Should you worry about a crack in your foundation? Not necessarily. Not all cracks threaten your home’s structural integrity. Some are just ugly.
Cracks that don’t threaten your home’s structural integrity are referred to as non-structural cracks. They are mainly just a nuisance. However, that doesn’t mean they’re entirely harmless. A non-structural crack in your basement wall could allow water to enter. So, that means they do need to be repaired.
Structural cracks are another matter. Structural cracks are a threat to your home’s structural integrity. Homeowners do need to worry about structural cracks. Don’t put off a repair because structural cracks worsen over time, which means a more expensive repair if you wait.
Note that we’re talking about cracks in poured concrete or concrete block foundation walls, not cracks in drywall or plaster. Those are just unsightly.
Let’s take a closer look at the difference between structural and non-structural cracks.
For more information about cracks see Cracks in Foundation: When To Worry And When You Can Relax.
You’ve got a crack in a foundation. Is it non-structural or structural?
As we noted above, a crack in a foundation will be either structural – and therefore more serious – or non-structural.
Non-structural cracks
Non-structural cracks are caused by shrinkage during the concrete curing process. They’re often vertical, and while they won’t threaten your home’s structural integrity, they can allow water to seep into your basement. Therefore, they will need to be repaired.
Signs a crack in a foundation is non-structural include:
- Cracks less than 1/10 inch wide – Be sure to monitor them, though. If they start to grow, they need to be looked at because they could be structural.
- Vertical cracks – A single, hairline vertical crack in a poured concrete foundation wall was probably caused by shrinkage. However, a series of vertical cracks next to each other indicate a more serious problem.
If the crack is limited to one block only in a cinder block foundation wall, it might have happened during transport to the construction site. However, a crack that runs across multiple blocks might have been caused by foundation movement and, therefore, could be structural.
All cracks – even non-structural cracks – should be watched for growth. If a crack you initially thought was non-structural starts to get bigger, it is best to have an inspection and elevations of the home performed to see if there is indeed a structural affect on your foundation.
Non-structural foundation crack
Structural cracks
Structural cracks are a sign the foundation has moved, and unlike non-structural cracks, they can threaten your home’s structural integrity. Structural cracks are mainly caused by something called differential settlement. Here’s what happens:
It’s normal for a foundation to settle slightly into the soil after construction. As long as the settlement is uniform, there’s no problem. Differential settlement is another issue. Differential settlement is when a foundation settles into the ground, but not at the same rate.
Structural foundation crack
Differential settlement can cause foundation movement and significant structural damage leading to cracks.
Differential settlement can be caused by various things, including:
- Soil that wasn’t adequately compacted before construction began.
- Expansive clay soil – Expansive soil expands when it gets wet and shrinks when it releases moisture and dries out. This is usually a seasonal occurrence and, over time, can cause differential settlement because the swelling-shrinking cycle creates movement in the soil under the foundation.
- Seasonal weather changes – An example of this would be building a house on top of expansive soil during the dry season. At first, everything seems fine. However, when the wet season comes around again, the soil swells and this creates movement under the foundation leading to differential settlement which can cause cracks.
- Earthquakes, floods, and other natural disasters – This one probably needs no explanation.
- Excavation next to the foundation – If your neighbor is doing some heavy excavation too close to your foundation, it could cause problems.
- Poor construction – It happens.
- Poor drainage – Getting groundwater under control is essential if you want to avoid foundation trouble. When excess water builds up in the soil, hydrostatic pressure pushes against foundation walls, causing cracks and bowing.
- Leaky plumbing – Leaky plumbing can be a source of excess groundwater.
- Added construction – A foundation might not be able to hold up an additional story, for example.
- Thirsty tree roots – Tree roots can “drink” moisture from the soil, creating voids into which the house will then sink. This causes differential settlement and foundation problems.
- Frost heave – This happens when the ground under the foundation freezes and swells, pushing up on the foundation.
- Slope creep – This is a problem for homes built on hillsides. The soil underneath the foundation gradually, over time, makes its way down the hill. This can cause lateral movement and foundation destabilization leading to cracks and other problems.
