Changing with the Climate: Understanding Wood as an Organic Material

Regardless of the methods you use to restrain it, it is a guarantee that if you are using wood for a project, it will, at some point, move. Whether it is 100 years old, protected with the best sealant, or fastened with the strongest screws, wood will move. However, if you are a knowledgeable contractor who understands how and why that particular species moves, you can make working with the material much easier and ensure a quality finished project for years to come.

As a tree grows in the forest, water is absorbed through its roots. When that same tree is cut down, the water will still be in the tree; however, as time goes on, the water will start to evaporate, causing the wood to shrink. If you install wood in a wet climate, the opposite effect will occur: water will be absorbed into the lumber, and the lumber may expand. Regardless of whether it is a wet or dry climate, it is part of wood’s natural characteristics to adapt to its environmental surroundings and climate, meaning it will shrink in a dry climate or expand in a wet climate.

How can you prevent such movement? Well, you cannot prevent wood movement 100%. However, when wood is properly air or kiln dried, then properly protected with a sealant, movement can be minimal. The only surefire way that a contractor can deal with movement in a wood product is to anticipate it, understand it, and build with this movement in mind.

By exploring the data charts on J. Gibson McIlvain’s product pages (see the chart in the left side bar of this Teak page), you can look at an individual species of wood and understand its tangential shrinkage and radial shrinkage. These numbers will help you plan for and anticipate movement based on the specific species; these numbers can be found on every species page on the mcilvain.com website.

Another aspect to consider is that when lumber is being shipped from one country to another or from one end of the U.S. to the other, each time it sits in a different climate, it will attempt to adjust and reach an equilibrium in that climate. By lessening extreme swings in temperature and climate, such shrinking and expanding can be prevented. Keep lumber out of the direct rays of the sun to prevent shrinkage. Lumber needs to be stacked in a well-ventilated area with “stickers” between each row to allow even drying and air flow. Give your lumber time to acclimate to its new climate when it finally arrives at your job site.

If you are using kiln-dried lumber, chances are the lumber supplier has already done the work for you, and movement will be minimal. Consider moving a piece of wood from humid Maryland to hot and dry Arizona. If you don’t take the aforementioned steps and let the wood acclimate, chances are you are going to have more problems with movement.

In short, wood is an organic material that will always move as the climate changes around it, and it works hard to equalize. Your job as a contractor is to anticipate movement and build for it. Our job as a supplier is to kiln dry or air dry the wood and use responsible measures during storing and shipping. J. Gibson McIlvain Company has knowledgeable representatives on hand to help you understand and anticipate wood movement.

J. Gibson McIlvain Company

Since 1798, when Hugh McIlvain established a lumber business near Philadelphia, the McIlvain family has been immersed in the premium import and domestic lumber industry. With its headquarters located just outside of Baltimore, the J. Gibson McIlvain Company (www.mcilvain.com) is one of the largest U.S. importers of exotic woods.

As an active supporter of sustainable lumber practices, the J. Gibson McIlvain Company has provided fine lumber for notable projects throughout the world, including the White House, Capitol building, Supreme Court, and the Smithsonian museums. Contact a representative at J. Gibson McIlvain today by calling (800) 638-9100.