One of the most common types of building materials is lumber, which is a term that refers to wood in any stage between being cut down as a tree and being machined for use. Hardwood lumber is most common because hardwoods tend to be exceptionally durable, strong, and resistant to water damage, though softwood lumber is also sometimes used, mainly for framing. Various types of hardwood lumber exist, and these types can vary by wood species or by the size, shape, and quality of the wood. Rough sawn lumber, for example, refers to wood that has not been kiln dried yet and may not be straight or even.
Rough sawn hardwood lumber is usually longer and wider than finished lumber because the person who uses rough sawn wood will need to cut the lumber down to shape after it has been kiln dried. A builder or contractor with the necessary skills and tools might buy rough sawn hardwood lumber rather than finished lumber to save money at the time of purchase, though people without such tools and expertise may have difficulty using such wood, as this wood can be easily damaged if it is not dried and shaped properly.
Pressure-treated hardwood lumber is often used for projects that require the lumber to make contact with moisture, particularly from the ground. This type of wood is treated with chemicals that help protect the wood from moisture damage; some types of pressure-treated woods are known as ground-rated woods because they have enough resistance to water damage that they can be placed directly onto or into the ground. Hardwoods in general tend to be resistant to water damage, so pressure-treated hardwood lumber is often even more resistant, but less environmentally friendly and in some cases less attractive.
Sometimes lumberyards will classify hardwood lumber even more specifically. Domestic hardwoods, for example, refer to woods taken from trees that grow in that particular country or region; exotic hardwoods are those that come from trees grown in other parts of the world, and these are usually woods that are quite beautiful. Exotic hardwoods are often used to make high-end furniture. Otherwise, wood is often classified according to the type of tree from which it came. Oak, mahogany, cherry, and some types of maple are considered reliable and beautiful hardwoods commonly used for a variety of construction applications as well as woodworking applications.
