Reader robinsk asks "I keep reading about them, why are kiln dried sofa frames better than air dried, or any other kind?
Kiln dried sofa frames are a safe bet that your sofa frame is strong enough to last you a long time.
What makes a kiln dried frame better is that kilns get rid of most of the moisture inside the wood. Kilns are huge ovens with very strictly controlled temperatures and humidity. The kiln drying process can remove approximately 93% of the wood's moisture.
This drastic reduction in wood's moisture content is important so that the wood doesn't warp or shrink with changes in humidity and temperature. Warping or shrinkage would destabilize your sofa, and even cause it to lose its shape. You would not see that happening in a quality sofa.
Air drying can also work well, but oftentimes the process is not controlled enough, so you cannot be sure that the wood's moisture content is sufficiently reduced.
Metal sofa frames are available, too, but metal can be prone to oxidation along with seasonal changes. Changes in humidity can affect metal frames, so look for one that has been treated to protect against atmospheric changes.
Kiln dried frames are superior because you can be sure about the reduction of the moisture content to a satisfactory level. Another thing to remember about sofa frames is that a sofa frame that is made of kiln dried hardwood is a much better choice than a softwood frame even if it is kiln dried.