Wood is an essential part of many houses, even those that are constructed mainly with concrete and metal. It is essentially a cantankerous substance. It is easy to work with, abundant and attractive. In fact, pound for pound, wood is actually more durable than steel, if it’s properly processed, finished and cared for. However, wood is also a perplexing and complex building material. Unlike plastics and metal; wood actually has relatively inconsistent properties. Not only there are hundreds of wood varieties; depending on the originating tree species; it also contracts and expands in all directions; especially when the humidity level in the surrounding area varies widely. However, we should be able to use wood as a wonderful piece of furniture.
There are unique properties of wood that we need to be aware of.
- Wood has grainy properties.
- Wood expands and contracts across the grain, instead along it
- Wood is stronger along the grain, instead across it.
- Grainy properties: Wood cells align themselves as trees grow. Wood cells form long thin of fibers that are bundled. This gives a special characteristic and wood may have specific grain directions. Trees also produce annual rings and they grow in concentric layers. In this case, we need to pay attention to the annual rings and grain directions. During a home improvement project, it is important to understand the distinct pattern of wood grains, which are determined by the species of the wood. Because of the unique structure, we know that wood contracts and expands constantly; so we should cope with this kind of movement.
- Contracting and expanding across the grain: Wood is an organic material and it’s the remains of a once living organism, so it is less stable than metal and wood. Wood contracts and expands constantly, depending on the surrounding condition. When the moisture content changes, wood contracts and expands accordingly. Sap and water evaporate when a tree is felled. However, even long after the tree died; fibers inside wood retain their capabilities for absorbing and releasing water. In a humid environment, about 28 percent of the wood mass can be consisted of water. Every 4 percent changes in surrounding humidity, the moisture content of the wood will change for about one percent, but it could vary slightly depending on the tree species. During the home improvement project, we should know how much wood will expand and contract; also at what direction. Of course we know that it expands and contracts across the grain. This is an important consideration when making windows made from wood.
- Better strength along the grain: This is an obvious fact. Meat is chewier when we cut it along the grain. The tough, long cellulous fibers are bound together by lignin, a glue-like substance. During home improvement project, we should make sure that we choose wood that’s cut along its grain. It is also a good idea to choose wood species that are naturally stronger, such as hickory, birch and hard maple.