My neighbor has contracted a new house to replace his existing. In Maryland we have already had 30 of our 39 inches of anual rain. His basement has had up to 6 or 8 inches of water in it after framing. (The builder did not have a temporary power source so the sumps have not been working.) The builder wants to close it in but my neighbor is concerned about mold and moisture. Our questions are: what is an exceptable moisture content of the framing lumber before closing in? Aside from fans and dehumidifiers are there any other steps to be talken before drywalling?? Thanks for any input. al be al
Edited 6/25/2003 8:11:28 PM ET by albeal
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Don't have a direct answer, but see if you can access the current issue of JLC or Journal of Light Constructiuon...I think there is an article in it about dealing with mold & mildew....maybe they give some numbers.
Do it right, or do it twice.
What do you mean by "close it in"?
It's always a fgood idea to get a roof on and doors/windows installed as soon as possible. Then you deal with drying it out.
Excellence is its own reward!
By "close it in" I meant insulation and drywall. The house has had a roof and windows for at least a 6 weeks. The water has been indirectly from above but mainly ground water from the sumps over filling (and the pumps not being plumbed or on). During excavation and pouring the foundation they discovered that the water table is very high at their site. They know that water will be a chronic issue. They have two sumps and with adequte grading they should be able to deal with it. The current question is how wet can the basement framing be and still put up insulation and drywall?
19% MC is considered air dry, but I would shoot for 10-12% and be ready to replace/fix some bowed studs and joists.Mr T
Do not try this at home!
I am an Experienced Professional!
Kiln dried lumber comes out at 19% but that can be at surface. Some deliverd is above that, especially in center of stud. But I would want to be sure that it is down to about 14-17% before closing the walls up. This is variable too based on your climate and construction materials.
Mold is very happy above 40% but there are other issues besides mold here. Studs that shrink after SR goes up will add to the number of nail pops. Too much moisture migrating out through the wall materials later will push the paint off in sheets. Moisture locked in above the ceiling can make it soften and sag. These things can be bad enough just from normal moisture in new construction - concrete, SR mud, and paint all add gallons of water to the environment.
Dehumidifier/AC is the way to speed up drying..
Excellence is its own reward!
I feel cocky today because I just finished a really tough job, so I will challenge you on the 19 % MC from kiln drying.
I've got a long history close up and personal with production dry kilns and the loads always rolled into the cooling sheds at 9%.
(Of course I'm a worm-driver in the West where OG Doug Fir was once king).
:-)
I believe that on construction lumber the requirement for "kiln dried" is to be NO MORE than 19%.
BTW, I am looking at a chart from the US Forest Products lab that indicates that the equaliberan point for exterior wood is;
Most parts of the US - 9-14%, average 12
Dry SW - 7 -12%, average 9
Warm, humid costl - 9-20%, average >12
I have to get out Hotley to get the exact number (and again that varies by area), but average interior is about 6-7%.
So even a structure that is dried out and accliamized will still have a bit of moisture to give up once it is enclosed and heated/cooled.
You're right; I just wanted to poke Piffin a bit.
Most of the OG mills around me are gone, and of those still around, kilns are seldom seen.
But in the "good old days" everything above Utility grade was kd'd and always to 9 %.
19 % is, for most softwood species, the level at which "free water" is gone, and also that critical point at which most wood destroying organisms go into inactive status.
As Bill has noted, the required minimum is 19. I recalled that from an extensice article on wood, drying, shrinkage and planning for waste in wood that I read a few years ago someplace.
You may be right that on the surface, some plants bring it out of the kiln at less than that but the interior of the wood is almost always higher than the surface tests out at.
I assume we would agree that less than 14% is a good goal before "closing in"???.
Excellence is its own reward!