Photo courtesy of Lauzon

Photo courtesy of Mirage
A trouble-free hardwood installation requires the proper jobsite conditions, as well as quality wood to install. FCI asked several hardwood manufacturers to clarify what conditions are necessary for hardwood installation, what are acceptable manufacturing tolerances, and other common hardwood-related questions.

Floor Covering Installer: What is considered an acceptable milling tolerance, in regard to the tongue and groove configuration, and the overwood?

Steve Sharko, product manager for Lauzon Distinctive Hardwood Flooring: Lauzon requires a tight fit with our tongue and groove allowing no overwood. In our Engineered NextStep, our tolerance for over wood is .002 inches.

Bernard Daigle, technical services director for Mirage Hardwood Floors: The milling tolerance is different for each manufacturer some are giving more or less importance to this. The overwood tolerance in the industry is about plus or minus .040 inches.

FCI: How much variation in tolerance, such as character marks, is not represented in samples, i.e. what percentage is not represented in samples? What can the installer anticipate to fall outside the guidelines?

Tembec marketing and technical staff: Industry standards allow for five percent waste, and most flooring samples display the "best" scenario. Tembec takes a conservative approach to samples targeting below average and striving to represent the spectrum of character in the grade, resulting in the consumer receiving a product that exceeds their expectations.

SS: Samples have always been a problem, and it is very difficult to represent a total look of the grade being sold on a small sample. We recommend the retailer explain the character of the species and grade at point of purchase. The installer should confirm with the homeowner by opening a box of wood and making sure that this is the product they purchased before the installer installs the floor.

BD: The sample in store will show an average of the color range specific to the species, the different specific marks that can be found in the species, like streaks, sap wood, knots and others. The sample must be the most realistic of the over all floor. Obviously the consumer can’t base his or her decision on a single sample board, but must look at a larger sample before buying.

FCI: Is there documentation on the moisture content of flooring when it leaves the plant, or at the time of manufacture?

Tembec: Yes, we accumulate daily data on each lot for internal purposes and in the event of a claim.

SS: Yes, this is always documented at both time of manufacturing and the time of shipment. Our product is climate controlled throughout the whole process and protected to maintain between six and eight percent moisture content.

BD: Yes, the moisture level is constantly control during and after the milling. The documentation related to moisture control after the installation is available in the store displays, in the boxes and on the Mirage Web site.

FCI: Are there installation specs for the nailing schedule, for notch or trowel, etc.? If so, do they specify subfloor thickness, type, etc.?

Tembec: After hand nailing a couple of rows of strips, use the hardwood flooring nailer. Use nails every eight inches or 10 inches, stopping at a distance of about two inches from the end of each strip. With respect to subfloor thickness, we refer to the NWFA's Hardwood Flooring Installation Guidelines. They recommend 3/4-inch CDX plywood subfloor/underlayment; or 3/4-inch OBS subfloor/underlayment, with joist spacing 19.2 inches on center or less.

SS: All boxes leaving our warehouse have instruction sheets inserted inside covering everything the installer will need to do.

BD: Yes, all this information is available from the Mirage technical service department. You can find technical information on nailers, staplers and their accessories. Information is available about recommended subfloor, its characteristics and the preparation it requires prior to the installation.

FCI: Regarding installation specs, are the instructions reader-friendly? Are they included in the carton?

Tembec: Our installation instructions were prepared for usage by installers and consumers in mind. In addition our website,, is a great resource to obtain installation information. We include a copy of our recommended installation instructions in every second carton that leaves our plant.

SS: All instructions are written for the do-it-yourself installer, making it easy to read and understand. Instructions are in every box.

BD: Every box of Mirage will have inside an installation guide that is very friendly to use.

FCI: What are the installation conditions, such as moisture, temperature, etc., that are recommended? Tembec: Building interiors are affected by two distinct humidity seasons: heating and non-heating. Recognizing that wood floor dimensions will be slightly affected by varying levels of humidity in your environment, take care to control humidity levels to within the 40-55 percent range. During the heating season, a humidifier is recommended to prevent excess shrinkage in wood floors due to low humidity levels. During the non-heating seasons, humidity levels can be maintained by using an air conditioner, dehumidifier, or by turning on your heating systems periodically during the summer months. Avoid excessive exposure to water from tracking during periods of inclement weather.

SS: This all depends on whether the application is solid or engineered. Solids require that the difference between the wood sub floor and the hardwood be no more that four percent moisture content. For example, if the hardwood is eight percent, then the sub floor cannot be more than 12 percent.

Concrete is totally different; it depends on the moisture level of the slab. Use a calcium chloride test or an electronic concrete moisture encounter to find out if the slab is suitable for gluing down the flooring.

