Lumber Moisture Content - NDS Wet Service Factor Question

[jgeng]

It is my understanding that most small sawn lumber used in light frame construction is typically kiln dried w/ <19% MC, what about pressure treated small dimensioned lumber is it reasonable to assume it is usually >19%? It is also my understanding that lumber greater than 4" nominal width is typically fabricated green w/ >19%, do you think that a typical untreated 3x12 would be > or < than 19%?

I am trying to analyze the following a bolted connections:
1.Combination 2x10+2x8 beam with (2) 1/2" through bolts to 10" diameter pile.
2.Nontreated?(not positive) 3x12 beam with (2) 1/2" through bolts to 10" diameter pile.

The structure is over water and all members are exposed to the air but they will be covered by a roof.

In analyzing the connection per NDS 2005 I am trying to decide the correct application of table 10.3.3 for the wet service factor during time of fabrication and in-service. It seams that they will require a Cm factor of 0.4! since they are likely >19% at time of fabrication and <19% during service. I want to make sure my approach is correct because 0.4 is a large reduction. If my approach is correct it seams I would be better off discounting one bolt and using foot note 3.1).

 

[JAE]

Over water sounds like wet service condition...splashing on the wood, etc.

 

[Ron]

Will experience wetting/drying from condensation alone. Agree with JAE.

 

[jgeng]

Thank you JAE & Ron for reponses. It is over a small water body where expect little to no wave/splashing action and it will be under a roof although not sheltered from sidways rain. There are other connections down near the water line that I will certainly assume as wet service but these are 3-4 ft above the water line Do you think the proximity to the water/humidity and sideways rain alone justifies wet service condition? If I remember correctly that will actually increase my bolted connection capacity assuming my treated 2x10+2x8 beam was >19%MC at time of fabrication and will also be >19% during service. Do you think this is an adequate assumption? or do I need to consider times when it will dry out to <19% which would give me the Cm of 0.4! Thanks

 

[Splitrings]

Check out the commentary section C4.1.4 in the NDS. It states, members protected by a roof that are occasionally subjected to wind blown rain are generally considered dry <19%.

 

[Splitrings]

I would agree that any treated lumber is generally greater than 19% at the time of fabrication. I think you are likely to have to use the 0.4 factor unless you place your bolts in a line parallel to the grain. Then I am guessing the bolts will be exposed between the members due to the round pile. There is guidance in TR#12 from NDS on connections with gaps between faces.

 

[efsinc]

Regarding your first paragraph, I assume lumber is MC>19% unless specified otherwise, but then, most of my work is in California where DF green is very very common. Standards may vary by geography as stated below in the western woods products association tech literature.
the following from the wwpa:
Moisture Content Standards
for Framing Lumber
The North American softwood
lumber industry has three
moisture content standards for
framing lumber. These standards
are reflected in the grade stamp
by the following abbreviations:
• GRN for unseasoned (or
green) lumber with a moisture
content in excess of 19%,
• DRY or KD for lumber air
seasoned or kiln dried (KD) to
a maximum moisture content
of 19% at the time of surfacing, and
• MC15 or KD15 for lumber air
seasoned or kiln dried to a
maximum moisture content of
15% at the time of surfacing.
While framing lumber is
regionally available both GRN
and DRY or KD, this publication
is limited to a discussion of
unseasoned (GRN) structural
lumber products.*
and this...
Why Framing Lumber is
Manufactured both GRN
and DRY
Whether framing lumber is
produced unseasoned or dry is a
function of economics, species,
climate, size and customer
preference.
Economics
Because drying (seasoning)
lumber at the mill increases its
manufacturing cost, much of the
structural material produced by
West Coast mills and shipped
short distances for use on the
West Coast is manufactured
unseasoned. This is particularly
true for Douglas Fir framing
lumber.