One of the most-common wood floor installation methods is the nail-down method. This installation method is detailed in the NWFA Installation Guidelines, beginning on page 121, where you can find information on substrate requirements, fasteners, fastener schedules, installation methods, and even when to use adhesive when nailing.
Many types of wood floors can be nailed down in many different situations. Arguably, the single most important factor to take into account when nailing down any wood floor is the wood flooring and the flooring nailer manufacturer’s installation instructions. The flooring manufacturer normally will define what type of fastener to use, as well as fastener placement, and how many fasteners are required to hold down their floor. This information will dictate which nailer will be required to install the floor. Once the type of fastener and type of nailer have been identified, it is critical to follow the specific instructions on proper use of the tool.
A flooring nailer is a type of tool used to drive flooring nails into wood flooring. There are three primary types of flooring nailers used in the wood flooring industry. They include manual mailers, mallet-actuated nailers/staplers, and trigger-activated nailers/staplers.
A manual nailer (photo to the left) is a tool that drives fasteners into the wood flooring by a plunger that is driven through blunt force. Manual nailers are available as single-hit or multihit/ratcheting-mechanism plungers, that allow the user to strike the plunger multiple times in order to drive the fastener.
A mallet-actuated nailer/stapler (photo to right) uses compressed air to drive the fastener. The plunger in these nailers is triggered by striking the plunger of the nailer with a flooringm mallet. Each model has different capabilities and magazine cartridges for use with specifically designated fasteners.
The nailer this article will be focused on is the trigger-activated nailer/stapler (photo to left). Trigger-activated flooring nailers/staplers are engaged by a trigger and capable of driving the flooring fastener into the tongue of a piece of wood flooring. Each model has different capabilities and magazine cartridges for use with specifically designated fasteners.
Trigger-activated flooring nailers can drive either narrow crown (¼”) staples or cleats. The length of these fasteners normally ranges from 1” up to 1 ¾”. (Each fastener is designed specifically to be used with a specific tool. Only use the nailer manufacturer-recommended fasteners with the tool being used.)
These nailers normally drive fasteners into 3/8” to 5/8” thick engineered wood flooring, and are easily adjustable to accommodate the thickness of the flooring being installed. To set the nailer to the flooring, use a sample of the wood flooring, slide the foot back on the channel, and set the nose of the stapler securely into the nail pocket. Orient the board as it is intended to be installed, with the floor board’s surface facing up. Always test fire into a test piece of flooring to ensure the nail is seated correctly into the nail pocket of the board.
Use of these types of trigger-activated nailers actually places the installer out in front of the flooring being installed, as opposed to when using a mallet-actuated nailer, where you are standing on the board you are nailing. While positioning yourself out in front of the floor being installed, you reduce the potential for marring, or damaging the surface of the flooring being installed. This is a good thing, and allows the installer to evaluate the installed flooring, as it is being installed, much easier.
However, there are some items that must be taken into account when using these flooring nailers to avoid installation-related failure:
- While positioning yourself in front of the boards being nailed, you must apply a downward pressure to the board as it is being nailed in place. This requirement plays a couple of critical roles in how the board becomes fastened to the subfloor. Once the board has been tapped into place, and the groove of the board has been fully engaged into the adjoining board’s tongue, the back side of the board should be flat against the subfloor. If you were to drive a fastener into the front tongue of the board without downward pressure on the plank, two things can happen:
» The underside of the flooring can blow out, lifting the board off of the floor. This blowout often results in a noisy, “snap, crackle, pop” sound in the installed wood floor (photo to left).
» The fastener can also chip-out the subflooring material upon entry, creating a lump where the wood floor comes into contact with the subfloor at that location (photo to right).
Both of these issues can be minimized, if not completely alleviated, by using a downward pressure on the flooring as it is being nailed into place, or by standing on the plank as it is being nailed.
