Wood Floor Installation | Installing Hardwood Flooring | Installation Tips
Solid Floor Nail-Down Installation
Please follow these installation procedures to ensure the successful installation of your hardwood floor. These procedures are written with an experienced installer audience in mind, so if you require more information on the basic procedures of installation, we encourage you to contact the NWFA for more information at www.nwfa.org or by phone at 1-800-422-4556.
Inspect all materials products prior to installation. Do not install defective materials.
Wood is a natural product with natural color variations, grain variations,
and tone variations. Though products do undergo a rigorous inspection process before leaving
the plant, it is still necessary to inspect the materials in order
to ensure their quality. Installation of defective materials could result in voiding
Order of Installation
In order to ensure that no damage is done to the wood over the course
of construction, particularly in the case of homes
under construction and renovation, wood flooring should always be installed after all
other installations are finished. Additionally,
foot traffic should be kept to a minimum after the installation of the floor is
complete. If a protective cover is placed over the floor
at this time, make sure that the entire floor is covered as many woods are
sensitive to light and will undergo color change.
Crawl Space and Subfloor Specifications
Before installation, ensure that all basements and crawl spaces are dry. The crawl
space also needs to allow for at least 18 inches between the joists and
the ground. A vapor barrier/retarder has to cover 100%
of the crawl space, with the joints of the vapor barrier overlapping at least
6 inches. The vapor barrier itself should extend six inches up the stem wall,
where it must be attached and sealed. Finally, there must be a constantly
operating mechanical exhaust and perimeter wall insulation or conditioned
air supply with insulation.
Wood sub-floors must be secured with screws or nailed. Nails need to be ring
shank and screws must be counter sunk. In the event that the wood sub-floor is
less than 3/4" thick, add a single cross layer with a
minimum thickness of 5/16" for a total of 1" inch of thickness in order to
combat possible squeaking after installation. There must be no oil, existing
adhesives, wax, grease, urethane, dirt, varnish, paint, etc.
on the wood subfloor. Particleboard is not a possible sub-flooring option for
staple or nail down installation, but it can be sufficient for a glue down
installation. Subfloors must not measure over
12% moisture content. Additionally, the hardwood flooring's
moisture content and that of the
subfloor can not have a difference of more than 4%.
Protecting Hardwood Prior to Installation
It is paramount that the wood is not delivered or stored at the site
until the building is enclosed, as storing wood in these conditions will
cause adverse effects as a result of fluctuating outdoor humidity and temperature
values. Once the building is enclosed, don't bring or install the wood
into the house until it has been brought to the temperature and relative
humidity that it will kept at with the future occupants present. Additionally, don’t
deliver or install the hardwood until painting of primer coats, drywall,
texturing, masonry, and concrete is finished.
For the different grades of a house, there are different restrictions for which
types of hardwood can be installed. For above-grade and on-grade installation,
engineered hardwood, solid hardwood, and a floating floor are all
acceptable. However, at below-grade, only floating floors and engineered hardwood
are options. Should the ground around a building be 3 or more inches above the
floor of that level, that level is considered below-grade, and thus
ineligible for solid hardwood.
Acclimating Hardwood Flooring
Preparing the Wood
Acclimating Hardwood is often an essential task for ensuring the wood doesn't
undergo any unforeseen dimensional shifts after or even during the installation.
While acclimating, make sure not to store hardwood in a location
where the temperature and humidity is not that of the living space within the house,
such as a garage or exterior patio. Preferably, the house should have all of
the heating, ventilation, and air conditioning systems running for
at least five days before the hardwood arrives for acclimation.
Checking Boards' Moisture Content
The relationship between the moisture content of the hardwood boards and that
of the subflooring determines whether or not the wood is acceptable for installation.
In order to ascertain these moisture values, check various boards'
moisture content, approximately 4 boards for every 100 square feet. If the wood is
solid and wider than 3", then there should be no more than a 2% difference between
moisture content of the wood after it has acclimated and the subflooring.
With hardwood that is narrower than 3", the difference between the moisture content
of the hardwood and the subfloor should be no more than 4%.
As a general rule, wood floor maintains dimensional stability best within a temperature
range of 60-80° Fahrenheit and a humidity range of 35-65%. The two exceptions to this
rule apply to imported and exotic wood species, as they may react differently
to these circumstances, and extreme geographical circumstances.
Processes of Moisture Testing
Subfloor Moisture Testing
In order to get an accurate reading of the sub-floor's moisture level, test approximately
2 locations per every 100 square feet and take the mean average of these values. If there
is an unusually high value in one particular region, this probably indicates
a problem which should be attended to prior to installation. There are various moisture
tests that can be performed to determine whether moisture levels are acceptable for
installation. The acceptable moisture conditions for installation are:
- Moisture readings of less than 14% when using an equivalent moisture meter on wood substrates.
