The effect of moisture on wood movement.

All solid wood, regardless of age or where it has been, will absorb or release moisture (water) depending on the ambient humidity of the environment at that time. Thus, if a dry piece of wood is introduced into a wet, or humid, environment, it will tend to take up moisture, causing it to expand. Similarly, if a wet piece is introduced to a dry environment, it will tend to lose moisture causing it to shrink. Naturally, different timbers have different rates of expansion and contraction, with a general rule that the denser the timber, the less the movement.

The advantage of a finishing coat.

Wood finishes, such as varnish or lacquer, greatly restrict the movement of moisture in and out of the wood, thus reducing, but not wholly preventing, the rate of wood movement. Eventually, with long use, the finishing coat will wear through, and the rate of moisture movement will accelerate. It is at this stage that the importance of design manifests itself!

Cross grain construction.

Wood will also expand more across the grain than along the length of the grain, further complicating matters! Thus, if a piece of furniture is made with a timber joined across the grain of another piece (or pieces), as is sometimes done with other manufacturers' railway sleeper table tops, they will expand and contract at different rates, eventually causing the top to break up.

The importance of design.

At Savanna Wood we design our furniture to allow for this movement. Thus tabletops, desktops etc. are fixed to their bases with metal brackets that clamp into slots in the base to allow the top to move. Side panels and doors are of ‘panel in frame’ construction that allows the panel to expand and contract within the frame. Large backs to cabinets etc. are individual slats tongue and grooved between to allow expansion of the slats to prevent them separating. Large bed headboard panels are loosely located in a frame of the legs and rails of the headboard so the whole panel can expand and contract within the frame.

Such construction methods complicate manufacture but are well worthwhile to ensure the long-term integrity of your spectacular purchase!