Gapping on Wood Flooring - Part 5 - Abnormal Large Gaps


As explained in the name, this is when regular or occasional large gaps, coincide with significant changes in the width of the flooring element.


This is caused by a high degree of moisture loss and accompanying reduction in the width of individual flooring elements. This can be caused by a number of things, with environmental heat being the first. In addition, a large quantity of natural light may be the reason why the flooring may experience gapping of this magnitude. This can also be caused by installing flooring at the wrong moisture content.

  • Installing flooring materials at the wrong moisture content for the environmental conditions.
  • Acclimatising flooring during drying of wet trades, leading to increased moisture content of materials.
  • Heat from under-floor heating, hot water pipes, large areas of glass etc.
  • Excessively dry atmosphere.


To ensure you reach the appropriate solution, it is highly advisable to correctly identify the area of concern. In the case of experiencing large gapping, floor temperature should be checked with a surface temperature sensor in order to see if heat has caused or contributed to the problem.

The moisture content of floors can be tested to check if the moisture content is unusually low. This may indicate that environmental heat and or dry atmosphere has caused some degree of moisture loss that is often accompanied by cases of shrinkage.


  • In order to solve this issue, we advise that you execute these steps in order to help you to resolve the issue that has arisen. These are the following:
  • Be sure to correct the environmental temperature and humidity where needed.
  • Follow this by sanding and filling the area. If the damage is more severe, you may be required to replace individual boards .


  • Selection of materials at the correct moisture content for the environmental conditions.
  • Ensure that the flooring is properly acclimatised in-situ prior to the installation process.
  • Randomly check the moisture content of the materials before installing the flooring.
  • Carefully check for potential heat spots using a surface temperature sensor.
  • Thoroughly insulate hot water pipes beneath the area where the flooring is to be laid.
  • Appropriately select your products, especially where environmental conditions are likely to cause shrinkage.
  • Ensure you understand that wood expands and contracts according to the changes in ambient conditions.
Fig.1 A, B ,C Show rows from packs that were opened on site six weeks prior to installation during the drying of wet trades. These boards expanded prior to installation, and subsequently shrunk after installation causing gaps. Simplified drawing – all flooring is same width, cutting type & species.(solid)
Gapping on Wood Flooring

Fig.2Shows floor with severe gapping. A, B,C. These boards were higher in moisture content at the time they were machined. All flooring is at expected approximate EMC for the temperature and humidity. Simplified drawing – all flooring is same width, cutting type & species.(solid))
Gapping on Wood Flooring
Note: some variation in moisture content is normal. Acclimatisation can help minimise moisture variations.

Fig.3 Shows rows (A) +(B) which has shrunk due to hot water pipes directly under suspended flooring. Pipes were not insulated. The moisture content of most of the flooring is at the expected EMC for the ambient conditions. The moisture content of shrunk boards is low due to environmental heat. Simplified drawing – all flooring is same width, cutting type & species. (solid)
Gapping on Wood Flooring