Changes to FM Approval standards 4470

Changes to FM Approval Standard 4470
Mark D. Tyrol, PE
FM Approvals
1151 Boston-Providence Turnpike, Norwood, MA 02062
Phone: 781-255-4786 • Fax: 781-762-4300 • E-mail: mark.tyrol@fmapprovals.com
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Abstract
Several significant changes have been made to FM Approval Standard 4470. Two of
the “new” requirements include checks of deck stress under service wind loads and deck
fastener stress. The test sponsor will submit calculations showing these elements are not
overstressed.
During wind uplift tests, the assembly must now maintain the service wind load for one
minute without visible cracking or visible creasing of the insulation or cover board.
Dynamic Puncture Resistance Rating of Roof Covers per ASTM D5635 and Solar
Reflectance of Roof Surfaces rating per ASTM C1549 are now optional ratings.
Speaker
Mark D. Tyrol, PE — FM Approvals – Norwood, MA
Mark D. Tyrol, PE , has over 25 years of experience with the evaluation, testing, and
approval of building materials. Tyrol began his career with FM Global in 1987 and joined
the Approvals Division in 1993. He is a graduate of the University of Massachusetts College
of Engineering at Lowell, with postgraduate studies from Northeastern University. He is
a licensed professional engineer in several states. He is also a member of the American
Society of Mechanical Engineers (ASME), Steel Door Institute (SDI), International Firestop
Committee (IFC), National Academy of Building Inspection Engineers (NABIE), National
Society of Professional Engineers (NSPE ), American Society for Testing and Materials (ASTM)
Committee E.05 Fire Testing, National Council of Examiners for Engineering and Surveying
(NCEE S), and RCI.
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In June 2012, FM Approvals revised
Approval Standard Class No. 4470, Approval
Standard for Single-Ply, Polymer-Modified
Bitumen Sheet, Built-Up Roof (BUR), and
Liquid-Applied Roof Assemblies for Use in
Class 1 and Noncombustible Roof Deck
Construction.
FM 4470 is used to evaluate single-ply,
polymer-modified bitumen sheet, built-up
roof (BUR), and liquid-applied roof assemblies
for their performance in regard to fire
from above and below the structural deck,
simulated wind uplift, corrosion of metal
parts, susceptibility to hailstorm damage,
foot traffic, water leakage, and optionally,
puncture resistance and solar reflectance.
Meeting the requirements of FM
4470 will qualify the roof assembly as
FM-Approved. FM-Approved roof assemblies
are not a significant fire hazard and can
resist rated wind uplift forces, hailstones,
etc. when installed in accordance with all
approval requirements. FM-Approved roofing
products and assemblies, the Ratings
Calculator, roofing-related FM Global
Property Loss Prevention Data Sheets, FM
Approval Standards, etc. are published in
RoofNav (www.roofnav.com).
This paper will discuss the latest revisions
made to FM 4470 and what these
revisions may mean to consultants.
A summary of the revisions to FM 4470
is as follows:
1. Checks of steel deck stress under
wind loads and steel deck fastener
stress calculations in order to
verify that these elements are not
overstressed. Note: this is not a
change from the previous edition of
the standard. This requirement was
included in the previous version of
FM 4470; however, the effective date
for compliance has been extended.
2. Wind uplift resistance tests acceptance
criteria: Some visible cracking
and creasing of the insulation or
cover board is now permitted at load
levels less than the service load.
3. For a reroof over steel deck, rigid
cover boards may be used to stiffen
existing decks that do not meet wind
design pressures. When a rigid cover
board is used, the allowable bending
stress of the deck shall be permitted
to be increased by 40%.
4. Dynamic puncture resistance rating
of roof covers per ASTM D5635
has been added to FM 4470 (as an
optional rating).
5. Solar reflectance of roof surfaces
rating per ASTM C1549 has been
added to FM 4470 (as an optional
rating).
6. Test requirements regarding combustibility
from below the roof deck
may now be met with either NFPA
276 or FM 4880.
7. The susceptibility to heat damage
test requirement, previously in FM
4450, has been added to FM 4470.
This is not a new requirement, as
this test has been required for the
approval of roof insulations.
8. Corrosion resistance: A second test
method is now offered.
The effective date of FM 4470 was
December 31, 2012. As of this writing,
FM Approvals was working to ensure all
RoofNav assemblies complied with all
requirements by the effective date. In the
interim, FM Approvals addressed currently
approved assemblies where the deck and/or
deck fasteners were overstressed.
Checks for Deck Stress
Under Wind Loads and Deck
Fastener Stress
Checks of deck stress under service
wind loads and deck fastener stress calculations
are required by FM 4470 in order
to verify that these elements are not overstressed.
