Woodworking FAQ: How to Deal With Wood Shrinkage and Expansion

Use this woodworking guide’s Q&A to craft around wood’s predisposition to shrink or expand with fluctuations in humidity or temperature.


| July 16, 2012



Wood Shrinkage Example

One challenge all woodworkers face is dealing with wood’s predisposition to shrink and expand in response to changes in humidity and temperature.  


MELANIE POWELL

For the problems and questions that arise as you work through new projects, count on finding the answers in Woodworking FAQ (Storey Publishing, 2012) by Spike Carlsen. This woodworking guide offers the know-how and experience to answer common questions and provides handy tricks of the trade and simple instructions that will improve your woodworking and building skills. The following excerpt on wood shrinkage and expansion is taken from Chapter 2, “Wood & Plywood.” 

Movement in Wood: Dealing With Wood Shrinkage and Expansion

One challenge all woodworkers face is dealing with wood’s predisposition to shrink and expand in response to changes in humidity and temperature. This may eventually result in cracks, gaps, and weak joints. This section offers some tips for meeting that challenge.

Q: Why is it so necessary to use dry wood?

A: Wood shrinks and changes shape as it dries. You want the bulk of that shrinkage and change of shape to occur before you start working with it. Freshly cut wood is also extremely heavy — in some species, over twice as heavy as when it’s dry. Plus, wet wood is more susceptible to decay and rot. That said, there’s an entire field of woodworking called “green woodworking” that focuses on building furniture and other items with wet or unseasoned wood. This furniture is often “rustic” in nature.

Q: Does wood shrink and expand equally in all directions?

A: No. The amount of shrinkage varies from species to species, but generally wood shrinks 8 to 10 percent tangentially, 4 to 5 percent radially, and close to zero percent lengthwise. In other words, the surface of the board where the grain intersects it perpendicularly, or close to perpendicularly, shrinks the most. This means woods of different shapes will shrink differently based on how they’re cut from the tree.





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