- Calcium chloride test producing results of less than 3 pounds/1000 square feet/24 hours.
- A reading of less than 5.0 on a Concrete Moisture Counter.
Vapor barriers for hardwood and wood sub-floors are sometimes referred to as vapor
retarders. They can be a membrane, vapor resistant material, or covering with a vapor
resistance rating at or above .7 perms, or at or below 50 perms. They are effective at
alleviating moisture problems by protecting the hardwood from ground moisture and
condensation. They also provide a number of other benefits, including noise reduction,
dust reduction, and the elimination of wood-on-wood contact.
However, different vapor barriers work more effectively than others in given circumstances.
In the case of a wood subfloor, an impermeable vapor barrier with a rating of .7 or
less shouldn't be used. With this level of impermeability,
the vapor barrier could possibly trap moisture in or on the wood subfloor.
In the case of a concrete subfloor, there are a variety of methods to test its moisture,
including calcium carbide testing, calcium chloride testing, or relative-humidity testing.
Before testing, the concrete is required to be at least 30 days old.
Various retailers provide concrete moisture meters and relative humidity kits. You can
contact the NWFA to find a retailer near you at 1-800-422-4556. Unfortunately, these tests
cannot guarantee a concrete slab that is completely free of moisture all year-round.
The vapor barrier specifications for a concrete subfloor diverge from the wood subfloor
specifications by requiring a very high level of impermeability at .15 perms or lower,
allowing for little or no moisture movement.
Installing Solid Hardwood Flooring
When preparing to install solid hardwood flooring, be sure that you do not install over an
area with radiant heat. 15 lbs. asphalt felt must be laid to install, and a moisture barrier
of 6 mil polyethylene film may also be necessary. This protects against moisture
rising up from below and also helps prevent squeaking. Install the vapor barrier parallel to
the direction of the flooring. Make sure that the vapor barrier has a 3" overhang around the
perimeter, and that it overlaps each previous run by at least 6".
Door frames in the flooring area can be cut approximately 1/16 of an inch higher than the
hardwood being installed to increase the ease of installation and avoid complex cuts.
Take boards out of several boxes in order to ensure good tonal variety and mixture in the
floor. Lay your flooring at a 90° angle to the floor joists whenever possible. Using an
external wall as a reference, snap a working line parallel to the reference wall, allowing
for the requisite expansion space indicated by the wood’s manufacturer.
Put down a row of planks that runs the along the length of the working line. Make sure the
tongues are always facing out as using the tapping block on the plank’s groove could damage
the board. Blind nail and top nail the first row, while being sure to use only the
Research the specie of wood you’re installing to determine whether or not it will require
pre-drilling in order to nail it down. The later rows of boards should be blind nailed whenever
possible. Also, attempt to nail the boards into joists whenever possible.
Nails should be 1-2" from the ends of the boards and every 4-6" along the edge of the boards,
going in at a 45° angle. Make sure to stagger your boards such that no two end joints are within
three rows or 6" of each other.
Once installation is complete, use appropriate
trim moldings and wall moldings along walls and doorways to cover edges and conceal gaps
resulting from any irregularities in perimeter dimensions. Use a flooring filler to fill in
any wide seems along joints that blends with the tone of the wood.
Clean the floor with a recommended hardwood flooring cleaner.
Sweep the floor often to remove any abrasive materials that could potentially damage your floor.
Felt protectors should be placed under the legs or bottoms of heavy furniture, chairs, etc.
Apply leading hardwood cleaner to towels to clean the floor. Do not apply the cleaner directly to the flooring.
Use a white washcloth and hard surface cleaner to remove spills on the flooring quickly.
Avoid wearing spike-heeled shoes or damaged shoes on the floor as they can cause damage.
Do not use a wet or damp mop to clean the hardwood floor. Any water can damage the flooring.
UV rays produced by the sun can alter the tone and color of your flooring.
Place mats at all points in the home with exterior entrances to avoid debris being tracked onto the flooring.
Do not use products containing wax, oil, or polish on hardwood, as doing so will
create a residue on the wood surface that will cause the finish to dull.
Keep your housepets' nails clipped short in order to avoid scratches. The larger
the pet, the greater the danger of scratches.
Put a rug in front of all water sources, such as kitchen sinks, dishwashers, and
any other place where water could spill onto the hardwood.
Maintenance and Installation Links
- Floor finish products and stains.
- Various hardwood care products
- Floor nailers, fasteners, and accessories
- Floor nailers, fasteners, and accessories
- Adhesives and other specialty construction chemicals
Repair Wood Floors
Installing Engineered Wood Floors