Wood Floor Glossary

GLOSSARY



TYPES & STYLES

Solid

Solid hardwood floors come in a wide range of dimensions and styles, with each plank made of solid wood and milled from a single piece of timber. Solid hardwood floors were originally used for structural purposes, being installed perpendicular to the wooden support beams of a building. Modern construction techniques now rarely use wood building frames and solid hardwood floors are used almost exclusively for their appearance.

For flooring, solid wood has many limitations due to the natural characteristics of wood. Expansion and contraction of wood from moisture and temperature fluctuation puts many dimensional restrictions on solid wood floors. Typically, 5" wide and 3/4" thick boards are the largest that can be manufactured from solid wood without compromising the structure of the flooring (some manufacturers produce wider boards using proprietary milling techniques). There is, however, no standard size which will perform well in every environment. For contemporary construction techniques, the most significant characteristic of solid wood floors is that they are not recommended to be installed directly over concrete.

Engineered

Wood flooring is a popular feature in many houses.

Engineered wood flooring is composed of two or more layers of wood in the form of a plank. The top layer (lamella) is the wood that is visible when the flooring is installed, and is adhered to the core (or substrate) which provides the stability.

Laminate, vinyl and veneer floors are often confused with engineered wood floors - laminate uses an image of wood on its surface, vinyl is plastic formed to look like wood, and veneer uses a thin layer of wood with a core that could be one of a number of different composite wood products (most commonly, high density fibreboard).

Engineered wood is the most common type of wood flooring used globally. North America is the only continent that has a larger solid wood market than engineered, although engineered wood is quickly catching up in market share.

Comparison of Solid Wood and Engineered Wood

It is very difficult to compare a solid wood floor to engineered wood floors, as there is a wide range of engineered wood floor qualities. There are several limitations on solid hardwood that give it a more limited scope of use: solid wood should not be installed directly over concrete, should not be installed below grade (basements) and it should not be used with radiant floor heating. Solid hardwood is also typically limited in plank width and is more prone to gapping and cupping with increased plank size. Solid wood products, on average, have a thicker 'sandable area' (the wood that is above the tongue), and can be installed using nails. Lastly, solid wood tends to be less expensive than engineered wood, but this, as with the 'sandable area,' depends on the quality of the engineered wood (most inexpensive engineered wood products are 'veneer' wood floors, and not 'engineered').

Engineered wood flooring has several benefits over solid wood, beyond dimensional stability and universal use. Patented installation systems (such as "click" or "G6") allows for faster installation, and easy replacement of boards. Engineered wood can use 'floating' installations, further increasing ease of repair and reducing installation times.

Wood Laminates

A wood laminate floor is simply plywood coated with a layer of veneer, making it appear to be solid wood. Today, there are a wide variety of choices when it comes to laminate flooring, from colors to thickness. Solid hardwood floors, at 3/4 inch, are twice as thick as wood laminates, which are typically 3/8 inch. This method of flooring is less expensive than solid wood flooring, and great if you need a quick, inexpensive fix and don't want to make a large investment.

Synthetic Plastic Laminates

Very similar to a wood laminate, plastic laminate is even more cost effective. It consists of a fiberboard that is thoroughly wrapped in layers of high-pressure laminate, a similar material to your kitchen countertop. Though cheaper, the disadvantage is that the floors wear out and cannot be sanded or refinished. The pattern of the floor repeats because laminate flooring is actually a photograph of real wood put onto a wood composite. When walking on laminates, they do not have the same sound as walking on real wood, but can be cleaned using most any cleaning products.

MANUFACTURING

Solid Wood Manufacturing

Solid wood can be cut in three styles: flat-sawn, quarter-sawn, and rift-sawn. However, because only one side of the wood is visible on flooring, "quarter-sawn" and "rift-sawn" will have the same appearance.

Many solid woods come with "absorption strips" - grooves cut into the back of the wood that run the length of each plank. They are used to reduce cupping.

Solid wood floors are mostly manufactured with a tongue-and-groove for installation.

Engineered Wood Manufacturing

Lamella

The lamella is the face layer of the wood that is visible when installed. Typically it is a sawn piece of timber.

The timber can be cut in three different styles: flat-sawn, quarter-sawn, and rift-sawn. However, because only one side of the wood is visible on flooring, "quarter-sawn" and "rift-sawn" will have the same appearance.

