This online tool is being released as part of Cross-Tech’s goal of making technologies available to the entire sport market. This calculator enables users to estimate how much Maple will expand and contract when between two given moisture content.
NOTE: This tool is informative. It’s results are provided as an educational tool. All results are provided as informative. Users accept any and all liability associated with any results provided by this calculator. The expansion coefficients in this tool are based on the properties from the 2nd Edition of the Wood Engineering Handbook, but have been slightly adjusted based on our internal and professional experience.
One of the key things this calculator shows is that Maple moves when its environment changes. Gaps are going to be present in your Maple sport or dance floor at various times in the year. Those gaps are integral to floors performance and longevity. Often we visit jobsites where someone complains about the gaps in the floor, and while there are times when the gaps can be excessive, those are rare.
Another key that this tool can help illustrate is how gaps can be reduced or minimized through the use of humidity control within the facility HVAC. This may include something as simple as not turning off the HVAC during the summer when the facility is not being used.
Example 1: The MFMA (www.maplefloor.org) recommends that facilities maintain temperature between 55 F and 75F, and relative humidity between 35% and 50%. Using the Cross-Tech wood moisture calculator 75 F/ 35 % corresponds to a moisture content of: 6.9%. While an environment of 55 F / 50% corresponds to a moisture content of 9.2%. This corresponds to 0.006″, or 1/200″, expansion for an individual 2.25″ wide flooring board. Non-linearities within the system such as finish bonding, and nailing, may cause these gaps to be irregular and not consistent across the entire floor.
Example 2: The calculator can also compute shrinkage but placing the highest moisture content in the ‘low’ input of the calculator and the lowest moisture content in the ‘high’ input. Assume that the floor is installed in a dry region or a region with cold winters and thus long heating periods. Such places might include Montana, Colorado, or even Calgary. If the Maple arrives to the jobsite in the summer at 6% moisture content and is then dried to 3% (75 F/ 15%), we would expect a 2.25″ wide board to contract by 0.008″, or 1/125″. Again, non-linearities within the system may cause these gaps to be irregular with some being larger as they represent a combination from multiple flooring rows. If these nonlinearities caused 4 boards to contract together, the gaps of 0.03 (1/32″) could be present. As a note, if 1.5″ wide flooring is selected, the contraction is reduced to 0.006″ per row, shrinkage gaps would tend to be more frequent but smaller.
There is another feature to this tool. It provides an estimate of how frequently expansion rows would need to be installed for a given environmental range. These gaps are far more visible than the small gaps between rows. This calculation can be used to illustrate the benefits of controlling the relative humidity, or running humidity controls through periods when a facility is not being used.
Example 3: First, let’s consider the results from Example 1, using the moisture contents provided. (6.9% and 9.2%). The calculator shows that a 0.006″ wide expansion row would need to be installed nominally every 14 flooring rows to accommodate the expected expansion. However, if we assume that the facility HVAC was turned off during the summer and the temperature was allowed to increase to 80 F, and relative humidity spent significant periods at 65% (levels that are common throughout many parts of North America) the result would be a moisture content of 11.6%. Using a MC range from 6.9 to 11.6, the calculator shows that an expansion row would now need to be installed nominally very 7 flooring rows. To put it another way, the lack of active humidity control can require double, or 100% more, expansion rows than would be required with active humidity control. This illustration is provided to show the importance of environmental controls within facilities and how the lack of control may alter the appearance of the floor.
