Not all foundation cracks should be treated equally. For example, vertical cracks can sometimes be ignored as a cosmetic problem. One type of crack, however—the stair step crack—is a type of damage that can mean you have a bigger foundation problem to address.
Stair Step Crack Basics
Stair step cracks are most often seen on concrete block or brick foundation walls, such as is common for many basement foundations. These cracks are less common, although not unheard of, on poured concrete.
Common Locations
These cracks can form on the outside foundation walls, or you may notice them on an indoor basement wall. Although they are quite noticeable on a bare block foundation, you may also notice stair-stepping on brick mortar or even coming through a stucco wall.
Concern Reasons
A stair step crack indicates that the wall is moving in different directions or at different rates, thus causing a stress crack to open up. This type of movement can quickly degrade a home’s foundation, leading to a loss of structural integrity in your home if it is not repaired.
Doors may fail to open or close properly, floorboards and walls will come out of alignment, and further cracking and failure of other parts of the home’s structure may follow.
Common Causes
Many root causes exist for stair step cracks, which must be determined if a full repair and future prevention is the goal.
Settling Issues
A variety of settling issues can lead to stair-step cracks. On new construction, the cause can often be traced back to poor soil preparation at the time the foundation was built.
Settling that begins to spontaneously affect an older home, on the other hand, may be due to vertical movement of a more direct cause. For example, building another structure or parking heavy equipment too close to a foundation can displace the soil, causing an older home to begin settling again as the nearby soil moves.
Expanding Soil
Certain types of soil are prone to expanding when exposed to moisture. When that expansion happens right next to a foundation wall, the soil puts pressure on the wall until cracks begin to form in the telltale stair-step pattern.
Fine textured soils that contain a lot of clay, for example, will absorb higher volumes of moisture than coarser, sandier soil particles. Areas with clay soil are at a higher risk of expansion damage on foundation walls.
Frost Heave
Frost heave is the soil movement caused by the repeated water expansion of freezing followed by the contraction of thawing. As the water in the soil freezes next to a foundation, it expands and puts pressure on the walls which may cause cracks to form.
Soil won’t experience frost heave unless it has too much moisture trapped within it, since it is the moisture that is actually displacing the soil as it freezes and expands. Causes for excess moisture include water runoff collecting near the foundation walls as well as overly absorbent soil types that don’t drain excess water quickly.
Repair Options
The great news is that stair-step cracks in your foundation are often repairable. Both the cracks and the conditions that caused them must both be repaired.
Gutters and Drains
For frost heave and other root causes that are due to too much moisture near foundation walls, gutters and drains may be the answer. Guttering should be installed around the perimeter of the roof, with the downspouts emptying down the slope and well away from the foundation.
Drains may also be needed, especially if there are concerns about runoff collecting near the foundation. French drains are underground drains that are installed around the outside perimeter of the foundation. You may also need interior basement drains and possibly a sump pump if there are issues with water collecting inside the basement foundation.
Soil Replacement
Expansive soil or soil that moves too easily has no place up against the foundation of your home. The best long-term repair option is to remove any expansive soil that sits up against the foundation walls, and then replace the old soil with less expansive soil.
The existing soil may be mixed with less expansive fillers and then backfilled back against the foundation, but this is only viable if the soil quality isn’t too bad. Otherwise, you may need to have all of the existing soil removed and new, less expansive, backfill installed.
Crack Mending
Once root causes are repaired, the cracks must also be repaired. Otherwise, moisture can seep in and cause ongoing issues. Further, the cracks are unattractive and can provide entrance to pests.
Flexible fillers are a common method for filling in cracks. These contain cement and resin epoxies that will move slightly in response to temperature so that the filler won’t put stress on the surrounding foundation. A better solution, especially if movement is still a concern, is carbon fiber repair straps. These are placed over a filled crack. The straps are designed to take some of the pressure off of the foundation wall so the crack doesn’t reform.
Contact Straight Line Construction if you notice any cracks stair-stepping up a foundation wall.
