Wet Concrete Floors
Do you have little white puffy clouds on your concrete? Did your carpet develop a mold problem? Does your garage have little puddles even when it isn’t raining?
Here on the Gulf Coast hurricanes bring a great deal of flooding. Whole buildings have spent time underwater with a variant ground saturation from dusty and dry to swimming in saturation. These conditions pose a serious vapor emissions problem with slabs on grade on the Texas Gulf Coast. Sadly, we also have moisture problems when were not dealing with hurricane weather.
Sure, this is an extreme picture of the wide range of moisture issues that can cause a floor coating failure. The reality is that even a simple everyday rainfall can cause pressure under your slab that seeks to push its way up and find relief. If you have a coated floor, the relief it seeks is to permeate your coating and cause adhesion failure.
Don’t worry, there’s good news in all of this. Crazy weather conditions, the tides of the gulf and unforeseen hurricanes have no destroying capabilities over a properly installed floor coating.
As a porous surface, concrete wicks water, it can actually pass water and water vapor through the surface much in the same way as a household sponge. We call this capillary action. It is also sometimes referred to as “vapor transmission”. This transpires when the temperature above the surface and the temperature below the surface contend for equality. This can also happen with properties that have poor drainage or where the original moisture barrier under the slab has deteriorated. In my years with Slip Free Systems I have noticed a particular problem with homes built in the late 60’s and early 70’s where the original moisture barrier has since deteriorated and homeowners are now experiencing exorbitant amounts of condensation under their floor coverings causing harmful mold problems and a host of other issues that are a hassle and a financial drain to the homeowner.
The ability of coatings and sealers to maintain their adhesion and clarity; as well as resist defects such as blistering, pealing, flaking loss of bond, gassing bubbles, and efflorescence issues are directly associated with vapor emissions.
How do we identify and address these issues? First we have to determine if there is a problem. Then we test for the magnitude of the problem using one of the methods outlined below. Finally, we establish a plan for remediation.
Common Testing Methods and Metering Devices
Plastic Sheet Method…(This is something you can do yourself)
Securely tape an 18″ x 18″ square of clear plastic on all 4 sides over the concrete in an area where you suspect a moisture problem. We recommend that you test two or more areas of the slab in question for optimal results. Wait 16-24 hours. Check for condensation. If condensation is found on the underside of the plastic or on the concrete, then you have a moisture problem. This test will not tell you how bad the problem is…just that there IS moisture transmitting from below the surface. It is important to note that not all tests by this method will be an effective sign of issues in your slab, this test is highly dependent on outside conditions such as rain, temperature control, humidity and other factors. In cooler temperatures (ambient/air or surface) the concrete may retain its moisture and fail to build up under the plastic. In warmer temperatures like we have here in Texas the moisture could actually shrivel up and die from heat exhaustion. So this test should be used with caution and as a general means of determining whether or not to proceed with obtaining professional help.
Calcium Chloride Test…
The Calcium Chloride Test is just a little bit more technical. This test measures the degree of water vapor emission rising out of a concrete slab over time. Contractors and architects frequently require this type of test on construction projects before moving forward with floor covering installations. Here at Slip Free we administer the test for a variety of customers. Testing by this method will provide readings, as related to lbs. (pounds) of moisture/vapor being emitted out 1,000 square feet of concrete during a 24 hour period.
For testing we use a gram weight scale and a Calcium chloride tablet that looks a lot like one of those toilet cakes you find at the ballpark or a chlorine tablet that’s used in swimming pools. The tablet is placed under a plastic dome in its own little dish. The calcium chloride is weighed before, and after the test (24 hours later).
The resulting gain in lbs. (pounds) will equate to the amount of moisture. Extremely wet, saturated concrete, can sometimes result in readings well over 10 to 15 pounds per 1000 square foot in 24 hours. The industry norm dictates that the moisture/vapor emission rate should not exceed 3 pounds per 1000 square feet.
ASTM Standards & Practices for Calcium Chloride Testing are…
E-1907-97 Standard Practice for Determining Moisture-Related Acceptability of Concrete Floors to Receive Moisture-Sensitive Finishes
E-1869-03 Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Sub-floor Using Anhydrous Calcium Chloride
E-l907-97
Document describes all the major tests commonly used for concrete floor slab testing (which includes the Calcium Chloride Test)
Electronic Moisture Meters…
These meters read moisture content immediately. Detects moisture beneath the surface by measuring the resistance between two low frequency signals transmitted from conductive pads on the base of the instrument.
