Foundation Cracks: Types, Causes, Repair Methods

foundation cracks types causes repair methods
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Foundation cracks are scary, and it’s natural for homeowners to assume the worst. However, foundation cracks are caused by a variety of things, including normal aging. They aren’t always serious, even though even small foundation cracks may allow water, debris, or pests into your home.

Of course, foundation cracks can also be a sign of structural failure. These foundation cracks – usually large and deep – are serious and should be inspected immediately by a foundation repair professional.

In this article, we’re going to cover the causes of foundation cracks, types, how to tell whether a crack is serious or not, repair solutions, and more.

Types of foundation cracks

There are several different kinds of foundation cracks that you might find in your California home:

  • Vertical cracks – Vertical foundation cracks run up and down the foundation walls or sides. Vertical foundation cracks are pretty normal in most foundations and aren’t necessarily a sign of structural damage. Wide vertical foundation cracks may be caused by hydrostatic pressure (caused by excess moisture in the soil) pushing against the foundation.
  • Diagonal Cracks – Diagonal cracks are generally caused by differential foundation settlement. If the settlement is severe, piers can be installed to lift the settled part of the foundation.
  • Horizontal Cracks – Horizontal cracks in a foundation are the most serious kind of cracks. They indicate soil pressure due to temperature fluctuations (if water in the soil freezes, it can put pressure on foundation walls) or hydrostatic pressure caused by excess moisture in the soil. Horizontal foundation cracks are best fixed using carbon fiber repair methods, which help stabilize cracked foundation walls.
  • Stair-Step Cracks – Stair step cracks in mortar are usually the result of foundation settlement. If they’re minor cracks that don’t go through the foundation, they can be fixed using injection techniques. However, if the foundation is cracked all the way through, pier installation may be necessary. Be sure to have these cracks looked at by a professional.

Types of Foundation Cracks and Their Repair Methods

foundation crack infographic 1

What causes foundation cracks?

Foundation cracks are caused by,

  • Aging – It’s not unusual for homes to develop foundation cracks as they age. Some would argue that this is to be expected. Usually, foundation cracks caused by aging are small cracks less than 1/6 of an inch wide.
  • Expansive soils – Expansive soils expand when they absorb moisture and shrink by that same amount when they dry out. This swelling and shrinking puts a lot of stress on a foundation and can, over time, lead to cracking.
  • Not enough moisture in the soil – This might happen because of dry weather or large tree roots seeking water are sucking moisture from the soil. Soil that’s too dry can shrink and cause voids to form under a foundation.
  • Inadequately compacted soil – Soil must be adequately compacted before construction starts. If it isn’t, there could be differential settlement later on.
  • Drainage problems – Plumbing leaks and gutter or downspout problems can cause water to pool near the foundation and sink into the soil. This can eventually cause foundation damage.
  • Improper design – A foundation that wasn’t appropriately designed for the soil or loads will eventually develop serious problems.
  • Poor construction – Sometimes, a foundation that was designed correctly isn’t built correctly.
  • Frost heave – Frost heave happens in cold climates. The ground freezes and then expands and pushes against the foundation.
  • Earthquakes and sinkholes – We probably don’t need to explain these two can cause foundation cracks.
  • Soil creep – Homes on hillsides are susceptible to something called soil creep. Soil creep can, over time, result in foundation cracks and other problems.

Foundation cracks to be concerned about

Small hairline cracks less than 1/10 inch wide usually aren’t a reason to worry. However, if you have larger cracks, hairline cracks that get bigger (monitor their growth), or cracks allowing water to get in, contact a foundation repair professional for an inspection.

Structural vs. non-structural foundation cracks

In a nutshell, structural cracks are a threat to your home’s structural integrity, and non-structural cracks aren’t.

Structural cracks
Structural cracks are cracks in poured concrete or concrete blocks foundation walls. (They are not cracks in drywall or plaster.) Structural cracks threaten your home’s structural integrity.

Structural cracks are caused by various things, including expansive soil, voids under the foundation, unstable soil that wasn’t adequately compacted before construction, and drainage problems.

Look for these signs of structural cracks:

  • Cracks over 1/6 inch wide
  • Cracks where one end is wider than the other
  • Cracks that get bigger over time
  • Horizontal cracks
  • Cracks accompanied by bowing
  • Large diagonal cracks
  • Cracks that run across the ceiling and down a wall
  • A series of vertical cracks grouped together
  • Stair step cracks in brickwork

If you see any of the above, contact an experienced foundation repair contractor right away.

Non-Structural cracks
The most common cause of non-structural cracks is shrinkage during the concrete curing process. Non-structural cracks don’t threaten your home’s structural integrity. However, that doesn’t mean they’re harmless. A non-structural crack in your basement foundation wall could allow water to flow in.