The Core / Substrate

1) Wood ply construction ("sandwich core"): Uses multiple thin plies of wood adhered together. The wood grain of each ply runs perpendicular to the ply below it. Stability is attained from using thin layers of wood that have little to no reaction to climatic change. The wood is further stabilized due to equal pressure being exerted lengthwise and widthwise from the plies running perpendicular to each other.

2) Finger core construction: Finger core engineered wood floors are made of small pieces of milled timber that run perpendicular to the top layer (lamella) of wood. They can be 2-ply or 3-ply, depending on their intended use. If it is three ply, the third ply is often plywood that runs parallel to the lamella. Stability is gained through the grains running perpendicular to each other, and the expansion and contraction of wood is reduced and relegated to the middle ply, stopping the floor from gapping or cupping.

3) Fibreboard: The core is made up of medium or high density fibreboard. Fibreboard has minimal expansion and contraction so the core is very stable. Due to the softer nature of fibreboard, wood floors with a thin lamella or veneer are more prone to denting. Fibreboard is less expensive than timber but is not VOC free and is not environmentally friendly.

Installation Systems

Wood can be manufactured with a variety of different installation systems:

1) Tongue-and-groove: One side and one end of the plank has a groove, the other side and end has a tongue. The tongue and groove fit snugly together to form the floor. Floors with a tongue-and-groove can be installed by glue-down (both engineered and solid), floating (engineered only), or nail-down (not recommended for engineered).

2) "Click" systems: there are a number of patented "click" systems that now exist. A "click" floor is similar to tongue-and-groove, but instead of fitting directly into the groove, the board must be angled in to make the curved tongue fit into the groove. This system only exists for engineered wood floor and is designed to be used for floating installations. It is designed for the Do-It-Yourself market.

3) Floor connection system: There are a wide range of connection systems, as most of them are mill-specific manufacturing techniques. The general principle is to have grooves on all four sides of the plank with a separate, unconnected, piece that is inserted into the grooves of two planks to join them. The piece used for the connection can be made from wood, rubber, or plastic. This installation system allows for different materials (ie. wood and metal) to be installed together if they have the same connection system.

Other wood manufacturing styles

Rotary-peel

This process involves treating the wood by boiling the log in water at a certain temperature for an allotted amount of time. Then after preparation the wood is peeled by a blade from the outside of the log, and it works its way around the log toward the center, creating a wood veneer. This veneer is then pressed flat with high pressure to make the veneer flat. This style of manufacturing tends to have problems with the wood cupping or curling back to its original shape. This problem is commonly known as "face checking" and is a manufacturing defect. Rotary-peeled engineered hardwoods tend to have a plywood appearance in the grain.

Sliced-peel

This process involves the same treatment process that the rotary peel uses. However instead of being sliced in a rotary fashion, this style of wood is sliced from the end of a log. From there it goes through the same manufacturing process as a rotary peeled product. However this style of engineered hardwood tends to have less problems with "face checking" and also does not have the same plywood appearance in the grain. However, this product can tend to have edge splintering and cracking due to the fact it has been submersed in water and then pressed flat.

Dry solid-sawn

Instead of boiling the hardwood logs, in this process they are kept at a low humidity level and dried slowly to keep moisture from inside of the wood cells. The manufacturing process to get this top veneer layer is similar to how a solid hardwood is manufactured. This style of engineered hardwood has the same look as solid hardwood, and does not have any of the potential problems of "face checking" that rotary- and slice-peel products have, because the product is not being exposed to added moisture.

Floor Finishing, Refinishing, and Sanding

Sanding provides a method for smoothing an installed floor, compensating for unevenness of the subfloor. Additionally, sanding is used to renew the appearance of older floors. Sanding using successively finer grades of sandpaper is required to ensure even stain penetration when stains are used, as well as to eliminate visible scratches from coarser sandpaper grades used initially. Prior to modern polyurethanes, oils and waxes were used in addition to stains to provide finishes. Beeswax and linseed oil, for example, are both natural crosslinking polymers are hardened over time. Modern polyurethanes, and polyester resins, used occasionally, are superior in toughness and durability.

WOOD SPECIES

Ash

Ash wood is extremely light to nearly white in color. This wood was formerly used to make tennis rackets and windmills due to its lightweight and sturdy nature. Floors made from ash wood are surprisingly durable given the weight of the wood, have excellent shock resistance, and remain smooth despite high traffic and friction, making the potential for damage minimal. For busy households with high levels of traffic, ash is an excellent choice.

