Intumescent Fire Barrier LetterBucky Sparkle, PE
378 Main St., #2, Easthampton, MA 01027
617.271.4004 or zengineerbucky@gmail.com
24 April 2019
Louis Hasbrouck, Building Commissioner
Building Department
Puchalski Municipal Building
212 Main St.
Northampton, MA 01060
lhasbrouck@northamptonma.gov
Re: R302.13 Fire Protection of Floors
Lou,
Thank you for your input as I navigate the best way to protect the floor assembly of my
home. As you know, the first floor is supported by TJI I-joists and over a basement. As
such, R302.13 requires “½-inch (12.7 mm) gypsum wallboard membrane, 5/8-inch (16 mm)
wood structural panel membrane, or equivalent on the underside of the floor framing
member.” Per the International Code Council’s (ICC) 2015 Significant Changes to the
International Residential Code1, the membrane or equivalent treatment “applied to the
underside of the floor system does not form a fire-resistant-rated assembly. The membrane
acts to shield light-frame floor systems from the heat of a fire originating in the space below
the floor. The intent is for the floor system to perform similarly to unprotected 2x10 solid-
sawn lumber floor joists and to delay structural collapse of the floor system.”
My basement is divided into two use areas. On the “finished” side, I will install standard 1/2-
inch gypsum wall board to the bottom of the I-joists (Type-X or Type-C wallboard does not
seem to be required). For the unfinished area, where I do not want to lose access to the
pipes, ducts and wires, I intend to paint the wood I-joists with an intumescent coating. This
will form a 2 hour fire barrier on the I-joists, making them perform better than 2x10 solid-
sawn lumber in a fire.
I have done quite a bit of research on fire barrier coatings! Some products did not have
sufficient technical data or manufacturer’s support for me to be comfortable with them.
However, one brand/company stood out in terms of performance and data. Contego makes
a Reactive Fire Barrier Intumescent paint which is exceptional. I am attaching a product data
sheet for you to review. As further support, I am also attaching the UL test for the Contego
Original formula. The test shows a Flame Spread Index of 0 – the same rating as asbestos
cement board2! As such, this intumescent coating will ensure the I-joists perform at least as
well as 2x10s (actually, much better as douglas fir has a Flame Spread Index of 65). The
1 https://codes.iccsafe.org/content/IRCSigChanges2015/r302-13-fire-protection-of-floors
2 https://en.wikipedia.org/wiki/Flame_spread
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product is also a low-VOC paint, as a bonus.
A 20 mil dry coating will provide a 2-hour fire rating. This is obtained by one 30 mil wet
coating of their High Solids formula or two 20 mil wet coatings of their Original formula. I
have purchased a wet film gauge so that I can verify that I have applied sufficient wet
thickness. Additionally, the product is designed to be applied at 145 SF per gallon to achieve
the proper coverage, so I will have a double check on the application thickness. I will take
photos/video of the wet film gauge test and document the remaining product to determine
coverage yield.
Before I embark on this effort and expense, please confirm:
1.That providing a 20 mil dry coating of Contego’s Reactive Fire Barrier Intumescent
paint to the TJI I-joists will meet R302.13.
2.That standard 1/2-inch gypsum wallboard applied to the bottom of I-joists will also
meet R302.13.
Thank you.
Brightly,
Bucky Sparkle, PE
Attachments
Contego RFB Product Data Sheet
Underwriters Laboratories test results “Test for Surface Burning Characteristics of
Building Materials” (ASTM E84)
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