Window Wall Crack
Window Wall Crack
(OP)
A few months ago I designed a window wall for a residence in Ocean Shores Washington. The structural plan is the following:
I get a call back today from the owner that a crack has opened up at the prow/apex of the wall towards the bottom of the wall and has gradually gotten wider since about March this year. See photo below:
At the bottom the crack is about 7/16" wide. Looking into the crack I don't see that the wall wrap or felt has broken or stretched to any degree. Checking along the sill plate I don't visually see any displacement of the wall itself or cracking of the stemwall or any other settlement issues. Also inside there is absolutely no cracking of the drywall, see photos below:
Unfortunately, I did not take pictures of the framing before the wall wrap went up so I don't know if the contractors installed the straps that connected the walls at the apex, or even how they may have nailed the studs along this seam. I probed with a small screwdriver where the MSTA30 strap should be that connects the lowest headers and did not find a strap. Of course this doesn't mean its not there, just that I couldn't find it with the means that I used. The residence was framed mid November last year about 6-7 months ago during the rainy season, the wood was completely saturated as were the PSL columns which probably should have been better covered. The building official had looked at the crack and he figured it was due to the wood swelling and then shrinkage, with the amount of rain we get here there is definitely some validity to that argument.
At this point I would like to talk with the framers and general contractor to determine if they installed all of the straps per the plan. I'm doubtful if they will remember exactly what straps went where and sizes etc...
Ultimately I need to write a letter with a course of action for the fix, which may involve tearing up the window trim to check for the straps and possibly install more if required. At the moment I'm very disappointed since I spent considerable time and effort designing this wall so that something like this would not happen.
I get a call back today from the owner that a crack has opened up at the prow/apex of the wall towards the bottom of the wall and has gradually gotten wider since about March this year. See photo below:
At the bottom the crack is about 7/16" wide. Looking into the crack I don't see that the wall wrap or felt has broken or stretched to any degree. Checking along the sill plate I don't visually see any displacement of the wall itself or cracking of the stemwall or any other settlement issues. Also inside there is absolutely no cracking of the drywall, see photos below:
Unfortunately, I did not take pictures of the framing before the wall wrap went up so I don't know if the contractors installed the straps that connected the walls at the apex, or even how they may have nailed the studs along this seam. I probed with a small screwdriver where the MSTA30 strap should be that connects the lowest headers and did not find a strap. Of course this doesn't mean its not there, just that I couldn't find it with the means that I used. The residence was framed mid November last year about 6-7 months ago during the rainy season, the wood was completely saturated as were the PSL columns which probably should have been better covered. The building official had looked at the crack and he figured it was due to the wood swelling and then shrinkage, with the amount of rain we get here there is definitely some validity to that argument.
At this point I would like to talk with the framers and general contractor to determine if they installed all of the straps per the plan. I'm doubtful if they will remember exactly what straps went where and sizes etc...
Ultimately I need to write a letter with a course of action for the fix, which may involve tearing up the window trim to check for the straps and possibly install more if required. At the moment I'm very disappointed since I spent considerable time and effort designing this wall so that something like this would not happen.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
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RE: Window Wall Crack
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Window Wall Crack
With that said, I would ask the contractor, in writing, what types of straps they used on the wall. I.e. Did they use Simpson or USP? Or something non confrontational. If you say, did you install the straps, the answer will be yes! If you ask another question about the straps that is innocent, they might be like "straps, what straps?" And then you'll know whether they did or didn't. Or you can ask them directly and then go take the trim off to see. If they didn't do it, it's on them, at least that's how I see it.
The point of the question is to see if they did it without asking them directly.
As Uncle Joe (Stalin) said, make yourself into a sheep and you find out where the wolves are...
RE: Window Wall Crack
RE: Window Wall Crack
I'd measure external dimensions such as window locations to prove that no other fundamental kinds of movement has occurred.
Then I'd focus on the exterior wood finishes, the trim as others have said above.
RE: Window Wall Crack
If the wood floor was spreading the walls apart then I think you would see cracking of the drywall but as you can see there is none at the base of the wall. No cracks of any type in the foundation, or any other signs of movement of the wall relative to the foundation. If the wall have moved relative to the foundation you would possibly see the sill plate overshooting the concrete at the right corner, there was no sign of this.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Window Wall Crack
If the wall is moving then the posts would move which would cause the rimboard to translate with the posts and hence the ledger board attached to the rimboard would move as well. From the pictures above you can see there is no significant separation of the ledger boards at the prow.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Window Wall Crack
I'm with others....Look at shrinkage in the trim. Remove the trim at the corner and you'll likely see that all below is ok. Check attachments and types of fasteners used for the trim. See if you have any displacement in the fasteners or any elongation in the fastener holes.
You might also get them to seal the intersection of the metal flashing above the rim board. It is allowing water into the miter at the corner. You will also note that the miter and the flashing have not separated the same distance as the trim above, again indicating the issue is outside the primary structure.
RE: Window Wall Crack
RE: Window Wall Crack
I think the wall is moving (walking around a bit) out at its outer face. The angle btwn. the two planes may be closing a bit, in some areas. It is moving in plane maybe do to a bit of shrinkage and due to lateral loading, and it is moving out-of-plane due to lateral loading and how this is transferred btwn. the two wall planes. I would really like to see your detailing, in cross section, (and the actual built detailing) at that corner joint. Your detailed horiz. straps will not solve the problem as I see it, and they should be neatly bent and tensioned when applied. You need several fairly heavy ga. steel straps 10,12-16" long, with two 5" (plus, plus, on each wing for the angle gap in the framing) wide wings, with the angle btwn. them to match the angle of that corner joint. These are applied parallel the long open joint/gap btwn. two 5.25" x 7" PSL columns and, in effect, they transfer shear flow as the fillet welds would btwn. the web and flange of a fabed. pl. girder. They prevent the two planes from sliding vertically, and parallel to each other. The walls are parallelograming (and moving, walking) w.r.t. each other, and you have to stop this. You also need solid blocking in the gap btwn. the two PSL columns behind these shear transfer plates and your straps. I’ve seen these kinds of problems and joint separations a number of times on these kinds of angled corners where they had two separated wall planes, at angles, which were not well connected together to transfer this shear load along the joint length.
RE: Window Wall Crack
@dhengr
I'm tending to agree with you. With the junction of the two walls non-coplanar the sheathing provides zero strength and stability between these two walls. It is all on the fasteners and straps. These two walls need to be stitched together.
I will provide further updates once I have opened up the wall for inspection.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Window Wall Crack
It looks like the HO/Contractor placed that white sealant? on other locations of this exposed trim? are other pieces of trim moving? Also, I am surprised that the trim at the the angle in concern was not taper cut and glued together. None of that is structural just observations and things worth noting.
It looks like a finishes issue to me, and one that will get worse with time and eventually mess with the structure.
Things worth noting during demo. how is the trim installed, condition of fasteners (rusted, bent, pulled out, too short), if the boards shrink they usually pull back on both ends (gaps on both ends?), maybe the obtuse angle looks 2x as bad since it has 2x the joints shrinking with nothing resisting pull back.
Good Luck!