Q&As: Normal Gaps & HVAC Delays

Q&As: Normal Gaps & HVAC Delays

By HF Editors
December 2013/January 2014


‘Normal’ Gapping

photo of wood floor with normal gapping

I’m receiving many complaints from customers related to gapping of their solid hardwood floors. What is “normal” when it comes to gaps between boards?

David Cathey, quality control manager at Mullican Flooring, answers:

When distributors and retailers receive gapping complaints, they often automatically contact the manufacturer. However, more often than not, gaps are simply normal changes in the wood based on the time of year (and, possibly, the result of errors during installation).

According to the National Wood Flooring Association, normal gaps occur “between individual boards and open and close with changes in humidity.” The identifying factor is that normal gaps should appear only during heating seasons and disappear or close in high-humidity seasons. The size of normal gaps depends on the width of the boards—the wider the board, the wider the gap. Also, square-edge floors show gaps more than beveled floors, and light-colored floors show gaps more than dark floors.

If gaps remain after the heating seasons have ended, then you’re likely facing a serious gapping issue and need to uncover the cause. Some of the common causes include: hot spots in the subfloor caused by poorly insulated heating ducts, hot water plumbing lines, radiant heating systems, register openings or appliance motors; debris left between boards during installation; improper nailing or nail positioning; cracked tongues; flooring installed with an extremely high moisture content or over a subfloor with excessive moisture; foundation settlement or subfloor movement; the use of improper subfloor materials that won’t hold nails; and crushed edges on boards due to prior exposure to extreme moisture.

To correct the issue, determine and eliminate the cause of the gapping before restoring the room to normal humidity levels and allowing the floors to stabilize. Then use filler in the smaller gaps (up to 3/32 inch) and recoat the floor. For larger openings, use a sliver or wider board to fill in the gap.

The important thing to remember is that gapping during “heating seasons” is perfectly normal. Informing consumers about this fundamental fact at the time of sale will go a long way toward eliminating gapping complaints that will naturally resolve themselves in the summer months.

‘Forced’ to Install?

I have a builder who wants me to install 7-inch reclaimed oak in a barn being converted into a home. The HVAC hasn’t been installed yet but the flooring and subfloor are within the necessary 2 percent moisture content difference overall. The builder is pushing me to get the floors in so he can continue the remodel in the required time frame. Can I install the floors?

Brett Miller, director of certification & education at the National Wood Flooring Association, answers:

No matter what the timeline is, wood flooring should be one of the last jobs on any construction project. If the HVAC hasn’t been installed in this residence and the conditions in the home are not at “normal living conditions”—that is, the temperature and humidity you expect the home to be at once it’s occupied—you will want to avoid installation of any wood products in this home, even if the MC of the subfloor and wood flooring are within 2 percent of each other right now. The flooring and subflooring must be acclimated to the environment in which they are expected to perform. Once you install the wood flooring, that constitutes your acceptance of the flooring material, the condition of the subfloor, the job site itself (including the ambient temperature and relative humidity at the time of installation), and any other impacting variables that may affect the wood floor.

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 HVAC system is fully operational. If you are “forced” to install these floors prior to the job site, subfloor and wood flooring being at normal living conditions, it’s likely you can expect a call back within a couple months related to excessive floor movement: Flooring installed during times of peak humidity is likely to later show excessive gaps, and flooring installed during the driest time of the year will tend to cup and can even buckle. If you go ahead with installation, you’d be wise to factor this likelihood into the cost of the entire job.