Bamboo

One of the newest and most popular materials used in the flooring industry today. Made from grass, instead of wood, bamboo is available in 1,000 species throughout the world, making it a very available and easy to find choice for floors. Bamboo flooring looks similar to a standard wood floor's golden blond color, but is available in over 30 colors, making it versatile enough to appeal to everyone. Additionally, bamboo is a very hard material, environmentally friendly and cleans as easily as all other wood flooring.

Beech

A white wood with a red tinge, beech is excellent for those looking to install a durable, shock resistant floor. Beech gained popularity because it is adaptable and looks great in any room with its clear, smooth appearance. The average Beech wood tree is 120 feet high with long, straight grains. The smooth grains are suitable for smaller spaces, making a room appear to be larger than it is. Beech flooring is a fantastic choice for families with pets or children, having a natural resistance to daily wear and tear.

Birch

Yellow birch is very common for wood floors. It has a light yellow or pale appearance, and is typically chosen because of the unique curly or wavy pattern in the grain. This wood is very strong and durable, making it an excellent choice for high traffic areas or active families.

Cherry

Cherry wood comes from trees up to 200 years old, and has a creamy white color. As flooring, it is appealing because of its fine, straight grain and satiny smooth texture. Though beautiful, this wood is usually considered too soft for an entire floor or large room and is mostly used in borders and accents. Cherry wood is an excellent choice if you are looking to upgrade a room in your home by adding a medallion to your foyer or redesigning an old staircase.

Douglas Fir

Because of its tan color, douglas fir is often mistaken for southern yellow pine. This floor is considered durable but can easily dent if used in a high traffic room. This wood is recommended for rooms that do not have windows because it can fade easily with sunlight. Small bathrooms or light traffic areas are ideal places for douglas fir.

Hard Maple

Maple floors are extremely durable and available in a variety of colors and grades. Typically, the wood is creamy white with a slight reddish brown tinge and a straight grain, giving a long, linear look to a room. Hard maple polishes well making it receptive to cleaners and suitable for enamel finishes.

Hickory and Pecan

The hickories are an important wood group, and split into two groups; the true hickories, and the pecan or fruit bearing hickories. Hickory is the hardest, heaviest and strongest American wood, and is most easily recognized for its very pronounced differentiations in color. Having hickory in a room allows for freedom in accessorizing the space. You can match paints, furniture or fabrics to the various light or rich colors in the wood.

Pine

Pine is one of the softer woods. It is not as resistant to scuffs, dents and abrasions as other hardwoods, but is very often chosen for floors. Pine is better used in bedrooms, or second living rooms-spaces that get regular but not heavy traffic. Pine is light tan to yellowish white in appearance and very similar in both appearance and durability to a douglas fir floor.

Oak

There are two common types of oak flooring, red and white.

Red Oak

Red oak is white to light brown in color and very similar in general appearance to white oak, possessing a very long straight grain, and a coarse texture prior to finishing. The color of wood and grain pattern is more prominent in red oak flooring, but red oak floors are easier to clean than white, because they are more porous, making the wood more tolerant of cleaners and refinishers.

White Oak

White oak is more durable than red oak, making it a better choice for a house that is well visited. It has a similar look to red oak, being lightly colored and having a long, straight grain, which can make a room appear to be larger than it is. Overall, white oak makes the appearance of a room, clean and simple.

Sycamore

The sycamore wood floor is white to light yellow in appearance and is preferred for use as a contrast to other woods. Because the wood is only moderate in weight, hardness and stiffness, it is best used as an accent wood for borders and medallions.

Walnut

Walnut is one of the most beautiful and rich species of wood available on the market. They are famous for their blend of creamy white and dark chocolate colors and their occasional purplish tone. Walnut is a tough hardwood with a medium density, and is known for growing more lustrous with age. Cleaning walnut flooring is similar to other woods.

GRADING

Grades

Grading refers to the system used by manufacturers to assess the appearance of hardwood floors. The National Wood Flooring Manufacturers Association created grades to reflect variances in color, grain pattern and other markings that occur in wood. The standards are meant to ensure that consumers get the best quality of wood possible. There are four standard grades your floors will be categorized into including clear, select, number 1 common and number 2 common; however some species may have multiple grades.

Clear

A clear grade notes that wood is light in color and looks flawless. The clear grade is pure, exposes grains that run evenly and has even color throughout. The wood is free of knots, discolorations and visible markings, like a shift in the wood's natural pattern. Upon installation, the clear grade is exceptionally durable but more expensive than other grades, and sometimes has limited availability.