Signs a crack in a foundation may be structural include:
- Cracks that are wider than 1/10 inch
- Cracks that are wider at one end
- Cracks that get bigger over time
- Stair step cracks in brick or masonry
- Horizontal cracks, with or without bowing
- Series of vertical cracks – As we noted above, one hairline, vertical crack, was probably caused by shrinkage. However, several vertical cracks next to each other are probably structural.
- Diagonal cracks – Look for large diagonal cracks. Sometimes you might see hairline diagonal cracks from the corners of doors and windows up toward the ceiling. However, these are usually harmless.
- Cracks that go across a ceiling and down a wall
- Cracks that go all the way across a floor, wall to wall – If the floor crack is limited to one or two tiles, it was probably caused when something heavy fell on the floor.
For more information about differential settlement see Foundation Settlement.
How to repair a crack in a foundation wall
Structural crack repair methods
Underpinning is a repair technique that anchors a settled foundation to stable soil that can support it. As the foundation is lifted and leveled, the cracks close in most cases. Ultimately this process stabilizes the foundation from any further settling.
Underpinning repair methods include:
- Steel push piers – This is the most common underpinning method used today. The piers are driven into the soil using hydraulic pressure and the building’s weight. Once they’re in place, synchronized hydraulic jacks lift the building back up. Here at Bay Area Underpinning we use Galvanized Steel Push Piers to protect the steel from any corrosion or rusting.
- Helical piers – Helical piers are shaped like giant corkscrews, and although they’re primarily used for new construction projects, they’re sometimes used to stabilize settled foundations. They’re turned into the ground until they reach stable soil, and then hydraulic jacks raise the structure.
- Drilled concrete piers – Concrete piers are drilled deep down into the bedrock and stabilize homes on hillsides experiencing lateral movement.
- Slab piers – Slab piers are push or helical piers installed through holes cut in the slab.
Other repair methods for repairing structural cracks include:
- Wall plate anchors – When hydrostatic pressure builds up in the soil outside a foundation wall, it can cause the wall to bow inward and even crack. Wall plate anchors are a solution for stabilizing bowed and cracked walls.
- Carbon fiber straps – Carbon fiber is another method for stabilizing foundation walls. Carbon fiber straps are very strong and stabilize both poured concrete and block foundation walls.
Non-structural crack repair methods
Hairline cracks caused by shrinkage during the concrete curing process can be repaired using epoxy injection. Once the crack is sealed, water won’t seep through the basement wall.
What about DIY repairs for a crack in a foundation?
We don’t recommend DIY repairs unless a crack in a foundation is small and non-structural. However, as we pointed out above, there are times when a structural crack starts out looking like a non-structural crack. Therefore, it’s always best to have a foundation repair professional check out any suspicious cracks. If the crack turns out to be structural, that’s a repair job for the pros.
How to prevent foundation cracks
Since water is responsible for most foundation problems, you can prevent a crack in a foundation by getting groundwater under control. You don’t want excess water to build up in the soil around the foundation:
- Ensure the yard slopes away from the home – This ensures that water doesn’t drain toward your foundation where it can cause trouble. A landscaper can help you with this, or you could DIY.
- Clean your gutters regularly – Clogged gutters will cause water to spill over the side of your home and into the soil next to the foundation.
- Install downspout extensions, if necessary – Downspouts that are too short will release water next to the foundation, precisely where you don’t want it.
- Install an underground downspout and bubbler pot – The water goes into the underground pipe and gets channeled away from your foundation into something like a little sump pump. When the bubbler pot is full, the lid pops up and releases the water.
- Install a drain tile system – When it comes to controlling groundwater around your home, a drain tile system is the way to go. They are two types, interior, and exterior. Their job is to collect excess water in the soil and channel it away from the foundation.
Good maintenance is always less expensive than foundation repair, and every homeowner should learn how to spot foundation problems early when they cost less to repair.
If you have a crack in your foundation, don’t panic. Many times cracks aren’t structural, and even if they are, they can be fixed. But, don’t put off a repair. Foundation problems get worse over time and will be more expensive if you wait.
If you’re in our service area in Northern California, contact us today for a free inspection and repair estimate.
