Wood Moisture Content Specification
Wood Moisture Content Specification
(OP)
A continuation of thread337-225812: moisture content...
I have typically spec'd all covered framing lumber to be kiln dried, or have max. 19% MC. 6x and pressure treated material can have a higher MC, which can lead to pretty noticable warping and shrinkage. Is my spec of max. 19% a reasonable spec for residential and some light commercial construction? I just got my first complaint about it in 8 years.
Thank you in advance for the input of the seasoned veterans out there.
I have typically spec'd all covered framing lumber to be kiln dried, or have max. 19% MC. 6x and pressure treated material can have a higher MC, which can lead to pretty noticable warping and shrinkage. Is my spec of max. 19% a reasonable spec for residential and some light commercial construction? I just got my first complaint about it in 8 years.
Thank you in advance for the input of the seasoned veterans out there.





RE: Wood Moisture Content Specification
Stick to your guns.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wood Moisture Content Specification
That said - I have found kiln dry delivered wood to be higher than 19% and if it sits around (say on the ground) for any period of time or subject to rain - all bets are out the window.
RE: Wood Moisture Content Specification
The only thing I found in NDS is "in service" moisture content with respect to adjusting design values. Nothing about requirements for during construction. I have heard it argued, and reasonably so, that spec'ing moisture content is useless due to building outdoors, shipping methods, pressure treated wood, lead time and expense with KD, typically green 6x mat'l, etc.
I have a note that says "the builder shall reject all poor quality lumber that is not suitable for its intended purpose, regardless of grade." Although a bit ambiguous, that should at least save me from the warped, split and twisted stuff.
RE: Wood Moisture Content Specification
Agree with both of the "Mike's" comments.
RE: Wood Moisture Content Specification
RE: Wood Moisture Content Specification
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Wood Moisture Content Specification
RE: Wood Moisture Content Specification
RE: Wood Moisture Content Specification
So under what circumstances would it be acceptable to specify "green" or unseasoned timber?
RE: Wood Moisture Content Specification
I think the best answer may be to state that the lumber must reach min. 19% (or 15% to be safer) prior to building enclosure. Apparently that is what California does. Including a statement like "the builder shall reject all poor quality lumber that is not suitable for its intended purpose, regardless of grade" may help cover designer liability.