Relative Humidity (RH) Test…
Method utilizes an instrument that measures relative humidity under a insulated box placed on the surface of the concrete. Test is performed by sealing the insulated box to the concrete and measuring the relative humidity inside the box with a capacitance-based humidity gauge. If the moisture inside the box measures less than 75%, the moisture content of the concrete is deemed to be less than 5%. Note: the air inside the box must stabilize for 12 hours prior to testing.
Another method is to drill a hole in the concrete and place a special plug in it. The probe of a humidity gauge is inserted into the plug and left to stabilize for 12 hours. RH reading is taken. The advantage of this method is that the RH measurement is not effected by sealers, curing agents, or coatings on the concrete.
Typical signs of rising moisture/vapor problems:
Excessive rising moisture being emitted from bare concrete typically exhibits itself on sealed surfaces in the form of efflorescence , which manifests itself in the appearance of little while puffy clouds that sit on your surface.
On floors where a coating has been installed signs of moisture include outgassing, blistering, pealing, loss of clarity, darkening of substrate beneath sealer, efflorescence issues, and total bond failure. This is why it is so important to educate yourself and choose a qualified installer.
Water will transmit to the surface when there is higher vapor pressure in the concrete than in the air above the surface. This condition is more apt to occur when the air conditioning is first turned on in a new building; therefore, it is best to allow the air in the building to stabilize for a minimum of 24 hours before sealing an interior surface.
Methods of Removing Moisture from Concrete Substrates
Want a simple solution to a complicated problem? Get a dehumidifier. If you live in a particularly wet area and you are finding that you have an ongoing problem with on-slab moisture, a dehumidifier will draw the moisture out of the concrete….HOWEVER, there is a theory out there that says you are not just removing existing moisture but rather you are drawing moisture up through the surface from the ground by providing a dry slab that will act as a sponge and suck up moisture that may not have been originally headed for the slab….a theory, but still worthy of an ounce of consideration.
Heat is another viable method for drying. Evaporation rates accelerate as temperatures rises, drawing the he moisture in the concrete to the surface, allowing evaporation to take place. Note: do not use direct fired heaters since they produce moisture due to combustion.
Circulating air, when combined with any/or all the above, being blown over the surface is recommended; as is ventilation if possible. We highly recommend this little addition to the process as it provides the most consistent atmospheric conditions.
The above methods will only produce solutions if the rising moisture emissions are determined not to be continuous. Standard rising moisture/vapor testing methods should always be performed to assure that the concrete is within acceptable limits, being not more than 3 lbs. per 1000 square foot over 24 hours.
Accurate testing of all concrete surfaces, as related to rising moisture/vapors is imperative in order to assure successful outcomes as related to adhesion, clarity, appearance, and longevity of coatings. Doing so will enable you to select the proper type/formulation of sealer and/or coating in order to achieve maximum bond, cured out properties, and performance characteristics.
We offer a variety of solutions to fit your need and budget requirement depending on the magnitude of your problem. Some moisture problems can be resolved with a method as simple as an acrylic sealer and others may require a more expensive multi layer fluid applied moisture barrier…and still others may prove to be excessive enough that we might suggest other alternatives. No matter what some salesman tells you, remember this: Moisture is a big problem and while we can resolve most instances, there are occasions when a fluid applied barrier is not your best option, at Slip Free Systems we want your business but not at the expense of selling you something we are unsure of. If it walks like a duck and talks like a duck…we’re gonna send you to animal control…but if it lays like a floor and sweats like a wooly mammoth…we are here for you.
In cases where the rising moisture/vapors being emitted are deemed to be continuous, and/or exceeds the 3 pounds per 1000 square foot over 24 hour period, there are potential solutions such as: crystalline waterproofing systems that form a gel in the capillaries of the concrete as rising moisture comes in contact with them (some even able to withstand hydrostatic pressure), as well as custom formulated impregnators. These modern chemically engineered products/materials are capable of deterring, or even in certain instances preventing, rising moisture from reaching the surface.