Select

The select grade is given to wood that is slightly darker in color (a mix of light and medium browns), but still looks smooth and flawless. The wood may contain some natural characteristics such as small knots. It is more common than clear woods and slightly more expensive than common grades.

Number 1 Common

Common grade wood is the most frequently used in homes because it is widely available and less expensive than clear or select grades. Consumers like the medium brown color and mix of natural features like swirls in the grain or small knots. The common grade has the best overall appearance to the human eye and looks very natural throughout the entire home.

Number 2 Common

Number 2 common grade has a rustic and raw appearance with a lot of color variations, from light to dark browns. It also has visible knots and changes in the grain. This grade of wood is best used in rooms that are used for utility purposes such as laundry rooms or closets, or where character marks and a contrast in color are desired.

Cuts

The cut of the wood determines how the pattern will look once installation is complete. Boards can be cut from a hardwood log in several directions, exposing rings in different patterns. The most popular methods of cutting include plain-sawn, quarter-sawn and rift-sawn.

Plain-Sawn

The plain-sawn cut of wood is the most common and cost effective choice when purchasing a floor. The log is cut from top to bottom, exposing the annual rings. You can actually see the tree's growth rings in the pattern of the wood, and because this cut produces the most lumber from each log, it is the most affordable.

Quarter-sawn

The quarter-sawn method for cutting wood means the log is cut at a 90-degree angle to produce a uniform pattern in the grain. This method yields fewer and narrower boards per log than plain sawing, increasing costs significantly. Quarter-sawn boards are typically popular for decorative applications such as cabinet faces, because the grain has an even pattern.

Rift-sawn

This method of cutting is very similar in appearance to the quarter-sawn, but the wood is cut at a 30-degree or greater angle. The wood produces the least amount of boards per log, so this cut is premium and expensive. It is often favored for fine furniture and other applications where matching grain is extremely important.

WOOD FLOOR FINISHES

Finishes

When installing hardwood floors in your home you have two options-purchase factory pre-finished planks or un-finished wood to be finished after installation. Both methods for finishing floors are widely accepted, so your choice should depend on the type of project, your budget, and the experience of your builder or installer. Having your floors finished at the time of installation can save you money. A builder often finishes a project in three steps: applying the stain, seal, and finish coat. Pre-finishing at the manufacturers can take twice as long, thus costing you more money. However, the benefit to purchasing a pre-finished floor is that the environment is controlled, eliminating factors like dust, traffic, temperature and humidity. Finishes are even and consistent due to the strict controls of manufacturers.

Oil-modified urethane

This is the most common floor finish. This finish can come pre-finished, or be applied by us and is available in gloss, semi-gloss, and satin sheen. Oil modified finish dries in up to 8 hours for each coat. This finish turns amber in color as it dries, is durable, and must be cleaned with a water-based cleaner. Due to it’s inexpensive nature it is an excellent choice if you are working with a more limited budget.

Water-based urethane

Choosing a water-based urethane finish for your floor is an excellent choice if you are seeking a durable floor finish. It is most commonly used in commercial, high-traffic settings like stores or offices because of its durability. It can come pre-finished or be professionally applied by our technicians at Raphael Hardwood Flooring. When dry, this finish leaves a very light, non-yellow color and dries more quickly than oil-modified urethane. This finish is more durable than oil-based urethane. We have chosen to exclusively use Radiant h2oil polyurethane.

Radiant H2Oil totally defies traditional classifications. It is an amazing blend of polyester, polyurethane, and polycarbonate with castor oil cooked into the backbone of the coating. The result is an extremely durable coating that enhances natural wood tones. Properties include exceptional build, clarity, and outstanding impact, scuff, and chemical resistance.

Moisture-cured urethane

The moisture-cured urethane is a moisture-resistant finish. This finish is available in a satin or gloss non-yellow formula, and usually ambers with age. This finish has a strong odor and is best applied by a professional. Cleaning a moisture-cured urethane floor is the same as most polyurethane floors.

Conversion Varnish

The conversion varnish is very similar to moisture-cured urethane and is a durable finish. It dries clear and non-yellowing in about 8 hours. Though easier to apply than moisture-cured urethane, it is best left to a professional due to very strong odors.

