Sawn Wood Versus LVL Header Strength

Sawmiller needs to verify the allowable bearing capacity of a sawn timber for code inspection purposes. February 9, 2008

Question
Are there any tables that compare the load bearing and span characteristics of fir glue laminated beams with solid hardwood beams? I am specifically interested in comparing solid Oregon white oak and bigleaf maple beams to commercially available fir glue laminated beams.

Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
Are you in Oregon? If so, you have some excellent Forest Products Extension people there and also a wonderful Forest Products Lab at OSU.

The real issue is, what is the grade of the solid oak and maple beams? With gluelam we can control the quality of the laminations and therefore the overall strength and stiffness within a narrow range. For an equal size, it would not surprise me to see gluelam with spans 50% to 200% more.


From the original questioner:
The solid wood beams would be clear rift sawn lumber dried to 9% MC (no defects). The span needed is only about 5 feet and the load is for a bearing wall on a single story home. I need a table of comparison for the building inspector. Any help you can provide would be appreciated. And yes, I work at OSU, I just don't know who to ask.

From Professor Gene Wengert, forum technical advisor:
Call the head of the OSU Forest Products Lab. A beam is usually not considered riftsawn.


From contributor W:
"The span needed is only about 5 feet and the load is for a bearing wall on a single story home."

In my experience, using gluelams for a 5 foot span in a single story residential structure would be like using a 50 caliber rifle to shoot a squirrel. Building code manuals (are you under the IRC code?) have tables for header sizes, and the strength characteristics for the clear species you mention would seem to exceed those of standard SPF lumber typically considered for code span tables.

"I need a table of comparison for the building inspector."
Sounds like he's being (overly) cautious to me (or covering his butt) - the span and loading are such small values.


From contributor Y:
Being a builder in Oregon, I can say they (building inspectors) are very strict. From past experience, never use anything that doesn't have a grade stamp or has been approved by an engineer. It isn't fun to tear something out and replace. Better to smile and say yes sir and follow the code. Never try to buck the code to please the owner - it can be very expensive, I know.

Try to get in touch with Scott Levengood - he is a wood extension agent for OSU. He knows what works.


From the original questioner:
Thanks for the contact information. I have passed this on to the homeowner to sort out the details.