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In our concrete crack repair guide you will find all the costs related to repair these cracks as well as DIY tips from our professionals.
Concrete is evidently one of the most long-lasting building materials used in construction. It is economical, durable and strong. It is a versatile, strong material that can be trusted in the construction of wall, driveways, floors, etc. However, concrete just like any other material has its drawback, in this case, it will crack. As the saying goes, nothing lasts forever, and concrete surfaces are not an exception. With time you will start seeing small cracks on concrete surfaces some of which will require your action.
Some of the cracks can appear immediately after placing the concrete while others happen gradually and can even take years before you start noticing them. Concrete cracks are very common and are usually a cause for concern to most homeowners.
Even though some concrete cracks may not result in any structural damages, most people find them unsightly and perceive them to be a cause of a bigger underlying problem. In this guide, we will discuss the causes of concrete cracks and outline a repair and control measures.
What causes concrete cracks? Perhaps this is one the most frequently asked question about concrete cracks. As a homeowner, if you notice cracks in concrete surfaces in your home you might wonder if the building contractor did a shoddy job. While in some cases this might be the case, in others it could be a combination of several factors, some of which are avoidable while others are out of contractor’s control.
Here are some of the reasons why cracks occur on concrete.
Cracks are classified into two categories:
I. Plastic shrinkage
II. Hardened concrete cracking
This happens when concrete is exposed to excessive loss of moisture through evaporation. This could be due to several factors such as windy conditions, hot temperatures, and low humidity on the concrete surface.
When combined, these factors result in loss of water on the concrete surface on either hot or cold weather conditions. If a newly placed concrete surface loses water at a higher rate than its being replaced by the bleed water, the quality of the concrete becomes compromised leading to plastic shrinkage cracking.
To avoid plastic shrinkage, you need to follow the proper curing process. You should manage the bleed water by allowing free water to move to the surface and evaporate. In short, you should keep the surface moist by plastic sheeting on the concrete or by letting the sprinkler run on the surface at mist settings.
Alternatively, you can use fly ash or silica fumes to manage concrete bleeding rates and reduce the evaporation levels. You can also make use of fog nozzles to soak the air on the concrete surface. All these processes should be done after the concrete has stiffened to avoid leaving marks on the surface.
While dealing with concrete, it’s essential to know the amount to mix and the allowable ratio. The concrete mix does not require a lot of water to get the right strength. However, most of the concrete that is used residential work has excess water. Most people add excess water to the concrete to make it easier to work with and install. But, this excess water contributes to the low strength of the concrete.
In addition to using the right ration of water in the concrete mix, you should continue watering the concrete surface for several days to manage the moisture and reduce bleeding. The hydrating process will also cure the slab as evaporation reaction continues to take place.
This happens when there is a loss of water and moisture from the cement mixture. When the water content is increased in the concrete, it will expand. If there is restraining slab or the slab is adjoined to another structure such as an adjacent wall, it will result in cracks. Normally, the cracks do not happen without restraint or on a free-floating slab.
This happens when there are temperature fluctuations within a concrete construction. The fluctuations occur when a structure loses moisture and heat at varying levels. It can also occur when the weather conditions cool one side of the construction structure at different levels than the other side of the structure. In some places. The temperature can rise during the day and drop significantly at night leading to contraction of the concrete surface.
The different level of temperature changes may end up causing the concrete surface to develop cracks due to varied volumes. The thermal expansion cracks are prevalent in concrete that is restrained.
To reduce cracks resulting from thermal stress, you need to ensure that the amount of internal temperature is reduced and regulated. Also, you need put in measures that will delay the start of the cooling process and also control the cooling levels of the concrete. Also, you need to make sure that the concrete is strong and tensile enough to accommodate different temperature levels.
Chemical reactions in concrete can lead to cracks. A chemical reaction in concrete happens in two ways. It can happen due to the reaction of concrete’s aggregates especially when not compatible. You might not have control over this kind of reaction because the manufacturer is supposed to model the aggregates to suit your locality or area.
The second type of chemical reaction that leads to cracks in concrete is due to type the of materials the concrete is exposed to after hardening. Cracks can develop over time as the concrete reacts to aggregates that consist of active silica and alkaline. These aggregates result from wet cement and other sources such groundwater, during cement hydration or, from curing water and sometimes from alkaline substances that are used on the concrete.
