How Dry is Your Wood?
Softwoods often take to the air
Because softwoods generally end up being used for building construction in higher relative humidity conditions than hardwoods, it's not necessary for suppliers to get their moisture content lower than 12-15 percent, and that can be done with air-drying. Softwoods used in interior locations, though, are dried to about 8 percent MC. More drying than that tends to cause brittleness and other problems in machining.
The term kiln-dried means that wood moisture was removed in a chamber where air circulation, humidity, and temperature were controlled. It also implies a moisture content lower than that in softwood construction lumber. For softwood lumber of 1" thickness, it means a MC under 12 percent. Softwoods also may be kiln-dried to make them dry faster, lighten them for shipping, or kill wood-born organisms.
Hardwoods sold for furniture, cabinets, and other interior uses are traditionally kiln-dried following a schedule that limits loss from drying defects. Kiln-drying lowers moisture content to somewhere between 6-8 percent. That's because the average indoor humidity in most of North America's homes ranges from 6-8 percent EMC.
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