What grade redwood beam do I have? Deflection failure.

[kmx]

Hi,
Is there a simple description of the different grades of redwood available to identify what properties I should use? There are three different structural grades shown in the NDS. I have been asked to determine if an existing outdoor deck structure is adequate for public use. It is constructed of what I believe is 4"x6" rough sawn redwood. Only a few of the beams have knots. The grain is straight but not necessary close. I can't view the beam ends.

Also, if the beams fail in deflection but passes in bending and shear should there be any concern with safety? I am assumming no, although technically does this meet UBC design criteria?

Thanks for any info or direction. KMX

 

[dicksewerrat]

If the beams fail the test of deflection, you will have a'spongy' feeling deck. This will make people very uncomfortable. I would add something to limit deflection also.

 

[uleaum]

Unless you or someone you can contract is qualified to visually grade lumber, I wouldn't guess. The lumber grade should be stamped on the peices somewhere, but it may have worn off.

You can always fall back on UBC 104.9.2. Perform a sample deflection test for your members. Back out your values for an E. Visually graded lumber has a factor of safety of about 5 on stress capacities, but the Modulus of Elasticity is pretty close. Still, those values are minimums for any grade of wood. Your really should be above the listed values anyway.

 

[boo1]

There are over thirty different grades of redwood lumber including general purpose grades and specialized grades for a single use. Redwood is graded by appearance and durability, with criteria defined by the Redwood Inspection Service. Standard Specifications for Grades of California Redwood Lumber; published by the Redwood Inspection Service (RIS), 405 Enfrente Drive, Suite 200, Novato, CA 94949; 415.382.0662; 415.382.8531(fax); e-mail info@calredwood.org


Note: Remember to include the wet condition reduction factor.

 

[kmx]

Thankyou for your input direction on this topic. We are going to be adding additional support to the beams to limit deflection.
Have a great day.
KMX

 

[edgeprod]

If the grain is wide (less rings per inch) it is likely faster growing second growth redwood which does not posess the strength or decay resistant qualities of its elderly "old growth" cousins. There are, in fact, different working values published by the RIS (Redwood Inspection Service) for old and second growth redwood.
Hope this helps.
Edgeprod