The Secret Enemy of Flooring Installers:
by Bob Higgins
Dewpoint
A floor is measured for moisture levels using the calcium chloride test method; pH tests
have also been conducted. The installer has taken great pains in ensuring the project will
go as error-free as possible. Several days later, the flooring is installed and in less
than a month; blisters begin to appear and/or adhesive begins oozing from the seams. The
floor is opened up and the adhesive has not cured. (According to some "moisture
experts" reemulsified). Next, a series of events begin to take place establishing the
guilt or failure of the flooring installer and/or manufacturer. The manufacturer is
brought in to establish whether their products are defective and the litigation cycle
(i.e. expense, time, damage to customer goodwill and reputation, etc.) begins yet again.
This all-too-familiar scenario will continue to play itself out, with the current
"facts" creating more questions and confusion than answers. The likelihood is
that this problem will continue to increase in frequency, with the confusion increasing -
unless the influences of dewpoint are considered.
We have found that dewpoint does a nearly indistinguishable imitation of classic moisture
"problems". Dewpoint is in reality, a transitory effect, which can easily be
controlled at time of installation, if the applicator is made aware of its existence and
how to control the potential detrimental effects. The cause, effect and avoidance of this
problem are the subject of this article.
What is dewpoint?
(Dewpoint: the temperature to which air must be cooled, at a given pressure and
water-vapor content, for it to reach saturation. Absolute humidity: the ratio of the mass
of water vapor to the volume of moist air within which it is contained. Relative humidity:
the amount of water vapor in the air, expressed as a percentage of the maximum amount that
the air could hold at the given temperature; the ratio of the actual water vapor pressure
to the saturation vapor pressure).
Dewpoint, as it pertains to concrete and other substrates, is when the environmental
conditions (humidity and temperature) conspire to create a "wet" substrate -
even if there is no direct exposure to a "water" source! This is a critical
factor to remember in any floor installation. The way dewpoint occurs in concrete is that
moisture migrates to a cooler source (water droplets/condensation on a cold glass, fog are
examples of dew formation or dewpoint). The reason moisture migrates to cooler areas is
that air pressure increases as temperatures rise and conversely, air pressure decreases as
air temperature drops.
Subsequently, if the concrete surface and/or interior concrete area are cooler than the
room temperature, moisture will tend to migrate towards that area.
The volume of moisture migration is then dictated by the available amount of moisture
(high humid conditions, or the water in water-based adhesives) and porosity of the
substrate.
The efficiency of movement is dictated by permeability of the concrete surface (this is
where good concrete practices become so important).
How can this create problems during and after installation?
The problem occurs as the water-based adhesive is installed over an already damp substrate
(even if the concrete surface appears dry!). If the room environment is humid, it is
difficult, if not impossible for the adhesive to properly "set". So even if
adhesive appears well-transferred to the floor and concrete, the moisture content of the
concrete surface may be high enough to prevent the adhesive from properly curing - if at
all. Basically, the adhesive still thinks it is in the container! Since moisture in a
liquid form is quite cohesive, it tends to move to towards pockets (small or large),
appearing as blisters in the floor. If the floor is VCT, the still plastic adhesive
complicates matters further by "squishing" out towards the seams (by foot and
other traffic) and partially setting. Since moisture tends to equalize, the moisture can
wick towards the seam area, retarding a complete set of the deposited adhesive. As
attempts are made to remove the unsightly adhesive residue, the still liquefied adhesive
moves to that area, creating a vicious cycle. There are other more complex scenarios that
may occur (and are too complex to be adequately explained within the constraints of this
article) as a result of dewpoint/condensation, but are errantly identified as "vapor
emission problems" since a dewpoint situation can actually "read" as a high
vapor emission condition. Remember that the calcium chloride test cannot distinguish what
the source of the moisture is, only that the moisture is present under the lid!
This is but one of the reasons it is vital for any testing "entity" to be well
schooled and certified as competent in the test protocol of using and interpreting results
from the calcium chloride test method. Without consideration of dewpoint and its effects,
there is a distinct danger of creating a totally avoidable problem. Errant testing and
evaluations can lead to spending time, resources and money on an unnecessary and usually
expensive moisture control system. As a point of conjecture (and I actually have seen this
scenario played out), how many times has a "successful installation" of a
moisture control product been used on a project where the problem was actually
misdiagnosed and the system amounted to nothing more than expensive "window
dressing"?
Avoiding Dewpoint Problems
The best way to avoid dewpoint problems is to become aware of your immediate surroundings
and the environment in which the flooring materials are to be installed. The surest way of
determining your environment is to conduct measurements of the temperature of the room,
concrete surface, relative humidity and dewpoint.
