Preparations Before Installing New Hardwood Floor

Job Preparation

Although most of the satisfaction of installing a beautiful wood floor comes from actually putting down the flooring and not from preparing for the installation, poor preparation often means that beauty will be short-lived. Whoever works on the wood floor is responsible for ensuring that all conditions are ready for the flooring project to commence. it’s always wise to look for potential problems, and many potential problems are water-related.

Preparing The Building


Most wood flooring failures are the result of excess moisture. It’s crucial for the flooring installer to verify the moisture content of both the flooring and the structure before proceeding.

The first step in preventing water damage to wood flooring is to ensure that no moisture can enter the building. inspect the exterior of the building thoroughly.

Water should drain away from the building and not into it; downspouts from the gutters should also drain away from the building, and windows and doors should be installed and not leak. moisture from any of these sources has ruined countless wood floors. houses under construction are invariably wetter than they will be in service.

Allow construction dampness—from fresh concrete, wet lumber, plaster and drywall finishing, and drying paint—to dissipate before delivering the wood flooring.

how long to wait depends on how much moisture was initially put into the building and what is being used to remove it. Wood flooring should be delivered only once the house is at the correct moisture level.

most manufacturers produce flooring with moisture content between 6 and 9%, and they recommend the flooring be maintained in this range for best performance. This coincides with the normal comfort range for humans, 30 to 50% Rh at 60 to 80ºf.

to help maintain this moisture content in the flooring, the average moisture content of the framing members should be below 14% before delivering the flooring. floor joists, framing bottom plates, and doorways are generally a good place to measure moisture content with a moisture meter. The heating and cooling system should also be running before delivering the wood flooring.

This will aid in removing residual construction moisture and help get the interior of the home to its normal expected environmental conditions. You may need to run temporary HVAC equipment such as portable heaters, air conditioners, blowers, and dehumidifiers on-site if the home’s permanent system is not operational. it may take a week or two with the HVAC operating to remove the residual moisture from the building.


Water stains on the subfloor are a telltale sign of leaky doors and windows. Be sure doors and windows are properly flashed so as not to leak before installing a wood floor.

Moisture in the baseMent


Buildings under construction get wet— from the rain before the house dries into moisture dissipating from materials such as green lumber, concrete, plaster, and paint. Always be sure the building is dry before installing hardwood floors.

Basements (and crawlspaces) in both existing and new buildings can be areas of high humidity. While the effect of this on flooring installed in a finished basement is obvious, moisture can migrate upward from any foundation and affect wood floors in the stories above.

moisture is liberated from the building’s foundation as the concrete cures. There may also be moisture vapor permeating through the pores of the concrete from the ground under the concrete slab. even in new construction, many concrete slabs do not have vapor barriers under them to prevent moisture migration.

The ones that do often have only a piece of 6-mil plastic with holes in it, which negates much of the effectiveness of the barrier. Throughout the summer in much of the country, basements and crawlspaces are cooler than the outside air coming into them. As the air cools, the humidity level rises—a problem exacerbated in humid areas, where the cool surface of the concrete may condense moisture out of the air.

This moisture can migrate into the flooring. it’s sometimes common for the subflooring and the bottom of the wood flooring above the foundation to have moisture contents ranging from 12 to 17%. This level is unacceptably high, and basements and crawlspaces may require dehumidification to remove moisture from the air.


Flooring grades take into account not only defects such as knots but also length and color variation. And what’s a defect to some people is a character to others, as evidenced by the range of color in the hickory (left) and the knots in the Australian cypress (right).

Choosing flooring materials: grades and species

hardwood flooring is classified by grade, species, and type. The grade generally describes the surface characteristics of the wood, lengths of the flooring, and milling tolerances.

There are several grading systems for hardwood flooring. Various associations create these systems, and use of the systems by manufacturers is voluntary, so caveat emptor.

two of the more common systems are those created by the maple flooring manufacturers Association (mfmA, and the National Wood Flooring Association® (nWfA, The former system applies primarily to maple; the latter is universal, but mostly used with oak flooring.

today, there are more options for hardwood floors than ever before. hundreds of exotic woods are available from all over the world. each species has its own characteristics, varying in color, hardness, and dimensional stability. selecting wood for a floor is mostly a matter of personal taste (and budget).

