Combatting High Moisture for Installations Over Wood Substrates

Photos courtesy of Sika Corporation

In the United States alone, moisture-related damage to flooring has caused upwards of one billion dollars to be lost on claims. Installations of wood flooring over wood subfloors can be particularly susceptible to moisture problems. A variety of negative effects resulting from unmitigated moisture could manifest immediately, or take weeks, or months following the installation to appear. Common indications include discoloration, warping, cupping, and rotting of subflooring and flooring planks. Mold, mildew, or bacteria also may result from a high moisture presence and present health hazards. To avoid these kinds of costly and hazardous scenarios, it’s strongly recommended to use professional-grade moisture retarding systems to protect the wood flooring from being adversely affected by moisture stemming from below the subfloor assembly.

Although most wood subfloors can withstand a slight degree of moisture fluctuation, avoiding long periods of exposure and properly preparing the subfloor is the first critical step for the long-term protection of an installation. While concrete slabs are known to emit moisture vapor via small capillary networks, wood materials will more commonly soak up moisture from surrounding sources. It’s therefore key to protect the substrate from these sources while also establishing a proper surface on which other materials can later be applied properly.

Among the latest innovations in the industry to serve this purpose are onecomponent, semipermeable, roll-on moisture retarders that offer some moisture protection while simultaneously providing the foundation for the rest of the installation. These solutions can help to fortify the subfloor and aid with adhesion promotion, allowing for a direct application of adhesive and making for the best option to combat moisture prior to a glue-down or glueassist installation. Many options on the market even contribute to sustainable building efforts by featuring solvent-free and low VOC formulas, while still boasting Class II perm ratings that meet the criteria set forth by the National Wood Flooring Association (NWFA).

Another layer of value is that the NWFA suggests this type of product as an appropriate option when installing over unconditioned crawlspaces or basements.

As an additional measure of proper subfloor preparation, installers may sometimes find the need for a self-leveling underlayment. A durable self-leveler specifically designed for wood subfloor systems can further guarantee that the surface is flat, level, and smooth.

The latest such solutions also feature rapid setting technology that helps to meet the expectations of time-sensitive and demanding projects. Some options incorporate high flow, high strength engineering along with cure times of just 90 minutes. These cementitious underlayments establish a self-smoothing substrate that is ideal for residential and commercial floor finishes alike. When used in combination with the roll-on moisture retarders, a secure system can be ready within just a few hours.

For additional information about mitigating moisture, check out the NWFA’s Installation Guidelines at

When contending with installation over unconditioned spaces, over wood subfloors, installers are faced with a wider range of products than ever before. These systems allow installers to address potential moisture concerns rapidly, establish an optimal surface profile, and utilize a compatible adhesive.

Nick Mizzone is the marketing coordinator for Sika Corporation in Lyndhurst, New Jersey. He can be reached at To learn more, please visit

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