Understanding Wood Floor Checking: Causes, Prevention, and Solutions

There’s an age-old misconception in the flooring world — that there are many conditions which cause wood to check. In truth, there is primarily only one. Checking in solid wood flooring has long been a leading concern in flooring claims, often misunderstood and misdiagnosed.

Most professionals recognize that checking is related to changes in moisture content within the wood — a result of drying stresses. However, what’s commonly overlooked is the fact that these stresses cannot originate in wood that’s installed within the normal environmental ranges of an interior living space.

Types of Checks

• Surface Checks: Surface checks typically occur in the wood rays on the flat-sawn faces of boards. They happen when drying stresses exceed the tensile strength of the wood perpendicular to the grain. In simpler terms, these are tension failures caused by the outer shell of the board drying faster than its core.

  
  

  They often appear near knots, mineral streaks, gum pockets, or in bacterially affected wood, as those areas are naturally weaker.

  
  

• End Checks: End checks, like surface checks, usually form in the wood rays at the end-grain. They develop early during drying because moisture moves far more quickly along the grain than across it. As a result, the ends of boards dry and shrink first, creating stress that leads to small cracks.

Common Hypotheses Over the Years

Over time, various explanations have been offered to explain why checks appear after installation. The following are some of the most commonly cited causes in post-installation environments:

The wood checked because …

• it was installed in an uncontrolled environment outside the industry-accepted 35%–55% relative humidity (RH) range

• it was installed within an acceptable moisture content (MC) range but dried excessively during winter when humidity levels dropped

• it absorbed moisture during humid summer months, causing excessive swelling

• it wasn’t acclimated properly before installation — either too wet or too dry

However, as stated earlier, the true cause of checking lies in drying the lumber too fast. Whether during initial milling or pre-installation handling, improper drying practices create internal stresses that later manifest as surface or end checks.

Preventative Measures

Unfortunately, grading standards are rarely discussed during the marketing and sale of wood flooring, even though these standards clearly outline the potential for checking and other natural characteristics. Including this information on samples and within product literature would create opportunities for education at every level — from the salesperson to the end client.

When consumers are informed about the natural properties of wood — including the potential for minor drying defects — they are less likely to misinterpret them as product failures. After all, wood is a living, natural material, and its color, grain, and movement are what make every floor unique. These natural variations are part of what defines the character and authenticity of fine hardwood floors.

In Summary

It’s important to acknowledge that drying defects can occur, and their complete elimination is neither possible nor realistic. Even in high-quality flooring mills, a very small percentage of boards will contain visible or microscopic drying defects. These are typically within the limits defined by manufacturer grading standards, which specify what natural features and defects are permissible.

When checks in a solid hardwood floor exceed these defined limits, claims should be addressed promptly and handled with transparency — with all parties understanding that the consumer is not at fault.

At Brickell Wood Floors, we believe education and communication are the foundation of successful projects. Understanding the science behind wood behavior ensures that every installation — from Miami’s high-rise penthouses to luxury Brickell condominiums — maintains its beauty and performance for years to come.