Moisture issues in concrete can lead to serious problems, from flooring failures to mold growth. Whether you’re installing flooring over concrete or dealing with persistent dampness, understanding the source of moisture is critical. This guide will break down:
How to check moisture levels in concrete
Solutions for high moisture content
The difference between moisture in the concrete vs. moisture intrusion from external sources
Checking Moisture Levels in Concrete
Before installing flooring or coatings, it’s essential to test for moisture. There are several reliable methods:
1. Calcium Chloride Test (ASTM F1869)
This test measures the moisture vapor emission rate (MVER) in pounds per 1,000 square feet over 24 hours. If MVER is too high, flooring adhesives and coatings may fail.
2. Relative Humidity Test (ASTM F2170)
This test uses probes inserted into drilled holes to measure internal humidity. Most flooring manufacturers require RH levels to be below 75-85% before installation.
3. Concrete Moisture Meters
Handheld moisture meters provide quick readings but are best for preliminary assessments rather than final decisions.
Solutions for High Moisture in Concrete
If tests indicate high moisture, there are several ways to mitigate the issue:
1. Concrete Sealers
Penetrating Sealers (Silicate, Silane, Siloxane): React chemically to reduce water absorption while allowing the slab to breathe.
Epoxy or Urethane Sealers: Form a barrier to block moisture transmission but require proper surface preparation.
2. Vapor Barriers & Moisture Mitigation Systems
Liquid-applied moisture barriers: These are epoxy-based coatings applied to the concrete to control moisture.
Sheet membranes: Installed beneath flooring, these provide an extra layer of moisture protection.
3. Allowing Proper Curing & Drying Time
Fresh concrete needs adequate time to cure and dry before flooring installation. Rapid installation without checking moisture levels can lead to failures.
Moisture in Concrete vs. Moisture Intrusion
Not all moisture issues originate from within the concrete. External factors can introduce moisture, leading to long-term damage.
Internal Moisture (From Within the Concrete)
Occurs due to incomplete curing or natural hydration reactions.
Typically dissipates over time with proper ventilation.
Can be controlled with vapor retarders and sealers.
Moisture Intrusion (External Sources)
When water enters from outside, it requires different solutions:
Overwatering Planters Near Foundations: Excess moisture seeps into the slab, causing elevated moisture readings.
Solution: Redirect drainage and use proper irrigation techniques.
Improper Drainage Around Buildings: Sloped landscaping or compacted soil can force water into the foundation.
Solution: Ensure proper grading and install French drains if needed.
Leaky Rain Gutters & Downspouts: Water pooling near the foundation can lead to intrusion.
Solution: Extend downspouts and direct runoff away from the structure.
Hydrostatic Pressure: Water beneath the slab pushes moisture upward, often due to a high water table.
Solution: Use sump pumps, vapor barriers, and waterproof coatings.
Final Thoughts
Moisture control is crucial when working with concrete, whether for flooring installation or structural integrity. Testing moisture before applying finishes, using proper sealers, and addressing external water sources can prevent costly issues. If you’re dealing with persistent moisture problems, consulting a professional can help determine the best long-term solution.
Need help selecting the right moisture barrier or flooring for your project? Contact Perry Floors today!
