Wood breathes constantly, to match the moisture and heat of the air around it. This means that in the dry winter, wood contracts, and in the moist summer, it expands. This is the reason that many pieces of furniture crack or split. This is also the reason that we air dry most of our wood.
Wood moves across the grain with a change in humidity, but it does not change its length. The secret is to design around the movement of wood.
We design furniture very carefully to accommodate this expansion and contraction. All of our joints are carefully chosen, and often made solely of wood, so that the whole piece of furniture can expand and contract together. Since they do not move the way wood does, screws, nails, or glue, if used improperly, can exert enough pressure on the wood to cause a split.
Design is not merely style. Designing furniture to allow movement improves its strength and durability, and ensures that the piece will serve well, and age well.