Over my four-plus decades in the flooring industry I have seen many changes in the way we prepare for the installation of flooring materials. I have observed calcium chloride testing done under a glass dome, bond tests, rubber matt tests, plastic sheet tests, phenolphthalein, calcium carbide bomb tests, moisture meter testing (both destructive and non-destructive), calcium chloride MVER tests, and now the internal relative humidity (in-situ) tests. These tests represent subjective, quantitative and qualitative types of testing. After all these years the question persists: Which type works best?
Over my four-plus decades in the
flooring industry I have seen many changes in the way we prepare for the
installation of flooring materials. I have observed calcium chloride testing
done under a glass dome, bond tests, rubber matt tests, plastic sheet tests,
phenolphthalein, calcium carbide bomb tests, moisture meter testing (both
destructive and non-destructive), calcium chloride MVER tests, and now the
internal relative humidity (in-situ) tests.
These tests represent subjective, quantitative and qualitative types of
testing. After all these years the question persists: Which type works best?
at some of the tried and true methods that often pre-dated much of the
technology we take for granted today.
Chloride Under A Glass Dome
anhydrous calcium chloride test for moisture emissions was developed in the
early ‘40s as a qualitative evaluation of concrete floor moisture conditions.
It was conducted by drilling three holes in a concrete slab in about a 6”
perimeter and using anhydrous calcium chloride crystals to determine the
presence of moisture. The crystals were sealed in place using clock glass and a
ring of plumber’s putty. After a period of time, you’d look for changes in the
crystals. No change meant the slab was dry. If the crystals caked-up that meant
there was moisture in the slab. The larger the caking of the crystals, the
wetter the slab. Standing water in the clock glass was a clear indication the
slab was extremely wet. The results are extremely subjective and required an
experienced person to conduct and evaluate these tests.
were just that: A square yard of material was installed on a predetermined area
of the slab where the installation was to take place, with the adhesive and
material that was going to be used. The material was placed and left for a
period of 72 hours. Then the material was removed and the condition of the
adhesive was checked. Some versions required the use of a water-soluble
adhesive in the center of the test. If the adhesive was dry and the material
difficult to remove and the adhesive in the center of the test was also dry,
the installation could commence. Like the early calcium chloride testing, results
of this type of test were extremely subjective and required an experienced
person to conduct and evaluate.
testing required the placement of a rubber mat on the surface of the
concrete. It was to be left on the
surface of the concrete for 24 hours and then removed. Upon removal the surface of the concrete was
examined for moisture. A slight darkening meant a marginal moisture level, and
water droplets meant extreme moisture. Unfortunately, this test could be
misleading because 24 hours is too short of a time to properly measure changes.
The test is very subjective and influenced by temperature, humidity and dew
sheet tests are even worse than the rubber mat tests. In this test a sheet of
plastic about 24” by 24” is taped to the surface of the concrete and left for
24 hours. It is then examined for moisture darkening or water droplets. Plastic
sheeting, especially recycled plastics, vary in permeability and allow for
moisture to pass through the material. The amount of time for placement is too
short and the results are extremely subjective. This test is also highly
influenced by temperature, humidity and dew point.
is a chemical that, when poured on the surface of the concrete, turns from pink
to red to purple if the concrete is too wet to install. The color change is an
interaction of the alkaline salts reacting with Phenolphthalein, creating the
color change. This too is extremely
Carbide Bomb Tests
In the mid
‘80s there was a surge in a European test called the Calcium Carbide Bomb
Test. This test involved placing chips
of concrete, fresh from the slab, into a small chamber along with a glass vial
containing Calcium Carbide crystals and some steel balls. The chamber was
sealed and shaken until the steel balls broke the glass vial. Then the moisture
in the concrete chips would mix with the calcium carbide and create acetylene
gas, which would register on a pressure gauge. A low reading was required for
an installation to begin. These tests
were expensive and subjective. Even though there was a quantitative result, it
required the concrete to be removed from the surface which was affected by temperature,
humidity and air movement. The results of this test were often inaccurate.
two types of moisture meter testing:
type testing requires the concrete surface to be broken, drilled or nailed. The
meters probes are placed on the contact area and measure a low-level electrical
current between the two contact points.
testing relies on a low level electrical impulse which travels between two
sensors. The impedance of the impulse determines the moisture content of the
surface of the concrete down to about 1”. Moisture meters do not measure the
moisture deep down in the slab which may not be in equilibrium. Once covered
with a flooring material, this moisture may migrate to the concrete surface and
affect the adhesive and material
Chloride Moisture Vapor Emissions Rate (MVER) Test
day calcium chloride test measures the moisture vapor emissions rate (MVER) and
became a quantitative test in the ‘60s. This test has become very popular;
there are nearly half a million of these tests performed in the U.S. annually.
In the past 10 years however, we have become aware that the test can be
unreliable, capable of producing both high and low false results. This is
because the test is dependent on a variety of factors, including ambient
temperature, humidity, presence of residuals on the concrete surface, and even
the hardness of a trowel finish. It is estimated that up to 80 percent of the
calcium chloride tests yield an inaccurate result.
Relative Humidity (In-Situ) Tests
floor testing is not new to the flooring industry. Though it has only truly
come to our attention in the last decade, the original tests date back to the
‘50s. First used in research by the Portland Cement Association (PCA), RH
instruments can be independently calibrated and are directly traceable to
national standards. More importantly,
RH testing give a much more useful picture of actual moisture conditions within
the concrete regardless of mix design, aggregate types, floor thickness or
surface conditions. While there are many types of RH testing equipment
available (and yes, they are often more costly than calcium chloride test
kits), they can prevent premature flooring installation failure, costly repairs
and litigation. Recently one electronics manufacturer developed a disposable RH
probe that does not require periodic calibration and readings that can be
obtained on demand.
While still considered new,
this type of testing is the most accurate in the industry. Understandably,
flooring manufacturers are slow to establish a “tiered system” for the various
flooring products. But once such a system is established, it will allow for
more successful installations without all the guesswork.
How Confident Are You In Moisture Testing?
December 11, 2007