Specifying, Installing Wood Floors in Office Interiors

By Brett Miller

Of the flooring options available in today’s ever-changing commercial marketplace, wood is the only one that is completely sustainable. On top of that, there is a growing body of research that suggests real wood may be good for people’s mental and physical health when incorporated into the built environment.

So, why is it most commercial builders, architects, contractors and design professionals do not specify wood and instead source products that just look like it?

The answer is actually quite simple. The perception is non-wood products are an easy sell and they won’t scratch.

However, looks can deceive. Many wood floors perform incredibly and often become even more appealing with time, use and patina.

Navigating the Selection Process
Wood floors can be found in countless commercial applications. But before moving forward with wood, specifiers should ask the following three questions to ensure it is the right fit, especially as some perform better than others in these high-traffic environments: Is the wood selection appropriate for the facility and region? Is the facility ready to receive wood flooring? Can the facility sustain an environment that’s conducive to wood flooring performing as it should?

Other considerations include the cut, width, type and species of wood.

Wood is a hygroscopic and anisotropic material, meaning it takes on and throws off moisture, and shrinks and swells differently in each direction depending on change in moisture. How wood changes dimension is largely influenced by the way in which it was cut from the tree. For solid wood flooring, these cuts are classified as plain sawn, rift sawn, quarter sawn, live sawn and end grain. The hardest and most durable cuts are quarter sawn and end grain. The most stable cuts are rift sawn and quarter sawn.

Wood changes dimension proportional to the width of the plank. Narrower boards expand and contract less than wider boards of the same species and cut.

Engineered wood flooring is generally more dimensionally stable than solid wood flooring. However, not all engineered flooring is recommended or appropriate for use in commercial settings. End grain flooring is by far the hardest and most durable wood flooring option for commercial spaces but a controlled environment is key to the long-term performance of this material.

In solid and engineered flooring options, certain species are known for their inherent dimensional stability. More stable species like mesquite, merbau and eastern white pine are better options for less stable environments. Hickory, beech and birch are not as stable, so they’re not ideal for these types of situations.

Laying Down the Rules
Concrete is the most commonly used commercial building material. It is cost-effective, energy efficient and provides superior fire resistance. Concrete also offers excellent sound control, so it works well as a subfloor material in commercial spaces and multi-residential buildings.

There are important guidelines to follow when installing wood over a concrete slab. Moisture must be accounted for by the flooring contractor. Common methods for measuring moisture in concrete include relative humidity tests (ASTM 2170), calcium chloride tests (ASTM 1869), calcium carbide tests (ASTM 4944) and electrical meter tests (ASTM 2659). The results may indicate further testing is required and/or the presence of moisture. It is critical to use an appropriate vapour retarder to help minimize future moisture issues.

The slab must be free of contaminants, such as wax, oil, grease, paint and curing compounds. It may be necessary to scarify, shot blast or grind the concrete to properly prepare it for wood floor installation. Removal must be deep enough to eliminate all contaminates and produce necessary concrete surface profile for the installation method being used.

Concrete subfloor joints (construction, contraction and isolation) must be honoured and not filled with underlayment materials or other products. A wood floor secured directly to a concrete slab should not bridge moving joints without allowing for a breaking point. When concrete decides to move, it is going to do so.

The compressive strength of the concrete must be accounted for when specifying an installation system to use for the wood floor. Normal weight concrete has a compressive strength between 3,000 pounds per square inch (psi) and 4,000 psi. Anything less will require additional preparation, such as an application of surface densifiers or hardeners.

Flatness tolerance for wood floor installation is 1/8-inch in six-feet, or 3/16-inch in 10-feet. No slab is poured to these specifications. Professional contractors can remove high spots by grinding and then filling depressions with approved patching compounds. Concrete subfloors can also be flattened using a self-levelling concrete product. (The disparity between concrete floor flatness tolerances in the wood flooring industry and tolerances for concrete flatness within 72 hours of it being poured is detailed in the American Concrete Institute standard.)

The building has to be within tolerance prior to wood flooring delivery or installation. This means it must be enclosed, wet trades completed and the HVAC system fully operational, including heating/cooling and humidification/dehumidification systems. Temporary HVAC may be used if it is capable of mimicking the expected in-use conditions of the space. Temporary heaters fuelled by propane are not acceptable sources of heat as the combustion of propane produces high volumes of moisture.

Installation of any wood flooring product must strictly adhere to the flooring manufacturer’s instructions. Where manufacturer instructions do not exist, National Wood Flooring Association installation guidelines should be followed.

Brett Miller is vice-president of technical standards, education and certification at the National Wood Flooring Association, an international not-for-profit trade association representing all segments of the hardwood flooring industry. Brett can be reached at [email protected].

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