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Pre-Installation Subfloor Requirements

All Subflooring must be:

  • Structurally sound
  • Clean: Thoroughly swept and free of all debris (If being glued down, subfloor must be free from wax, grease, paint, sealers, & old adhesives etc., which can be removed by sanding)
  • Level: Flat to 3/16” per 10-foot radius
  • Dry and will remain dry: Subfloor must remain dry year-round. Moisture content of wood sub floors must not exceed 11%, concrete must not exceed 3.5 as measured with a Tramex Commercial Concrete Moisture Meter.

Wood Sub floors:

  • Must be flat to within 3/16” of a straight edge in a 10’ radius and without any abrupt height differences. “Hills” should be sanded down flat and valleys should be filled with a self-leveling cement compound developed for use with wood flooring such as Ardex K-15 Portland Leveling Compound or equal. Follow the manufacturer’s instructions for use.
  • Must be structurally sound, with the recommended subfloor to be at least a 5/8” min. thick plywood installed onto joists, which are 16” on center and adequately sized for the length of the span. Prior to installing the wood floor, check to make sure the subfloor is well nailed to the joists. Re-nail any loose areas or sections with squeaks. Also check any areas where there is excessive up and down movement of the subfloor and joists and shore them up from below by adding blocking and/or additional support.
  • The wood subfloor must be 10% M.C. or below. Take several moisture meter readings from different areas of the subfloor and save them as part of the permanent job record. Make sure, prior to installation of the wood flooring, that the space below the subfloor is not excessively damp as moisture from this area may later “wick” through the subfloor into the wood floor itself.

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Concrete Sub floors:

  • Must be flat to within 3/16” of a straight edge in a 10’ radius and without any abrupt height differences. “Hills” should be ground down flat and valleys should be filled with a self-leveling cement compound such as Ardex K-15 Portland Leveling Compound OR EQUAL. Follow the manufacturer’s instructions for use. Avoid leveling large areas of concrete with thin layers of leveling compound due to the inherent weakness of the bond.
  • Must be at least 60 days old and dry. Do not install on concrete unless YOU ARE SURE it stays dry year-round. All concrete should be tested for moisture and be below 3.5 moisture content as measured by a Tramex Commercial Concrete Moisture Meter. Other concrete testing methods may be used, see Other Concrete Testing Methods.
  • Must have a density of at least 90 lbs./cu. in.
  • Must be free from excessive alkaline, as in gluedown installations you may risk bond failure with the mastic used. On all glue down installations first test for pH and if excessive, neutralize using an acid wash and recheck before installation. Follow the specific instructions of the mastic manufacturer in testing for and correcting high pH subfloors.
  • Old concrete subfloors should first be roughed up with a sander in order to improve the bond between the subfloor & the mastic – please follow the mastic manufacturer’s specific instructions.
  • It is highly recommended, that if gluing down on concrete, (even if you believe it is dry), which is on or below grade, to install Sheet Vinyl first and then glue the wood flooring on top of the vinyl, as this provides an effective permanent moisture barrier. Another alternative to sheet vinyl is to use the Bostik or Franklin Moisture Barrier Systems and they provide warranties to you.
  • Remember, a concrete slab on/below grade that measures dry today may become moist in the future due to rising groundwater. Installing a moisture barrier now may be viewed as an insurance policy against concrete becoming wet in the future. This will lead to subsequent floor failure. Wood Flooring International is not responsible for site related moisture issues.