Cracks in Drywall Bulkhead
Cracks in Drywall Bulkhead
(OP)
Description of the Issue:
In renovations carried out in the room of an existing building, a new ceiling bulkhead was constructed along the exterior wall. The bulkhead is framed with steel studs and clad side and soffit with drywall. The vertical depth of the bulkhead is about 2 feet, the length is about 70 feet, and the width of the bulkhead soffit is about 3 feet.
The construction was carried out about November of 2011. About February of 2013, several vertical cracks were observed in the vertical face of the bulkhead, and also in the soffit at the same location as in the vertical face.
The relative humidity in the heated / air conditioned room varies from about 25% in winter to about 60% in summer. The room is used for assembly purpposes for about an hour in the morning and an hour in the evening every day, and is empty the remainder of the time.
All the cracks occur where a re-entant corner is created in the vertical face of the bulkhead, by the old concrete beams that extend thru the vertical drywall.
The cracking is most probably caused by shrinkage of the drywall as the RH drops during the winter heating season, and the accompanying stress concentration caused by the penetration of the beam thru the vertical drywall. It is also possible that there is a drywall joint that has cracked open at these locations.
There would not be any structural settlement issue, because the building has been there for 50 years and has performed very well. There have been no structural changes. The 50 year old plaster walls in the building are uncracked and performing well.
Please see attached photos of cracks.
Questions:
1. What is the approximate expansion and contraction of drywall over the RH range that I oultined above?
2. How is that movement usually accounted for in the design?
3. Is it usual to put movement joints in drywall? If so, at what centres and how are they constructed?
4. What is the appropriate repair? Rout and patch and tape the cracks during the winter heating season when they are widest, or should movement joints also be installed at some appropriate centres?
4. There is also distress (looks like debonding of a corner piece) in the new drywall ceiling-to-new wall corner region (see photo). What is causing this? Is it a workmanship issue, or materials issue, or something else?
In renovations carried out in the room of an existing building, a new ceiling bulkhead was constructed along the exterior wall. The bulkhead is framed with steel studs and clad side and soffit with drywall. The vertical depth of the bulkhead is about 2 feet, the length is about 70 feet, and the width of the bulkhead soffit is about 3 feet.
The construction was carried out about November of 2011. About February of 2013, several vertical cracks were observed in the vertical face of the bulkhead, and also in the soffit at the same location as in the vertical face.
The relative humidity in the heated / air conditioned room varies from about 25% in winter to about 60% in summer. The room is used for assembly purpposes for about an hour in the morning and an hour in the evening every day, and is empty the remainder of the time.
All the cracks occur where a re-entant corner is created in the vertical face of the bulkhead, by the old concrete beams that extend thru the vertical drywall.
The cracking is most probably caused by shrinkage of the drywall as the RH drops during the winter heating season, and the accompanying stress concentration caused by the penetration of the beam thru the vertical drywall. It is also possible that there is a drywall joint that has cracked open at these locations.
There would not be any structural settlement issue, because the building has been there for 50 years and has performed very well. There have been no structural changes. The 50 year old plaster walls in the building are uncracked and performing well.
Please see attached photos of cracks.
Questions:
1. What is the approximate expansion and contraction of drywall over the RH range that I oultined above?
2. How is that movement usually accounted for in the design?
3. Is it usual to put movement joints in drywall? If so, at what centres and how are they constructed?
4. What is the appropriate repair? Rout and patch and tape the cracks during the winter heating season when they are widest, or should movement joints also be installed at some appropriate centres?
4. There is also distress (looks like debonding of a corner piece) in the new drywall ceiling-to-new wall corner region (see photo). What is causing this? Is it a workmanship issue, or materials issue, or something else?






RE: Cracks in Drywall Bulkhead
2. I see architects specifying control joints. See http://www.gypsum.org/technical-information/techni...
RE: Cracks in Drywall Bulkhead
I do not know the recommended spacing, however. I would think every 25 ft. would be plenty.
RE: Cracks in Drywall Bulkhead
- do you know where I could see what a drywall control joint might look like, and its details?
- the hygrometric coefficient of expansion for drywall is given as
6.5 / 1,000,000 in./in./%RH for the 10% to 90% RH range. Does that mean for a RH change of 40% (i.e. from 60% to 20%), and a length of 70 feet (or 840"), the length change is 0.22"? Seems like a lot!
- the coefficient of thermal expansion is given as 9.3 / 1,000,000 in/in/deg. F. That is the same as steel! I am surprised. Or am I misinterpreting something?
- in the same room, a new stud and drywall wall that has been constructed directly in front of the exterior wall (at the same time as the ceiling bulkhead was constructed), seems to have pulled away from the original exterior masonry wall assembly, as can be seen from the gap that has opened at the window sills (see attached photo) and also to a lesser extent at the jambs. Would such a new steel stud/drywall wall behind an existing exterior masonry wall, normally be tied into the existing masonry wall to prevent separation, or would it not be tied in but a control joint with sealant installed where the gap has now developed?