BD: Prior to installation, the heating system must be in operation, and room temperature must have been maintained at plus or minus 72 degrees Farenheit for at least one week. To avoid any moisture-related damage, subfloor must be dry and basement well ventilated. For below grade installation, ensure that foundations and concrete slab are thoroughly leak proof. The radiant heat system must have been tested and in operation for a few weeks prior to installation. The surface temperature must never exceed 85 degrees Farenheit. If the radiant heat pipes are visible or exposed in the subfloor, you must cover them with 3/8-inch plywood to spread the heat more evenly.

Conduct a subfloor moisture level check; the differential between strips and subfloor must be less than four percent. If moisture reading is too high, postpone installation, find moisture source and correct if needed; raise heat and increase ventilation until proper conditions are met. Prior to installation, concrete subfloor should preferably be 45 to 90 days old. A concrete moisture meter must be used to check subfloor moisture level; in case of positive reading, calcium chloride test must be performed. Install an approved waterproof membrane if reading exceeds three pounds but scales less than seven pounds.

For example using an approved adhesive, you may glue down an approved vinyl membrane over whole subfloor surface; you may also smear adhesive over entire concrete floor surface to create a skim coat moisture barrier. Never install hardwood flooring if calcium chloride test reading exceeds seven pounds/1,000 square feet/24 hours.

FCI: Is it possible to install hardwood flooring in a basement? If it is, what steps must be taken to ensure proper installation?

Tembec: No, solid strip hardwood flooring is not recommended to be installed in a basement.

Photo courtesy of Tembec
SS: Solid hardwood is not recommended to be put into basements as there is a potential risk of moisture. We recommend an Engineered NextStep, which has been designed for this purpose and can be glued down direct to the slab. Always follow the installation guide provided in every box.

Photo courtesy of Mirage
BD: Yes it is, but you cannot install every type of floor. We recommend the installation of an engineered hardwood floor, which is much more stable than a 3/4-inch solid floor. The moisture is the most important thing to control. It should be set between 40 percent and 60 percent, and the floor must be installed over a dry subfloor.

FCI: When installing hardwood flooring over a subfloor on concrete slab, is it better to use treated or untreated plywood? Is it better to use a moisture barrier, or none?

Tembec: We do not recommended using a treated or untreated plywood sub floor, so long as it is 3/4-inch thick. Yes, a moisture barrier is recommended between the concrete slab and the plywood subfloor.

BD: There are many ways to install a hardwood floor in a basement but they all have to follow the same rules: there can be no moisture; the subfloor must be dry prior to and during, and must stay dry after, the installation.

FCI: Can hardwood floors be installed over an existing ceramic tile floor, or does the tile have to be removed prior to installation?

Tembec: Remove the tile prior to installing the hardwood flooring and prepare the flooring according to manufacturer's recommendations.

SS: Yes it is possible to glue down our Engineered NextStep Hardwood directly to the ceramic tile, but you must follow the instructions of the adhesive manufacturer. Also make sure that there are no tiles that are loose, or it will create hollow spots in your floor. Make sure that the glaze of the tile is ruffed up using recommended pad or screen.

Photo courtesy of Mirage
BD: If a floor is installed over a ceramic tile floor or over any other material, the responsibility of the installer will be engaged and he will have to make sure that the subfloor is sound and if the subfloor will be able to remain stable under the new hardwood floor. The best way is always to install the hardwood floor directly on the structural subfloor.

FCI: What are the causes of popping and cracking noises in hardwood floors, and what can be done to prevent this condition?

Tembec: Popping, cracking, and squeaking are most likely caused by subfloor problems including being nailed instead of screwed, as well as unevenness. Excess movement in the flooring fit can also allow the boards to shift when they are walked on. Some flooring manufacturers have a very loose fitting product that is easy to lay, but permits "speaking" as the floor is exposed to traffic. Tembec holds extremely tight tolerances avoiding the squeaking of the floor and ensures your floor will stay tight and squeak free years after installation.

SS: Some of the problems that can cause this are: movement of the wood flooring system, sub floor system or under floor supports; inadequate or improper nailing; weak sub floor; improper sub floor material; insufficient or incorrect adhesive; floor subjected to excessive moisture or excessively dry conditions.

As for the cure, noises in only certain areas may be fixed by injecting adhesive into the problem area, screwing the floor down from below, strengthening the sub floor from below or using face nails or screws and plugs. Squeaks also may be lubricated with graphite, wax or baby powder, although such solutions will contaminate the floor for future finishing.

Floors that are noisy and loose throughout the entire area usually have to be pulled and reinstalled, correcting the problem, whether it is caused by the sub floor, fastening schedule or adhesive.

BD: This problem occurs when the floor is not efficiently nailed down or when the subfloor underneath is too weak and allows movement. The moisture conditions can also modify the pressure and cause friction between the boards.