Hardwood Flooring Grades

All of the grades listed here will make a serviceable floor. The differences are mainly aesthetic, such as the presence of knots, sapwood, and color variations.

However, wood with fewer defects tends to be more stable and predictable, so you might expect greater or more varied seasonal movement with lower grades. Of course, price is another difference, with higher grades usually costing more.


Clear red oak.


Select red oak.

MFMA Maple Grades

First Grade. The highest standard MFMA (Maple Flooring Manufacturers Association) grade is hand-selected to minimize the natural character variations of the species.

Second Grade. The most commonly specified maple flooring; this grade exhibits more natural variations than first grade. Third Grade. This grade has the same structural integrity as first and second grades and exhibits more natural variation than either grade.

Third and Better. This grade is comprised of a mixture of first, second, and third grades of MFMA northern hard maple. Utility Grade. This grade of MFMA maple may contain all defects common to maple, but the wood must be firm and serviceable.


No. 1 common red oak


No. 2 common red oak.

NWFA Hardwood Grades

Clear. Clear wood is free of defects, though it may have minor imperfections.

Select. Select wood is almost clear but contains some natural characteristics such as knots and color variations.

Common. Common wood (No. 1 and No. 2) has more natural characteristics such as knots and color variations than either clear or select grades and is often chosen because of these natural features and the character they bring to a room. No. 1 Common has a variegated appearance, light and dark colors, knots, flags, and wormholes. No. 2 Common is rustic in appearance and emphasizes all wood characteristics of the species.

should also be taken into consideration. for example, light-colored floors make smaller rooms feel larger. harder woods stand up better in high traffic areas. And areas subject to moisture fluctuation should be floored with more dimensionally stable woods.



There are over 100,000 different types of woods in the world. Practically every color, weight, hardness, texture, and grain pattern imaginable is available.

Wood flooring is available in a variety of colors that can change the feel of any room, making color one of the most critical aesthetic design elements. The palette of colors seems limitless. American walnut provides deep rich brown tones, hard maple has white with tan hues, and purpleheart really is purple. You can stain wood floors, but with the availability of so many colors, I generally try not to—when a stained floor is scratched, it can be hard to match the color exactly. however, I do use stain to highlight individual elements in an ornamental wood floor.

oxidation and sunlight change the color of wood flooring, which can be a big consideration in a room with many windows. American cherry undergoes an extreme color change, darkening to a dark reddish color within a few weeks in direct sunlight. Walnut has a medium to a high degree of color change, lightening from dark brown to a golden brown. Red oak ambers slightly. Brazilian cherry starts out a tan-salmon color with some black striping and turns a rich, deep red.


The color of the flooring can change the feel of a room. Dark flooring makes a large room seem more intimate, while light-colored flooring tends to enlarge small spaces.


The relative hardness of wood species is commonly measured using the Janka hardness Rating (see the chart at right). This test measures the force needed to embed a steel ball (0.444 in. diameter) to half its diameter into the wood being tested, with the rating measured in pounds of force.

While you’re not likely to be embedding steel balls in your floor anytime soon, the hardness of the wood is an important consideration. The average woman wearing high heels can exert 2,000 lb. per sq. in. on a wood floor (and I’ve seen many floors severely damaged by women’s heels). if you have a big dog with long nails, eastern white pine floors with a hardness rating of 380 lb. might not be your best choice.

Brazilian walnut with a hardness rating of 3,680 lb. would pass the high-heel test and give dog nails a run for their money. one last word on high heels: if a heel of one of the shoes is damaged and has a protruding nail, it can attack the floor with 8,000 lb. of force. no wood flooring can stand up to that.

The hardness of wood usually varies with the direction of the wood grain. Quartersawn flooring is a little harder than plainsawn flooring. end-grain floors were a traditional floor covering in factory buildings, heavy-traffic commercial buildings, museums, bridges, and boardwalks. They absorb energy and noise, and the angle of cut allows the growth rings to resist scraping and general wear more effectively than traditionally flatsawn or even quartersawn boards.

