Choosing Wood Species
The four most popular wood species in the U.S. are White Pine, Yellow Pine, Douglas Fir, and Oak. Other species such as Maple or even Wild Cherry can be used but the are expensive.
Choice of wood species usually depends on client desires, engineering needs, and local availability. Each wood species has its particular qualities including color, texture, veining, strength, price,… White Pine is the most stable (comparing green versus dry) and Oak is the strongest, for instance.
Sometimes engineers may request different species for certain beams. This is usually because strength properties of species chosen by a client does not allow long open spans (lead in unreasonable beam sizes) or the wood is not suitable for particular application (e.g. Eastern White Pine is obviously not the right wood to use for a swimming pool roof, red cedar should be chosen instead).