In addition, placing or storing alkaline solutions on the concrete can result in chemical reactions that can eventually lead to cracks. The alkaline and silica solutions cause a chemical reaction in concrete surfaces by drawing water from some parts of the concrete. As a result, some parts of the concrete expand leading to a restraining effect on the concrete slab, and eventually, craps show up.
Weathering process results from natural occurrences such freezing, drying, thawing, wetting, heating and cooling. All these processes can cause the concrete to weather and develop cracks with time. Cracks that result from weathering process usually appear unsightly and can actually raise concerns of disintegration among most people. However, in some cases, the cracks may not have penetrated below the surface, and they might actually be very shallow.
To protect concrete from damages that may result from thawing and freezing, you need to use the right water and cement ratio, probably the lowest and ensure that the water content is at the correct level. You also need to make sure that concrete structure has enough time to dry up and to cure to boost and extent its ability to withstand freezing and thawing.
Weathering process such as heating and cooling, wetting and drying make the concrete shift and change which results in cracks.
These kinds of cracks happen when there is a shift of the ground under the concrete. The shift happens if the soil is not properly compacted or when concrete is built over the wrong type of soil. The shift can also be due to water erosion or presence of roots from trees.
To solve the issue of poorly compacted soil, you can dig and remove the soil, and then replace the soil with crushed stones before you install the concrete.
Corrosion on happens when concrete that has reinforcing steel is exposed to oxygen. For corrosion process to occur, it will require moisture, an oxidizing agent, chlorides and also an electron flow in the metal element. If the concrete surface has small cracks as result of other factors, the cracks will allow water to seep through. Once the water reaches the steel reinforcement, it begins to rust.
Normally, rust expands, and as the steel bar reinforcement continues to rust, it keeps expanding as it causes stress on the adjacent surface resulting in cracks. To prevent corrosion related cracks, you need to take care of small cracks the minute they happen before they develop into bigger cracks. You can make use of coated reinforcement bars as a protective measure. Also, you can use sealers on the concrete or corrosion inhibitors admixtures to prevent oxygen and moisture from getting to the steel.
Concrete surfaces are designed to take in heavy loads but only to some limit. Sometimes during construction, the concrete might be exposed to extremely high loads that might cause stress on the surface and eventually lead to cracks. This mostly happens during the early stages of concrete when it’s still fresh ad susceptible to damages which result in cracks sooner or later.
The only way to avoid this type of cracks is to employ control measures to avoid overloading circumstances. The contractor should be able to inform you and the other personnel in the construction of the load limitations of the concrete structure to protect the surface.
Concrete cracks are likely to occur if the proper construction practices and procedures are not followed. Some people add water to concrete to make it easy to work with which consequently reduces its strength, intensifies settlement and causes high rates of shrinkage.
If concrete is further mixed with high ratios of cement to reinforce its strength, it will require more water which leads to temperature differences between the exterior and the interior parts of the concrete structure. As a result, the structure will experience thermal expansion leading to possible cracks on the surface.
In addition, insufficient or lack of curing will also lead to more cracks in the concrete. If you stop the curing process in the early stages when the concrete has low strength, it will result in shrinkage. Additionally, if the cement is not sufficiently hydrated, it will dry up prematurely causing it to lose its strength and durability.
Other incorrect construction practices that can result in concrete cracks include less formwork support and sometimes placing the control joints on high-pressure points. Also, inadequate consolidation can lead to settlement cracks on the concrete. The only way to avoid these types of cracks it’s to follow the right construction procedures that are known to most contractors.
As a homeowner, you might be wondering at what point the cracks in your concrete become a threat. Spotting a few cracks in concrete surfaces, it’s not unusual. In fact, some cracks are hardly visible such that you might actually not notice them.
As a rule of thumb, a crack that is more than an eighth in width it should actually be a cause for concern and action should be taken. This is because a crack that wide can allow water to seep through to the slab which can result in this two issues:
If water seeps down to the rebar, the steel reinforcements may rust. As mentioned in the causes concrete cracks the guide earlier, if the steel bars rust they will expand and cause the concrete to crack. Extensive rusting and cracking can weaken some portions of the concrete surface.
Water can seep into the cracks, and then it freezes. If this happens, the frozen water will exert pressure on the sides of the concrete and lead to cracks. As a result, the cracked areas could become weak with time meaning the integrity of the structure will be compromised.