2. If you are applying adhesive along with the mechanical fasteners (i.e., glue assist), you also must apply a downward pressure on the plank as it is being fastened. In this case, the adhesive becomes smooshed against the subfloor and the underside of the wood floor, properly adjoining the two surfaces, and alleviating any potential for lifted points below the wood floor. Once again, without the downward pressure during glue-assisted installations, noisy floors may result.
3. When using a trigger-activated nailer, you also will need to be cognizant of compressor air pressure. Adjust the compressor pressure regulator to the proper pressure. Normal operating pressure should be adjusted between 70-120 psi based on the fastener and wood being used. Normal air pressure should not exceed 120 psi to avoid damage to the nailer. Always use the tools at the minimum operating pressure that allows the fastener to be seated into the nailing pocket appropriately. A higher pressure could be necessary, for example, to use the tool with different species of harder wood. Do not continue to use a tool that leaks air or does not function properly.
Another consideration to take into account when using this type of nailer is the condition of the subfloor. The most common subfloor that wood floors are installed over today is OSB; commodity OSB subfloors, in specific. As manufactured, these subfloors can be an appropriate substrate below most wood flooring. However, during the construction process, and where the builder does not adequately execute a moisture control plan to protect these subfloor materials, they can lose some their ability to hold a fastener.
New construction poses the highest risk. Moisture introduced to the subfloor through the construction process soaks into the wood. The wood fibers swell. Then, as the building begins to dry out, the wood fibers lose moisture, and begin to shrink. As we drive fasteners into this subfloor material, we test for moisture, and hope that all of the construction moisture has been removed from the subfloor. In the case where it hasn’t, the fasteners no longer have wood fibers holding them in place; in essence, creating a void pocket around the shank. Without an alternative method of holding the boards in place, you can get movement in the entire system, resulting in squeaks, pops, or crackles. That is where the builder and the flooring contractor must work together to ensure all components of the building are adequately protected and prepared prior to installation of a new wood floor. Most flooring manufacturers simply do not warranty against squeaking, popping, or crackling when using staple-down or nail-down installation methods.
The type of the fastener used can greatly affect how the boards perform as well (photos below).
Typical fastener spacing for this type of flooring is 3”-4” intervals along the length of each board. And within 1”-2” from each end-joint of every board, with a minimum of 2 fasteners per board. The type of fastener used is normally an 18g-20g flooring cleat 7 or narrow crowned (1/4” crown) 18g staple. The fastener should be no less than 1 1/4” in length. Some manufacturers (and even old NWFA Guidelines) used to allow for fasteners as short as 1” in length. This is no longer acceptable (unless otherwise required by the flooring manufacturer) as the fastener penetration into the subfloor, and withdrawal capacity is not sufficient with this short of a fastener.
A study from the USDA Forest Products Lab found that in the OSB filler, in most cases, reduced fastener withdrawal strength can be as much as by 25 percent. This reduction was proportional to the reduction in depth of nail penetration into the main solid wood member. Nail length should be increased in connections where composite lumber filler materials like used in commodity OSB are used in nailed connections. The increased penetration depth of the nail restores the withdrawal capacity of a joint when this type of filler material is present.
The greater the length of the fasteners’ embedment in the wood subfloor or the larger the shank diameter of the fasteners, the greater the fastener withdrawal capacity. This is a balance that the installer must address, between what fastener is required by the flooring manufacturer to nail the flooring in place, versus what may be necessary for the site conditions in the space. Never go outside the manufacturer requirements, but always lean toward being cautious. For example, if the flooring manufacturer states, “nail the floor every 3”-4”, consider placing a fastener every 3”. Fasteners placed at intervals less than the required blind-nail spacing requirements are acceptable as long as the tongue and core material of the flooring is not compromised or split during installation.
Trigger-activated nailers are great tools that have been developed for a very specific installation method and for a specific type of wood flooring. When properly used, they can assist installers in providing a beautiful, long-lasting floor for their customer. However, as with any tool, it is critical to know the tool you are using, and fully understand its capabilities and limitations.
The complete Installation Guidelines can be located online at NWFA.ORG/TECHNICAL-GUIDELINES/.