CMU wall cracking photos

[eng003]

Looking for opinions on cause of minor exterior wall cmu cracking see attached photo. Cracking starts small at ground and start steps up as it widens to left bottom corner of window opening, second crack starts small from bottom right of window opening stair steps downward widening to corner of bearing wall (window is on non-bearing load wall). Based on the nature of the cracks I tend to think this is due to minor settlment of the bearing wall with the trapezoid shaped section under the window being "racked" causing the cracking. But could just be shrinkage/temperature cracking.

 

[Ron]

Eng003...read my apology post in Geotechnical forum!

When you see cracks following mortar joints it is usually related to shrinkage restraint, not settlement (although very minor settlement can cause).

Often the bond strength between the unit masonry and mortar is not so great. When shrinkage occurs, this is a logical weak point. Restraint occurs at the slab/masonry interface and the window is a break in that restraint.

As for settlement, I don't get too excited until there is through-block cracking.

 

[hokie66]

Although I don't disagree with Ron that this could be a simple matter of volume change (could be either shrinkage or temperature related) leading to these cracks, I wonder how well the wall under the window is supported. Could it be on a more flexible support than the wall to either side so that the trapezoidal section of masonry is dropping relative to the rest of the wall?

eng003, differential settlement of the bearing wall would result in cracking extending upward from the right bottom window corner, or else downward from the top corner.

 

[haynewp]

I would have guessed settlement under the window area also. How long is that wall? With the corner being so close on the right side of the picture it also makes think that it is not shrinkage causing the dual cracks.