Slab crack basement

One of the common problems is cracks. These cracks can appear anywhere, from little cracks in walls or tiling to major cracks in basement floors. As a homeowner, you need to know what the cause is and, more importantly, how critical of a problem is it? The two primary parts of concrete are cement and water.

As the concrete dries, it will shrink. The degree of shrinkage is largely affected by temperature. If temperatures drop while your basement cures, that can cause cracks. Likewise, sweltering heat will rapidly dry your concrete — and curing too quickly also causes cracks. Even in perfect conditions, over time, your basement concrete will experience some degree of shrinkage. There are certain areas that are more likely to develop these cracks than others, such as around doors or other sharp corners.

On the bright side, cracks in your basement floor due to shrinkage rarely result in any structural problems. The resulting uneven surface can create a tripping hazard. What to Do: Concrete basement floors that are uneven should be leveled. PolyLevel uses a high-density polyurethane formula to permanently lift and stabilize a sinking concrete slab.

Penny-sized holes are drilled into the slab and a structural-grade polymer is injected into the void. The polyurethane material expands, lifting and leveling the slab. The area in the basement where the walls and floor meet called the cove joint is a common problem area for water seepage. During construction, when the concrete walls and floor are poured, a small gap is left between the floor and walls.

When the groundwater level rises and the soil becomes saturated, hydrostatic pressure forces water through the cove joint. What to Do: Sealing the gap isn't recommended since the sealant can crack. The most effective solution to keep water and moisture out of the cove joint is with a basement waterproofing system interior drain tile and a sump pump , which helps relieve hydrostatic pressure. Small cracks in the basement floor commonly result from shrinkage as the concrete dries, which pulls the concrete apart.

These types of cracks can show up as long as a year after the basement floor is poured, depending on how quickly the slab dries and how humid the basement is. What to Do: Nothing. Like hairline cracks, these cracks that are slightly wider are likely the result of shrinkage and are not a sign of a serious foundation problem.

However, even small cracks in the basement floor can allow water, moisture, and radon to enter into the basement. Straight or jagged? Also, when was the slab poured and when did the crack appear? Can you send a photo? Read more on Shrinkage Cracks in Concrete. Steve, Thank you very much for your response. Attached please find photo of crack.

My thought has been the contractor should have placed a joint similar to what he did on the second photo. Thanks for the pics. The idea is that the cracks occur at the weak points in the slab created by the control joints, rather than randomly across the face of the slab. You are correct that the angled control joint in the photo would probably have helped here, since stresses tend to concentrate at inside corners of slabs and other masonry surfaces like window corners in a wall.

Either an angled control joint or extra reinforcement is needed to prevent this type of cracking. This is a polyurethane sealant that will outlast cheaper acrylic sealant. It will not give you a perfect color match, but will keep out water and dirt and help stabilize the crack. You can find additional technical info at this link. Our house is built with a concrete slab foundation. We have lived here for almost 10 yrs. It is more concrete rather than hollow blocks. Do you happen to know the thickness of your slab and whether it has rebar?

A slab-on-grade foundation, like you have, usually has rebar running both ways at about 18 inches on-center. Slab foundations typically run 4 to 6 inches thick depending on local codes and practices.. They may also use a stronger mix with lower slump less water. Basement floors, on the other hand, rarely use rebar and typically run 3 to 4 inches thick.

That may explain why your slab has fared so well vs. There are a lot of variables. Your email address will not be published.

Hairline cracks in a concrete slab are rarely a cause for concern. They can be controlled, but not eliminated. These are both serious problems that need to be addressed. They may or may not be related. Concerned About Hairline Crack in Slab and Tile We bought a foreclosure that seems to be in relatively good condition.

Do we need to worry and consider adding an under-slab support system? These cracks take several years to form and occur well beneath the surface.

The repeated freezing and thawing of moisture inside the foundation gradually wears on the aggregate and crumbles the concrete, making it quite vulnerable once the cracks are visible on the surface. Offset cracks cause a difference of height in the concrete on either side of the crack.