Polyurethane

Polyurethane finishes are very strong and durable, and can come pre-finished, be applied by a professional or by you. The polyurethane finish is comparable to the strength of lacquer, making it a mainstream choice for very durable floors. A new trend among polyurethane finishes is adding Aluminum Oxide particles to the polyurethane finish. This increases the abrasion resistance of the wear layer.

UV-cured

UV-cured floors are stronger than normal polyurethane floors. Though similar to polyurethane, these floors are finished at the factory and the polyurethane finish is cured with Ultra Violet lights instead of using heat. This is a more expensive option for finishing your floors, but is recommended if you need a durable finish.

Acrylics

This finish is extremely hard and durable, acting as a barrier to dirt, moisture and daily wear and tear. Acrylic finishes must be applied by the manufacturer and installed pre-finished, making it a more expensive option. At the manufacturer, the finish is actually forced into the pores of the wood through extreme pressure. Because of the high price, these floors are mostly used in commercial settings.

Ceramic

Ceramic flooring is very rare and only applied when specifically ordered. The ceramic finish requires a technology that injects ceramic onto the surface layer of the wood, in order to increase abrasion resistance.

Sheen

The level of sheen you choose for your floor should be a reflection of how much shine you would like your floors to have. Certain finishes are high gloss and others have a low or satin gloss. With a high gloss floor, you'll notice scuffs and scratches more readily than low gloss or satin finishes. High gloss finishes reflect more light and are typically used in more commercial or contemporary settings, while satin finishes reflect less light and are favored for more traditional settings, like homes and apartments.

Color

Wood colors range from light colors to the darker richer colors. Heartwood is the center of the tree and the oldest and most dense section of the log. It is darker and richer in color than sapwood, which lies closest to the bark. The color difference may be so pronounced that heartwood and sapwood from the same species are marketed under separate names. Each species of wood has a range of color, so you'll be sure to find the color that is right for you.

Grain

The grain refers to the wood's natural growth pattern, and is viewed in the wood as lines. These grains are the wood's natural growth pattern and will affect the appearance of the wood. Depending on how the wood is cut, the grain can either be seen as a wavy or curly pattern, or more symmetrical in organized lines.

Janka Hardness Test

The Janka hardness test is a standard in the hardwood flooring industry to gauge the ability of the wood to tolerate denting and normal wear and tear. It is also a good indication of the effort required to either nail or saw the particular wood. The test is a measurement of the force necessary to embed a .444-inch steel ball to half its diameter in wood. Numbers typical range from the hundreds to the thousands, the higher the number the harder and more durable the wood.


What Should I Expect?



INSTALLATION & SANDING EXPECTATIONS

Having your floors done will add value & beauty to your home, but with any home improvement you should expect some disruption and inconvenience. We will employ our experience, the latest and the most environmentally safe materials to complete the work with the least possible disruption. However, you should be aware of the following factors.

  • Even though we use state of the art sanding machines equipped with vacuums to collect dust, some dust will infiltrate to other areas of the house.
  • Please keep pets and children away from the work areas.
  • Our crews meet at our warehouse at 7:00am Monday through Friday and will arrive at your home after our daily company briefings. The time they will arrive at your home varies due to your specific location & job requirements, however it usually ranges from 7:45-8:45 a.m. Unless additional overtime charges are approved by the homeowner we will not work on Saturdays. We do not work on Sundays.
  • On our “Sand & Finish” (not factory finished) floors, finishes may appear dry however they are not fully cured and will not support heavy foot traffic until so. Furniture may be replaced after 48 hours & area rugs after 1 week. Factory finished floors may have furniture replaced 24 hour after installation.
  • Please understand that after the normal process of floor installation, sanding, & finishing, your baseboards & or walls may need to be touched up with lightweight spackling & or paint.
  • We will likely need to use the 220V power supply behind your dryer to power our sanding equipment. Your clothes dryer may be disabled while we are working on your floors.
  • PRE-INSTALLATION & SANDING REQUIREMENTS

  • All other trades should have completed their work, and no other foot traffic should be allowed during the installation, sanding, & finishing processes.
  • The building should be completely closed in, with outside windows, and doors in place.
  • Air conditioning, heating, and ventilation systems must be operational for a minimum of 2 weeks prior to the job commencing. The temperature should be at “normal living conditions”.
  • Furniture should be removed. If a kitchen, bath, or utility rooms to be installed, washer, drier, or refrigerator will need to be removed. They must be disconnected by the homeowner before installation. Please fully read our “Floor Care Essentials” guide for instructions on how to correctly move appliances onto your wood floors after the installation is complete.
  • Customer should assure the removal and safe storage of all loose objects, i.e., knickknacks, breakables, books, boxes, valuables, and any items on floors and walls before installation and or sanding.
  • A toilet or porta-potty must be present at the work site.
  • Unless Custom work (borders & anything outside of the normal straight lay installation) has been specified in writing in the contract, it is not included. Should you desire to have us provide you with a custom installation, our hourly rate is $75.00 per hr. for the foreman & $45.00 for the apprentice.

