I am working with a major track builder who is having a problem a small vertical crack (approximately 1/64th inch) form from the top of the foundation to under the bond beam. The homes are 2-story. The 1st floor is masonry and the second floor is wood. The wall section is approx 40' long. What is the probable cause?
The most likely cause is normal block shrinkage. Standard control joint spacing would call for a control joint about mid way in your 40' long wall. Sounds like mother nature has taken care of supplying that. You also might check for aggravating circumstances such as an interior partition at approximately that location with a vertical row of fasteners.
If the crack is the same width at the top as at the bottom my guess is that it is not caused by settlement.
Would a #5 rebar in the front cell of the Omni Block provide the same structural strength as using on #5 in the Insultech 5x5 core?
Or would you have to run some engineering calculations to determine if this is the case?
The Omni block shows placing 2 bars in the 2 ½” core holes front and back - - but the question is, can we eliminate the #5 bar in the rear core hole and still achieve the same structural strength as the Insultech block using one #5. The core hole being so much smaller with the grout, we were thinking that this probably would not provide the same strength? What are your thoughts as a structural engineer?
No, The #5 does not provide as much strength because the distance between the center of the bar and the compression face of the masonry is not a far and the strength depends on that. However, the bending strength in the other direction is considerably more. Alternating the side that the steel is on could make a big difference in the overall bending strength when checked in both directions.
Jerry Painter, FASTM
Don Beers, PE, GC