Wood hardness Scale

The hardness of wood is ranked by the Janka Hardness Rating. The higher the number, the harder the wood.

diMensional stability

As we saw in some earlier posts, wood flooring shrinks and swells as its moisture content changes, some species more than others. Plainsawn red oak flooring is the most readily available species and is often used as the baseline to compare with other species for dimensional stability.

teak is about twice as stable as plainsawn red oak. of course, we could compensate for that by using quarter sawn oak flooring, which would be almost as stable as plainsawn teak.

Wood Flooring Throughout the House

People tend to expect wood flooring to be in certain parts of the house, such as halls and other high-traffic areas and formal dining rooms, but it offers advantages in most areas of a home.

Hardwood flooring will outlast other materials like carpet and resilient-type floorings such as vinyl or linoleum. It also provides a comfort level that ceramic floors cannot match.

Wood flooring can even work in kitchens and baths, as long as you take certain precautions: Water spills must be wiped up, bathrooms should have ventilation to remove humid air, and bath mats should be placed outside the shower.

I must have seen thousands of wood floors in bathrooms and kitchens, and the only problems I have come across were associated with leaking plumbing fixtures or dripping condensation from an un-insulated toilet tank. Wood flooring is also a good choice for bedrooms.

Carpeting can be nearly impossible to keep clean of dust and pet dander, and many people with allergies find they sleep better after installing wood floors. About the only place where wood flooring is not my first choice is the foyer. I prefer stone or tile, which stands up better to the puddles of water and bits of gravel my kids track in with their snow-covered shoes.

Types of Wood flooring

There are three main categories of wood flooring: strip flooring, plank flooring, and parquet flooring. for the most part, all three categories are sold as 3⁄4-in.-thick, tongue-and-grooved boards. (engineered flooring is an exception—while it can be plank or strip, it’s usually under 3⁄4 in. thick and made up of different layers of wood glued together like plywood.) strip flooring, the most popular category, has boarded up to 3 in. wide.
Wood Plank flooring can be considered any boards 3 in. or wider. (There is some confusion between the two because some strip flooring manufacturers occasionally produce flooring up to 31⁄4 in. wide to ensure the greatest yield from the raw material supplied to the mill.) Parquet flooring is individual wooden tiles that can consist of many pieces. strip, plank, and parquet flooring are available in solid wood or engineered, and as unfinished or prefinished.

Bamboo and Cork Flooring

With the growing interest in all things “green,” bamboo and cork have become more popular as flooring materials in recent years. Bamboo is the fastest growing woody plant in the world and actually considered a grass. After harvesting, the bamboo is cut into strips, steamed, dried, glued, and placed in a heat press. Bamboo makes a good flooring material, but its quality varies dramatically between manufacturers. cork flooring comes from the bark of the cork oak tree. The cork trees are unharmed by the harvesting of the bark, and they continue producing cork for an average of 150 years. cork flooring has millions of microscopic air pockets that give it the ability to return to its original shape after an impact.

End-grain flooring is made from sections sliced from the end of thick beams. Typically glued down, end-grain flooring is extremely durable and was a favorite for old factory floors.

Estimating Flooring

calculating the amount of wood flooring needed for a project depends on a number of factors. The first, of course, is the actual square footage of the space, but you also have to consider the shape of the room.

There will be some waste on every installation, but there’s usually less in rooms that are simple rectangles. most strip or plank flooring installations in a square room require about 5% extra flooring to allow for cutting waste and any culling defects. Rooms with many angles jog or bays will require 15 to 20% more wood.

Both lower grades of wood and diagonal installations can add 15 to 20% waste. lower grades may have more defects that need to be removed. And the end boards on a diagonal floor are not cut at 90°, which means that the cutoff waste has to be re-cut before they are used as starter boards on the next rows.

Parquet wood flooring generally requires 10% extra material in a square room and 15 to 20% for rooms with lots of angles and corners.

national industry standards allow manufacturers to sell products with a maximum of 5% defects that do not fall within that grade of flooring. most manufacturers of unfinished flooring abide by these standards. however, many manufacturers of prefinished wood flooring have proprietary grades for their products.

A knowledgeable dealer should be able to help predict the amount of waste. lower grades of wood will have more defects, which might lead to more waste. Then again, a defect to one person might be an aesthetically pleasing element to someone else.

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