Vertical cracks can be found on nearly every slab or basement foundation. Just because they are common, though, doesn't mean that they should be ignored.
Vertical Crack Severity
Vertical cracks are not necessarily perfectly vertical. A vertical crack is generally defined as any crack that runs roughly upward at 90 degrees from the ground, but the crack can slant up to 30 percent off of 90 degrees to the ground. Anything variance that is greater than 90 degrees is considered a diagonal crack and requires a different assessment and repair plan compared to vertical cracks.
The crack may be very narrow, which is defined as a hairline crack, or it may gap open slightly. It is also possible for the crack to gap more widely at one end compared to the other. Vertical cracks tend to form in the first few years following construction, but in some cases, they may form on older foundations.
Causes of Cracking
Nearly all vertical cracks are caused by tension on the concrete, which is why they appear during the initial years after the home is constructed. Tension exerted on the foundation from the outside soil causes the cracks to form in order to relieve the tension. The cracks aren't actually damage so much as naturally occurring tension relief joints that prevent more extreme damages to the foundation later.
On older homes, vertical cracks may form in response to groundwater pressure. If water is collecting in the soil next to the foundation, perhaps due to nearby drainage or grading issues that have developed over time, then the pressure of the water against the foundation may cause increased tension as well. Cracks then form in response to this increasing tension in the soil surrounding the foundation.
Fortunately, vertical cracks are easily repaired. The best course of action is to fill and patch over the cracks. Hairline and narrow cracks can be covered with an epoxy patch to keep moisture from seeping in. Wider cracks are first filled with a flexible epoxy, which allows for the tension relieving movement in the crack, and then covered with a patch to prevent water incursion.
If the cracks have formed on an older foundation in response to water pressure, your foundation repair team will first determine why the pressure has increased. You may need to have ground drains or grading done to prevent water pressure against the foundation. They will then patch the crack as detailed above.
Contact a cracked foundation repair service for more help if you notice vertical cracks on your foundation.