As established, a combination of factors such as drying shrinkage, restraint, thermal expansion and contraction, subgrade settlement and weathering can lead to concrete cracks. It’s hard to prevent cracking in concrete completely, but you can substantially reduce and control the rate of cracking by making use of the right preventive measures.
For example, the shrinkage cracks are to be expected. This is because they are as a result of sand, cement, and aggregates drying up faster than the underneath part of the concrete. Consequently, this, the process results in tensile stresses between the lower and the top part of the concrete. In the process of relieving this pressure, the concrete will crack. When this sort of cracks appears, you do not need to be alarmed as they are perceived to be normal.
Some certain types of cracks are a cause of concerns and should be attended to immediately they are spotted. This is because they can potentially be a risk to the structure and can lead to adverse issues.
Here are the signs that imply that a crack is problematic:
If you notice any of the above symptoms, it’s advisable to contact a skilled contractor to take action right away. Concrete cracks such as the ones described above can affect the structural integrity and can ultimately lead to extensive damages that can be costly.
When it comes it repairing concretes, some repairs can easily be a DIY project while others will require the input of a professional contractor.
First of all, you need to identify the type of crack you are dealing with and how the how extensive it is. If a crack’s pattern, size, and its size appear to indicate that the underlying problem is more severe such that it’s affecting the foundation you may have to involve a professional contractor for more evaluation.
To evaluate and identify a concrete crack problem, a structural engineer will charge you an average cost of $300 to $800. To repair major concrete cracks, a professional contractor will charge you about $250-$ 500. If a concrete crack is more than 1/8 in width it is usually a cause of concerning and contractor may have to deal with foundation issues.
Concrete racks in the foundation are more complicated to handle, and they require extensive procedures such as underpinning. This means that the contractor may have to install steel reinforcements to support the foundation and make it stronger. To install the steel reinforcement, a contractor will you charge an average of $1000 to $3000 each corner or more depending on the state of the concrete foundation.
For average to moderate foundation concrete crack repairs for an entire house, a professional contractor will charge you a range of $8000 to $30000.
If you have minor cracks that need patching, such as cracks in the driveway, basement floor, walkway, patio, or on the garage floor, you can fix these through DIY. You need to purchase patching compounds which cost about $3 to $15 for the small tube. Or if you are patching up a larger area, you will need a bag or a bucket of patching compound which cost around $5 to $35.
If you opt to hire a handyman to patch minor cracks on the patio, basement floor or on walkways, expect to spend about $25 to $250. The cost can be higher depending on how much the handyman charges you for labor, amount of material and products used and also the amount of time taken to complete the patching job.
An epoxy patching that is applied to like a flooring will cost you about $50-$150 which will depend on the amount to be used and also the brand of the product. If you hire a professional to apply epoxy flooring over a surface that is already patched and leveled expect to spend about $3.50 to $12 per square foot. For example, if repairing a one-car garage, a professional will charge an average of $750-$3000 for epoxy flooring application. The cost doubles if it’s a two car garage.
When you patch concrete cracks, you achieve a smooth surface. But after patching the concrete crack, you are usually left with an unsightly surface full of patches. This problem can be solved by resurfacing using an overlay of cement or in some cases you can opt use cement, sand and other additives with a blended polymer resin.
The DIY materials for resurfacing will cost about $2 to $6 per square foot. The overall cost will depend on the square footage of the area to be resurfaced. A professional will charge you about $3.50 to $10 per square foot for resurfacing the patched concrete surface. However, the charges will also depend on how the professional charges or the local rates, the state of the existing concrete and the resurfacing method. For example, if you are resurfacing an area of about 500 square foot, a professional will charge an average of $2500 to $5000 which includes repairing the existing cracks and other related issues.
|Cost of hiring a structural engineer to evaluate foundation concrete crack||$300-$800|
|Hiring a professional to repair major concrete cracks||$300-$1500|
|Installation of steel reinforcements bars||$1000-$3000 each|
|Repair moderate foundational concrete cracks for an entire house||$8000-$30000|
|Hiring a handyman to patch minor cracks||$25-$50|
|Hiring a professional to apply epoxy flooring||$750-$3000|
|Hiring a professional to resurface||$3.50 -$10 per square foot|
|Cost of material||Average cost|
|Purchasing patching compound|
A bag or a bucket
|Resurfacing materials||$2-$6 per square foot|
As mentioned in the guide, the majority of the small cracks are not a cause for concern, and they can be repaired through easy DIY methods. Concrete cracks can look unsightly, and if neglected they can develop into bigger cracks which might be costly to fix. Repairing the concrete cracks will also prevent external elements from going through the cracks and causing further damages.
