Vertical crack at center of block foundation wall (C) Daniel Friedman Vertical Cracks in Concrete Block Walls
Vertical Crack Causes & Remedies

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Vertical cracks in masonry block foundations & walls:

This article describes and evaluates vertical cracking that may appear in some concrete block or masonry block walls or foundation walls. Some readers may use the term "cinder block" - an older form of masonry block wall construction.

This article series explains types of foundation cracks, crack patterns, differences in the meaning of cracks in different foundation materials, site conditions, building history, and other evidence of building movement and damage are described to assist in recognizing foundation defects and to help the inspector separate cosmetic or low-risk conditions from those likely to be important and potentially costly to repair.

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Vertical Cracks in Masonry Block Walls

Straight vertical crack in a concrete block wall of a New York home (C) Daniel FriedmanVertical cracks in block foundation walls & expansion and shrinkage cracks in a concrete block wall may occur but are less common than in some other materials.

Our page top photo shows both vertical cracks and step cracks around a large vent opening in masonry block foundation wall. No header was used across the wall opening top and the two single concrete blocks simply fell-inwards. That movement may explain the step cracks around the top and sides of the opening. Elsewhere in that wall we found significant inwards bulging and horizontal mortar joint cracking, worst at the center of the wall.

At above-left is a vertical crack in a different concrete block wall, also of the type we discuss in this article. [Click to enlarge any image]

Cracks in masonry walls tend to be more severe in the center of walls from external loading and pressure (from any source).

The damage to the wall occurred during backfill - pressure from both the backfill earth itself and the machine operator who drove heavy equipment too close to the foundation wall.

It is possible that that same event caused what appears to be a vertical crack below the window - thought that's unusual: usually backfill produces bulging and horizontal cracks in the mortar joint.

Perhaps the wall was constructed without steel mesh nor other reinforcement.

Question: what is the cause of the vertical cracking in concrete block foundation wall shown in these photos and sketches?

We are considering buying a home that has two vertical cracks in the block basement walls. I have scoured your site and have not found a description that fits our situation. I am providing descriptions, images, a diagram and a potential conclusion of my own.

Could you please take a look and let me know what you think? - anonymous by private email 2017/06/11

Vertical crack in a concrete block wall: cause & repair? (C) JSA Vertical crack in a concrete block wall: cause & repair? (C) JSA

Information about the home where these vertical block-wall cracks were observed

Vertical crack in a concrete block wall: cause & repair? (C) JSA

Vertical crack in a concrete block wall: cause & repair? (C) JSA

Questions about these vertical cracks in the block wall:


Vertically cracked concrete block or cinderblock foundation wall (C) Daniel FriedmanInteresting vertical cracks in the block walls in your photos. Here I include one of our photos, a closer look at a vertical crack in the masonry block wall of a New York home that was shown at the start of this article. You can see that the crack runs almost-straight vertically through the center of alternating courses of masonry block and through the mortar joints between blocks of the other courses.

I think that this wall cracked in its center as a result of expansion or contraction caused by significant changes in the moisture content of these blocks - but I'm not certain.

In discussing your block wall cracking, I must give this apology in advance: without a detailed onsite inspection and more information, my comments are speculation.

Vertical cracks in any sort of masonry wall (brick, concrete, concrete block, stone) are pretty easy to identify and are shown at VERTICAL FOUNDATION CRACKS - how to identify this type of damage, though complicating their evaluation is that these cracks often appear together with other crack patterns, particularly stair-step cracking in foundations made of brick or masonry block and in a rougher-pattern also in some stone foundation walls.

The causes of vertical cracks are usually traced to vertical dislocation of the foundation footing or entire wall. Details ar at VERTICAL MOVEMENT IN FOUNDATIONS.

These cracks in a concrete block wall are unusual and are discussed here at VERTICAL CRACKS in BLOCK WALLS.

A quite-straight crack in a masonry wall or foundation usually is due to shrinkage (concrete), occasionally expansion (brick). Concrete block walls might shrink or expand in response to moisture changes but usually these forces are low, usually occur as slight shrinkage, and rarely appear in the wall below -grade where moisture content is less variable. Thermal expansion can crack brick walls - not something we've seen in concrete block. We discuss these distinctions at SHRINKAGE vs EXPANSION vs SETTLEMENT

Vertical cracks in masonry foundations or walls don't usually appear as the only crack pattern. So you'll want to review other crack patterns and causes explained at BLOCK FOUNDATION & WALL DEFECTS.

Your acute observation that the wall sections across the crack are slightly displaced - one section inwards - is an argument for loading on the outside of the entire wall, provided that the dislocation extends over the height of the wall. If on the other hand the displacement is only at the wall top and is all above grade, that is more-likely due to impact.

The construction of the addition onto this home is worth considering as related to the cracking, just as you suggested. But I don't see how activity to add a crawl space addition on one wall would have pushed both existing foundation walls in the same direction: towards the addition by your sketch. To do that one would have had to move the entire end of the building at once. That's possible but rather unlikely.

Still, digging and driving heavy equipment outside of a building can break a wall; what trips up this reasoning is that in my experience equipment earth loading will usually cause horizontal cracks in the mortar joints of a block wall, often in the wall's top 1/3 assuming backfill was to near the wall top.

Severe vertical break in a concrete block wall (C) Daniel FriedmanLook very carefully at the the wall for bulging - possibly caused by backfill or equipment + backfill during original construction. I'm not sure that there aren't some fine cracks in the horizontal mortar joints in the wall - and some bulging. Our photo of a severely-damaged concrete wall - shown here - includes the most-significant break and dislocation along a roughly-vertical line up through the wall. This wall is collapsing, unsafe, and needs to be reconstructed.

I didn't see such evidence of bulging in your photos but a careful look and measurements might be diagnostic.

Footing settlement over a hinge point: Another cause could be a defect that disturbs both footings under or near the crack - e.g. a pipe or object that ran under the whole structure. This would be more likely if the crack were wider at top than at the floor. We discuss this in an article series starting with BUILDING SETTLEMENT.

A point of impact strike would have trouble breaking BOTH walls at once and usually would show up as damage having a visible center rather than a straight vertical crack.

An impact that hit the whole structure near grade top and pushed the floor structure so that both walls were moved would want to break blocks at joints near the wall top rather than tipping the whole structure and breaking in the pattern you show - I'm presuming from your comments that the wall was backfilled to near its top.

The efflorescence and water stains low on the wall are more-likely leaks that have found their way through the existing crack than a cause.

Follow-up questions on diagnosing these wall cracks

Readers are invited to use the page bottom COMMENTS BOX to offer opinions or suggestions.


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Articles on Vertical Cracks & Movement in Foundations

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