Installation of synthetic flooring shall not commence until the concrete substrate is determined to be "dry" by industry standard testing procedures. Testing the moisture content of the concrete is significant as “wet” slabs may lead to poor performance and/or insufficient bonding of the adhesives.  WSFI does not recommend testing for concrete moisture content within 60 days of pour. The required vapor barrier or under-slab membrane will likely increase slab drying times. Some factors affecting the concrete slab‘s drying time include:
  • Slab thickness
  • Surface applied treatments
  • Type of construction
  • Concrete formulation
  • Location of the building
  • Climatic conditions
  • Power troweling

It is the general contractors’ responsibility to provide a dry concrete slab within WSFI standards for moisture content and flatness. WSFI recommends using a third party testing agency when testing the concrete slab. The flooring contractor shall verify slab conditions prior to the commencement of any synthetic flooring installation to ensure compliance with flooring manufacturer specifications.

When conducting slab moisture testing, follow the most recent ASTM F2170 method to calculate the number of tests that should be performed - regardless of the age of the slab, document all tests. If the test(s) indicate a wet slab, delay installations of the synthetic flooring until specified conditions are met.

The only WSFI recognized method for reading concrete moisture levels within a slab is by testing its relative humidity level in conformance with the most recent ASTM-F2170. Please refer to the instructions of the manufacturer’s relative humidity test kit for complete details on how to administer the test correctly. WSFI recommends that the relative humidity level should be 75% or lower before installation. For concrete relative humidity conditions above WSFI’s recommendation consult your WSFI Sport Floor Contractor or WSFI Synthetic Flooring Supplier.

Concrete Relative Humidity Test

Relative Humidity Test (In-Situ Probe Test)
  • Use a prepackaged relative humidity testing kit (must be compliant with the most recent ASTM F2170) and  follow the manufacturer's instructions. This test method involves measuring relative humidity levels inside of the concrete slab.

Pre-Tests

The following can be administered as pre-tests for testing the moisture content of a concrete slab but should not be used to confirm a concrete slab has dried to acceptable levels:
  1. Polyethylene Film Test
  • Tape a 2' x 2' square of 6 mil clear polyethylene film flat to the slab, sealing all edges with moisture resistant tape. Suspend a 250-375 watt heat lamp 2' above the plastic film. After 24 hours, check the film - if no condensation or "clouding" develops on the underside of the polyethylene, the test area shall be considered dry enough to test the concrete slab’s relative humidity.
  1. Calcium Chloride Test
  • Use a prepackaged calcium chloride test (widely available) and follow the manufacturer's instructions. The Calcium Chloride Test measures the quantity of moisture passing through a concrete floor. This measurement is stated as pounds of moisture over a 1,000 sq. ft. area during a 24-hour period. An acceptable level is 4.5 lbs. or less.
  1. Electronic Concrete Moisture Meters
  • Due to the different types of electronic concrete moisture meters on the market, WSFI recommends following the manufacturer’s instructions for proper on-site testing procedures.

If you have additional questions, please contact WSFI's Technical Director at 888-480-9138 or email at wsfi@maplefloor.org
Disclaimer: The MFMA provides general information to architects, specifiers and consumers. The MFMA, its members, officers and agents disclaim any responsibility whatsoever for the accuracy or applicability of these guidelines under all circumstances and conditions.
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