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Shrinkage cracks in masonry walls

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Bob,

A number of years ago, I inspected a school (in Tucson) that was still under 
construction (walls were up and roof was on) and the cmu had cracks 2 feet to 
4 feet on center.  I got the block production record and found that the 
average age of the block when delivered to the jobsite was *8* days.  To top 
it off, all, except for the last delivery, had been on site and subjected to 
rain or snow, a record snow (7") I might add.  No weather protection, of 
course.  (Who needs it in Tucson?)  The lot that was subjected to snow was 
laid up the following day.

I don't know if your building had a similar scenario, but this is one 
experience for you to consider.

Roger Turk, P.E.(Structural)
Tucson, Arizona

Bob Conley wrote:

. > I have recently inspected a newly constructed single story CMU building 
. > and have noted shrinkage cracks in the walls below a significant number of
. > windows.  Typically there is a crack below the window sill that runs
. > vertically (4'-0") from the window sill to the foundation.  The cracks do 
. > not stair step but have split the face shell of the block at alternate 
. > courses. The walls are reinforced (#5 @ 32 vert. & #5 @ 40 horiz typ.) 
. > solid grouted 8" CMU. After reviewing the design docs, contractor 
. > submittals and inspection reports I have good idea of why this happened.  
. > 
. > My problem is what to do, if anything, to mitigate this visually for the 
. > owner who lets say is not fully satisfied. The blocks are a mix of split 
. > and smooth face colored CMU and the mortar is colored to match. The 
. > mortar could be re- pointed but trying to fill the cracks in the face 
. > shell probably highlight the problem.
. > 
. > This is a dessert environment and the cracks are tight (~1/32") but would
. > moisture penetration through these pose a significant problem to the 
. > interior wall finishes? There are no planters near the wall so it will 
. > not get wetted during irrigation of the grass. 
. > 
. > Any thoughts of this would be appreciated.
. > 
. > Bob Conley, P.E.
. >