When EIFS with drainage first appeared on the market
in the 90s, all sorts of ways of providing the drainage
capability were initially tried. Some were pretty
straightforward and are still used, while others were
unusual and quickly fell into disuse. All EIFS with
drainage share a few basic design features. This includes
some type if weather-resistive barrier over the substrate,
as well as some way of creating a drainage cavity.
The weather-resistive barrier usually takes the form
of a sheet material, such as building paper, or a
liquid-applied coating. The cavity can be created
by such methods as using thick layers of attachment
adhesive to make the EIFS foam stand off of the surface,
by using grooved foam, by adding various spacer materials,
and so on.
of these drainage systems use fewer materials and
less labor, and hence are not as costly as others.
This caused the competitive spirit to kick in, with
each EIFS producer hailing the virtues of their way
of doing drainage. This competition also raised the
issue as to whether or not some of these systems drained
or not. For instance, do barrier EIFS actually drain?
Yes, but to what extent.
the ASTM says
ago, ASTM¹s E6.58 committee on EIF took on the project
of developing a test method that determines the extent
to which an EIFS with drainage actually drains.
first question that comes up is, ³What do you mean
by drain¹?² Some drainage designs allow rapid draining
of water. Some drain slowly. Some also retain water
for quite a while but eventually do dry out. For example,
if one applies building paper onto a sheathing substrate,
and attaches flat EIFS insulation to the substrate
using mechanical fasteners, it will drain-well, sort
of. This is despite the fact that the foam is directly
against the substrate. The question thus becomes one
of efficiency and time. The question about the drain-ability
of an EIFS then becomes ³how fast?² and ³how much
water is left?²
ASTM drainage test is a system test, that is, it tests
the EIFS as part of an EIFS wall mock-up. It does
not test individual EIFS components but rather an
EIFS mounted on a substrate. The test does not include
window openings, which is a whole different type of
test. In other words, what we are trying to find out
is how the EIFS itself fares regarding draining and
not about the limitless number of other wall components
that can make up a complete wall system. By the way,
ASTM is also working on a wall assembly test for EIFS,
which does incorporate openings of various types,
so that the effectiveness of flashings, windows and
so on, can be evaluated.
new drainage test uses a 4-foot-wide-by 8-foot-tall
panel. The panel uses typical wood or metal studs
to make a frame, to which some type of sheathing is
applied. The EIFS with drainage is then applied over
the sheathing. This cladding system includes a weather
resistive barrier, such as building paper, some form
of drainage cavity and the EIFS itself.
horizontal slot is cut through the EIFS near the top
of the panel. The slot goes all the way back to the
weather resistant barrier that is on top of the substrate.
The bottom of the panel is treated in whatever way
a real wall would be treated. This could include the
use of flashings, or extruded trim with holes punched
in it, or simply left open. The point is that the
water needs a way to get out. It goes without saying
that some method of finishing off the bottom of the
EIFS is needed for several reasons.
is obviously so that it looks reasonable, such as
at the head of a windows. Another is so that the water
can freely leave the wall and not back up within the
wall. Clearly, the usual method of finishing the edge
of an EIFS, by back wrapping, will not work, as the
wall would fill up with water. Conversely, a wide-open
bottom edge would look bad, and would also be an invitation
for termites to enter the wall.
the test, water is sprayed into the cavity via the
slot in a controlled manner and is allowed to migrate
downward and exit through the bottom into a trough.
The rate at which the water collects in the trough
is a function of how freely the water moves through
the system. The amount of water that is applied into
the slot, vs. that which ends up in the trough, is
the amount retained in the EIFS test specimen. The
test panel is weighed before and after the test to
determine how much water remains in the wall.
test is mostly useful in a laboratory for developing
EIFS with drainage products. It could also be used
as a regulatory tool, provided someone decided what
kinds of numbers are needed in terms of the test results.
