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What are the Different Types of Basement Cracks?

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Cracks on the basement floor can cause owners to panic. The good news is that most basement cracks are natural and don’t require repair. However, some basement floor cracks can allow water, moisture, and dangerous soil gasses to enter (including radon). This guide can assist you in understanding the different types of basement cracks.

Stair Step Cracks

Stair-step cracks are common in block foundations. These cracks occur along mortar joints and pose a significant threat to the structural integrity of your basement foundation. Two factors commonly cause stair-step cracks:

  • One area of the foundation is sinking or settling.
  • Moisture issues outside of your foundation.

Call a basement crack repair contractor for professional inspection and repair options. While some hairline basement cracks in mortar are popular, anything extraordinary risks.

Hairline Cracks

Small cracks in basement floors are frequently caused by shrinkage as the concrete dries, dragging the concrete away. Based on how quickly the slab dries and how humid the basement is, these types of cracks can appear up to a year after the basement floor is poured.

In new construction foundations, hairline cracks are popular. They mostly appear within a year and are induced by the new foundation settling and drying. The good news is that these basement cracks are usually cosmetic and can be fixed by DIY house owners or basement crack repair professionals.

Horizontal Cracks

Horizontal cracks in the foundation of your basement are dangerous. This type of crack is usually triggered by uneven soil and hydrostatic water pushing against your foundation wall. You may realize that the foundation is capitulating inwards and that water is starting to leak into your basement. Horizontal basement cracks can occur in both blocks and poured foundations.

According to HydroHelp911, horizontal basement cracks are prevalent; they are identified below grade near the frost line and are frequently caused by the freeze-thaw cycles. This can cause unbalanced stress on your foundation wall, resulting in a horizontal crack.

Vertical Cracks

Vertical foundation wall cracks are less severe than horizontal cracks and do not represent a structural risk. They’re most typically found in poured foundations that run straight up and down your basement wall. Vertical cracks are amongst the most common types found in basements. They are prompted by the foundation settling overtime or the organic setting time of concrete.

An epoxy or polyurethane crack injection is the most common vertical crack repair method used. There is no immediate issue if there is no moisture, and you can use epoxy injection to repair a crack.

Diagonal Cracks

Most diagonal foundation cracks, like vertical cracks, do not pose a severe risk to the structural stability of your foundation. They can be found running up to 30 degrees steep and are caused by the organic treatment and prevention of the concrete foundation wall or settlement over time. Our team uses epoxy crack injections as the most common repair.

When encountering a diagonal crack, take a photo and record the date. You should not be concerned if the crack is a hairline. Check back in 6 months, and if the crack has grown larger, seek advice from a foundation repair professional.

Foundation Slab Cracks

Poured concrete slabs are likely to crack over time. The difficulty is determining why the foundation slab cracked. There seem to be three reasons for this:

Curing of Concrete: The concrete slab’s natural drying, settling, and healing are familiar sources. This is mostly purely aesthetic and poses no structural risk.

Slab Settlement: If your new foundation slab develops settlement problems, you’re in big trouble. This could be due to poor artistry, such as not compacting the supporting ground or poor soil conditions. Immediately contact a professional for an inspection.

Frost Heave: Crawl space slab foundations at or above grade are vulnerable to frost heave. The water beneath the slab can thaw through freezing temperatures, causing the concrete to buckle.

If the crack is more significant than a hairline, consult a foundation expert for cause and repair options.

Wet Non-Structural Foundation Crack

This type of crack is caused by foundation shrinkage due to water evaporating from the concrete. It mostly happens within the first month of laying a foundation. The more wet the concrete mix is at the start, the more shrinkage occurs, increasing the probability of cracks forming. Cracks can also develop due to the concrete’s natural setting.

Basement crack professionals usually use urethane to seal wet and assertively leak foundation cracks. Whenever it comes in direct contact with water, it expands to fill the cavity and becomes a flexible substance conveniently injected into the crack.

If you notice moisture coming from a crack, act quickly. The crack can be caused by rapidly changing weather patterns which cause more water problems.

Shrinkage Cracks

Shrinkage foundation cracks, like hairline cracks, occur when poured concrete foundations start to dry out and end up losing moisture. During the first year of construction, new homes are susceptible to shrinkage cracks. These cracks are frequently vertical and face no structural risk to your foundation. The greatest danger is living in an area with elevated amounts of Radon Gas, which can leak into your basement.

If you are in the process of building a new home, speak with your contractor about your home warranty. Foundations that have shrunk may be covered. If not, take a picture and record the crack. If it expands or you notice more cracks, consider getting an epoxy crack injection repair done.

Non-Structural Foundation Crack

A non-structural foundation crack does not endanger the home’s structure and usually causes leaks, mostly during rainstorms or when the snow melts. However, despite the lack of a structural threat, moisture leaking into your basement is a serious problem that must be addressed.

Water leaking into your residence can damage your belongings, walls, and floors, as well as contribute to mold growth. These types of cracks may worsen if left unattended. It is just a matter of time before you discover that water has entered your home; if you don’t act immediately to resolve a crack in your basement, no matter how minor it appears.

Because of the organic curing process, concrete basement walls may have minor cosmetic cracks. If the crack is 1 to 2mm in diameter and runs vertically or diagonally, it may very well be non-structural.

Structural Foundation Crack

These types of cracks are hazardous because they jeopardize the structural integrity of your home. Horizontal cracks and cracks wider than 1/4 inch are sure signs of a structural flaw. Movement, whether prompted by temperature changes, soil pressure, or soil shrinkage, is usually the cause of structural foundation cracks.

In this case, epoxy is the best material for repairing the crack. Because the crack was first affected by severe stress caused by movement, which can proceed, epoxy alone is not usually sufficient to ensure crack repair. Additional reinforcement, such as carbon fiber countersunk staples or straps, is frequently needed to guarantee that the crack does not expand.

See what is Hydrostatic Pressure! Get a First-Hand View of What That Is.


What causes basement floors to crack?

Cracks in a home’s foundation are prevalent after it is built. The cracks are usually normal, non-structural settlement cracks. However, there are numerous reasons why a foundation cracks, including home settling, concrete shrinkage and curing, stress, and poor construction.

How does faulty drainage affect the foundation structure, and how can it be improved?

Suppose the soil around the foundation is not graded correctly or drained. In that case, water can accumulate and exert pressure (referred to as hydrostatic pressure) on the foundation, starting to cause it to crack. However, there are steps to help alleviate hydrostatic pressure and prevent basement cracks.

Methods for improving drainage include:

  • Ensure that the landscaping is correctly graded and slopes away from the foundation.
  • Maintain the cleanliness and functionality of your gutters. If you don’t already have them, install gutters and downspouts.
  • Broaden your downspouts away from the property to prevent water from accumulating near the foundation walls.
  • Install interior perimeter drainage and a sound sump pump system in the basement.

Identify the type of crack and what induced it to decide how to solve your problem best if you have a break in your basement floor.

Why should the gap between the basement wall and floor not be sealed?

The cove joint is a common source of water seepage. When the concrete walls and floor are poured, a small gap is left between the surface and the walls. As a result, hydrostatic pressure pressures water through the cove joint when the groundwater level rises, and the soil becomes saturated.

What to Do: Sealing the gap is not advised because the sealant may crack. A basement waterproofing system is the most effective way to keep water and moisture out of the cove joint and relieve hydrostatic pressure.

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