separate 1 : wood SUBFLOORS
pg51_editedAs an installer, it’s critical to understand the different types of underlayments for moisture control and how each can affect installation. Part one of this series will address the guidelines for moisture control underlayments over wood subfloors. Many flooring manufacturers recommend specific underlayment materials to be used below their flooring. Follow manufacturer recommendations whenever applicable.
As an installer, it ’ randomness critical to understand the unlike types of underlayments for moisture restraint and how each can affect initiation. Part one of this series will address the guidelines for moisture operate underlayments over woodwind subfloors. many flooring manufacturers recommend specific carpet pad materials to be used below their deck. Follow manufacturer recommendations whenever applicable. A arduous moisture invasion can migrate up through a wood subfloor. It may occur lento, but its effects are damaging. Proper facility of flooring calls for testing subfloors for moisture. In any case, the moisture content of solid comic strip deck, corporeal < 3 ” should be within 4 percentage points of the woodwind subfloor. ( That is, if the subfloor is measured at 10 percentage moisture content, the strip shock should have no less than 6 percentage moisture capacity and no more than 14 percentage. ) For solid plank deck, material 3 ” or wide, the difference should be nobelium more than 2 share points.

When installing wood shock over a forest subfloor, an acceptable carpet pad is a vaporization retarding corporeal, membrane or covering with a vaporization permeance ( perm evaluation ) of greater than or equal to 0.7, and less than or equal to 10, when tested in accord with ASTM E96. This is the necessity chemical element determining whether or not a material is an acceptable vaporization retarder .
NWFA Guidelines follows the IRC definition for vaporization retarders as : class I < 0.10, Impermeable ; Class II 0.10 < 1.0, Semi- Permeable ; Class III 1.0 < 10.0, Permeable. Materials with a perm evaluation of 10 or greater are not considered to be vapor retarders
by the IRC .
facility of a vaporization retarder reduces the rate of moisture vaporization migration from below the wood floor. Do not use an impermeable membrane as this will trap moisture, which can lead to subfloor bunk, cast or mildew. It is not a good idea to place a material with a lower or about equal permanent wave rat over a wood subfloor with a higher permanent wave rat. 23/32 ” plywood is by and large recognized to have a permanent wave rate of .55. This why the NWFA limits the humble end of the perm military rank to 0.70 .
In situations where unconditional crawl spaces or bare basements are immediately below the wood flooring, it is always significant to check and record the temperature, relative humidity and moisture levels below and above the subfloor to ensure the gradient between the two floors is not besides drastic and besides that the facility is able to be maintained at appropriate levels .
A vaporization retarder will not stop the moisture below the floor from migrating into the install flooring ; it will merely slow the procedure allowing the forest shock to adjust gradually to seasonal worker changes. When applicable attend for vapor retarders that have passed California indoor air quality regulations .
early benefits of these types of vaporization retarders may include :

  • Elimination of wood on wood contact, making flooring strips or planks slide more easily when positioned during installation
  • Reduces dust and airflow from below solid wood subfloor systems
  • Minimizes the impact of seasonal moisture changes from below the flooring system

Install a vapor retarder over wood subfloors before installing complete down solid or mastermind deck ( unless otherwise directed by the floor manufacturer ). The vapor retarder should cover the entire flooring surface. Overlap seams a minimum of 4 inches or more as required by the manufacturer.

Some examples of acceptable vapor retarders may include :

  • Asphalt laminated paper
  • Asphalt saturated Kraft paper
  • ASTM rated roofing felt
  • Some foam padding may be acceptable vapor retarders under floating wood floors, when meeting the above perm rating requirements (.7<10), but are never recommended under nail down applications

Proper use of an carpet pad material will help you control moisture migrations from below the install floor. As always, check with your manufacturer for proper use, capability and facility of the product .
Roger Barker is Market Manager Flooring at Fortifiber Building Systems Group in Fernley, Nevada. He can be reached at rbarker @ .

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