Question:
In these days of rampant mold litigation, are
there special considerations that the spray applied
fire-resistive materials contractor should
be aware of to avoid problems? —E-mail
Answer:
AWCI’s technical committee on SFRM recent-ly
released a guide for the contractor, “AWCI
Guide on Mold for Spray Applied Fire Resistive
Materials Contractors,” that can be downloaded from the
AWCI Web site www.awci.org/guideonmold.pdf. This docu-ment
offers several points that need to be factored in by not just
the SFRM applicators, since much of this is not news to them,
but designers, general contractors and other trades as well.
SFRM by its very nature introduces a lot of water to the job site.
Once applied, the SFRM must be given ample time and proper
conditions for the water to dissipate before either testing or
other work is done, otherwise that moisture lingers and could
contribute to the conditions favorable for mold growth. The
above mentioned document explains: “Proper ventilation and
drying practices significantly reduce the effects that available
moisture has on the SFRM surface as well as other building
products and thereby reduce the probability for mold growth.”
The document advises the contractor of four points to keep in
mind for the prevention of mold. First, make sure the product
used is suitable for the application. There may be adverse drying
conditions that require using a specific product. Second, make
sure that there is sufficient fresh, dry air to remove the moisture
added by the new material. According to the document: “Typically
a minimum of four complete air exchanges per hour are recommended
until the SFRM is fully cured. Proper ventilation is
even more critical in high humidity, hot temperatures or rainy
weather conditions. Under theses conditions, dehumidifiers
placed in the affected areas may be required.” Third, make sure
that proper building sequencing is followed; in other words, don’t
apply the fireproofing before the roof is on the building, lest it get
soaked in the next rainstorm. Finally, make sure that any avenues
that would allow excessive moisture in are identified and fixed
both before and after the SRFM application.
One more important note about drying, whether it is for SFRM
or any other building material: One of the products of combustion
is moisture. The use of some heaters, such as propane or
kerosene heaters that burn hydrocarbon-based fuels, can add as
much as six gallons of moisture to the air for every gallon of fuel
burned. So using such a heater and sealing the job site up tightly
with plastic sheeting and duct tape (assuming these items can
still be found now that the Department of Homeland Security
has put them on the “must have” list) is a recipe for not only
ensuring that the already available moisture doesn’t go anywhere,
but adds enough moisture to ensure swamp like conditions until
dehumidifiers are brought in and running for some time.
Question:
When is the correct time to install interior drywall?
After exterior wood sheathing, building
paper and lath for stucco finish have been
installed (prior to actual scratch coat application to allow build-ing
walls to be loaded to minimize cracking of the scratch coat),
or is it more correct to install it after the three coat stucco
process is completed! —E-mail
Answer:
As is occasionally my practice, I will post such
a question on AWCI’s Netforum, located on
the Internet at www.awci.org/netforum/awci/a,
because I’m not always confident that my answer agrees with
others closer to the specifics, and second because others will
surely benefit from viewing the answer. In this case, Robert Ek
from National Gypsum Company answered that the correct
time to install the interior gypsum board is after the sheathing,
building paper and lath, but before the scratch coat.
About the Author
Lee G. Jones is AWCI’s director of technical services. Send your
questions to him in care of AWCI’s Construction Dimensions,
or send your e-mail question to jones@awci.org.
