Termites will eat any type of wood, as long as the wood is dead. You can get special termite treated wood that they will not eat, ask at your local timber supplier, most of them will probably have to order it in.
Termites can eat through Douglas-fir but it is more resistant to termites when compared to hemlock or spruce. Any type of wood used should be treated to resist termites.
PRESSURE TREATED WOOD, CEDAR, REDWOOD
Hemlock and spruce are woods that are not very resistant to termites. There are treatments that can be done to wood to make it termite proof. Redwood, cedar, and black walnut are all very resistant to termites.
Wolmanized Wood is a brand of pressure treated wood.
Pressure treated wood is already treated with preservatives to resist decay and insects. It is recommended to let the wood dry thoroughly before painting or staining it to ensure the treatment has fully penetrated. However, adding a sealant or water-resistant coating can provide additional protection and prolong the life of the wood.
Lumber used to be pressure treated with arsenic - a lethal poison - specifically chromated copper arsenate - which turned the lumber slightly green- but legislation was passed several years ago ( 2003 ) stopping the use of arscenic and going to less toxic substances. Another copper solution called ACQ is used. The copper makes the wood more rot resistant and is toxic to some insect life. Termites would tend to favor untreated wood. While the bottom sill of balloon frame structures may be pressure treated, the framing above the bottom sill is most often not treated. It is too expensive to build structures entirely from pressure treated lumber. The best defense against termites is to keep the wooden parts of the structure well off the soil with stone or concrete foundations and keep those foundation lines clear of flower beds mulched in wood chips so as not to give termite colonies easy access.
Termite-resistant woods such as cedar, bois d' ark and redwood are best for patio furniture. Many wood furitures are treated with a chemical to repel termites and insects.
There are not woods resistant to carpenter ants. The ants must be destroyed by extermination. They chew through the wood to make their homes but do not actually eat the wood like a termites.
Pressure treated wood is soaked in a special chemical to prevent rotting. Pressure treated wood products have "holes" in them, so the liquid can be readily absorbed for optimal saturation.
Because of the problems of termites, wood borer, and the fact that if not treated properly, can rot. Wood also burns well and treated wood gives off poisoness gases when burned.
The tensile strength of pressure treated wood can vary depending on the type of wood and the treatment process used. On average, pressure treated wood can have a tensile strength ranging from 2,000 to 4,000 pounds per square inch (psi).