Step One – Sweep and Clean the Floor
Before you start patching the concrete cracks its essential to make sure that the floor is clean and free of oil or other elements. Clean out the dirt and if the floor has grease, make sure it’s completely cleaned out.
Step Two – Chiseling
Repairing the concrete cracks requires being precise. You need to widen the crack a bit using the cold chisel and hammer to remove any debris and dirt inside the concrete cracks. This process is called keying, and it prepares the concrete crack for patching. Place the cold chisel at an angle and use the hammer to pound on the chisel to widen the crack. This process ensures that the base is wider enough for placing the patching compound and enables it to bond properly with the existing crack.
Step Three – Clean Concrete Crack and Then Vacuum
After keying the cracks, you need to remove the debris and get rid of dust from the area. Using a brush or whisk broom, remove all the particles and then vacuum to clear the dust. Debris and dust can prevent the patching compound from bonding with the concrete cracks that’s why brushing and vacuuming is essential at this stage.
Step Four – Mix the Concrete Patching Compound/Spread the Concrete Patch
If you are using a concrete patch filler, cut off the nozzle and start filling the concrete cracks slowly. If you are mixing the concrete compound yourself, follow the manufacturer’s instructions to mix. Once you have mixed the concrete patching compound, trowel the mixture into the keyed cracks. Allow the patching compound to sit for a few minutes then check to see if it has settled. If it appears loose, add more and use a trowel to smooth and level out the now filled up cracks to match with the rest of the surface.
Step Five – Give It Time To Cure
After applying the filler or the concrete patching compound, let it cure for the duration advised by the manufacturer or overnight. After the curing time has elapsed, check the patch to see if requires more filling.
Step Six – Sealing
Once you are done with patching, and you have allowed the concrete patch to cure, it’s a good idea to seal it. Since concrete tends to absorb stains, sealing the patch will prevent that possibility. When it comes to sealing products, there are several of them in the market. However, it’s recommended that you use heavy-duty water-based polyurethane. Apply the sealer with a brush and use the bristles to apply the sealer to the surface. If you want to achieve a smoother surface, use a roller.
The reason why the water-based polyurethane is ideal as a sealer, it’s because it dries up quickly which gives you another chance to apply a second coat after a few hours. In addition, this particular sealer doesn’t have an unpleasant smell compared to other the other types of sealers. When using the polyurethane sealer, it’s recommended that you apply around three to four coats especially in areas with high traffic.
Concrete cracks are prevalent in most homes, but this should not be a reason to leave them unattended. Here are reasons why you should ensure that concrete cracks are repaired and sealed in time.
Concrete cracks on the floor can be a safety hazard to you and your family members. If the crack is big enough, someone can easily trip and fall leading to injuries. Other foundational cracks that put the integrity of the building into question can be potentially dangerous. You risk putting your life in danger if your home has major foundation concrete cracks. This is because such cracks can eventually weaken the structure and put you and other occupants at risk.
Cracks also act as avenues and entry points for pests and insects in your home. Majority of pests and insects access your home through small gaps such as cracks in the wall, and some can even nest inside the cracks. To safeguard your home, it critical to be proactive and repair and seal cracks the moment you notice them.
If you are planning to put your home on the market for sale in future, it is important to take care of concrete cracks. Potential homeowners looking to buy a home may shy away from a home that has a significant number of visible cracks. Taking care of concrete cracks will ensure a return on investment in the long run.
If you have concrete cracks, they won’t diapers or repair themselves. In fact, some will get bigger with time and eventually it will cost more to repair them. To avoid risking a weak structure or bigger repairs in future, its recommended you repair small cracks when they become visible. It will cost you less, and the repair won’t take much of your time.
As the saying commonly goes, prevention is always better than cure. Even though it’s impossible to prevent concrete from cracking entirely, some useful measures can be used to minimize concrete cracking.
