By Brett Miller, NWFA Vice President of Education & Certification
Any flooring contractor who has been in the business for a while knows there are a multitude of issues that can arise when installing wood floors, and chances are that most contractors have experienced a few of them during their careers. The good news is that with a little planning, and thoughtfully selecting the right products, most wood flooring installation issues can be avoided.
Acclimation is perhaps one of the most neglected preventative performance issues for wood floors. This process involves conditioning the flooring material to the environment in which it will be installed. This can happen away from the jobsite if the materials will be acclimated to the same conditions as the jobsite, but optimally, should occur on the jobsite.
The jobsite should be maintained at the expected living conditions for a minimum of five days before installation takes place, and be kept at these conditions both during and after installation. Deviating from these conditions will impact the performance of the flooring.
Engineered flooring may not require on-site acclimation; however, the manufacturer will likely require specific temperature and humidity conditions for their flooring. This is just another form of acclimation.
Moisture typically is the number one culprit for many wood flooring failures. Many contractors do not adequately test for moisture before installing wood flooring, which leaves the floors susceptible to performance issues and potential failure that could require complete replacement.
Fortunately, moisture issues can be identified, and avoided, before they pose a problem. A moisture meter should be in every flooring contractor’s tool box. For wood installations, both the wood and the subfloor should be tested. Tests should be conducted in several locations in the room where the wood will be installed, a minimum of 20 tests sites per 1,000 square feet. For solid strip flooring less than 3″-wide, there should be no more than a 4% moisture content difference between properly acclimated wood flooring and subfloor materials. For solid plank flooring 3″ and wider, there should be more than a 2% moisture content difference.
Moisture retarders can help prevent moisture-related failures as well. One such product is a one-coat moisture control system, which is also referred to as a multi-functional adhesive. These systems are designed to work as an adhesive for installing the flooring material, but also can have additional functions as well. These can include moisture control, sound control, crack bridging, and even anti-microbial properties.
Traditional moisture control systems require application of the sealer and adequate dry time prior to the flooring installation. Some common urethane sealers have dry times that could be 24 hours or more, which could potentially shut down a jobsite for days, so these new systems can save installers significant time. These systems generally cost more, but the additional cost is offset with time saved on the jobsite. Application of these systems is specific to each product and can require specialized trowels for proper application, which require 100 percent coverage and transfer. These application requirements also typically require extensive substrate preparation.
Another problem-solving product is a self-leveling underlayment. These products are often used to achieve flatness tolerances for concrete substrates.
Before wood flooring can be installed over a concrete substrate, it must be flat to within 3/16” in 10 feet, or 1/8” within 6 feet. If the substrate is not within these tolerances, then high spots must be removed and low spots must be filled in. For grinding high spots, proper safety equipment should be used to avoid breathing silica, which is a health concern. For filling low spots, self-leveling compounds can be used.
To use these products, always follow the manufacturer’s recommendations. This will include instructions for preparing the slab, identifying the primer to use, mixing the materials, applying the compound, and drying time. It is important to not use adhesives or moisture control systems as leveling agents, and to apply all products within the system at the rate recommended using the method required by the manufacturer.
Maintaining proper expansion space is another easy way to avoid potential wood flooring performance issues. As a general rule, solid wood flooring must have a perimeter expansion space on all four sides greater than or equal to the thickness of the material being installed. The reason for this is simple, and has to do with the anatomy of wood.
Wood is a hygroscopic material, and it gains and loses moisture in response to its environment. In dry environments, wood loses moisture and contracts. In humid environments, wood gains moisture and expands. Wood expands primarily in its width, which would lead one to believe that expansion space would only be required on the sides of boards. However, the flooring is not the only wood product in the system that expands or contracts. The 2x4s used in a framed wall, as well as a plywood or OSB subfloor, can expand and contract as well. This can affect the wood floor, which is why expansion gaps are needed on all four sides.
Because of its construction, engineered wood flooring will expand and contract in all directions, not just through its width, so maintaining expansion space at all vertical obstructions is necessary. However, engineered flooring typically requires minimal expansion space compared to solid wood flooring. Follow the manufacturer’s directions to ensure optimal performance.
Expansion space for floating floors is even more critical. Anywhere the flooring comes into contact with a stationary object, the floor will pivot and become stressed beyond its capabilities.
As you can see, many potential wood flooring performance issues can be avoided with a little preparation and planning. The situations outlined here may seem tedious or even unnecessary, but just one failure due to skipping just one of these steps could result in a costly and time-consuming repair that could have been entirely avoided.
You can learn more about common mistakes to avoid when installing wood floors in the NWFA Wood Flooring Installation Guidelines. These guidelines are provided to all NWFA members as a member benefit. They are available to non-members for purchase. For more information, contact the association at (800) 422-4556 (USA and Canada), (636) 519-9663 (international), or visit www.nwfa.org.