Non-structural cracks are:

  • Less than 1/10 inch wide. However, you’ll want to make sure they’re not getting bigger. If they grow, they’re probably a structural crack.
  • Often vertical. A crack from the top of the wall to the floor is rarely structural because the load has an unobstructed path to the footing.
  • Limited to one concrete block in a concrete block foundation wall

Foundation crack repair

The chosen foundation crack repair solution depends on the crack’s type, cause, and location. If it’s a non-structural crack, you may be able to repair it yourself. However, keep in mind that serious foundation cracks need to be fixed immediately. Therefore, only attempt to repair cracks if you’re sure they’re cosmetic and not structural.

To repair a non-structural foundation crack,

1. Clean the area to remove loose chips of concrete.
2. Mix concrete to a thin paste. Use latex for added flexibility.
3. Wet the crack slightly and apply the patching paste into the gap.
4. Use your trowel to scrape excess paste and smooth the finish.
5. Clean your tools right away to remove the patching paste before it dries.

If the cracks reappear after patching or additional cracks form, contact a foundation repair contractor immediately.

If the cracks in your home are structural and due to settlement, we can use one of the foundation repair methods described below to fix them. These three foundation repair methods transfer the weight of the building to load-bearing soil.

Steel push piers (also called resistance piers)
Steel push piers are driven into the soil – down to the load-bearing strata – using the structure’s weight along with hydraulic pressure. Once they’re in place, a synchronized hydraulic system lifts the building back up. At that point, the jacks are removed, and the push piers stay in place to support the structure.

galvanized steel push pier
Helical piers
Helical piers look something like giant screws. Like steel push piers, they’re driven deep down into the soil until they reach the load-bearing strata. The torque required to advance them down into the ground determines their bearing capacity. Once they’re in place, the same synchronized hydraulic system raises the structure. Helical piers are often used to support new construction projects requiring a deep foundation system.
helical pier installation

Slab piers

Slab piers are helical piers or steel push piers installed via core drilling small holes into the slab. Anchors are inserted into the holes and driven down to load-bearing soil. Once they’re in place, steel brackets attach the anchors to the foundation.

Photo of a slab pier

Other repair options: Carbon fiber reinforcement

If foundation cracks are caused by bowing or leaning basement or foundation walls – a common result of excess soil moisture and water pressure in soil – carbon fiber strips are a solution. These tough carbon fiber strips are applied to bowing and cracking basement or foundation walls to provide extra strength and rigidity.

carbon fiber reinforcement

How much does it cost to fix foundation cracks?

That’s hard to say because it depends on various factors, including your geographical area, whether the cracks are structural or non-structural, and what type of repair method is necessary to fix them. Therefore, we recommend contacting an experienced foundation repair professional in your area for a foundation inspection and estimate. Most contractors will do the foundation inspection for free.

How to prevent foundation cracks?

Since water causes most foundation problems, preventing foundation cracks involves controlling the water in the soil around your home by,

  • Keeping gutters free from debris – Clogged gutters can cause water to spill over the side of your house and down into the soil next to the foundation.
  • Installing downspout extensions, if necessary – Downspouts that are too short can dump water next to the foundation. Downspout extensions channel rainwater away from your home.
  • Regrading your yard, if necessary – Your yard should slope away from your home, preferably about 1 inch for every foot. This will allow water to drain away from your foundation.

As a homeowner, your focus should be on preventing foundation cracks because you’ll save money in the long run. Cleaning gutters regularly, installing downspout extensions, and regrading your yard are far less expensive than a foundation repair.

Is fixing a foundation crack a DIY project?

Only attempt to fix a foundation crack if you’re 100% sure it’s a non-structural crack. However, keep in mind that some structural cracks can appear to be non-structural. If there’s any doubt in your mind, contact a foundation repair professional. If you allow a structural crack to go unrepaired, it could mean big trouble later. For more information, see our article DIY Foundation Repairs: The Truth You Might Not Want To Hear.

If you’re a homeowner, it’s natural to worry about foundation cracks. However, the good news is they aren’t always a sign of structural damage. Many times it’s just normal aging. However, it’s always best to error on the side of caution. If you see any foundation cracks in your home, call a foundation repair professional in your area for a foundation inspection.

If you’re in our service area in northern California, contact us for a free foundation inspection and estimate.

Steve Egloff

Steve Egloff

Steve is the CEO at Bay Area Underpinning, a foundation repair contractor serving the San Fransisco Bay Area, California. Bay Area Underpinning was founded in 2005 with the goal of providing a cost-effective, engineered solution to foundation settlement problems with an emphasis on educating customers to make them feel comfortable with the various methods of foundation repair.

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