14 Types of Foundation Cracks & How to Fix Them

The foundation is the most important part of the building, given that it determines the integrity of the rest of the building. If you see cracks in a building, it’s often a sign of an underlying problem you should address.

There are many foundation cracks on buildings, including vertical, horizontal, diagonal, hairline, and stair-step cracks. While most cracks don’t pose a hazard, horizontal cracks or those wider than ¼ an inch indicate danger.

To address a vertical crack in your foundation, thoroughly remove any debris or dirt from the crack using a brush or vacuum. Next, follow the manufacturer’s instructions to apply an epoxy or polyurethane injection filler. Allow sufficient time for the filler to dry and cure. Monitor for any signs of the crack reappearing or indications of additional repairs being necessary.

Although you can fix most foundation cracks, I recommend the services of an expert, having dealt with a few over the years. They provide lasting solutions and will point out issues you didn’t know existed.

Types of foundation cracks

Types of foundation cracks

The most common types of foundation cracks include the following:

Foundation CrackHow to fix
Vertical cracksDIY or hire an expert
Horizontal cracksHire an expert
Diagonal cracksDIY or hire an expert
Hairline cracksDIY or hire an expert
Stair-step cracksHire an expert
Bulging or bowing wallsHire an expert
Foundation heavingHire an expert
Craze cracksDIY or hire an expert
Settlement cracksDIY or hire an expert
Spalling DIY or hire an expert
Shrinkage crackHire an expert
Non-structural crackDIY or hire an expert
Wet non-structural crackDIY or hire an expert
Structural crackHire an expert

1. Vertical cracks

Vertical crack

Vertical cracks run straight up and down the foundation and are often caused by the natural curing and settling of the concrete. 

What to do

Small vertical cracks on your foundation shouldn’t be a reason for concern. If they’re large ones, you should consult an expert to assess and fix them. You can repair vertical foundation cracks with a DIY kit for $75, while a professional one costs $400.

2. Horizontal cracks

Horizontal crack

Horizontal cracks, on the other hand, cause concern since they result from pressure from outside the foundation and basement wall. They can also result from poor drainage or excessive soil pressure.

This type of foundation crack develops or both block and poured foundations and, if left unchecked, can allow water to leak into the foundation. With time, it can compromise the whole building and the basement.

What to do

You should call for an expert to assess and fix this issue. If you sell your home, lifetime warranties can fix horizontal cracks permanently.

3. Diagonal cracks

Diagonal cracks

Diagonal cracks in the foundation occur at 30-45° angles and may result from the foundation settlement or movement. They don’t pose a major danger to the foundation or building.

What to do

You can fix diagonal foundation cracks with a DIY kit for $75, while a professional will cost $400. For the best results, consult a professional on how to fix this type of crack, especially if it keeps growing.

4. Hairline cracks

Hairline cracks

Hairline cracks are the most common type of crack on new buildings. They can occur in the house’s foundations, walls, and other parts. They occur due to the drying and settling of the foundation.

What to do

You can fix hairline cracks for about $200 as a DIY project. However, as with all types of cracks in a building, always consult an expert to find the way forward. A professional will charge about $400-$600 to fix hairline cracks.

5. Stair-step cracks

Stair-step cracks

These cracks are similar to a flight of stairs viewed from the side and are common in masonry and brick foundations. They are often a sign of structural problems which require immediate attention. 

Stair-step cracks are caused by foundation settlement or sinking and moisture-related problems outside the foundation.

What to do

Stair-step cracks are common and mostly harmless. However, if it’s a crack with wide gaps that can fit a quarter, you need a professional to assess and fix them.

6. Bulging or bowing walls

Bulging or bowing walls

Soil pressure and water infiltration cause horizontal and vertical cracks in walls close to the foundation. In most cases, the walls will start curving inward or outward.

What to do

The most suitable approach depends on the extent of the damage. Carbon fiber straps offer an optimal solution for walls with minor cracks or bowing less than 2 inches. However, if the wall exhibits more pronounced bowing or bulging, it is advisable to consider wall anchors and helical tiebacks for a thorough solution.

To keep water away from your basement floor and walls, install a footing drain to soak up the excess water and channel it elsewhere.

7. Foundation heaving

Foundation heaving

Expansive soils and frost can also cause foundation heaving, whereby the foundation heaves or lifts upward. This major problem may require a new foundation or part of it altogether.

What to do

If the heaving crack is larger than a hairline, call a professional to assess and fix the issue before it becomes too late. 

8. Craze cracks

Craze cracks

Craze cracks are fine, surface-level cracks in concrete which are mostly cosmetic but can allow water infiltration. They’re caused by shrinkage during the foundation’s curing process.

What to do

While craze cracks aren’t dangerous, you should grind them down to remove them when they’re 2-4mm deep or use grout to seal and hide them.

9. Settlement cracks

Settlement crack

Settlement cracks appear as the foundation settles into the soil and can be seen around doors, windows, and the perimeter. They can be small enough to be ignored or large enough to indicate an underlying issue.