This requirement was included in
the previous version of FM 4470; however,
the effective date for compliance has been
extended. Further details and guidance are
provided below.
Stresses induced to steel roof decking
shall be determined by rational analysis
using allowable strength design (ASD)
principles and shall not exceed the allowable
stresses per the North American
Specification for the Design of Cold-Formed
Steel Structural Members, AISI S100-
2007; and Approval Standard for Profiled
Steel Panels for Use as Decking in Class 1
Insulated Roof Construction, FM 4451.
What does all this mean to the consultant?
Here are some general guidelines:
• For 1.5-in.-deep, 22-ga., wide-rib
steel deck spanning 6 ft. (1.8 m)
with mechanically secured covers,
mechanically attached covers have
varying ratings, based on roof cover
securement row spacing. See Figure
1. For example, for roof membranes
secured in rows 8 ft. (2.4 m) wide:
— 33-ksi (kips per square inch)
(230-MPa [megapascal]) steel
deck limited to Class 1-60
maximum
— 80-ksi (552-MPa) steel deck limited
to Class 1-120 maximum
• For 1.5-in-deep, 22-ga., widerib
steel deck spanning 6 ft. (1.8
m) with fully adhered covers and
mechanically secured covers with
row spacings less than or equal to
half the deck span. See Figure 2.
— 33-ksi (230-MPa) steel deck limited
to Class 1-165 maximum
— 80-ksi (552-MPa) steel deck limited
to Class 1-300 maximum
Ratings for assemblies that currently
exceed these limits shall be modified.
Modifications may include reduced winduplift
ratings, shorter deck spans, changes
in minimum deck yield strength from 33 to
80 ksi, increases in minimum deck thickness,
etc.
Changes to FM Approval Standard 4470
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Details
1. Stress calculations are completed in
accordance with AISI using the following
parameters:
a. A three-span deck condition
exists (this is slightly less conservative
than the two-span condition
used for deck deflection).
b. For row-attached membranes,
the first row is assumed to have
been placed midspan of the first
span. The remaining rows are
spaced based on row spacing.
c. All fully adhered covers and
mechanically attached covers
where row spacing does not
exceed half the deck span are
analyzed as fully distributed
loads.
d. The standard requires the customer
to submit calculations;
however, FM Approvals has completed
calculations for common
mechanically secured membrane
assemblies and fully adhered
membrane assemblies.
e. Stresses are determined using
allowable strength design (ASD)
and cannot exceed AISI S100-
2007 allowables.
2. Similarly, deck fasteners will be tested
for pull-through and pull-over. In
addition, allowable stress calculations
of the deck/fastener heads are
conducted and the lower value used
as the basis of approval. Essentially,
testing demonstrates fastener performance
(i.e., no pullout or head
fracture), and calculation shows
that the deck is not overstressed.
These are conducted per AISI. Note:
Generally, deck-bending stress will
be the limiting condition. See Figure
3.
3. The steel deck deflection (FM 4451)
evaluation now assumes a 200-lb.
(0.89-Neston [N]) load vs. the 300-lb.
(1.3-N) load previously used.
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Figure 1 – Maximum wind uplift ratings
for 1.5-in. deep, 22-ga. wide rib-steel
deck spanning 6 ft.
Figure 2 – For all fully adhered covers and mechanically attached covers with row
spacing < one-half the deck span (generally 3 ft.), 22-ga., 33-ksi is limited to Class
1-165, and 80-ksi is limited to Class 1-300.
4. Testing on 33-ksi steel deck can
be extended to include 80-ksi steel
deck, but testing on 80-ksi steel deck
does not allow 33-ksi steel deck,
regardless of stress calculations.
5. Steel deck thickness that is tested
is the minimum deck thickness that
can be granted from that test.
6. Steel deck span that is tested is the
maximum deck span that can be
granted from that test.
7. Minimum steel deck design of 0.0276-
in. (0.7-mm) steel deck (slightly less
than 22-ga.) is now allowed. The
previous minimum was 0.0295 in.
(0.75 mm). This change is intended
to allow evaluation of deck typically
used outside North America. The
uncoated minimum steel thickness
delivered to a job site shall not be
less than 95% of the steel design
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Figure 3 – Use the capacity numbers vs. rated load and tributary area to determine adequacy for deck fasteners. Above are
values for fasteners with integral washers (first group of values, assuming a 0.4-in.- (10-mm-) diameter head and values for
separate ¾-in.- (19-mm-) diameter washers (second group of values). For example, a 0.4-in.- (10-mm-) diameter screw head at
6-ft. x 6-in. spacing with a fully adhered cover or mechanically attached cover with row spacing less than or equal to deck
span is 3- sq.-ft. tributary area = 595/3 = 198 = Class 1-195 maximum rating. Compare with limit of deck stress to determine
the governing condition for this case. (595 is from spreadsheet for screw with 22-ga., 33-ksi steel deck.)
thickness at any location. (Exception:
Lesser thickness due to cold forming
is permitted at bends.)
