There are three main grades of lumber that are commonly used in structural framing. A fourth category may be found in pre-made trusses but this material is not normally available to the general contractor.
The first grade of lumber is light framing. This grade of lumber is considered utility grade lumber and should not be used for framing walls or used as joists in either residential construction, commercial construction or where structural support is required. It may be used for small projects such as framing cabinetry or building furniture.
The second grade of lumber is stud grade. This grade of lumber is used for structural support of vertical members. It’s normally used in walls and is produced to a maximum span of 10 feet. This grade of lumber is normally number two or better.
The third grade of lumber is structural joist and plank. This grade of lumber is available in widths of 6 inches or wider. Its use is for joists, rafters, headers, built up beams. The grade of the lumber is number one through number three grade.
Engineered lumber is also available for structural support systems and is often found in beams. Glue laminated engineered lumber can be designed to your specification or he can be delivered from a manufacturer’s available stock.
Pressure treated lumber is available for both direct contact with wet or exposed locations or where lumber is embedded in the ground such as vertical support posts. If the lumber you are using comes in direct contact with the soil it must be rated for direct contact.
California redwood, western red cedar and cypress material can also be used where moist conditions or found.
When selecting lumber for structural grade projects it is important that you inspect the material at the time of purchase. If you building a large project then you should work with your supplier and make sure that they will give you credit or take returns of any product that does not meet specifications.
When inspecting your lumber for use you should understand the grieving process. Structural grade lumber is not free of defects. You can expect a reasonable amount of knots and waining on the edges. It is important that all stunts and joists are inspected for cracking. Cracking will reduce the structural feature of this product.