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Drywall - does it need time to dry afer manufacturing

Drywall - does it need time to dry afer manufacturing

Drywall - does it need time to dry afer manufacturing

(OP)
Does drywall need time to dry after manufacturing, to reduce shrinkage? I realize that drywall expands and contracts subtantially with changes in the relative humidity in the room, but is there also a shrinkage component due to drying out after manufacturing, or has that all occurred by the time of shipping of the drywall?

RE: Drywall - does it need time to dry afer manufacturing

See link for a segment from How Its Made. I love this show. Looks like its fully cured before it leaves the factory.

http://m.youtube.com/watch?v=tmbk8Pfau0I

RE: Drywall - does it need time to dry afer manufacturing

Agree with Caneit...when it leaves the factory it is dimensionally set with the exception of the ambient absorption of moisture during storage, transportation and construction. This can; however, be considerable.

As is common with construction, the buildings are relatively open for a long period of time, even after the drywall goes up. As with most construction sequencing, there is no time allotted for acclimation once the drywall is installed but before the joint taping takes place. This usually occurs at the same time or in very close proximity to the placement of the drywall. The problem all of this creates is that once the building is closed up and the HVAC system is commissioned and running, the interior humidity drops quite a bit and removes moisture from the drywall, which in turn, causes shrinkage of the drywall. Since all the joints were done at a higher relative humidity, you commonly see cracks develop at re-entrant corners and room corners from the shrinkage. This is almost always alarming to occupants, but is cosmetic only.

RE: Drywall - does it need time to dry afer manufacturing

(OP)
Thanks Caneit and Ron. Much appreciated.

Do you think that if the wider cracks at th re-entrant corners are repaired (and the hairline cracks at other re-entrant corners are left as is), and the repair is done on a cold winter day when the inside relative humidity is very low (around say 25%), that the repaired cracks will stay good? I have a feeling that they will re-open in the next winter, although perhaps only to hairline width. What do you think?

RE: Drywall - does it need time to dry afer manufacturing

I have never had any luck with repairing drywall cracks. I suspect that the cracks can never completely close if the humidity goes up, and then after a few cycles of opening and closing, they become progressively larger. Same experience with stucco cracking.

RE: Drywall - does it need time to dry afer manufacturing

(OP)
AELLC - that is what I suspected, but it is nice to hear it from someone like you who has had experience with it. Thanks again. Much appreciated. Would you happen to know if there is any standard way of introducing control joints in the drywall at re-entrant corner locations? I can think of ways of doing it, but it has to look good architecturally, and that I do not know how to do.

RE: Drywall - does it need time to dry afer manufacturing

I have never seen drywall control joints, or perhaps I never noticed them.

The usual stucco control joints are either a 3/4" deep "V", or a 1" x 1/4" "C" using galvanized sheet metal.

Usually when I see stucco cracks they occur just about anywhere, not just wall to ceiling and at corners of windows and doors.

RE: Drywall - does it need time to dry afer manufacturing

In Australia, control joints are recommended at 12 metre centres. While I don't know of a specific recommendation at corners, the same detail could be used. Page 9 of the attachment shows the idea.

http://www.gyprock.com.au/Documents/GYPROCK-570-Ce...

RE: Drywall - does it need time to dry afer manufacturing

(OP)
AELLC (Structural) - thanks for the info about stucco.

hokie66 (Structural) - thanks for the info about spacing of drywall control joints, and the link. How do you come to know about Australian control joint recommended spacing...are you based there? Is it a Code there that makes this recommendation, or is it just standard practice there?

I will try to send you a photo of the condition that I am referring to...either later this evening or Monday morning...

RE: Drywall - does it need time to dry afer manufacturing

Yes, I live in Brisbane. I doubt there is a code about this...I wouldn't know as it is not a structural issue. And I don't think compliance is universal by any means, but those are the recommendations by the major supplier in Australia, and the provision of control joints as shown is fairly common practice.

RE: Drywall - does it need time to dry afer manufacturing

ASTM C840 and Gypsum Association GA-216 specify control joint spacing (typically 30'). These standards are specified in IBC section 2508.1.

RE: Drywall - does it need time to dry afer manufacturing

(OP)
hokie66 - thanks for this added info.

wannabeSE (Civil/Environmental) - those references are really good stuff. Thanks so much.

I don't have a really good photo of the condition where there is a crack, but the attached does show it. I think it is caused by the retraint to horizontal movement caused by the concrete beams that extend thru the vertical face of the bulkhead.

I wonder if a fix would be to rake out a 6 mm wide gap betwen the edge of the drywall and the vertical face of the beam and fill it with white silicone. I suppose that would not work if there is a metal stud that is fastened to the beam side and the drywall is fastened to the metal stud.

RE: Drywall - does it need time to dry afer manufacturing

(OP)
Is there a drywall type that does not expand and contract so much with humidity?
Would moisture resistant drywall react less to humidity changes?

RE: Drywall - does it need time to dry afer manufacturing

ajk1....there are numerous variations of drywall. Some have treated cores that react less to moisture changes (green board, blue board, etc.) and there are exterior grades of drywall that can be used on the interior. All will have some sensitivity to moisture changes. The photo you showed is a re-entrant corner condition and would likely require reinforcement (fiberglass scrim) over the area to mitigate the condition.

Cementitious backer board has less sensitivity but cannot be finished to the same level as drywall. It will appear rough. If you wanted to put a sparge coat of plaster over it, that would probably solve the appearance issue.

The Gypsum Association information that wannabeSE referenced is downloadable. The ASTM standard is about $40 US.

RE: Drywall - does it need time to dry afer manufacturing

(OP)
Ron - thanks for all the useful information. I will look at the referneces, and likely buy the ASTM Standard if we do not have it in our library. Thanks again.

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