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Concrete Moisture Myths Debunked

Concrete Moisture Myths Debunked


Concrete is a durable, strong, and visually appealing material, which is why it comes as no surprise that it’s one of the most popular choices in the construction industry. Unfortunately, millions of dollars are wasted on moisture-related concrete damage each year that could easily be avoided. Why? Because there are a lot of myths about concrete moisture, which lead to inaccuracies when measuring the dampness in concrete. It is important to have a complete understanding about concrete moisture and how it dries, otherwise, you may find yourself behind schedule, going over budget, needing to repair grave mistakes, and dealing with an ugly, unstable result. Before beginning your floor installation, give the professionals at Flood Services Canada a call to ensure you don’t run into any unnecessary challenges.

Myth #1: If the Concrete Surface Is Dry, the Slab Is Too

It may seem reasonable that if there is no moisture on the concrete surface, there is no extra moisture inside. This is because for most slabs that dry from one side, the surface is the only way for moisture inside to get out. As the moisture evaporates from the surface, more moisture can rise to the surface through the slab. However, this reality cannot serve as an accurate indicator of complete moisture levels. There are many other variables that can impact how quickly the slab dries. These variables include ambient temperature and relative humidity, air movement, and more. The only way to know for sure that the slab is dry enough is through relative humidity (RH) testing, which provides a clear picture of exactly how much moisture is in the slab.

Myth #2: Concrete That Is Old Must Be Dry

Another myth is that old concrete must be dry, when in fact, it is common for old flooring systems to exhibit signs of moisture-related problems. This is possible because although older concrete systems were more moisture-resistant than products on today’s market, signs of moisture issues can be difficult to spot, even if the levels are high. Another possibility that debunks this myth is that it is possible for older slabs to face moisture intrusion from an unknown source such as an appliance or plumbing leak. The slab’s moisture content may be high, but not high enough to notice.

Myth #3: Non-Grade Slab Doesn’t Require Moisture Testing

All types of concrete are affected by the conditions of the environment and are susceptible to complications due to moisture if they are not adequately tested before continuing with the next stages of construction.

Myth #4: Surface Testing Gives Accurate Results

It is important to keep in mind that any method of testing that focuses only on surface conditions is at a high risk of producing a false reading. The three current test methods that only provide results at the slab surface include the following:

  • Calcium Chloride Test (MVER)
  • The Hood Method
  • Moisture Meters

Each of these methods fails to gather an accurate result of the moisture levels in a concrete slab. The levels tend to be higher at the bottom of the slab but balance out through it once it is sealed by a floor covering or other technique. These test methods do not measure underneath the surface, which is why they cannot give a good measurement of what moisture levels will become after floor installation.

Myth #5: Dust Doesn’t Impact Drying Time

When working with concrete, dust and grit are inevitable, but that doesn’t mean you should ignore debris. These particles can impact the accuracy of RH testing if the hole to be tested is full of residue. Residue compromises the air volume around the sensor and limits its ability to provide accurate readings. Professionals will have the right equipment to not only drill and test the moisture levels, but dislodge and vacuum any loose particles before testing, so you can have the most accurate result.

Myth #6: Additives Don’t Impact Drying Time

Another myth is that additives don’t impact the drying time. The irony of this belief is that additives are intended to impact drying time—most of them are designed to shorten the drying time. Other additives are designed to reduce shrinking or to damp-proof to allow more time to add pigments for colour applications. Different additives ultimately affect moisture test methods.

Let Flood Services Canada Handle Your Concrete Drying

RH testing is the only way to find out accurate moisture levels of a concrete slab after the floor covering is applied. If the moisture level is too high, you risk compromising the entire floor system. Getting proper moisture testing before beginning a tile or flooring installation project is one of the most important steps, and buying into these myths will do you no good.

At Flood Services Canada, our technicians are fully certified by the Institute of Inspection Cleaning and Restoration Certification (IICRC). We have years of experience in moisture testing and extraction procedures and are capable of remediating any discovered water infiltration through wall dampness treatments. We have rapid response teams strategically placed around the GTA, so that they can provide quick response.

Contact us at (416) 302-2107 for more information about our concrete testing services and moisture removal testing in Toronto, or use our emergency hotline at (416)-999-3930 to get our rapid response teams deployed to your location in Toronto, Mississauga, or Burlington if you experience a flood.

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Chad Vanvari

Chad Vanvari has over 20 years of experience as a cleaning & restoration professional. He started out in Montreal, establishing a commercial carpet cleaning company in the early 1990’s. By 2001, Chad had relocated to Toronto and now had extensive knowledge and experience in responding to fire/water related emergencies. He has been instrumental in the cleanup of several catastrophic floods. Currently, Chad is the president and owner of Flood Services Canada, a 24/7 emergency service restoration company.