Engineered flooring is a popular choice for homeowners due to its durability and aesthetic appeal. However, wooden flooring is susceptible to warping caused by humidity or moisture, which can result in cupping, bowing, or lateral bending.
Lateral bending, also known as spring in standard provisions, refers to the lengthwise curvature of an element perpendicular to its edge (as defined in EN 13489:2017 3.2). An example of lateral bending, or spring, is shown in the illustration below.
[Source: EN 13489:2017 Annex E]
The spring is measured with a feeler gauge or a calliper. Measure the maximum gap between the laid edge and the ruler or the reference plate — generally around the centre of the element.
Spring deformation is a common issue with hardwood flooring, but even engineered flooring can experience this problem, especially if the planks are narrow. While the multi-layered laminated structure of engineered flooring makes it more dimensionally stable than hardwood, it is still susceptible to spring.
According to EN 13489:2017 4.5.2, the permitted deviation of spring across the element should not be greater than 0.1% over the length. However, this gap tolerance is still too wide for practical installations. The Chinese standard, GB/T 18103-2022 5.3.2, recommends that the maximum spring gap should not exceed 0.3mm/m.
Spring gap in engineered flooring installation
How to avoid spring in engineered flooring?
To prevent spring deformation in engineered flooring, several measures can be taken from different aspects:
- Optimizing width-to-length ratio
Flooring planks that are long and narrow are more prone to spring deformation. Based on our experience in quality control, we suggest that the width-to-length ratio of flooring size should be no less than 0.08. While this is an approximate number, it generally works well.
- Using robust core material
Fast-grown wood species like eucalyptus and poplar are often used as plywood veneer due to their abundance, but they are less dense than other hardwood species. Engineered flooring with loose core plywood is more likely to warp. Therefore, it is recommended to use birch plywood as the core material for its sound and robust texture. Engineered flooring with birch plywood as the core material generally has better dimensional stability than those using eucalyptus or poplar plywood.
- Prolonging acclimation time
For flooring production orders with critical configurations, such as low width-to-length ratios or specified core materials, it is important to pay attention to production and acclimation time. The pasted plywood boards should be acclimated for at least one month before being divided into flooring width to achieve better internal stress and moisture equilibrium. Therefore, it is essential to arrange the order and shipping times appropriately to allow for enough production time.
- Proper installation
Fixing the flooring onto the base floor is crucial to prevent warping and displacement. Instead of floating pavement, long and narrow engineered flooring pieces should be nail-down or glue-down during installation.
By taking these measures, it is possible to prevent spring deformation in engineered flooring and ensure its long-term durability and stability.
It is important to understand the different types of warping that can occur in engineered flooring to properly diagnose and address any issues. Lateral bending, in particular, can affect the structural integrity of the flooring and cause problems with installation and appearance. It is recommended to consult a professional if you suspect that your engineered flooring is experiencing lateral bending or any other type of warping.