Existing Wall Cracks
Existing Wall Cracks
(OP)
I was asked by a client to investigate some cracking that is occurring in the interior drywall of the exterior walls at one of their properties. The cracking is occurring in the 2-1/2 story main entrance of the building consistently at the window head-jamb joint on the second floor only (in the attached exterior picture where the grey masonry façade meets the dark grey efis). Cracking is no observed at any other location along the height of the wall except for this spot.
The building is steel framed with metal stud walls and was constructed in 1996. Structural drawings have not been located at this time although an architectural section of this wall was sent by to me by the client (attached). The cracks were found while the owner was investigating the cause of some water damage that had occurred due to the interior walls (that cause of this problem was found and corrected by the owner).
As you can see from the pictures, the cracking is minor and perfectly horizontal. I’m not really happy with the architectural detail as it requires the metal stud to cantilever off the WF steel beam. I wonder if, under wind conditions, the WF beam is rotating slightly causing the cracking to form at a weak joint between two drywall panels. I find it very interesting though that the cracking is occurring at the masonry façade efis interface though. Also, the only room where the cracks were not observed had a wall paper finish applied to the drywall (although I suspect a crack is hidden under the drywall).
Do others have any additional insight?
The building is steel framed with metal stud walls and was constructed in 1996. Structural drawings have not been located at this time although an architectural section of this wall was sent by to me by the client (attached). The cracks were found while the owner was investigating the cause of some water damage that had occurred due to the interior walls (that cause of this problem was found and corrected by the owner).
As you can see from the pictures, the cracking is minor and perfectly horizontal. I’m not really happy with the architectural detail as it requires the metal stud to cantilever off the WF steel beam. I wonder if, under wind conditions, the WF beam is rotating slightly causing the cracking to form at a weak joint between two drywall panels. I find it very interesting though that the cracking is occurring at the masonry façade efis interface though. Also, the only room where the cracks were not observed had a wall paper finish applied to the drywall (although I suspect a crack is hidden under the drywall).
Do others have any additional insight?






RE: Existing Wall Cracks
RE: Existing Wall Cracks
RE: Existing Wall Cracks
RE: Existing Wall Cracks
In my opinion, it is usually due to several causes, not the least of which is regular thermal and moisture cycles that cause expansion/contraction of the various parts of a structure, sometimes differentially due to different material types. This repeated cyclical loading within a structure simply stresses the gypsum board assembly and usually cracks or separations form at the likely areas- corners of openings, and along joints in the assembly (or both). Based on the section detail, maybe some of the stress is due to deflection of the beam and some rotational movement at the ends of the steel beam. Or some slight differential foundation movements. Either way, for a building built in 1996, a little drywall work could just be chalked up to life-cycle maintenance in my opinion.
The cracks look perfectly horizontal in the pictures, and from the pictures I would guess the gyp was hung in a manner where there is a horizontal joint at each corner, so this is a weak spot. I usually suggest as a first try to cut out the joint tape and replace with fiberglass mesh tape for reinforcement, and re-finish the area. They could also place a few small strips vertically to act as stitches for some additional reinforcement.
If the cracks re-form or larger cracks appear, then you may have them cut out an L-shaped piece of gyp that is 4'x4' at the legs and replace, so that you have a solid piece of gyp at the corners where your stress concentration is likely the highest.
Bottom line, I would not view this as a structural issue.
RE: Existing Wall Cracks
I would try to see if there is a specific load path for the wind.
Based on this presumption we'd have a simple bent light gage track at the top of the windows which may not be enough to span horizontally across the window width so the
wide flange beam is being torqued and this twist causes stresses in the interior sheathing.
The thermal aspects could also be a contributing cause per a2mfk.
RE: Existing Wall Cracks
RE: Existing Wall Cracks
RE: Existing Wall Cracks
Any moisture in the wall board while it was stacked prior to installation, which is easily possible because of a rainy day, that would dry out as the structure is enclosed and air-conditioned.
RE: Existing Wall Cracks
Staining on the exterior shows a reasonably significant water issue. Use a borescope and see if the metal studs have corroded.
The window is not subject to wetting/drying cyclic movement; however, the wall facades above and below, particularly below are very susceptible to wetting/drying cyclic movement. This would show as a horizontal crack at the location you show in the photos. The fact that it corresponds to a taped drywall joint is more evidence of minor movement, mostly drying shrinkage or wet/dry cycling.
RE: Existing Wall Cracks
The water issue had to do with a drain that was installed in the building next to the corner column of the building (see picture 2 where the square portion of drywall was removed). The client said the drain wasn't installed correctly and the repair done during the construction of the building finally failed leading to the water problem.
At this point, the client is more interested with coming up with a repair. Since the building is occupied and this is a two story building, and there is a stair in a large portion of the opening that need to remain open staging is going to be difficult.... so they would like to repair it once and be done with it. We discussed reinforcing the opening, installing a flexible joint there, using fiberglass tape at the joints for reinforcement, installing wall paper in the atrium to cover the cracks and provide some flexibility (a crack isn't a crack if you can't see it). I think some sort of flexible joint is the best option but just wanted to get he opinion of others.
RE: Existing Wall Cracks
1. The Architectural detail showing 5/8" plywood under the gutter and t]at the top and bottom of the windows, apparently in contact with the masonry, is bad and prone to rot, causing leaks.
2. The horizontal steel wind beam sees not only an eccentric load from gravity loads, but also an eccentric load due to wind as the wall stud extends more to the bottom of the wind beam than to the top.
3. Consequently, due to this eccentricity, the wind beam is rotating inward at the bottom, causing the cracking in the tension face of the drywall you are seeing.
In my opinion, the wind beam should have been placed more to the center of the intermediate wall studs to minimize that eccentricity. Not really much you can do now but periodically patch and paint.
And as for the exterior staining, better find out what is damming up the gutter to cause it to overflow under the flashing.
Mike McCann
MMC Engineering
RE: Existing Wall Cracks
OFF TOPIC:
AE- maybe, but gypsum board is very stable (see attached PDF, page 4). Now, the tape and compound, not so much, and very dependent on workmanship. But if you are talking about wood framing, I would more likely chalk it up to creep of vertical framing, long term drying shrinkage, and short term humidity cycles as the likely causes of cracks in gypsum board. Very common along truss (ceiling) and wall joints to get separations of the joint tape.
RE: Existing Wall Cracks