How to Fill Foundation Crack?

From the day mankind decided to live in a house rather than living in a cave, the concept of the foundation came into existence.

From the day mankind started existing in this world, they chose caves as their primary living place, to safeguard them from the attack of wild animals and also from the effects of severe storms, cyclones, and other natural calamities.

But as humankind grew their intelligence level, they started to think of building a “home” for themselves, rather than taking shelter in a cave. Since that day, the foundation came into existence.

As we all know, a foundation is the lowermost structure of the building, which carries the complete load of the superstructure, which includes a dead load of the structural components, live loads of the building, wind load, snow load(if that particular structure is constructed in heavy snowfall region, this load is to be considered) and Earthquake load(Particularly applicable in Earthquake-prone regions).

In the case of a framed structure, the live load is transferred to the beams and columns, which are then transferred to the foundation.

In the case of a load-bearing structure, the dead load of the slab, and all the live loads are being carried by the thick Masonry wall constructed.

Thus the types of a foundation constructed differ from the load-bearing structure to the framed structure.

From an economic point of view, it is safe to say that framed structure is very much as compared to load-bearing structure, as well as it very long-lasting, thus it is adopted for most of cases.

Thus a crack appearing in a foundation can be very detrimental concerning its durability as well as the longevity of the structure itself. The cracks can appear in a foundation for various reasons, which are going to be discussed afterward in this article.

Thus designing the building with expected future detrimental effects can be impactful for the building in a way of the greater good in the future.

Also, even if there is an appearance of cracks in the foundation, Preventive measures must be taken to ensure no propagation of such cracks.

As the foundation is the most important component of any structure, which carries the dead as well as the live loads of other components, it is advisable to consult a professional agency or a foundation expert before implementing any Preventive measures to repair the cracks.

The benefit of hiring foundation professionals experts is that they can suggest several techniques, which is economical as well. Also, they ensure the durability of the foundation to its greatest.

Also Read: What Is Raft Foundation | Types of Foundation | Detail of Raft Footing

Reasons of Foundation Crack

The reasons for foundation cracks can depend upon several factors such as the geological and topographical properties of the soil(which particularly includes sulfate content present in the soil and the increasing or decreasing water table), the atmosphere condition, and also on the design error of the foundation as well as of the concrete mix.

The reason for foundation cracks can also be determined by periodical inspections of some local agencies which expertise in inspecting building foundations; as they appoint some person to inspect the site.

The reasons for foundation cracks can also be determined by reaching out to a foundation expert who excels in inspecting foundations.

They check the foundation and several other factors which contributes to the crack(such as checking the geological and chemical properties of the soil; increasing the water table; Atmospheric condition and several other factors); and suggest remedial repair for it.

Some reasons for foundation cracks are generally included in the following sections:

Foundation Design Error: Many a time, it happens that the design proposed for that foundation, Includes several errors and mistakes. In that case, the probability of the failure of the foundation is very high.

As the strength of all structural components primarily depends upon the design criterion, the wrong design may result in the complete failure of the foundation.

This design should be made very accurately for the foundation, and it should be approved by government officials. If necessary, foundation experts must be hired to suggest appropriate ways to build the foundation, and the work should only be given to reliable and well-known contractors.

Uneven Settlement of Soil: Whenever a house is built, the characteristics and properties of the soil might change with time. Along with that, the level of the groundwater table may also change with time.

As the groundwater table increases, the soil becomes more and more permeable, thus of inferior quality. As soil condition falls, the safe bearing capacity estimated earlier before building the foundation also falls.

Thus due to poor bearing capacity, the subsoil becomes unable to carry the loads transferred from the structure to the foundation. Thus, as a result, the foundation fails severely.

To prevent that, care should be taken to periodically conduct soil investigations by local testing agencies and also to conduct investigations on the conditions of the foundation.

Improper Mix Design of Concrete: Due to inadequate mix design of concrete, cracks may be formed on the surface of the concrete as well.

Many a time it happens that mixed design of concrete which should be poured in the foundation, becomes inadequate, and thus does not attain its design strength.

As the foundation is the most important structure of the building, which practically carries all the loads, including dead and live loads coming from the slab; inadequate design strength may result in the severe failure of the foundation.

Growth of roots of trees beneath the foundation: Many a time, while constructing a building, many trees are cut from below. But the roots of the trees in most of the time left out from cutting.

As the roots are left out, in presence of the adequate Climatic condition and water content(which the roots adequately receives from the groundwater table) it starts to grow again.

After the passing of several years, the strength of the foundation also decreases, and along with that, the roots of the trees start coming beneath the foundation.

As soon as it reaches the foundation’s bottom, it starts to press the foundation, as the foundation becomes an obstruction to its growth.

