CMU Wall Cracks
CMU Wall Cracks
(OP)
About 2 years I designed a one-story 16ft tall middle school addition with 8" load-bearing walls and roof composed of vulcraft joists (@6 ft on center) spanning between 8' and 20' + 1.5" metal roof deck . The CMU walls are reinforced with #5@32" and #5 rebar at window and door jambs and headers. All the headers have bond beams with 2#5's. Also, control joints are located at 40-ft O.C.
No additional rebar was called out at the window sills.
Having said this, hairline cracks are developing in the CMU walls at several of the window sill locations, and at the headers of some of the double doors. We have total of 4 cracks on this 30,000-SF addition (about 3,000 LF of walls), but they occur in some of the most visible locations.
The owner is concerned that these cracks could somehow compromise the intergrity of the building.
Question: How do I go about re-assuring the owner that the building is safe and the cracks are cosmetic, without seeming dimissive??
No additional rebar was called out at the window sills.
Having said this, hairline cracks are developing in the CMU walls at several of the window sill locations, and at the headers of some of the double doors. We have total of 4 cracks on this 30,000-SF addition (about 3,000 LF of walls), but they occur in some of the most visible locations.
The owner is concerned that these cracks could somehow compromise the intergrity of the building.
Question: How do I go about re-assuring the owner that the building is safe and the cracks are cosmetic, without seeming dimissive??






RE: CMU Wall Cracks
You probably can show him your calculation or let him to see other buildings you designed that similar to this one.
RE: CMU Wall Cracks
Did you provide any joint reinforcement or other horizontal steel?
Either one of those systems should provide adequate horizontal steel.
If you have adequate horizontal steel and steel around the openings per ACI 530, Section 1.13, you've followed the code and the cracks shouldn't be critical.
RE: CMU Wall Cracks
Were any control joints designed near the openings to control the cracking and provide proper sealing from the elements?
The National Concrete Masonry Association (NCMA)TEK notes include valuable guidelines that you could use to explain the potential cosmetically objectionable cracks. they can be found at the NCMA site (ncma.org). Just look to the right upper corner on the home page and click on the TEK note, then select a state (any state) and a producer member (any producer) to access the over 100 TEK notes on structural and architectural subject. - It is a well hidden resource.
All the TEK notes are written and approved by registered engineers that are active in all code and standards activities.
RE: CMU Wall Cracks
RE: CMU Wall Cracks
Dik
RE: CMU Wall Cracks