Wood Movement: The Secret to Successful Woodwork

Hall table drawers Hall table detail of dovetailed drawers.

I create custom-made, bespoke furniture and other wooden objects based on the vital knowledge  that all good design must allow for timber movement.

 Changes in temperature and atmospheric moisture levels (relative humidity) cause wood to expand or contract, explaining why wood expands in winter and contracts in summer. Most timber shrinkage or expansion occurs across the grain (ie across a plank) with very little along the grain.  So a basic rule of woodwork is to avoid gluing timber components with end grain to long grain. An example is a solid wooden table top with mitred edges. As the timber tries to expand or contract, the mitred ends prevent it from moving, causing glue joints to fail and the top buckling or cracking.

 Contrary to what many believe, indeed even some experienced woodworkers, older and recycled timber still moves, though to a lesser extent than newly-dried timber. Coatings and finishes, such as polyurethane, can decrease the level of movement, but are unable to completely prevent it from occurring.

The ability to allow for timber movement and a critical understanding of the properties of each type of timber ensures precise, handcrafted furniture that will last a lifetime. This is why I make my bowls from Birch plywood, as plywood is more stable than solid timber due to the grain of different layers lying in varying directions.

For those interested in exploring timber movement in more detail, the Wood Movement Calculator 3.1 (an Excel spreadsheet), provides a quick and simple way of estimating the amount of timber movement based on weather patters in moisture content. There are separate estimates for Australian and other timbers. You can download the calculator here.. Also, your comments and suggestions are highly valued. Please feel free to forward them to stephen@ecowooddesign.com.au.