We use Grade No1. 1 thick kiln dried Hardwood Lumber. The type of wood changes periodically, but typically we use a poplar or oak hardwood. We complement this with a 6 ply, engineered hardwood that is also 1 thick. This may be used on large, or form fitting areas that are too large to use Hardwood Lumber. All of our hardwood frames are guaranteed for as long as you own the furniture. Unlike much of what is out there in stores in todays furniture market, we will never use any press wood or laminate in our frames.