Wood 101

NATURALLY DURABLE SPECIES AND EXOTIC HARDWOODS

There are two kinds of wood – softwoods and hardwoods. Contrary to their names, the “hardness” of the wood species does not define the characteristics:

• Softwood refers to wood from coniferous (with needles) or evergreen trees that grow quickly and can be cut easily. They tend to keep their needles throughout the year. Softwoods are frequently used as building materials. Examples of softwood trees are cedar, Douglas fir, juniper, pine, redwood, spruce, and yew.

• Hardwood refers to wood from broad-leaved trees such as oak, ash or beech. These are deciduous trees that shed their leaves during autumn and winter. Hardwoods are more likely to be used in high-quality furniture, decks, and flooring. Examples of hardwood trees include beech, hickory, mahogany, maple, oak, teak, and walnut.

  See the two videos below to see sawmill plant operations and the pressure-treating process.
  

Understanding Pressure-Treated Lumber and How to Use It

Before using pressure-treated lumber, it is important to understand some of its properties and how to use it properly for the safest and most satisfactory results.

In the creation of pressure-treated lumber, it is important that the right type of wood is selected for the right job. The most commonly used woods are typically spruce, pine or fir and sometimes other similar softwoods with pine probably being the most commonly used wood in the treatment process. These woods can be more easily engineered by the lumber industry for use on projects that are exposed to the many changes in the weather and are more quickly replaced in managed forests due to their rapid growth.

The engineering process of pressure-treated wood includes the selection of a preservative formula which is then pressure-applied to softwood so that the preservative is forced into the core of the wood.

When installing pressure-treated lumber in your outdoor building projects, the directions usually call for the lumber to be installed with gaps between the wood. It is recommended, however, that you install each board so that it is butted against the next board as tightly as possible. This is because as the wood begins to dry and the shrinkage occurs, the gaps will appear between the boards. You will also want to take into consideration how long the lumber has been sitting around your building site before you use it. If it has been sitting around for more than a short period of time, you will want to leave a small gap because the shrinkage will be minimized due to the drying that has already occurred.

Take safety precautions when working with and cutting pressure-treated lumber or lumber of any kind, by wearing a dust mask, goggles and safety gloves. 

When using pressure-treated lumber, it should be used only on outside woodworking projects. Moreover, you should never burn pressure-treated wood.