crack at top of grouted CMU basement wall (@window sill) 3

[PSUengineer1]

The attached pic shows the top of a portion of a CMU basement wall. Pic is taken at a basement window. Exterior grade is approximately equal to the sill. Brick veneer is attached to the outside of this 1990s house.
The crack extends across the width of the block sill. Another similar crack in the block is about 48 inches away. Portions of the crack in attached pic are spalled (older), while portions of the crack along the drywall-concrete sill intersection are sharp (newer). No other cracks in drywall nearby, and no cracks in above grade (i.e. visible) brick veneer on the exterior wall side of this crack. Without being able to see any other portion of this basement wall, would you agree that this is possibly a shrinkage crack? Thanks.

 

[XR250]

It is likely due to the wall bowing inwards, Notice how the crack is wider on the interior face? You usually will not see cracks in the bricks as they go into compression in this case.

 

[PSUengineer1]

@ XR250. Thank you, XR250. Without removal of the drywall I cannot tell for sure if this is a wall bending failure, but I agree with your observation on the crack width. thanks again.

 

[DaveAtkins]

My vote is for shrinkage, not flexural. The wall has less cross section at a window opening, making it more susceptible to shrinkage cracking at that location.

DaveAtkins

 

[chicopee]

To me, the pic that you present looks like it is due to subsidence in that section of the CMU wall, not bending.

 

[MotorCity]

A few observations.....It does not look like there is any fill being retained outside the window, so other than wind load there is probably not much that would cause a flexural crack. However, if there was any lateral load, it looks like there is a small knee wall outside the window that could have acted like a support or restraint (since the crack looks like its pretty close to that knee wall)

 

[msquared48]

I see the first picture and three to four others in the same file.

Are you only looking at the first picture? Or others too?

If the third photo is also involved nd the window is one of the two in the front wall of the picture, I would say definitely subsidence - more specifically differential settlement due to a discontinuity between the windows over the crawl space access.

Mike McCann, PE, SE (WA)

 

[PSUengineer1]

@msquared48,
only one pic i submitted. shows a ruler across a sill. is it shrinkage?

 

[oldestguy]

This old a situation can be many things. A common situation is temperature expansion and contraction, resulting in some cracks not closing all the way. Doesn't look like anything to be concerned about.

 

[MotorCity]

Cracks just mean the rebar is doing its job......if there is any

 

[msquared48]

OP:

Hard for me to say that it is definitely shrinkage as I would need more information, particularly the situation outside the structure, and the construction of the wall housing the window.

Seems like the window is set to the inside edge of a CMU wall, with a build-out to the inside?

Brick veneer not showing in the picture on the outside of the CMU?

Seems strange, and the transverse retaining wall on the outside could play into this too.

Just don't know at this point.

Mike McCann, PE, SE (WA)

 

[PSUengineer1]

i agree with msquared48. You can't opine on what you can't see Thank you all for responding.

 

[DaveAtkins]

I looked at the picture again, and it appears they may have a bigger problem than the crack--why are there so many dead ants inside the window

DaveAtkins

 

[dhengr]

PSUengineer1:
I agree with MikeMc, we just can’t see enough to make any definitive determinations; and I agree with Oldestguy, my guess is that it is really not a problem worth worrying about. I would watch it and see if anything changes with time. I do offer a few observations worth considering, after viewing only the one photo... There does not appear to be any relative vert. displacement from on side of the crack to the other, a good thing. That concrete surface actually appears to have been applied after the window was installed. It was just applied and sloped to finish the sill area on top of the conc. blk., a topping. I would bet that there is a head joint in the conc. blk. immediately below that crack, and it may be cracked too. The crack also pretty much aligns with the inside face of a perpendicular exterior wall which appears to be part of an egress pit. This would be a significant change in wall stiffness in terms of expansion and contraction. Can you see any cracking at the reentrant/inner corner out in the pit? You only have about 3-4' of fill against that wall in that immediate area, so wall bending shouldn’t be too great. Does the window still work easily? Then, you have some assurance that the whole window opening has not been parallelogramed by any wall movement. To the right of the window jamb, is the wall construction conc. blk. up to the first fl. sill pl., maybe two different blk. thk., or is it stick framed with short 2x studs from the window sill on up? The latter construction detail is a hinge in the wall system, and it can cause problems at times. The hinge does not provide continuity in wall construction material, or provide good support for the top of the 3-4' high cantilevered conc. blk. wall below. No sht. rk. cracking is also a good sign of no major wall movement or displacement.