In most cases, this is due to an uneven seat for the slab itself, such as poorly compacted subsoil, invasive pressure from tree roots, previous concrete slabs that have not been removed, or repeated expansions and contractions in the rebar.

While many causes for foundation cracking have been illustrated above, it is useful to know the common weather and environmental phenomena that result in such damage.

This can help you head off cracks in the foundation by knowing what to expect in such circumstances. Most commonly, cracks in the foundation are out of your control and can be attributed almost wholly to sudden and extreme changes in weather. Accumulated snow near the building can melt and create a sudden flood. If the foundation already contains cracks, even thin ones, the water will enter and widen them in time. A reduction in the moisture of the subsoil can cause it to shrink and move further away from the foundation.

This creates a gap between the soil and the foundation, leading to possibly dangerous slab movement if the foundation is not adequately supported by other means. Some soils have a large capacity to absorb moisture and are heavily affected by it. High moisture could expand the soil below the foundation and heave the concrete slab.

The damage can vary, and with evenly compacted soil, it could even be negligible. This phenomenon is the opposite of expansion in soil. While the result is similar to that of a drought — i. Flooding after by a storm can suddenly increase the moisture content of the soil and expand it, forcing the subsoil up against the foundation and causing it to become uneven or crack.

When tree roots extend under or around the foundation, they soak up moisture from the soil, causing it to shrink away from the slab or in some way alter the stability of the foundation. Negligence on behalf of the constructors can also cause crack in slab foundation and land your home in trouble. Leaks in the house that make their way to the foundation tend to worsen any expansive soil problem, because this supplies more water to the soil, which in turn expands upwards.

This category includes any use of substandard incompatible materials or a badly planned process of pouring out the slab foundation. Mixed brands or strengths of cement, incorrect cement-aggregate ratios, uneven curing or reinforcement of the concrete, all contribute to the appearance of cracks. The soil upon which the foundation slab is to be placed must be compacted as much as possible. If this is not done, or if the soil is not properly compacted, the slab will likely become unstable over time.

Leaks or poorly planned drains can cause the slab and subsoil to come into contact with excess water. Regularly cleaning the gutters and ensuring that waste water is led far from the building are simple preventive measures to keep the slab and soil away from too much moisture. It is possible to repair a few small or shallow cracks in the foundation by yourself, but only after successfully identifying it. As discussed above, seemingly thin cracks can be indicative of a larger problem, and should then be left to professionals.

For extreme cases, it may be necessary to seek the advice of a geotechnical engineer, in order to tackle more fundamental problems. It is important to remember that although concrete is primarily rigid, it does have some capacity to accommodate tension and flexibility, as it naturally expands and contracts according to the surrounding temperature.

Clear the area of any loose chips. For a small crack in slab foundation, this can be done with a steel brush or any hard-edged tool. For wider cracks, you may have to use power tools or a large chisel to properly chip away loose material. Mixing the dry patch powder with latex instead of water gives it the necessary elasticity mentioned above.

This is the best way to fix cracks in cement slab foundation. Add more bonding agent to small amounts of the mix as you apply it to the crack. Dampen the crack with water before applying the patch. This allows the patch to retain its moisture and thus set properly , instead of having it soaked up by the surrounding concrete.

If it loses its moisture too quickly, the patch may itself crack, being unable to bond properly with the concrete. This should solve all issues pertaining to a small crack in slab foundation. Similarly, this is procedure required to rectify a hairline crack in concrete slab foundation. M ake sure to clean your tools as soon as possible to avoid the patching compound drying on them.

The main methods for fixing sunken foundations are slab-jacking and piering also known as hydraulic jacking. In slab-jacking, grout a coarse mix of gravel, cement, and lime, for large scale use is pumped under the slab through strategically made holes, to lift the foundation and restore it to its original or intended elevation. In piering, steel posts are inserted into the unstable soil for reinforcement, and hydraulic jacks are used to stabilize concrete slabs if the subsoil has caused movement.