As the strength of the foundation also decreased throughout the years, due to pressure from the root of trees, it becomes unable to bear the stress and cracks appear on the side as well as on the top surface of the foundation. Although it can not affect the foundation in a short time, it can severely affect the foundation in a long time.

Also Read: Difference Between Footing and Foundation | What is Footing and Foundation

Types of Foundation Cracks

The foundation cracks can be of different types which particularly depends upon the construction materials used for building the foundation; whether is it a Masonry foundation or it concrete foundation.

The types of Foundation cracks also depend upon some factors which are mentioned below as follows:

Construction material used for the foundation
Geological properties of the soil(sulfate content and water table of the subsoil)
Nature and chemical properties of the soil; whether it is prone to settle or not,
An atmospheric condition of the topographical area.

Depending upon these several factors, the cracks can be of the following types

Masonry Foundation Cracks

Nowadays Masonry foundations are extinct as compared to concrete foundations. But there are many places where erecting a Masonry foundation is still in use.

Masonry foundation is a very economical and low-cost solution for building any foundation, although it is not that conventional and does not provide the required strength, as compared to concrete.

Some types of cracks which can be formed over Masonry Foundation, are as below:

As the Masonry foundation is primarily built on bricks and mortar, the failure of a masonry foundation means the failure of its construction material, that is, bricks and mortars. The main reason for masonry foundation cracking is the groundwater table.

As bricks can absorb water to a high extent, it affects the strength of the masonry foundation as well. A brick is termed as good when it absorbs water up to 20 percent.

If the bricks used for building the foundation, are not that good (which have a water absorption percentage of more than 20 percent), and if the groundwater table is at a lower depth from the foundation, the bricks start to rapidly absorb water from the soil.

In the presence of high water content, the strength of the bricks falls rapidly, thus failing the foundation as a whole. Many a time, chemical reactions may take place between the constituents of bricks and soil ingredients.

As an example, if the presence of sulfate is very high on a particular soil, due to the chemical reaction, a high amount of efflorescence may be found on the surface of the bricks, which adversely results in a fall of strength as well. Thus due to the chemical reaction, cracks may appear on the surface of the bricks.

Concrete Foundation Cracks

Nowadays, concretes are constructed using concrete as a major material. Various types of cracks may form over the surface of the concrete, some of them are explained in the following:

1. Plastic Shrinkage Cracks:

Whenever concrete is poured in the Reinforcement caging of the foundation, in the presence of sunlight and an open atmosphere, the water content present in the concrete starts to dry.

As a result of the continuous evaporation of water, large voids may form between the aggregates of concrete. This happens as soon as the concrete is poured, that is when the concrete remains in the plastic state.

As voids are formed between the Aggregates, the formation of cracks is noticed at the top surface of the foundation. Although it comes under the category of fine cracks(cracks having a width less than 5 millimeters) and is mostly present in all concrete structures; it should not be allowed to propagate. Plastic Shrinkage Cracks are generally formed throughout the foundation.

2. Drying Shrinkage Cracks:

After the concrete becomes completely dry and attains its stipulated strength in the required time, it is called hardened concrete. Forming of cracks can also be seen in hardened concrete as well.

These types of cracks are termed drying Shrinkage Cracks. The concept behind the formation of these types of cracks in the internal voids is present inside the concrete.

Due to vibration, most of the air voids get depleted, but a little of them remain inside the concrete, which over time, starts to shrink. Thus drying Shrinkage Cracks occur.

Similar to that of plastic Shrinkage Cracks, drying Shrinkage Cracks come under the category of fine cracks as well and are not much detrimental to the concrete structure.

3. Expansion Concrete Cracks:

Whenever the depth of the concrete is very thin and is placed in direct sunlight and an open atmosphere(particularly happens in the case of Pavement Quality Concrete for building of pavement); the water rapidly evaporates from the surface.

Thus one type of crack that is very common to this type of Concrete, is plastic Shrinkage Cracks, explained earlier. As concrete is placed directly over sunlight, there is a high probability of concrete expansion in this case.

As concrete shows the tendency to expand, if any obstruction is found along its length or its width, it pushes the obstruction. Due to the outward thrust, high-stress forms within the concrete as well.

Due to this stress, concrete cracks occur along its length or its width. This type of crack is termed an expansion crack. To prevent this, care should be taken to leave a minimized number of expansion gaps along its length.

4. Heaving Concrete Cracks:

Whenever concrete is poured in the Colder region, it is subjected to frost action. Due to the frost action, the concrete for that particular portion(especially for pavements), and its surrounding portion freezes.

After the temperature rises, the concrete surface melts, which is again followed by freezing in a cold climate. This cycle is termed the Freezing and thawing cycle, and thus, a huge factor contributing to the cracks in concrete.

