CMU Cracking from top of wal at corner
CMU Cracking from top of wal at corner
(OP)
Hello,
I have an issue that has come up on a building under construction. At one of the corners there is a hairline crack starting at the top of the wall and extending down about 12', see attached photo taken by contractor. The wall is 8" CMU reinforced with #5 @ 48" oc. I do call for a bar in the corner cell and joint reinforcing every 16". The max roof height is about 17'-4" with the top of wall @ 18'-0". There is a bond beam at the roof level / top of wall. The crack goes through the head joint and through the face of block in a almost strait line. What are possible causes for this and what can we tell them to do to remedy this?
Thanks.
I have an issue that has come up on a building under construction. At one of the corners there is a hairline crack starting at the top of the wall and extending down about 12', see attached photo taken by contractor. The wall is 8" CMU reinforced with #5 @ 48" oc. I do call for a bar in the corner cell and joint reinforcing every 16". The max roof height is about 17'-4" with the top of wall @ 18'-0". There is a bond beam at the roof level / top of wall. The crack goes through the head joint and through the face of block in a almost strait line. What are possible causes for this and what can we tell them to do to remedy this?
Thanks.






RE: CMU Cracking from top of wal at corner
My guess is the wall was up and unbraced / poorly braced. Wind pressure put some bending moment right at that end joint.
It doesn't look concerning, there is horiz reinforcement.
RE: CMU Cracking from top of wal at corner
With a crack like that near a corner I would look into the possibility that it is due to thermal shrinking/expansion where the orthogonal block is resisting the
wall movement near the top (parapet areas where thermal movement is higher).
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RE: CMU Cracking from top of wal at corner
on the front wall the wall ends 9'-0" from the corner and along the wall with the crack the control joint is 24'-0" away.
RE: CMU Cracking from top of wal at corner
I've done my share of schools and have seen more than a few cracks which I could not really explain. Unfortunately, most owners don't want to hear the "concrete masonry shrinks and therefore sometimes cracks" defense. Owners do, however, seem to buy into the engineer's statement that such a crack is not a structural strength issue. One the building is up and at room temperature, the crack can be filled, painted, and be made to disappear (by a good contractor).
RE: CMU Cracking from top of wal at corner
RE: CMU Cracking from top of wal at corner
RE: CMU Cracking from top of wal at corner
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RE: CMU Cracking from top of wal at corner
Yes, that is correct, in a nutshell. The wire ladders to fit concrete masonry construction don't exist here, to my knowledge.
RE: CMU Cracking from top of wal at corner
Do you fill the cells with standard concrete using cleanouts throughout like the Kiwis as well?
RE: CMU Cracking from top of wal at corner