Weathered oversized wood beam

[thejonster]

My question is buried below: does anyone know if the code says anything about weathering in regard to the Cm factor?


A beam that was oversized, 6x14 x 14' (butts to a 6x4 x 24') used on one end of a 38' long open patio built in the 80's has a weathered/grey end (45 deg from the open end), but no dry rot as far as I can tell.

The porch is being enclosed, and weight is being added to the roof & ceiling such that the shear capacity being used goes from 19% to 25%, not considering the Wet Service (Cm) factor.

I understand that the intent of the factor is:

Wet Service Factor, CM – A reduction required for lumber used under conditions where the moisture content of the wood in service will exceed 19% for an extended period of time, such as for uncovered outdoor decks regularly exposed directly to rain or other sources of moisture. Members that are protected from the weather by roofs or other means but are occasionally subjected to windblown moisture, such as for covered porches, are generally considered dry applications.

I can't imagine that this covers weathering of the beam.. the Cm factor is .97 for shear (per NDS supp. table 4A), I would think that the capacity has been reduced by more than 3%

... I could test the beam and hang a bunch of weight (~1100 lbs), but does anyone know if the code says more about weathering?, if it still has 25% of it's shear capacity it's good to go!

The other longer beam is getting an intermediate column because it was designed pretty tight to start with.

 

[woodman88]

The code no. Engineering yes. The Wood Handbook Chapter 16 is a good source for information on weathering of wood. You can download it for free at

http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.