Most people assume that cracks are a result of a bad foundation. This is partly true in some cases, but, other factors can lead to concrete cracks. As established, concrete cracks that are generally about 1/6 to ¼ wide are acceptable, and they should not be a reason to give you sleepless nights. In fact, according to American Concrete Institute, it is unrealistic to have 0% concrete cracks in your structure.
However, it is possible to employ preventive measures that will control occurrence of concrete cracks. These measures include:
Maintaining a low water-cement ratio will effectively influence the quality of concrete. As mentioned, most people tend to use a lot of water on concrete to make its usability easy. However, this reduces the strength of the concrete and may lead to shrinkage. A lower water-cement ratio gives the concrete higher level of strength and lessens the occurrence of cracks. It also increases the durability of the concrete surface.
Since concrete shrinks and expands with temperature and moisture changes, it’s essential to control the most expected reaction which is shrinkage. As concrete hardens, it will expel the excess moisture through evaporation which results in shrinking. The shrinkage is one of the causes of concrete cracks. Therefore, lesser water content leads to lesser chances of cracking.
Another reason why concrete cracks happen is using improper proportions to mix cement and water and poor quality aggregates. For example, if you use a lot of water in the mixture, you will weaken the concrete and result in shrinkage issues leading to cracks. On the other hand, if you use little cement than the recommended ratio, the concrete will develop cracks.
To get the right proportions, use quality aggregates to minimize possibilities of shrinking. Remember, concrete is a brittle material that will crack if restrained or stretched. A poor quality aggregate will compromise the concrete and result in shrinkage. Also, it’s essential not to use shrinkage-promoting admixtures. They will increase the water demand and cement which only results in shrinkage hence cracks.
When using concrete, ensure that you follow the right finishing techniques. Use the right timings after each process. Do not rush to the next level before giving the previous process time to settle. If you don’t employ the proper finishing techniques, you will overwork the concrete, and as a result, the aggregate will settle. When this happens the concrete will bleed water and the excess water will not evaporate. It will go back to the concrete and lead to cracks.
Once you have put up the concrete, it’s important to cure the concrete to prevent loss of water. Curing will also prevent the concrete surface from drying as a result of hydration. It’s essential to make sure that the slab is filled with water all the time. You can cover the slab using moist sheeting or wet cotton mats to control and prevent loss of water.
During the curing period, it’s important to make sure that the concrete is not exposed to any weight or heavy loads. The curing process takes at least a month after which the concrete is well settled.
To reduce cracks in your concrete, you should properly place and vibrate it. Vibration releases air that could be trapped in the concrete. If left inside the concrete, the entrapped air could lead to cracks.
Another cause for concrete cracks is the failure to fully compact the soil in the area below the concrete slab. Before installing the concrete, you should make sure the soil underneath is not loose. If left loose, the soil has to settle after a while, and when this happens, it will result in concrete cracks.
In addition, always make sure that you place the concrete on a flat, leveled hard subbase. Ensure that there are no holes or ruts and if the subbase seems rough, you can use a fine material to cover and fill any voids appearing on the rough surface. This way, you will have eliminated restraints, and the bottom of the slab has room to move.
Also referred to as contraction joints, they are usually placed in concrete slabs to prevent and control concrete cracks. The control joints should be placed at regular intervals to accommodate and adjust the shrinkage of the concrete. This way, when the cracks happen at the predetermined locations, they will appear below the finished concrete surface. In this case, you will not have to deal with unsightly concrete marks on the surface when the concrete cracks.
Concrete is undoubtedly one most one of the most durable construction material. It can withstand harsh weather conditions and still stay strong and last for a long time. It’s used in a majority of building constructions and structures. This versatile material maintains your structure in a condition without compromising on the aesthetic appeal of your building.
However, concrete materials, just like any other construction material have their drawbacks, and with time they wear down or produce cracks. Due to some factors such as shrinkage, thermal contractions, corrosion, settlement and improper construction practices, concrete cracks can happen.
Some of the concrete cracks are not a reason to worry other than looking unsightly. You can fix most of these small cracks through DIY methods. However, foundation cracks that are more than a 1/8 in width should be left to professional structural engineers to handle. It’s essential to repair cracks even if they appear small. Neglecting concrete cracks may cause them to continue getting bigger with time, and as a result, you might be faced with bigger structural problems.