It is really not well suited for testing in-place
EIFS walls, although I suppose it would be possible,
although difficult, to stimulate the as-built conditions
of a wall in question.
bigger question, once a reasonable method for testing
drainage has been agreed upon is, ³What is good enough?²
The jury is still out on that question. ³Good enough,²
in terms of being adequate to serve its function and
produce a ³good wall,² depends on the circumstances.
The baking heat of a desert building site is different
from a perpetually damp place like the Pacific Northwest,
where I live. In the former case, a thunderstorm might
cause a lot of water to get into the EIFS drainage
system due to improperly performing flashings and
other wall details, but the relentless heat will quickly
dry out whatever happens to be left inside the wall.
Also, such downpours are rare and short in duration.
In the Northwest case, continuous drizzle would keep
an EIFS¹ drainage system wet for extended periods,
especially because the dampness of the climate does
not promote drying because the air is moist for months
on end. This matter of what constitutes adequate performance,
in terms of the numbers generated from this test,
is a subject worth of additional research. This test
method, which was developed by a consensus process
with the input of dozens of people, can be used for
this type of research.
test was developed with the assistance of a number
of companies in the EIFS business. The test is the
result of several approaches to doing such a test.
In other words, various ways of applying and collecting
the water have been tried. This test has been proven
a number of times, and is simple and predictable.
The test has proven a number of things, many of which
are obvious, but heretofore unproven, such as:
* Bigger drainage cavities drain faster.
* Vertical ribbons of adhesive are effective in creating
drainage channels. Conversely, horizontal ribbons
do not work well.
* Even mounting the foam directly against the weather
resistive barrier does drain to an extent, but some
water is retained between the foam and the weather
* EIFS insulation having vertical grooves on its backside
It seems to me that what is desirable, in terms of
the performance of an EIFS with drainage, is one that
drains fast and dries quickly. This hair splitting
dialogue about systems that drain marginally is avoiding
the real question, namely, having a wall that stays
dry all the time. In particular, the idea of fugitive
moisture lurking in the drainage systems, and having
unknown effects on the wall, is not a smart concept.
For instance, consider the effects of moisture on
metal mechanical fastener screws, or that of prolonged
moisture on adhesives that hold the foam onto the
Conversely, it¹s not clear to me that drainage is
needed at all in certain types of EIFS walls. Take,
for instance, prefabricated EIFS panels on commercial
buildings that have no openings and are simply one
big continuous frame covered with EIFS and sheathing.
Adding drainage to these types of EIFS walls is a
nightmare, as the prefabricated nature of the construction
makes incorporating the drainage difficult. For instance,
how do you marry the drainage system within the panel
to the flashings at the panels¹ edges? It also raises
the question of how the water is supposed to enter
the wall in the first place, considering that the
EIFS basecoat is bonded to the edge of the panel frame,
and not back wrapped.
To my mind, the real key to EIFS is drainage is not
the drainage in the field of the wall. Rather, it¹s
the proper design and execution of the EIFS at its
perimeter. This maxim holds for EIFS with drainage
and barrier systems. Carefully designed and installed,
it¹s the capability of the wall to capture and immediately
route leakage water to the outside that makes the
wall work, not routing it into some circuitous drainage
system and hoping it relieves itself to the outside
In the end, the real solutions to the pervasive wet
wall problems of the construction industry are walls
that stay dry because the whole wall works, not because
an EIFS happens to have a drainage system. The decades
of successful performance of barrier EIFS is a testament
to this fact. Drainage is an add-on feature for EIFS,
and should not be relied-upon to make up for the inadequacy
of the rest of the wall. The sooner the design and
contracting community gets this fact into their heads,
the sooner there will be a lot less problems with
walls of all types. Robert Thomas, president of CMD
Associates in Seattle, is a nationally known EIFS
consultant and author of the ³EIFS Design Handbook²
and the ³EIFS New Construction Inspection Manual.²
of Walls & Ceilings