What to do

If it’s a shallow crack, you can cover it with grout. However, if the settlement crack is deep, consult an expert to assess the whole foundation for other underlying issues.

10. Spalling


Spalling occurs when the concrete surface starts flaking or chipping away due to water damage or the freeze-thaw cycles. It’s not a major structural issue but can cause further damage when left untreated.

What to do

You can fix spalling in the following ways:

  • Remove the spalled concrete and any dirt and loose material.
  • Treat the steel in the foundation to prevent rusting.
  • Saturate the concrete with a bonding agent, then add mortar and a brush finish to match the rest.
  • Add a damp cloth for a few days to prevent the concrete from drying too fast, or use a sprinkler to keep it damp.

If the damage is more than you can handle, consult a structural engineer to fix it.

11. Shrinkage crack

Shrinkage crack

Shrinkage cracks occur when a concrete foundation is drying and losing moisture after being poured. They’re thus common in new homes and pose no danger to the building. Most shrinkage cracks are vertical and, although not dangerous, can allow Radon gas into the basement.

What to do

Even with little risk of danger to the building and its occupants, always have a professional assess and fix all foundation cracks, including shrinkage cracks. The home warranty may cover them; hence free to fix.

12. Non-structural foundation crack

Non-structural foundation crack

Non-structural foundation cracks don’t have a specific shape and are usually less than 3 mm wide. These cracks don’t pose any threats to the structure of the house. However, they can allow water, Radon gas, and others to enter during extreme weather conditions.

What to do

Most diagonal and vertical foundation cracks less than 2mm wide are non-structural and shouldn’t be a reason to worry. However, have an expert assess them to determine if they need to be fixed. 

13. Wet non-structural foundation crack

Wet non-structural foundation crack

A wet non-structural crack results from the shrinkage of the foundation due to the evaporation of water from the concrete. It usually occurs within the first month of pouring the concrete slab. The wetter the concrete mix, the more it’ll shrink, and the larger the cracks will be.

What to do

If you identify a wet non-structural foundation crack, fill it with urethane sealant, which fills the crack and expands on contact with water. If it doesn’t work or the cracks are larger, enlist an expert. If there is too much water in your basement or area, install a sump pump to get rid of the excess water.

14. Structural foundation crack

Structural foundation crack

A structural foundation crack poses a major risk to the building. Most cracks are wider than ¼ inches, and horizontal ones are structural cracks. They result from movement caused by soil shrinkage and pressure and temperature changes.

What to do

Given the level of risk involved, you shouldn’t attempt to fix a structural crack on your own. While you can use epoxy and reinforcements like fiber countersunk staples or straps, this work is better left for the professionals.

Signs of foundation problems

Cracks are the most visible sign that your foundation has problems. However, you can also look for the following signs to determine whether your foundation needs fixing or not:

  • Uneven floors which were initially level.
  • Cracks at the corners of window and door frames. It’s worse if the cracks are wider at the top.
  • Doors and windows are harder to open as they get stuck or rub against their frames.
  • Uneven gaps between the base molding and the floor covering.
  • If you place a marble on the floor and it rolls around, the floor is uneven.

An expert will help you determine the problem and how to fix it. 

How to avoid foundation cracks and other problems

Although it’s possible to repair foundation problems such as cracks, it’s wiser and cheaper to prevent them in the first place. Some of the practices that can prevent foundation problems for your house include the following:

  • Slope the soil away from the foundation to keep the water away. The first 10 feet from the foundation should be sloped 6 inches away, while harder surfaces such as driveways should slope ¼-inch-per-foot away from the foundation. 
  • Install irrigation systems away from the foundation to keep it dry. 
  • Install gutters to keep the walls and foundation dry. Ensure the gutters discharge water at least 5 feet from the foundation. 
  • If you have plants close to the foundation, ensure they only grow to a foot at most from the foundation. This helps prevent shade and damp walls.
  • Use good soil around the foundation to control water and keep it dry. Soils like stale clay, gravel, and coarse sand help drain the water away and keep the foundation dry. 
  • Plants close to the house should not have branches overhanging the house or roots cracking the foundation and basement. 

To have all these aspects working together, you need proper planning with the help of an expert. It’s better and cheaper this way than incurring the repair costs along the way.

Frequently Asked Questions

What types of foundation cracks are bad?

Vertical cracks commonly arise from foundation settling and are generally easier to address. Nonetheless, it’s important not to overlook them, and it is advised to arrange an inspection to assess the underlying issue. On the other hand, horizontal cracks typically signal more significant concerns regarding the integrity of the foundation.

How do I know if my foundation crack is structural?

Cracks wider than 1/10 inch are typically considered structural, often exhibiting asymmetry in width and a tendency to enlarge gradually. Horizontal cracks in wall foundations, whether accompanied by bowing or not, are generally indicative of structural issues.

What do settlement cracks look like?

It’s not uncommon for a home to develop a 1/16-inch crack during the initial settling phase. These slender, vertical hairline cracks typically range from 2 to 6 inches in length. However, the presence of horizontal or diagonal cracks, regardless of size, suggests more than the usual settling and should be cause for further investigation.

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