8. Steel deck material is now specified
as minimum 33 ksi (230 MPa) and
minimum 80 ksi (552 MPa), rather
than an ASTM specification. Again,
this is to allow evaluation of steel
deck typically used outside North
America.
9. The previous version of FM 4470
included steel deck stress limits.
Implementation was extended to the
effective date of the revised FM 4470
(December 31, 2012).
Wind Uplift Resistance
Testing Acceptance Criteria
The acceptance criteria for 12- x 24-
and 5- x 9- simulated wind uplift pressure
testing has been relaxed to allow limited
cracking and creasing of the insulation or
cover board. No changes to the actual test
methods and acceptance criteria have been
made; the revised test procedures now more
accurately reflect actual judgments typically
made.
In the previous version of FM 4470,
insulation or cover board was not allowed
to fracture, crack, or crease; and no delamination
of the insulation facer or membrane
was allowed.
The revised acceptance criteria allow
limited visible cracking or creasing of the
insulation or cover board when tested at
less than the service load. Limited visible
cracking or creasing may not exceed half
the minimum board dimension (e.g., maximum
24 in. [1220 mm] for a 48 x 96-in.
[1220 x 2440-mm] board). In addition, the
assembly must now maintain the service
wind load for one minute without visible
cracking or visible creasing of the insulation
or cover board.
Below are the definitions:
Crack – During wind uplift testing, when
an insulation or cover board is stressed to
the point that it separates from itself while
continuing to maintain the applied uplift
pressure without catastrophic failure of the
test assembly.
Crease – During wind uplift testing,
when insulation or cover board is stressed
to the point that it bends at a sharp, defined
angle without breaking. Often a crack will
form on the opposite face of the insulation
or cover board.
Service Wind Load – The uplift load
resulting from a windstorm that a roof
assembly must resist. The service load is
equal to half of the rated load in psf (or kilopascals
[kPa]). FM-Approved roofs are rated
for wind uplift—for example, “1-90.” The “1”
refers to FM Class 1, which means the roof
assembly is not a fire hazard; and the “90”
means the roof meets a wind uplift resistance
of 90 psf (the rated load). The service
load is equal to half of the rated load–in this
case, 45 psf.
The revised acceptance criteria also
allow minor adhesive delamination, provided
it does not continue to grow in size by
more than 50% from the end of one pressure
level through the end of the following
pressure level. During wind uplift testing,
pressure is slowly increased to 60 psf (2.9
kPa) and held for one minute. The pressure
is then increased by 15 psf (0.7 kPa) and
held for one minute at each pressure level
and repeated until failure is observed. An
example of minor adhesive delamination is
shown in Figure 4.
Credit for Rigid Cover Boards
For Reroof Over Steel Deck
For reroof over steel deck, rigid cover
boards may be used to stiffen existing
decks that do not meet wind design pressures.
When a rigid cover board is used and
performance is demonstrated via a test, the
allowable bending stress of the deck shall be
permitted to be increased by 40% over the
above calculations.
A rigid cover board is defined as a hard,
dense board that, in the sole judgment of
FM Approvals and through testing, has
demonstrated the ability to act in a composite
manner with the steel deck to increase
the moment of inertia and the section modulus
and, thus, the wind uplift capacity of
the roof assembly. Rigid cover boards must
be used over minimum 1.5-in.- (38-mm-)
thick insulation and secured to the deck,
either alone or in combination with the roof
cover, using fasteners placed within a contributory
area of less than or equal to 1 sq.
ft. (0.09 m2) per fastener.
A rigid cover board differs from a cover
board, which is defined as a board stock
product used over insulation, applied as
the top layer of some multilayer insulation
assemblies. This application is only for rigid
cover boards used in a reroof assembly over
steel deck.
Dynamic Puncture Resistance
Rating
Dynamic puncture resistance rating of
roof covers has been added to FM 4470.
Testing is performed in accordance with
ASTM D5635, Standard Test Method for
Dynamic Puncture Resistance of Roofing
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Figure 4 – Minor adhesive delamination of fully adhered single-ply during wind
uplift test.
Membrane Specimens. This test is optional
and is not a requirement of FM 4470.
Solar Reflectance Rating
Solar reflectance of roof surfaces has
been added to FM 4470. Testing is performed
in accordance with ASTM C1549,
Standard Test Method for Determination of
Solar Reflectance Near Ambient Temperature
Using a Portable Solar Reflectometer. This
test is optional and is not a requirement of
FM 4470.
