Introduction

Correct seasoning and drying will ensure that your wood floor is stable, and that it behaves predictably as ambient moisture content and temperature vary throughout the seasons.

This is an enormous topic that fills technical volumes, but for the property owner it is only necessary to understand the basics of seasoning and kiln drying, but important to grasp the concepts of relative humidity (RH) and equilibrium moisture content (EMC). If RH and EMC are understood, you will be able to ensure that your floor is trouble free and beautiful for years to come.

What is Seasoning?

Seasoning is the process of drying sawn wood slowly and naturally to a level that prepares it for kiln drying. It is also known as air-drying because the wood is usually stacked out such that air can pass through the stacks. During seasoning moisture content will fall with minimal cracking and distortion as the free water slowly evaporates from the wood. High quality wood flooring is seasoned before it is kiln dried. Low cost manufacturers often skip this step.

Kiln Drying

Kiln drying is the process whereby wood is stacked in a kiln where air temperature, humidity and circulation are controlled. By carefully increasing the temperature while ensuring the humidity is at the correct level, fixed water can be driven from the cells in the wood without excessive cracking or distortion.

Moisture Content Explained

Moisture content (MC) is the percentage of water in the wood compared to its dry weight. The appropriate MC will depend on both the wood species and on its application.

Moisture content must be stable and suitable for the specific environment where the flooring will be installed.

5. Relative Humidity (RH) and Equilibrium Moisture Content (EMC)

• Relative Humidity (RH) refers to the amount of moisture in the air compared to the maximum amount of moisture the air can hold at a given temperature.
• Equilibrium Moisture Content (EMC) is the moisture content that wood will reach when it is in balance with the surrounding environment. Understanding RH and EMC helps in maintaining the proper conditions for wood

As RH increases, wood tends to absorb moisture, raising its MC. Conversely, if the RH decreases, wood will release moisture until it reaches a new equilibrium. Understanding these concepts can help property owners maintain the stability and appearance of their wood flooring throughout seasonal changes.

Keeping the relative humidity (RH) between 35% and 45% is a good strategy. This range is generally safe and should help maintain the integrity of wood flooring, minimizing issues related to both excessive moisture and dryness.

In hot dry weather you may need to use a humidifier to bring humidity up to 35%, while in very humid weather it is usually enough to run refrigerated air conditioning (not evaporative) as this will reduce humidity. If conditions are particularly humid and the AC does not bring humidity below 50%, then it would be wise to use a dehumidifier.

If all this sounds like a lot of trouble, just remember, you are also doing your skin a big favour! The conditions that are perfect for your floor, are also perfect for your skin.