This is actually a lot easier than it sounds, thanks to improved and less expensive
testing apparatus! There are places such as Radio Shack and Cole-Parmer (mail order) that
supply virtually all the tools necessary for a good installation and prediction of
dewpoint. It is vital to have the following: hygrometer (measures humidity) as opposed to
a hydrometer (measures specific gravity), thermometer (one for air, and another for hard
surfaces-usually a lot tougher to find) and a dewpoint meter. Radio Shack has several
devices that simultaneously read temperature, humidity and dewpoint which are inexpensive
and easy to read, and accurate enough for a majority of critical applications.
During installation it is critical that the humidity within the room to receive flooring
installation be less than 60% r.h. It may be necessary to have air circulators (i.e. fans,
blowers) and one or more dehumidifiers to precondition the room and maintain a good
working environment throughout the installation process.
We have been involved with several installations where the floor appeared to be suffering
from a "moisture problem", but when we tested the floor (in strict accordance
with ASTM E 1907-97), the moisture levels were insufficient to create such high levels of
liquefied moisture beneath the flooring material(s). We then had the room preconditioned
and conditioned all throughout the installation process. The installation went flawlessly
with the exact, same materials as used before. The accusations of "defective"
adhesive and "moisture problems" were soundly refuted.
Why have Dewpoint Problems Become More Common?
There are several reasons for this;
1. Water-based adhesives: as more water is added to the adhesives, the more critical a
dewpoint condition can become since more water has been added to the equation. Water-based
adhesives also tend to cure more slowly than their solvent-based counterparts, leaving
them more susceptible to moisture-related problems. It is important to note that many of
the so called "moisture sensitive" modern adhesives are at least as durable in
moisture conditions, once they have completely cured as their former solvent-based
counterparts!
2. Changes in construction requirements: Unmodified older buildings have a natural air
exchange, up to 1 to 4 exchanges per hour. This in turn may help control moisture by
diluting moisture within a building. The tighter the building construction, the lower the
infiltration rate and natural circulation of air. In traditional historical restoration,
the worst method/approach to correcting moisture problems has been to seal the building so
completely, the building cannot breathe.
3. Fast-Track Construction: Time is Money, and as a result, more buildings are being built
faster and with little or no regard for the natural curing and/or seasoning of the
building materials. Concrete cures very slowly and contributes to overall moisture
problems by pore water evaporation (mistakenly referred to a "vapor emission")
for several months. Drywall and interior plaster can also contribute to interior moisture
problems due to their water content as well. Artificial heating is a sneaky and often
overlooked contributor to interior moisture content. One commonly used material - propane
- contains water, approximately 90% by volume (this is why it is referred to as a
hydrocarbon). As it is burned, the two most common by-products are water and carbon
dioxide. If you've ever visited a site where this is being used, it is very common to
watch the windows sweat (where water is literally running down the glass). If the concrete
is cold (which is common in winter months), the moisture moves to the cooler, damper areas
(i.e. concrete) and not only doesn't allow the concrete to dry out, the carbon dioxide and
moisture conspire to increase the propensity of immediate and future moisture problems.
Even the wood products are damper than they used to be. When was the last time you were
able to obtain true kiln-dried lumber? It is typically "surface-dried" lumber,
with higher moisture levels and can act as another contributor to potential moisture
problems!
4. Bad information: We as an industry have been fed a LOT of bad information by many
so-called "moisture experts". Most of the information the industry has been led
to believe as factual could be categorized as "urban myth". Some of the worst
are the following;
- vapor pressure can, with the benefit of time rupture even an epoxy floor -this is a
pretty amazing statement since vapor pressures cannot exceed 1.0 psi in any
livable environment, and epoxy bond strengths can be several hundred, to several
thousand times higher than vapor pressure!
- vapor pressures can build-up, creating a "backpressure" condition that can
fail
the floor (vapor pressure responds only to temperature and humidity and
therefore cannot "build-up"),
- water vapor carries alkalis to the surface (water vapor behaves as any other gas and
therefore cannot make a solution, meaning that it cannot carry or "hold" solids)
- vapor pressure is the "engine" of moisture problems (the moisture problem is
extremely complex and this oversimplification is not unlike visiting the doctor only to
have him tell you, "your are not feeling well"). Actually, the moisture levels
can be completely independent of vapor pressure.
These are ALL unscientific fairy tales that help confuse and distract from the true basis
of moisture problems.
Dewpoint is an important consideration and in our analysis, constitute upwards of 30-40%
of the "moisture problems" we have been involved with. Considering the high
percentage of misdiagnosed dewpoint conditions, it is no wonder many of the questionable
moisture control efforts have shown apparent "success". Our industry needs to be
properly informed of this and other conditions. This will help to avoid wasting money,
time and resources on misdiagnosed problems, and ultimately allow us to spend our time and
resources wisely.
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