  • EXPECTATIONS


    Floor Acclimation



    FLOOR ACCLIMATION


    How to make sure that your flooring is properly acclimated.


    Below are guidelines defined by the National Wood Flooring Association for proper hardwood flooring acclimation.


    Part I

    GENERAL ACCLIMATION/CONDITIONING GUIDELINES

    ACCLIMATION: The process of adjusting (conditioning) the moisture content of wood flooring to the environment in which it is expected to perform.


    EQUILIBRIUM MOISTURE CONTENT: The moisture content of wood when in equilibrium with its environment. When wood is neither gaining nor losing moisture, equilibrium moisture content (EMC) has been reached.


    STORAGE and CONDITIONS

    Do not store wood flooring at the jobsite under uncontrolled environmental conditions. Garages, and exterior patios, for example, are not acceptable areas to store wood flooring.

    Ideal interior environmental conditions vary from region to region and jobsite to jobsite. It is the flooring professional's responsibility to know what the “ideal" climate conditions are and customize the floor around those conditions.

    Determine what the expected seasonal change of wood moisture content is for your geographical location. For a general view of moisture-content averages by region, See Appendix D - Moisture (USA) and Appendix E - Moisture (Canada).

    Upon delivery, check wood flooring moisture content with a moisture meter to establish a baseline for acclimation. Check the moisture content of multiple boards. A good representative sample is typically 40 boards for every 1,000 square feet of flooring. Calculate what the optimal wood moisture content is (baseline) by dividing the high season and low season. Example: If your region has an expected EMC from a low of 6% to a high of 9%, the baseline MC of the wood would be 7.5%. If wood flooring is delivered and recorded to its baseline MC for the geographical location and proper relative humidity conditions are maintained, no acclimation may be required. If the moisture content of the product received is well outside of the range of optimal moisture content, it will be very difficult to acclimate the product properly without substantial dimensional change, distortion, and structural damage. Example: If the moisture content of the delivered wood is 12% and the optimal range is 6%, excessive shrinkage, bowing, cupping and other physical anomalies would be expected during the acclimation process. The wood flooring should not be accepted.

    Optimal wood moisture content represents only a baseline to begin from and does not represent the final EMC required for the interior environment. Acclimation is often required to customize the moisture content of the wood flooring to the interior environment in which it is expected to perform.

    GENERAL

    NOTE: Some manufacturers do not require acclimation for certain products prior to installation. If the manufacturer recommends that the wood flooring be acclimated before installation, proceed as follows:


    Ensure that the building is enclosed.

    Verify that the building is maintained at normal living conditions for temperature and humidity.

    Where building codes allow, permanent heating and/or air conditioning systems should be operating at least five days preceding installation to promote proper acclimation and should be maintained during and after installation. For radiant heat, see Appendix H.

    If it is not possible for the permanent heating and/or air conditioning system to be operating before, during and after installation, a temporary heating and/or dehumidification system that mimics normal living (occupied) conditions can enable the installation to proceed until the permanent heating and/or air conditioning system is fully operational.

    Acclimate the wood flooring as necessary (see Acclimation, Part II below). Note: Not properly acclimating wood flooring may cause excessive expansion, shrinkage, dimensional distortion or structural damage. The worst-case scenario is one in which wood flooring is stored at the jobsite in an uncontrolled environment, then immediately installed. This is especially true when the materials are stored in an area that is subject to excessive moisture and humidity conditions. Acclimation outside of the area in which the wood is to be installed does no good at all; in fact, it is likely harmful to store wood flooring at the jobsite under conditions that don't reflect expected normal environmental conditions.

    Prior to installation, ensure that wood flooring is within acceptable range of moisture content with the wood subfloor. For solid strip flooring (less than 3" wide), there should be no more than 4 percent moisture content difference between properly acclimated wood flooring and subflooring materials. For wide-width solid flooring (3" or wider), there should be no more than 2 percent difference in moisture content between properly acclimated wood flooring and subflooring materials.

