-be-introduced RoofNav computer
program being developed by FM Research is supposed to replace its
Approval Guide and provide up-to-the-minute information
about FM Research-approved roof systems and roof system components.
RoofNav promises to be a significant challenge for roofing
contractors.
The Approval Guide probably is the least user-friendly,
most misunderstood, basically unreadable document ever published.
But RoofNav is supposed to resolve these issues. The Property
Loss Prevention Data Sheets are much more understandable than
the Approval Guide but usually fail to provide the
information necessary to install roof systems in some
configurations. For example: The only reference in Property Loss
Prevention Data Sheet 1-29 to mechanical attachment of a base
sheet is over a wood deck 3/4 of an inch (19 mm) thick or thicker
using large-head (1-inch- [25.4-mm-] diameter) roofing nails. There
is no recognition for fastening of base sheets to cementitious wood
fiber decks, poured-in-place gypsum or gypsum planks, or
lightweight insulating concrete decks (and no differentiation
between perlite or vermiculite aggregate lightweight insulating
concrete and lightweight insulating cellular concrete) even though
it is certain FM Global covers insureds with these types of roof
decks in their inventories. There is no differentiation between
base-ply fasteners with 1-inch- (25.4-mm-) diameter heads and
base-ply fasteners incorporating FM Research 1-90 stress plates
even though common sense would suggest a 3-inch- (76.2-mm-)
diameter 1-90 stress plate should increase the uplift properties of
base sheets over those of base sheets secured with 1-inch-
(25.4-mm-) diameter heads and allow installation of fewer 1-90
fasteners for given...
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