Types of Foundation Cracks and How They’re Fixed

Posted on: Oct 01, 2021


Stair-step cracks, one of the most serious types of foundation cracks in masonry block walls

As a property owner, being able to recognize different types of foundation cracks is an important skill. After all, a problem well-stated is half-solved. When you know the types of foundation cracks that you are dealing with, you also get a sense of how urgent the repair is and what type of repair must take place. 

Some types of foundation cracks are normal, some cause leaks, and some can point to more serious structural problems concerning your property’s foundation. In this complete guide, we discuss the various kinds of foundation cracks, how they come to be, and what steps you need to take to fix them. 

Diagonal and horizontal cracks on a brick basement wall

Identifying Cracks in Basement Walls 

Before discussing the types of foundation cracks, let’s quickly go over the types of basement walls and what cracks they are susceptible to. 

1. Poured Concrete Walls 

Poured concrete walls are constructed by pouring concrete into a wooden or metallic form in the basement itself. Once the concrete dries, the forms are removed. 

Poured concrete can have these kinds of cracks: hairline cracks, vertical cracks, diagonal cracks, horizontal cracks.

2. Masonry/Concrete Block Walls 

Concrete block walls are made using cinder blocks or concrete blocks. These walls have joints between the blocks that could be susceptible to leaks or crack formation. However, even the cinder blocks themselves can have cracks.  

Masonry/concrete block walls can have these kinds of cracks: vertical cracks, diagonal cracks, horizontal cracks, stair-step cracks 

3. Precast Concrete Walls 

Precast concrete is oftentimes stronger than poured concrete. This type of basement wall is built offsite, typically in a factory with highly controlled conditions.

Even with its strength, precast concrete can have these kinds of cracks: hairline cracks, vertical cracks, diagonal cracks, horizontal cracks.

4. Bricks or Stone Walls 

Brick or stone is more commonly found in older houses. Because most have stood for decades upon decades, they typically also have the most number of cracks. Similar to masonry block walls, brick or stone walls are weakest at the joints but even the bricks or stones themselves can also sustain cracks.  

Brick or stone walls can have these kinds of cracks: vertical cracks, diagonal cracks, horizontal cracks, stair-step cracks.

Concrete foundation with hairline cracks

Types of Foundation Cracks 

1. Hairline Cracks 

Hairline cracks are the most common in concrete foundations. These cracks are mainly due to the shrinkage that takes place while the concrete cures.  

Hairline cracks are really thin and do not run the whole length of a wall in any direction. Instead, they tend to go in many directions and are typically just shallow cracks. Though these cracks are small, water can still seep through these seemingly harmless cracks.  

What to do with hairline cracks: A professional waterproofer will be able to repair this kind of crack easily. 

2. Diagonal Cracks 

Diagonal cracks are one of the types of foundation cracks that should not be taken lightly just because it “doesn’t look so bad.” On one hand, they can be caused by a concrete foundation’s curing process. These kinds of diagonal cracks are not a threat. 

However, diagonal cracks can also be a sign of differential settlement of your home’s foundation – which is a serious problem. We discussed differential settlement, along with other factors that cause basement cracks in our article, “9 Causes of Foundation Cracks.” 

What to do with diagonal cracks: Call the pros to inspect and assess the diagonal cracks.  

3. Vertical Cracks 

Similar to diagonal cracks, vertical cracks can either be structurally harmless or a sign of bigger problems. Generally, vertical cracks don’t pose any danger when they are cold joints, or when they are merely due to concrete shrinkage. 

Typically, cold joints appear as vertical cracks. However, cold joints are not technically cracks; they are points in the wall where there had been a delay in between pouring concrete batches. These are typically found in poured concrete foundations. These cold joints are planned by the contractor, however, these will still leak like regular cracks.

Vertical cracks may also be due to the shrinkage of the cement, especially if the concrete mix had too much water. These types of cracks are at a maximum width of 1/8 of an inch. Again, these kinds of vertical cracks are structurally harmless but could still allow water to seep through. 

However, if you have vertical cracks that are wide at the top and taper down, they can be a sign of a cracked foundation footing or differential settling. Both of which are serious structural problems. 

What to do with vertical cracks: Call in the pros to have the vertical cracks assessed.   

4. Horizontal Cracks 

Horizontal cracks are nearly always caused by structural problems. If your home has one, you need to call a professional as soon as you can. 

Generally, horizontal cracks are due to lateral force.  

One common source of lateral force is clay-rich soils. When it rains or snows, these types of soil will expand and push against the basement wall. Poorly compacted soil around the basement can exert the same type of force through stored water that can expand when frozen. 

Another source of lateral force could be vehicles or heavy equipment parked near, or adjacent to the basement. The weight of the vehicle or equipment will push the soil down causing it to apply lateral force against the basement wall. This can potentially lead to a horizontal crack. 

The above kinds of horizontal cracks appear over time. However, these cracks can also appear in new homes. Typically this happens when the area around the basement is backfilled too soon. The cement in the wall isn’t able to cure to its full strength and thus, the lateral force from the soil will cause horizontal cracks.  

What to do with horizontal cracks: Have them inspected by a professional at once before the walls bow.

5. Stair-Step Cracks 

Stair-step cracks exclusively appear in walls that have cinder blocks, bricks, or stones. The tendency is that the joints in between are weaker than the material used, resulting in cracks that are shaped like a set of stairs. 

Similar to horizontal cracks, these kinds of cracks are nearly always linked to more serious structural problems and are a sign of differential foundation settlement.  

What to do with stair-step cracks: Get them inspected by a professional immediately. 

Stair-step cracks in a brick foundation wall

Professional Foundation Crack Assessment and Repair 

Now that you know the different types of foundation cracks and the way they are repaired, you are prepared for anything. However, you may still have questions and doubts about your foundation’s cracks. Are they harmless, or more serious? PRO Waterproofers can help! 

PRO Waterproofers is one of the most trusted waterproofing companies in Ontario. One of our specializations is foundation crack repair. We’ve also done repairs on numerous properties over the years, using durable and environmentally friendly materials. 

If you have questions or if you’d like to take advantage of our FREE in-home consultation, reach out to us today!

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