Drying Hardwood Floors - Moisture Content


There can be vast quality differences from one hardwood to the next, especially with more of the lesser known manufacturers of exotic hardwoods, unfinished and prefinished. By Drying hardwood floors outdoorslooking at the properties of a tree once it's cut down in the forest to the time the final product is installed in your home, one can get a better idea how moisture and hardwood react with one another.

When hardwood used for flooring begins it's trail from the forest to your home it loses a lot of moisture content. Looking at it from that standpoint, once a rough sawn board is produced it is generally cut into one inch thickness and eight foot lengths. Width will vary depending on how much good usable material is taken from each individual log. At this point a typical board can weigh as much as much as 60 pounds; some more, some less depending on the denseness of the hardwood specie. Using this weight as an illustration you will see how much weight and moisture is lost during the drying periods.

Stick Or Open Air Drying

Most hardwood mills have their own drying areas. The next step calls for air drying outdoors. Products are cut to similar dimensions from the log for another reason; to allow for proper stacking. Without doing so boards will take on new shapes during which time moisture will be lost.

As example, think of any type of wood product you may have left outdoors that was affected by the elements. How about all those 2'x 4's sitting in a pile next to the shed outdoors. What were once straight boards when purchased are now crooked in all directions. With air drying, boards are stacked on top of one another and separated by sticks; also called stick drying.

During this procedure lumber is stacked proportionally and stickers are inserted between the boards, running vertical to the width of the boards. This allows air movement to pass through during a drying time of two to three months. Once this period has passed our example board has actually lost 25% of the moisture it had at the beginning. It now weighs in at 45 pounds.

Dimensions have also changed with the exception of the length as solid hardwood only expands by width and thickness in this case. The board has lost approximately 1/32" in thickness and 1/4" in width (12 inch board). We haven't even seen the kiln drying process, so you can just imagine what happens to the flooring once it is brought down to the Kiln dried hardwood testmoisture content it needs before it can become viable flooring material.

Kiln Drying Hardwood

Kiln drying is a process where dry heat is forced into an environment to further reduce the moisture content in the raw hardwood product. Pictured on the right is a lumber technician measuring the moisture content of a stack of dried hardwood that has been brought from an open outdoor air drying area. Once satisfactory levels are achieved the lumber is then brought into production and sawed for flooring.

Related Pages:

• Moisture Testing Wood Floors - how, tools
• Moisture Control - environment in and outside home
• Drying Hardwood Flooring
• Humidity and Hardwood Floors