Construction grade lumber MC?

[busenitzcww]

I got some 2x4s for a rustic furniture project I building for a client. I knew they were wet just from handling them, but when I cut one in half and tested it, the reading was around 25% MC. So I'm wondering is this MC acceptable even in the construction world? I mean just air drying should get it under that MC. I got it all stickered and weighted in my shop and going to put a fan on it for a while. It's decently clean, and straight(as of now ;D) lumber just wondering why it's so wet? 

[alan gage]

I've always heard 19% as the number batted around for construction lumber. No idea if that's an industry accepted number or not.

Alan

[Southside]

It is Alan you will see KD19 stamped on most of that lumber and that is exactly what it means.  Kiln Dried to 19%.  Of course that is an average and not every single stick in the 4 million BF kiln, so..

[K-Guy]

The general standard is from 12-20% depending on what part of the country you are in. All mils get the odd boards that don't completely dry, the good mills cull them out and put them in the next load but others just let them go for sale.

[Don P]

Storage after it leaves the kiln is another wild card, its not at all unusual to see wrapped (leaky wrapped) bunks of lumber out in the weather just steaming away at many building supplies. Most framing is kiln dried to 19%, KD19, but another stamp you'll see is SGRN, surfaced green, green lumber. There is no building code requirement that lumber must be dried.

[GeneWengert-WoodDoc]

MC 19 or KD19 is a common number for syp.  It means that all the pieces except possibly a very few pieces, maybe 3/100, can be slightly wetter.  So, most are closer to 15% MC.  We can also see KD15, with similar meaning.  Then 1" boards are 12%MC or drier.  Then there are AD (air dried) S-GRN and S-DRY which can be over 19% by quite a bit. Various species have various rules.  None of the rules have a minimum MC, but drier means more warp which means large loss of value. So, basically, there is no universal standard for MC of 2x lumber.  

 The ink stamp on the lumber tells you the MC at the time of grading.

[Ianab]

19% is the common number for pine because at that level the wood wont grow mould or fungus any more. So it can be flat stacked, stuffed in a shipping container, wrapped in plastic etc, and it will be OK. 

Of course many mills are pushing their drying schedules, so not every board may be at that level, especially in the core. 

For "rustic" work, it's probably close enough to dry. 

[busenitzcww]

19% is the common number for pine because at that level the wood wont grow mould or fungus any more. So it can be flat stacked, stuffed in a shipping container, wrapped in plastic etc, and it will be OK.

Of course many mills are pushing their drying schedules, so not every board may be at that level, especially in the core.

For "rustic" work, it's probably close enough to dry.

Yeah, I got a fan on it for a couple days but it shouldn't really be a issue in any of the design elements as far as moving as it drys. I'm kinda curious to dig a piece out and see what's stamped on it.

[petefrom bearswamp]

My friend and I built our ADK camp out of air dried (1 yr) Eastern White pine and Hemlock lumber 
32 years later all is good with the camp.
No clue as to the MC.
Back then no standard code that we knew of for "home made" lumber.

[Don P]

 "that we knew of" is the key part of that phrase, I've built in plenty of places where it is not known of. If memory serves the grading and stamping standardization came about in the late '20's with basically the stamp format we see now. At some point I ran across an NDS from the WWII period where they had temporarily assigned less conservative strength numbers to the different species and grades for the war effort. There are no prohibitions on moisture content but there are adjustments to strength if over 19%, for instance bending strength goes down 15% at over 19%, basically the mechanical properties of wood change at fiber saturation. One biggie is nail withdrawal strength takes a 70% hit if the nail is driven into green lumber that subsequently dries.