Wachuwannano
By Lee G Jones
Q How do you
determine whether glass mat gypsum substrate is
still good after being exposed to the weather
for some time before attaching EPS board for
the installation of an exterior insulation and
finish system? Can you do an "X test," similar
to how you test regular gypsum sheathing? A
The "X test" that is used to check
the condition of gypsum sheathing does not work
for glass mat gypsum substrate. In fact, when I
called a manufacturer's technical service
department to pose the question, there was a
long pause followed by some quick conferring,
then a "Sure, you can try it, but we've never
heard of anyone doing that before." When I
pushed further, asking how then does one
determine whether the material is still viable,
I was told that to date this has not been a
problem. Clearly, though, it is important to
ensure that the substrate is in fact in a
usable condition before attaching the many
components of an EIF system, especially having
been exposed to the elements for an
indeterminate period. So, to follow up on this
question, I called one of my gurus who told me
that the best way he's found to evaluate the
condition of a glass mat gypsum substrate is to
find an edge that has been cut for an opening
or penetration and check the condition of the
core. If it's beyond its time, the core will be
crumbly, in which case it should be replaced
before continuing. Q How do I find
out what the correct pattern for installing
mechanical fasteners is when attaching EPS
board for an EIF system? Some say to stagger
the fasteners, others say to keep them in
straight rows. A Naturally,
getting the correct answer depends on a couple
of factors. For starters the type of substrate
will affect the recommended pattern: for
instance, if the sheathing is a wood product
(plywood or OSB), you can attach the fasteners
right into the sheathing; however, if the
sheathing is a gypsum product, you must find
the framing member to properly install the
fasteners. Then there's the thickness of the
EPS, which may affect how tightly you must
space the fasteners. According to ANSI/EIMA
99-A-2001: "Mechanical fasteners and washers
shall be of a type and spacing in accordance
with the EIFS manufacturer's current published
instructions and shall be included in the
project plans and specifications." So, if
you're on the job and there's a copy of the
contract documents handy, you might find the
recommended fastener pattern spelled out in the
specks, but if you know who the EIFS
manufacturer is and what system is going to be
used, you can probably download this
information from the manufacture's Web site.
Just by pulling up a couple of EIFS
manufacturers' Web sites and typing in
"mechanical attachment," I quickly had several
different sets of patterns for mechanical
attachment in a variety of situations. Q
Where should window head flashing
be installed on a drainable EIF system? A
Now that many EIFS jobs are
switching to "water managed" systems, there's
usually some kind of weather-resistive barrier
(house -wrap) that must be integrated with the
flashings, and in some cases the necessary
layering is counter-intuitive. The key thing to
remember is that the flashing is normally
designed to direct intruding water to the
exterior surface of the wall, not to the
drainage plane behind the EPS board. So, over a
window, the flashing should be between the
substrate/sheathing and the weather-resistive
barrier, where moisture captured by the
weather-resistive barrier will be directed via
the flashing back outside where it belongs.
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.