Whenever a particular concrete surface melts Having the surrounding portion in freezing condition, a high stress is formed in concrete due to temperature variation.

Due to that high stress, the heaving of concrete occurs, resulting in forming of cracks. This type of crack is termed as heaving concrete crack, and is, very much detrimental to the concrete.

5. Settling Concrete Cracks:

Due to the change in soil characteristics and also the groundwater table level, the settlement of the Concrete Foundation can be noticed due to the low bearing capacity of the soil.

As the foundation is a rigid structure, whenever it settles due to the soil settlement, cracks can be formed vertically as well as horizontally on the foundation surface. Many a time major vertical cracks can be noticed in the concrete foundation, which is excessively detrimental to the structure itself.

Thus utmost care should be taken to ensure proper repairing of cracks if they appear on the concrete surface and to implement Preventive measures before the appearance of the cracks.

6. Concrete Cracks Due to Overloading of Slab:

Due to the high overloading of the slab, cracks can appear on the surface of the slab as well as on the surface of the foundation as well, due to being under high stress.

Also Read: What Is Pier Foundation | Types of Drilled Piers | Advantages and Disadvantages of Drilled Pier Foundations

Repair of Cracks

Before taking any measures to repair the foundation cracks, local agencies which expertise in the foundation repair field must be consulted.

They come and inspect the foundation, depending upon the condition of the soil and several other factors, they also suggest the proper procedure for filling up the cracks.

If possible, a foundation expert is to be hired for consultation on the same. While repairing the foundation, only trustable and popular agencies must be employed for the repairing work.

There can be many types of Foundation repair, or filling up the foundation cracks; which depends upon several factors, some of which are mentioned in the following:

Length of the crack
Width of the crack(whether it falls under the category of fine cracks or in the category of extensive danger type)
An atmospheric condition of the area
Topographical and geological properties of the soil
Chemical composition of the soil(to check whether the soil reacts with the present crack-sealing chemicals, or is it chemically inert)
Finally, financial implications and cost-effectiveness of the repair methods; whether it can achieve higher strength with low cost and within the stipulated time.

Depending upon the following factors, the type of foundation crack repair(or filling up the foundation cracks) is discussed in the following paragraphs.

1. Filling up the cracks using Epoxy Injection:

This is one of the most common and popular ways to seal up the cracks. Being used for Horizontal as well as vertical cracks, the Epoxy injection procedure can be used mostly in residential buildings as well as in commercial buildings.

Some of the reasons why the epoxy injection procedure of filling up the cracks is very popular are as follows:

Epoxy injection is found to be very economical and easy to use. As a suitable procedure for remedial crack repairs in residential buildings, using Epoxy Injection can retain the earlier strength of the foundation in a very few time.
Thus a crack appearing in a foundation can be very detrimental concerning its durability as well as the longevity of the structure itself. The cracks can appear in a foundation for various reasons. Epoxy Injection is very easy to use and it does not require any specialized equipment for filling up foundation cracks.
Epoxy can attain strength in a very rapid manner as compared to concrete. It is said to be attaining the same strength at 1 day of 3 days strength of concrete.
In addition to the previous point, Epoxy can achieve higher strength as compared to concrete as well.
Epoxy injection does not have any side effects and is chemically inert, and does not react with the chemicals of concrete. Also, it does not react with the chemicals of the soil as well. Thus Epoxy injection is found to be the best procedure for repairing foundation cracks.

The procedure of applying epoxy injection consists firstly of cleaning the inside of the cracks and the surroundings with brushes, which is then followed by the application of cement slurry.

After the slurry is applied over it, injecting the epoxy starts using specialized equipment. The application should be evenly distributed over the entire length and width of the crack.

After the application of epoxy, the surface is finished smoothly and thus the procedure is completed. Precautions must be taken as the chemical epoxy is very much harmful to humans and only specialized workers must be adopted for doing this kind of job as this is a very specialized job.

2. Routing and Sealing:

This is another common method for filling up the foundation cracks as well. Although this type of repair is only for remedial repairs and can not be used for structural repairs of the cracks.

Also, this type of foundation repair method can only be used if the cracks fall under the category of fine cracks and are of inactive type, thus does not involves restoration of tensile strength.

In this type of foundation repair, at first, a groove is cut along the width of the cracks. The width of the groove may vary from 6 millimeters to 25 millimeters.

After the groove is cut, it is then cleaned using a brush. The cracks should be V-shaped as this shape provides equal width to be cut on both sides of the crack.

After cutting the groove and leaning the groove with brushes, suitable sealants must be applied over it to properly seal it. It must be taken into note that the sealants must be chemically inert and not react with the concrete surface.

Precautions should also be taken to keep the sealant material far from the direct human touch, thus while working with sealant materials, gloves are a must. Also, specialized experts must be hired who can perform this type of job.

