CMU Wall Repair

[kxa]

I have a situation where a residential house was built with CMU exterior walls and due to some settlement has a few 1/4” to 3/8” wide cracks as shown in the attached photo. This is a 50 year old building and has wood lintels and masonry lintels. The owner wants it repaired. I can take care of stabilizing the foundation but wanted to know what is commonly being practiced out there for the repair and sealing the cracks. Any help or reference material will be greatly appreciated.

 

[Ron]

For the "non-structural" cracks (those that follow mortar joints), use a polymer repair mortar (Sika or similar)and re-point. For structural cracks (through block, lintels, tie beams, etc.) inject structural epoxy (Sikadur 33 or similar).

If structural cracks are contiguous with an unfilled cell, pump or gravity feed polymer concrete in "soupy" consistency to fill void and provide crack repair.

 

[kxa]

Thanks, I can do that from inside of the house and the attic so that holes won't be visible from the outside. Have you used any metal reinforcements. I also thought about installing long metal straps horizontally on the inside face (house interior) of the wall with at least one small anchor bolt through each block.

Are there any good reference materials for these types of situation?

 

[w12x26]

This seems to be a differential settlement problem. Repairing the crack as suggested by Ron would be enough. You need to address what is causing parts of the footing to settle. This is most likely due to an improper or missing drainage system. As far as repairing the foundation you can either use pressure grouting or underpinning.

 

[hokie66]

The crack near the corner and the crack under the window are essentially vertical, going right through the blocks, and I can't see any indication that there is vertical separation. From this one photo, I would doubt that the cracking is due to footing movement.

 

[kxa]

Ron, do you have any mix spec on polymer concrete?

It may not be that clear from the photo but the corner crack is close to 1/2" wide and due to settlement.

 

[hokie66]

You may be correct, but the width of the crack does not determine if it is due to settlement. The key is whether there is vertical separation, not horizontal.

 

[kslee1000]

Take advise from w12x26. Once the question around foundation has settled, take Ron's suggestions to perform the repair.

 

[BAretired]

I agree with hokie. The crack near the corner at the right occurs at the top of the wall. I cannot see it below the lower sloping roof. Its cause is probably temperature related i.e. the masonry reacts to temperature change more than the wood roof. It may suggest a discontinuity in the horizontal steel at the top of wall.

The crack on the left under the window is probably shrinkage or temperature related as well.

There is no clear evidence of foundation settlement in the photo provided.

BA

 

[hokie66]

The building has not been protected against the elements. Note the "hungry" wood trim which appears never to have been painted. And the block walls have no coating to prevent moisture infiltration. Blocks can act like sponges. I think your cracking could be due to freezing of trapped water in the walls.

 

[w12x26]

I assumed that foundation problems were a given and that they were verified.

Now if there is no indication of settlement or foundation failure then I would address the roof framing. Are there ceiling joists or is the roof cathedral ceiling? the cracks could be induced by the lateral thrust at the wall plate in case of a vaulted ceiling.

 

[hokie66]

That could certainly be a factor in the crack under the roof, but probably not for the one below the window.