Why do Foundations Crack – Things Every Homeowner Should Know

Why do Foundations Crack – Things Every Homeowner Should Know

Why is there a crack in my basement wall? Should I call a contractor? Will my house collapse at any minute? 

Foundation repairs are often times expensive, exhaustive, and not always visible to the naked eye. This article aims to teach you about the causes of foundation damage, what to look for on your own home inspection, and various types of foundation cracks/issues I have encountered in the field.

Foundation damage is commonly caused by three main reasons 

1. Poor Drainage

2. Native Soil Types

3. Tree Roots

Common Causes of Foundation Damage

Poor Drainage

When inspecting any building, it is important to first take an overall look at the land it sits on. Is the building situated on the top of a hill, or the bottom of a hill? Does the landscaping slope towards or away from the building? 

Rainwater will follow the path of least resistance, so try to imagine where rainwater from your site – or any surrounding sites – will drain. An ideal recommendation is to ensure that landscaped areas are graded away from the building foundations in order to promote positive drainage patterns.

Next, identify any concrete or asphalt surfaces and try to visually determine whether they slope towards or away from the building. Unlike grassed or landscaped areas, water will sheet freely over these non-porous surfaces and may cause drainage concerns on your property. Patios, driveways, concrete sidewalks, decks, balconies, etc. should all be pitched away from the building exterior.


No leader. No splashblock. Rainwater drains directly onto building... Poor Drainage!

Outside of the landscaping and grading of the property, take note of the gutters and  ownspouts. All downspouts should be equipped with splash blocks or leaders to direct rainwater away from the building foundations. If downspouts discharge into underground pipes, check the landscaped areas around the pipes for evidence of standing water, eroded landscaping materials, etc. 

If you are considering purchasing a property and are concerned with the drainage patterns, re-visit the site on a rainy day. This will allow you to gain a better understanding of the on-site drainage patterns and may even help identify other concerns which you may not have noticed on your first visit. Leaking gutters, damaged downspouts, pooling water, etc. are often hard to identify on a dry day. 

Some areas of the country are inundated with soils that have high “shrink-swell” potential –  when exposed to moisture (i.e. rain or irrigation), the soils will expand/swell and when dry, the soils will contract/shrink. Over time, the constant shrink-swell cycles will create stress on the foundation and can lead to damage.

I wrote a separate article on how to determine the native soil types in your area, found here.

Expansive soil types are often times apparent when looking at the concrete or asphalt surfaces. The constant movement of the soils will cause cracks in the streets, driveways, sidewalks, etc. Take note of the sidewalks and driveways on your own property and any neighboring sites. Chances are, if your neighbors are having issues with expansive soils, you will be too. 

The photo at left depicts the impact expansive soils may have on the concrete flatwork. The metal staircase is anchored to the building and therefore does not “float” up and down with the concrete slab which is likely the cause for these cracks.

Tree Roots

Tree roots are the third most common source of foundation damage and thankfully the easiest to identify. When looking at a building, take note of any mature trees (or stumps) in close proximity to the building perimeter. 

How to Identify Foundation Damage

Building Exterior

The biggest tell-tale signs of underlying foundation issues can be found by inspecting the building exterior. For brick or stucco buildings, inspect each wall of the building and take extra time to inspect any door and window frames. Cracks will often begin at the corners of exterior doors, windows, patio/balcony doors, etc. 

In addition to cracks, you may want to look out for previous repairs. Are there any sections of the brick or siding that appear to be a different color, texture, etc.? Is there any evidence of recent or isolated tuckpointing? Do any areas of the building exterior appear to be older or newer than other sections? These may be visual indications of previous repairs.

What to Look For - Building Interior

The inside of the house can tell a lot about the state of the foundation. Similar to the building exterior, inspect all of the window and door frames throughout the building. Cracked drywall – particularly around door/window frames – can be a tell tale sign of foundation damage. 

Check that all windows operate smoothly. All windows should open and close easily without excessive force.


Check all doors – both interior and exterior. Look out for excessive gaps between the door and door frame and ensure that doors open and close easily without contacting the floor below. Exterior doors should operate smoothly and not require a hip check to close. Interior doors should remain in the position you place them in. If doors continue to swing back to either the open or closed position,, it might be an indication that the flooring or door frame is no longer level.

If the building has a basement, take a long “hard” look at the basement foundation walls. Some degree of small cracking is to be expected, often times referred to as hairline cracks.

Hairline Crack - Not an Issue
Big Crack - Big Issue?

Keep an eye out for any larger cracks (i.e. any crack large enough to stick a credit card into) and watch out for any shifting. If there is a vertical crack which spans from the basement floor to the
ceiling, check to make sure that the left and right hand side of the crack are level. If a foundation slab is sinking, one side of the foundation wall may have “sunk” or vertically shifted lower than the other side.

Identify the location of any cracks in the basement foundation wall(s). If there is a crack at the northwest corner of the basement, go back outside and check the northwest corner of the building. Is there a patio, driveway, downspout, large tree? Take a second look and try to determine what might be causing the damage. 


Differing Types of Foundation Cracks

Notice the cracks typically follow the mortar joints and often times originate at around a window. These buildings were constructed on a steep slope, towards the bottom of a hill. We believe that these cracks were likely caused by foundational movement due to poor drainage. 

Concrete cracks noted at a stucco wall.

Hairline cracks noted in a basement in the midwest. Cracks of this size are typically not an issue. The homeowner may want to monitor the cracks over time for changes in size, any horizontal / vertical shifting, or for evidence of water infiltration.

Notice how the bricks seem to have shifted. This would warrant a second opinion from a structural engineer. 

Closing Thoughts

Before the purchase of any Property, DIY recommends contracting a local, certified home inspector. This article barely scratched the surface of what to look out for when inspecting a building foundation, so leave that up to the professionals!

Feel free to bring up any concerns to the home inspector that you may have noticed at your property after reading this article. If needed, consult with a local structural engineering firm for a second opinion.


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