ExcelEngineering - thanks for the very useful information about your actual experience. That is very reassuring.
RE: Cracks in Drywall Bulkhead
Just wondering how these interior partitions were detailed to accomodate vertical deflection of your floor system.
The picture of the cracking at the corner doesn't necessarily look like thermal expansion cracks to me. They look more like differential vertical movement type cracks.
If the partition is a metal stud with a slip track at the top, and then you hang a soffit, you need to make sure the 2-systems play nice together. Just something else to consider.
But back to you OP, 70' is very long with no expansion joint.
RE: Cracks in Drywall Bulkhead
RE: Cracks in Drywall Bulkhead
RE: Cracks in Drywall Bulkhead
RE: Cracks in Drywall Bulkhead
RE: Cracks in Drywall Bulkhead
Per your question about architectural sites like this, if it is this problem you are talking about, most architects are not going to be able to help much. No offense to them, but most do not expansion/contraction and the necessity of movement and control joints as well as structural/building engineers. You can try and post it in the Building Engineering forum, which is more in line with this topic and those related to building forensics.
RE: Cracks in Drywall Bulkhead
RE: Cracks in Drywall Bulkhead
To reinforce a re-entrant corner condition, I would use the plastic or fiberglass scrim tape placed in several strips perpendicular to the crack, in addition to a strip along the crack. These should be feathered 8 to 10 inches on either side of the crack to prevent an obvious "lump" at the crack. Normal joint feathering is about 4 to 6 inches on either side of a joint, but the thicker the joint material, the greater the need for wider feathering before sanding.
Since there does not appear to be shearing along the separations in the photo, it appears that your shrinkage is biaxial with respect to the ceiling plane.
Your computed shrinkage of 0.22" over 70 feet is not out of reason.
RE: Cracks in Drywall Bulkhead
I believe that I have not posted a photo of the re-entrant corner crack to which I am referring. The photo I had posted some time ago was of a different condition, at the end of the bulkhead, which is also an issue but not the issue that I had in mind this morning when I posted my question. I will find the appropriate photo and post it. My apologies.
The cracks that I am currently concerned about start at the re-entrant corners and extend vertically down from the re-entrant corner i.e. as you quite correctly surmised, the re-entrant corner was created by a penetration (in this case a concrete beam). Most probably this is a tearing apart of the drywall joint. My apologies for not posting the specific photo pertaining to the condition of the re-entrant corner. I will post the correct photo this weekend.
Do you think that remedial work should be covered by warranty, or would the contractor say that it is not his fault because there were no movement joints or isolation joints specified for the work, and no special joint reinforcement like fibreglass scrim specified? There were in fact no specs as far as I am aware. Bad.
Again, thank you very much for the help.
RE: Cracks in Drywall Bulkhead
RE: Cracks in Drywall Bulkhead
http://www.finehomebuilding.com/toolguide/departme...
I also see they are now selling it in a wider roll, which I wish I would have known about a couple of months ago.
http://www.homedepot.com/p/BOEN-6-in-x-75-ft-Self-...
However- from the picture, is the concrete beam that protrudes through the ceiling just painted, with drywall abutting it? Or is there a layer of gyp around it? I ask because where gyp meets a dissimilar material, this junction is a very common place for these types of separations to occur. If the surface was painted concrete and they tried to flush out the bulkhead with tape and compound, this was asking for trouble. See the attached sketch, with one possible alternative detail (I know, too late now). I am guessing at the actual construction.
From doing forensic investigations like this, it is my opinion that the gypsum board industry, architects, and builders need to collaborate a bit more when it comes to alternative joint details and installation methods. Often gypsum board is "asked to do things it wasn't meant to do". Lack of expansion joints are another issue, which likely contributed to this problem, at least on the right side of the picture.
Another big problem area in residential is the wall-ceiling joint, with separations caused by truss bottom chord movements which causes rotation movements at the joint. Tape with compound is really bad at accommodating movements.
RE: Cracks in Drywall Bulkhead
RE: Cracks in Drywall Bulkhead
RE: Cracks in Drywall Bulkhead
www.homedepot.com/p/BOEN-6-in-x-75-ft-Self-... I am not following your sketches. I assume that they are sections, but they do not seem to correspond to the condition that I am dealing with and I do not have a scanner here at home to make a sketch. But I understand your point, to keep the drywall unattached from the concrete beam.
I can come to no other conclusion than that the cracks (actually tearing open the taped joints where the concrete beams penetrate the drywall) is caused by the drop in RH from when the drywll was insatlled in the fall, till midwinter when RH is lowest and the drywall shortening the maximum. That and the reduction in cross section caused by the concrete beam penetration, and the stress concentration created by the notched corner out of the drywall where the beam goes thru.
Seems to me the solution is either to introduce control joints at the concrete beams or to reinforce the drywall joints with a fibreglas scrim.