Designing residential and storage buildings, has been a dynamic process, that has required Cad Northwest (cadnw.com) to conform to continually changing materials and codes. Thirty years ago, we were able to specify 2X12 Douglas Fir, # 2, for rafters and Joists up to 20’ spans. The modern lumber will not span the same distances as the old lumber. The strength of the lumber was reduced when the old growth timber was used up and we began using replanted trees that have grown much faster. Faster growth means wider growth rings and that means weaker lumber.

If you have ever torn down an old building, built sometime in the early to mid 20th century, you would notice how tough that old wood was. It is nearly impossible to remove nails, or cut with a hand saw. If you examine the end grain, you would see that the growth rings are much tighter than the typical 2X12 purchased today. New lumber not as strong as the old lumber, so that more of it is required to hold the same load.

We have moved toward engineered lumber, such as Glue Lam Beams, LVL boards, and I beam joists. Per linear foot, these materials are more expensive than dimensional lumber, but there is a cost savings in the installation labor. An I beam joist will weigh much less than a 2x joist, so they are much easier to carry around. A Glue Lam garage door header will be smaller and lighter than a 4X12 beam. Another advantage with engineered lumber is that longer lengths are possible. It is very difficult to find 20' long dimensional lumber, but engineered lumber can be manufactured to any reasonable length.

Old vs New

I Beam Joists

LVL Beams

Cad Northwest Custom Home Design is an Internet based home design company established in 1989 in Portland Oregon. We offer a large selection of pre-designed garage plans, cabin plans, and house plans. We also provide a custom design service for customers that have not found the right plan. Just call for a quote for the plans.