Alternative Test For
Combustibility From Belo w
the Roof Deck
Combustibility from below the roof
deck test requirements may now be met
with either NFPA 276 or FM 4880. NFPA
276, Standard Method of Fire Tests for
Determining the Heat Release Rate of Roofing
Assemblies with Combustible Above-Deck
Roofing Components, was formerly known
as the FM Approvals Construction Materials
Calorimeter Test. This 30-minute fire test
measures the fuel contribution rate of a roof
assembly to determine if the roof assembly
meets Class 1, which means the roof assembly
will burn in a slow, controlled manner;
is not considered a hazard; and may be
installed in accordance with the Approval
without requiring automatic sprinklers
(when permitted by FM Global Property
Loss Prevention Data Sheets). NFPA 276 is
recognized by building codes throughout
North America and overseas.
test for Susceptibility to
Heat Damage
The susceptibility to heat damage test
has been added to FM 4470. This test is
used to assess the damage to roof insulation
applied to decks (other than concrete) from
exposure to radiant heat as a result of an
interior building fire.
After the test exposure, the insulation
shall not be decomposed, discolored, or
otherwise damaged beyond a depth of 1/8
in. (3 mm), and there shall be no curling
or bowing of the sample. There are no new
requirements due to this change, as insulations
previously had to pass this test based
on a separate approval standard.
Corrosion Resistance
Alternative Test Method
A second corrosion resistance test
method has been added to FM 4470. As
an alternative to ASTM D6294, Standard
Test Method for Corrosion Resistance of
Ferrous Metal Fastener Assemblies Used in
Roofing and Waterproofing, the following
test method may also be used: Guideline
for European Technical Approval of Systems
of Mechanically Fastened Flexible Roof Waterproofing
Membranes, ETAG 006, European
Organisation for Technical Approvals
(EO TA).
When and How Will Roof Nav
be Updated ?
The current edition of FM 4470 has
an effective date of December 31, 2012.
As such, all assemblies approved after
that date must meet all requirements. FM
Approvals is working to ensure all existing
RoofNav assemblies comply with all requirements
by the effective date. During this
period, any currently approved assemblies
where the deck and/or deck fasteners are
overstressed shall be addressed.
One plan is to update the “generic”
decks in RoofNav to include maximum wind
ratings for various membrane spacings. By
updating these products, all approvals will
be updated simultaneously. This allows
manufacturers to then evaluate their own
proprietary systems individually (Figure 5).
What Has Not Changed
Roof assemblies have to meet all of
the performance requirements and tests
described in FM 4470 in order to be considered
FM-Approved. Virtually all other thirdparty
certification organizations rate a roof
assembly vs. one-performance criteria and
grant a listing based on that (for example,
an external fire test only or wind uplift test
only).
More About FM
FM Global
Most readers have heard of FM Global,
and many will interact with FM Global on a
regular basis. So who is FM Global?
In 1835, a group of mill owners formed
their own mutual fire insurance company,
known today as Factory Mutual Insurance
Company, which conducts business as FM
Global. Today, FM Global has over $5.1
billion in gross premiums in force, 5,300
employees—including 1,500 loss prevention
engineers—and serves clients in more
than 130 countries from 65 office locations
worldwide.
FM Global is one of the world’s largest
business property insurers, whose clients
include more than one out of every three
Fortune 1000-size companies. FM Global
believes the majority of all property loss
is preventable. The use of FM-Approved
products and roof assemblies is recognized
around the world as one of the keys to property
loss prevention.
FM Approvals
FM Approvals is a member of the FM
Global Group and offers product testing
and certification. FM Approvals certifies
products and services with a unique focus
on objectively testing property loss prevention
products and services and certifying
those that meet rigorous loss prevention
standards and encouraging the development
and use of FM-Approved products and
services that improve and advance property
loss prevention practices.
FM Approvals is headquartered in
Norwood, MA, with offices throughout Asia,
Europe, and North and South America. FM
Approvals is recognized as a testing lab
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Figure 5 – Generic steel deck listings in RoofNav under “Products.”
and/or certification agency by the world’s
leading regulatory authorities and offers
manufacturers a single source for global
certification and direct access to critical
markets.
FM Approvals is also a Notified Body in
the European Union (EU), which allows FM
Approvals to offer the CE mark for products
covered by the Construction Products
Regulation (CPR ).
FM Approvals publishes the Approval
Guide (www.approvalguide.com), a source
for more than 48,000 FM-Approved products
and services; and RoofNav (www.roofnav.
com), a free Web-based roofing reference
and configuration tool.
To download a copy of FM 4470, visit
RoofNav at www.roofnav.com.
For more information about FM Global,
visit www.fmglobal.com.
For more information about FM
Approvals, visit www.fmapprovals.com.
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