    Part II

    ACCLIMATION

    Wood flooring is a hygroscopic material subject to dimensional change as a result of variations in moisture, temperature and humidity within the surrounding environment. Wood flooring simply needs to reach moisture content level in equilibrium with the surrounding environment (EMC) in which it will be installed, at or near normal living conditions. The process of reaching this equilibrium is defined as acclimation, which allows the wood to properly adjust itself to the normal living conditions within the structure; that is, the temperature, humidity conditions and moisture content that will typically be experienced once the structure is occupied.


    THE PROCESS OF ACCLIMATION

    If the manufacturer recommends that the wood flooring be acclimated before installation, proceed as follows:


    Acclimation can be facilitated by breaking the floor units into small lots and/or opening the packaging. A common practice is to cross-stack the materials with spacers (" to 1" sticks) between each layer of flooring to allow air circulation on all sides of all boards.

    Most recommendations state that the materials need to acclimate from a minimum of 3 days up to no given maximum. While it takes time to acclimate a product, the most important aspect is that the materials reach a moisture content that is in equilibrium with its expected use. Acclimate the materials as long as necessary to accomplish this task, taking the necessary moisture readings to indicate when the materials have reached the proper moisture content and when no further changes occur.

    For site-finished wood flooring, before installation and before sanding and finishing takes place, allow the flooring to acclimate (settle-in) to the controlled environment, and to stabilize for a period of time. Some flooring professionals suggest 5 to 7 days. Engineered flooring installed using an adhesive application system may require a longer post-installation acclimation period to allow all residual off-gassing to occur prior to application of a finish. Follow adhesive manufacturer's recommendations.

    Tropical imported species generally require more time in order to properly acclimate the wood flooring. Some tropical species lose moisture or gain moisture at faster or slower rates than domestic species due to higher overall density, oil and resin content and interlocking cell structure. In addition, the resins and oils make accurate MC readings more difficult. Resistance (pin type) meters require multiple readings of multiple boards in order to arrive at a more accurate average MC reading. Pinless meters that include multiple depth level adjustments may offer faster and more-accurate internal readings.

    Engineered and solid factory finished flooring follows specific manufacturer's recommendations and some may not require acclimation. Follow manufacturer's guidelines to retain all warranty coverage. Warranty coverage generally requires that jobsite conditions be maintained between 30% to 50% relative humidity and that those conditions must be maintained before, during and after installation for the life of the floor. Failure to comply with these manufacturer's requirements may result in irreversible structural damage and void related warranties.

    WOOD'S COMFORT ZONE

    As a general rule, with geographic exceptions, wood flooring will perform best when the interior environment is controlled to stay within a relative humidity range of 30 to 50 percent and a temperature range of 60° to 80° Fahrenheit. (In some climates, the ideal humidity range might be higher or lower, 25 to 45 percent or 45 to 65 percent, for example.)

    The chart below indicates the moisture content wood will likely have at any given combination of temperature and humidity. Note the equilibrium moisture content in the recommended temperature/humidity range (shaded area) coincides with the 6-to-9 percent range used by most flooring manufacturers during the manufacturing/shipping process. Although some movement can be expected between 6 and 9 percent, wood flooring can shrink or swell more dramatically outside this range. When wood is neither gaining nor losing moisture, equilibrium moisture content (EMC) has been reached.

    Equilibrium Moisture Content of Solid Wood Species at Various Temperatures and Relative Humidity Readings Wood flooring has a comfort level too. Wood flooring will perform best when the interior environment is controlled to stay within a relative humidity range of 30% to 50% and a temperature range of 60° to 80° Fahrenheit. Fortunately, that's about the same comfort range most humans enjoy. The chart below indicates the equilibrium moisture content of wood flooring at various temperatures and humidity conditions. The left column indicates temperature in degrees Fahrenheit and Celsius. The bottom row indicates percent relative humidity. The values in the chart indicate the equilibrium moisture content (EMC) for any given combination of temperature and humidity. For example, at 70° Fahrenheit and 40% relative humidity, the equilibrium moisture content is 7.7%. The shaded area indicates the generally recommended range for wood flooring – 6% - 9% EMC, which occurs when temperature is 60° - 80° Fahrenheit or 15° - 26° Celsius, and 30% - 50% relative humidity.