What Does Kiln Dried Wood Mean?
This is a question I get a lot about wood.
Kiln dried means that the moisture has been removed from the wood beyond what is possible by air drying, and is in a range that it would experience in a house or other structure with modern heat and air conditioning. For hardwood, it is generally accepted that once wood has been brought down to 6% - 8% moisture content it is kiln dried, and for framing material for houses, such as studs, it's only dried to about 15%, as required by the American Lumber Standard. Most people think kiln drying means drying the wood as much as possible, but really, the intent is to match what the boards experience indoors. If the wood has been dried too much, it will have excessive warp, and other defects. The wood will also if not dried down to the appropriate MC will also experience drastic changes when placed inside a climate controlled structure. Kiln drying also means (when done properly) the added process of sterilization in which the wood is heated up to an internal temperature of 133 degrees or greater to kill any "bugs" that might be present inside the wood.
Now I am not against air dried wood, it has its place, and with proper technique can be used in projects that end up inside modern day homes.