First, what are the species generally available for flooring choices? Temperate hardwood species from the United States and Canadian forests are the most readily available and overall are considered the most environmentally responsible. They are generally manufactured according to a recognized standard such as NOFMA: The Wood Flooring Manufacturers Association, which certifies manufacture of flooring that includes the species- both red and white oak, hard maple, beech, birch, hickory/pecan, ash, cherry, and walnut. The MFMA (Maple Flooring Manufacturers Association) also administers manufacturing standards for hard maple, beech, and birch primarily for sports floor applications. The CLA (Canadian Lumberman's Association) has voluntary grading guidelines for red and white oak, maple, and birch. Also, most of the lumber comes from forest that are managed to meet sustainability criteria.
In addition, some imported species from Central and South America, Africa, or Australia are available as flooring. These products are generally manufactured to proprietary standards and may or may not come from managed forests. Also, some of the species can have dual uses for both exterior and interior use. If manufactured to the less strict parameters of outside application and placed inside, significant shrinkage can result.
Some softwood species are also available for wood flooring. New wood as well as old recycled building members are made into flooring. These species may be made with allowance for a wide range of moisture content and should be checked by the contractor prior to installation to determine proper installation and related acclimation.
The most common temperate hardwood flooring species choices are: oak - both red and white, hard maple, and hickory/pecan. Ash, cherry, and walnut are not as common and, birch and beech have limited availability. Others species locally available for flooring typically on a limited special order basis are: locust, mesquite, alder, elm, soft maple, and tanoak. These species have their own unique characteristics and often are selected for their particular look to fit the special decor. Although the look may influence species choice, it is not the only criteria. Other items that will affect performance are: the stability of the product, finishing characteristics, dent resistance or hardness, color, and the expected color change.
Oaks are the most readily available and have the widest use. Oak is considered the base line for dimensional stability. Other species are generally compared to it when making choices where this attribute is important. Overall oak is considered moderately stable. For the typical seasonal change of 2 percent to 3 percent, the seasonal winter gaps will not be prominent when using widths of 5 inches or less. Choosing a wider oak plank flooring of 6, 7, or 8 inches and placing in an area with seasonal swings of 3 percent and greater may not be a good choice since the seasonal shrinkage will likely result in prominent gapping. Oak is easily finished, takes most any stain uniformly, and accepts finish well. The oak grain pattern is quite prominent with the open pores of the springwood and the tight dense pattern of the summerwood. When stained this difference is highlighted and is frequently listed as one of the desired characteristics for this species.
Oak is separated into red oak and white oak groups or species. The main difference between the two is the color contrast of the sapwood and heartwood of white oak. White oak has the very light cream colored sapwood and the rich brown heartwood and the occasional greenish tint. There is little heartwood-sapwood contrast for red oak which is generally pink to flesh toned. White oak is generally slightly harder than red oak and both are relatively the same dimensionally. If a white floor is desired, however, certain tannins in white oak can interfere and discolor white stains. This may not be evident until staining is completed.
Ash is more dimensionally stable than oak, is generally as hard, with a similar grain pattern and finishes similarly to oak. Ash is a good choice where a very light color or a white floor is desired. The NOFMA Clear and Select grades should be selected since they require these separations to include mostly white sapwood. A draw back or caveat when selecting wide widths for a white floor with a wide range of seasonal variation is that noticeable gapping is likely. Customers should be informed of this during the selection process.
Maple, beech, and birch flooring have a nondescript grain without obvious open pores and the contrasting springwood-summerwood. They generally fall in the lighter wood category for the higher grades. Seasonal gaps can become prominent with the contrast between the light wood and darker gap which creates the perception that the gaps are much bigger than they really are. Maple and birch are about as stable as oak so width choices are similar. However, beech flooring is less stable than oak and seasonal changes resulting in wide gaps or cupping can initiate the dreaded call back. These three species do not stain easily and "blotchiness" is the usual result. For the site finished floor staining is not recommended. Commercially, the main species choice for basketball courts is hard maple.
Hickory/Pecan is generally selected for its variety of color, prominent grain, and character marks. This variability of sapwood-heartwood color from cream to brown to a variety of pinks to reds and intermittent streaks and darker grain is generally associated with the "rustic" look. Much harder than oak, it wears well. However, abusive conditions of grit and very small pebbles can indent and scratch even this species. Dimensionally, it expands and shrinks more than oak, so stick with the more narrow widths, less than 4", will perform best if noticeable seasonal gaps are an issue. Hickory/Pecan can be stained but conditioning prior to staining is suggested in order to get a uniform color. For commercial use it is the preferred species for roller skating rinks.
Cherry and walnut are species generally selected for their particular natural color. Cherry is a lusterous deep reddish brown and walnut a purple black. Both are relatively less dent resistant than oak so high traffic areas with associated debris can create significant wear patterns. Coloring? They are selected for their natural colors so additional color is not generally necessary. They also do not stain uniformly. Cherry is one species that will noticeably change color over time. As it ages the color becomes a darker reddish brown so new wood and old wood will not match. Over time they will blend together. Both species are significantly more stable than oak.
The other temperate hardwood species choices have their own unique characters. Locust is very hard, has an iridescent component, and glows in black lights. Mesquite is generally selected for its chocolate heartwood color, and the sapwood is vulnerable to insect attack. Alder is light in color that changes to reddish tint with age, is soft and stains poorly. Elm is selected because of the unique flame characters within the grain pattern.
Softwood species choices include southern pine or heart pine, fir, and larch. These are similar in performance and finishing characteristics. Staining is not recommended because of inconsistent or blotchy results. They are also classified as soft, except for specialty products from reclaimed old growth timbers that exhibit very tight grain patterns.
Imported species come in a myriad of colors, graining, and physical characteristics. One of the keys in selection is to identify the actual species selected. Many of the names are marketing names or common names and include two or more species. The differences within these classes can be quite different region to region. So what is expected may be different from what is received. For this article imported species will not be discussed.
Qualifying the customer is the most important step in directing the selection of species for a particular project. The following questions will help qualify the customer.
What "look" does the customer want in a flooring product?
What activities will occur on the flooring?
What environmental conditions will be established?
The "look" such as light or white or dark to ebony can be accomplished by staining those species that will stain or by selecting a naturally white or naturally dark wood. Other characteristics such as grain and color as noted in the foregoing descriptions will also direct the species choices. The oaks and ash species have a virtually unlimited color pallet when using stains.
The traffic and conditions surrounding the site will help determine whether wear is an issue. Harder materials should be the options for heavy traffic and abrasive conditions. The environment associated with the site also qualifies the species options. The options for width will be determined by the stability. For wide ranging environmental conditions those more stable species and the more narrow widths are the best choices. This can apply particularly with radiant heated flooring where shrinkage may be an issue. Also, for assurance of quality and proper manufacture select a certified NOFMA hardwood product, an MFMA stamped maple, birch or beech product, a CLA member's oak, birch or maple product, or an SPIB stamped softwood.