3. Grouting Method of Filling up Cracks:

This is, by far the most common method adopted for Concrete raft foundations of multi-stored industrial buildings, commercial buildings, reservoirs, dams, and other large-sized concrete structures.

As in the case of those large-sized concrete structures, the probability and thickness of the crack are much higher as compared to the residential building, a specialized method of filling up the cracks is very needed.

This method is very similar to that of the epoxy injection procedure, the only difference is that epoxy injection is not very costly and can be economically used in any residential building where the cracks are not of extensive danger type.

While in the case of the Grouting method, the cracks formed are an extensive danger, and thus the grouting method is needed to fill up the cracks which is found to be a little more costly as compared to the epoxy injection.

There can be two types of Grouting methods, they are discussed as follows:

Portland Cement Grouting: Although not very effective in sealing the structural cracks, still it is used in filling up the cracks in large-sized gravity dams and concrete walls.

The procedure of Grouting with Portland cement is mentioned in the following:

At first, the portion of the crack where the Grouting is to be done is cleaned thoroughly with a brush and the undesired particles are cleared away.

Then the existing surface is wet with slurry(cement slurry is mostly used). This slurry is provided so that the grout can be effectively applied on the surface and can attain sufficient strength. Next, a grout mesh is applied over the surface. This grout mesh is effectively applied over the surface at suitable intervals.

After the grout mesh is applied, the crack is sealed using grout(which might be a mixture of cement and sand and water or cement paint or other chemical sealants). Next, the crack is flushed followed by cleaning and testing the seal.

The mixture of the grout applied depends upon the width of the crack to be sealed. But precautions are to be taken while adding water to ensure a low water Cement ratio to show Shrinkage and low proneness to crack of the grout and so that grout can attain sufficient strength within the stipulated time.

1. Dry Packing

For filling up the small-sized cracks which is inactive, this type of Grouting for filling up the cracks is most economical in use.

In this method, at first, the grout is prepared using cement sand and adequate water, which is then followed by hand placing the grout and ramming or tamping it to achieve adequate compaction. After that, proper finishing is to be done.

While using the grout, precautions are to be taken care of to lower the water content, so that the mix remains in tight condition, and does not have any Shrinkage and swelling. This type of crack is suitable for filling or repairing cracks of inactive nature.

2. Drilling and Plugging the Cracks

This is another cost-effective method of sealing the cracks(for remedial measures, not for structural crack repairs).

This method is found to be less time-consuming as well. This method is used for treating vertical cracks in the foundation. The procedure for drilling and Plugging the cracks is as follows:

At first, the cracks are cleaned thoroughly using a brush.
Depending upon the length of the cracks, drills are holed at suitable intervals. The number and spacing of the holes drilled should be consulted by the local agencies’ expertise in foundation repair.
After the holes are drilled, a key is then formed by passing down the grout. This helps in preventing the propagation of the crack itself.
After the key is formed, suitable sealants are provided along the total length of the crack, and the surface finishing is done.
While applying the sealants precautions are to be taken to use gloves. The application of sealants should be done by trained personnel who have expertise in this kind of work.

Frequently Asked Questions (FAQ)

What Are the Common Causes of Foundation Cracks?

Foundation Design Error: Incorrect or flawed design can result in weak foundations.
Uneven Settlement of Soil: Variations in soil properties or groundwater levels can lead to uneven settlement.
Improper Mix Design of Concrete: Inadequate mix design can weaken the concrete.
Tree Roots: Roots growing beneath the foundation can exert pressure and cause cracks.
Temperature Changes: Expansion and contraction due to temperature fluctuations can cause cracks.

How Can I Identify the Type of Crack in My Foundation?

Hairline Cracks: Minor and less than 1/16 inch wide.
Non-Structural Cracks: Cracks that do not affect the building’s structural integrity immediately.
Structural Cracks: Larger cracks that indicate significant movement and potential structural issues.

When Should I Be Concerned About Foundation Cracks?

If the cracks are wider than 1/4 inch.
If the cracks are increasing in size or number.
If the cracks are accompanied by other signs of foundation problems, such as doors and windows sticking, uneven floors, or gaps around doors and windows.

Can I Fill Foundation Cracks Myself, or Should I Hire a Professional?

Minor Hairline Cracks: These can often be filled by a homeowner using appropriate sealants.
Larger or Structural Cracks: It is advisable to consult a foundation expert or professional repair service to ensure proper repair and avoid further damage.

What Materials Are Used to Fill Foundation Cracks?

Epoxy Injection: Suitable for both horizontal and vertical cracks, providing strong bonding.
Polyurethane Foam: Flexible and can expand, suitable for dynamic cracks.
Concrete Sealant: Used for smaller, non-structural cracks.

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