Here is part 3 of 3 - Why does oak hardwood flooring costs vary. In this final segment I would like to address the drying process and how it relates to quality.
There are 2 ways of which to dry hardwood - air and kiln.
The definition or air drying is the drying of timber by exposing it to the air. "The technique of air drying consists mainly of making a stack of sawn timber (with the layers of boards separated by stickers) on raised foundations, in a clean, cool, dry and shady place. Rate of drying largely depends on climatic conditions, and on the air movement (exposure to the wind). For successful air drying, a continuous and uniform flow of air throughout the pile of the timber needs to be arranged."
On the opposite end of the spectrum is kiln drying. "The process of kiln drying consists basically of introducing heat. This may be directly, using natural gas and/or electricity or indirectly, through steam-heated heat exchangers, although solar energy is also possible. In the process, deliberate control of temperature, relative humidity and air circulation is provided to give conditions at various stages (moisture contents or times) of drying the timber to achieve effective drying. For this purpose, the timber is stacked in chambers, called wood drying kilns, which are fitted with equipment for manipulation and control of the temperature and the relative humidity of the drying air and its circulation rate through the timber stack."
Kiln drying is a much more uniform and controlled method of drying. It is a more costly process, but yields a much better result. Remember the goal here is to produce boards that have a moisture content under 12% and less that a 3% variation.
Because air drying wood is not a controlled method, erratic moisture levels, warping and cracking can become an issue,. What is even worse is that if you install hardwood flooring planks that have a moisture content of 12% or higher and a variation of more than 3 % the boards will continue to dry over time. This is where warping, twisting and splitting happens. Once this happens, there is little you can do to stop this process.
Please keep in mind just because the wood is milled in the US or Canada does not mean it was harvested or dried there. Some mills will purchase timber over-seas and then mill it here. Over-seas hardwood is generally much cheaper (both $$ and quality) and comes with a cheaper retail price. Make sure you know where your hardwood it is harvested and dried before you purchase. Always ask your salesman.
As you can see, kiln dried hardwood yields a much more stable product. And stability is a major factor where it relates to quality. Most of your better mills in the US and Canada kiln dry, and air dry is much more common over-seas, so it is best to find this out BEFORE you purchase. All these factors are part of the pricing.
I hope this helps shed a little light on why oak hardwood flooring can have such varied costs.
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