Here's a little info on Spruce, Pine, Fir, Cedar, and Redwood 2x4's.
Here's the link:http://www.ehow.com/about_6510849_di...ood-types.html
And here's a copy of what this says:
For the most part 2 by 4's all look the same but they are not. Common 2 by 4's like the kind that can be bought at home improvement and construction supply stores are usually stamped S-P-F on the end. This means the 2 by 4 is either spruce, pine, or fir; these are used mostly for framing. Other 2 by 4's like cedar and redwood are used mostly for decking and railings.
1. Spruce 2 by 4's are one of the most common and are characterized by the straight grain attributed to its slow growth pattern and tight-knit fibers. This translates into straight 2 by 4's. Spruce is the lightest in weight of the 2 by 4's and is considered to have the highest strength-to-weight ratio. Spruce can be recognized by its whitish-amber color. It's strong and resilient, and can stand up to the elements better than pine or fir, for this reason spruce 2 by 4's work well for outdoor applications as a cheaper alternative to cedar or redwood.
2. Pine, or more particularly "Southern pine," has the distinction of being referred to as the stronger of the 2 by 4's. Southern pine is recognized by its warm, golden color and is often pressure treated for outdoor use. The density factor of Southern pine is something that has been noted, the more density, the better fasteners, nails, and screws hold when driven into Southern pine. Southern pine is used mostly for interior framing but is also a popular choice for decking, arbors, and even playground sets for children.
3. Douglas fir has been called the "standard" for many builders. It has an elasticity that has made it a favorite for builders, and has documented proof that Douglas fir has superior performance against strong forces and natural phenomenon such as winds, storms and earthquakes. Doug fir has tight knots and close grain, with a semi-dark warm red tint. Douglas fir is utilized in framing when maximum strength is required.
4. Cedar is one of the more exclusive 2 by 4's. It has a beautiful, almost translucent gold color. It has natural aromatic, insulating, and decay-preventing properties, which make it the premier outdoor building 2 by 4. The stability of cedar also make it a good choice for exterior framing in exposed areas like open beam construction found in mountain lodges and rustic buildings. Cedar also takes stain and preservatives readily and is very easy to cut and work with.
5. Redwood 2 by 4's are relatively expensive 2 by 4's. They are used for furniture and decking, as well as in in log homes and around hot tubs and saunas. Environmental laws prevent the mass production of redwood 2 by 4's, so they are a sought-after commodity for those who can afford to use them. Builders love working with redwood because of its inherent dark red beauty and its smooth and pliable characteristics.