Different Soils & How They Affect Foundations
Example of healthy soil. Source. (CC).
Every house has a foundation, and every foundation must be constructed efficiently, safely and correctly so it will last. The materials that make up the building block and the process of building it are equally important; however, one thing that’s often overlooked is the soilsupporting them because even foundations need a solid foundation. Each type of soil has different properties that affect foundations differently. Generally, soil will be more stable the more rock and compacted sand/gravel it contains.
A diagram showing the different soil levels.
The Types of Soils
- Peat – Peaty soil is usually dark brown or black and is easily compressible because of how much water it can hold. However, during the summer it becomes extremely dry and can even be a fire hazard. It is very poor subsoil and not ideal for support, as foundations are most stable on soil that does not shift or change structure.
- Clay – Clay is made up of tiny particles so it stores water well, but because of its tight grasp on water it expands greatly when moist and shrinks significantly when dry. When clay is moist, it is very pliable, and can easily be moved and manipulated. These extreme changes put a great deal of pressure on foundations, causing them to move up and down, and eventually crack, making clay a poor soil for support.
- Silt – Silty soil can be smooth to the touch and retains water longer because of its smaller particles. However, because of its tendency to retain moisture it is cold and drains poorly. This causes the silty soil to expand, pushing against a foundation and weakening it, making it not ideal for support.
- Sand/Gravel – Sand/gravel has the largest particles of the different soil types. It is dry and gritty to the touch and does not hold moisture because of the large openings, but drains easily. When compacted and moist it holds together fairly well, and if compacted these make for good soils to support a foundation because of their non-water-retaining properties. However, when moist, the particles will lose their friction and can be washed away, which can leave gaps beneath the foundation.
- Loam – Loam is the ideal soil type: typically it’s a combination of sand, silt and clay. It is dark in color and soft, dry and crumbly to the touch. Loam is great for supporting foundations because of its evenly balanced properties, especially how it maintains water at a balanced rate. Loam is a good soil for supporting a foundation, as long as no miscellaneous soils find their way onto the surface.
- Rock – Types such as bedrock, limestone, sandstone, shale and hard chalk have high bearing capacities. These are very strong and good for supporting foundations because of their stability and depth. As long as the rock is level the foundation will be well supported.
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Types of Soil for Your Building Foundation
Apr 14, 2020 | Foundation Repair
Different types of soil will affect your building’s foundation in different ways. Determining the type of soil a building will be built on affects the project’s construction and future repairs.
Here are several of the most common types of soil foundation used in construction. We explore which type is generally the best type of soil to build on.
Common Types of Soil Used in Construction
Clay is not an ideal soil for buildings due to its tendency to shift around as it dries or moistens. This can cause cracks or fissures in the building and result in uneven floors. Clay soil foundation depths are generally deeper to increase stability.
When it comes to clay soil, the best house foundation would be between a drilled pier foundation or a slab-on-grade foundation. Drilled pier foundations will anchor deeper into the clay for more structural stability while slab-on-grade foundations combat clay soil’s tendency to shrink and expand.
Sand and Gravel
Sand and gravel have large particles which allow this soil to drain water quickly (which is good for buildings). Retaining less water means less risk for the building to shift around and form structural and non-structural cracks. Compacted sand and gravel offer even more stability and are a great option to build a foundation on.
Over time, sand can be washed away. In these cases, a helical pier (also referred to as helical anchors, screw piles, or screw anchors) is a suitable foundation technique for sandy soil.
There are many types of rock (sandstone, limestone, etc. ) and they are all excellent options due to their high bearing capacity (making this type of foundation ideal for larger buildings). Bedrock is a layer of rock underneath a surface layer of soil.
Unlike with clay, which can expand and shift, bedrock is more stable and resistant towards water damage. Your building is, therefore, less likely to crack as it shifts or settles. The most important thing about building foundation on rock is to ensure the surface is level before construction.
Loam is the best soil type for construction due to its ideal combination of silt, sand, and clay. It combines the best of all their qualities into the ideal balance for supporting a foundation. Loam generally does not shift, expand, or shrink drastically and handles the presence of water very well.
The one potential drawback of building on loam is the possibility of undecomposed material, which can and should be filtered prior to construction.
Peat is often found in areas such as bogs and other wetlands and consists of decaying vegetation and/or organic matter. It can hold a large amount of water and is considered a very poor soil type for a foundation due to how much it can shift around and its low bearing capacity. You can build on peat soil, but the building would be at great risk of cracks or other types of damage.
Like peat, silt is another poor soil option for building a foundation due to its prolonged ability to retain water. This quality causes silt to shift and expand, which does not provide the building any support and puts it under repeated, long-term stress. This can cause structural damage or failure. If possible, construction should be pursued with a more suitable type of soil.]
Effects of Not Considering Soil Type Before Construction
Failing to select the best type of soil for your project can result in immediate or future foundation issues. Make sure you understand the different characteristics of each soil type and prevent possible damage.
There are several factors beyond water retention that builders should be aware of, so it’s crucial that you get an expert opinion.
Contact URETEK for Expert Foundation Repair in Houston
Proper soil knowledge and foundation experience are vital for a building’s structural integrity and safety. If you’re concerned that the type of soil you’ve built on is leading to foundation problems, URETEK Gulf Coast can help.
Contact our dedicated team of Houston foundation repair experts today for a free estimate.
Basic types of foundation
Choosing the foundation is an important and responsible task.
The foundations of the future home should be: solid,
stable, durable and reliable.
It all depends on the right foundation for the house.
There are four main types in construction:
Before you start forming the foundation of the house, you need to study all the criteria and choose the right foundation for your case.
Each type of foundation has its own requirements that must be taken into account:
Ground structure. Prior to construction, it is advisable to call a service that is engaged in geological research. They will take samples and study the soil. After that, the following will be identified: the level of groundwater depending on the season, heaving and the likelihood of subsidence. The level of groundwater must be taken into account. If water is close, it can have a negative effect on the foundation. Non-heaving soils are considered strong.
Foundation load. The load depends on the gravity of the entire house. It is necessary to take into account the bearing area of the entire foundation, the pressure on the ground depends on it. And also take into account the features of the architecture of the building, this is the presence of a basement or basement.
Freezing depth. It is necessary to take into account the structure of the soil and its humidity, the maximum negative temperatures in the winter season and the groundwater index. Swelling of the soil in winter is the main danger for the foundation, the frozen soil begins to increase in volume, thereby pushing it up. High-quality waterproofing and drainage system will eliminate cracking and reduce subsidence.
Let’s analyze the types of foundation in detail.
Pile (screw) foundation suitable for problematic soils:
- Areas with groundwater;
- Areas subject to the force of frost heaving;
- Flooded areas.
Piles are deepened to hard rocks and are securely fixed in them. The upper strapping is possible from a monolithic reinforced concrete tape or from wooden or metal blocks. An excellent option for sites that are on slopes and slopes.
Such a foundation is suitable for frame buildings, wooden and foam – aerated concrete, as well as from SIP panels
Varieties of foundation piles.
Screw piles are steel pipes that are screwed into the soil.
Driven piles – reinforced concrete piles that are driven into the soil.
- Bored piles are made from concrete in pre-drilled holes in the ground.
Strip foundation – suitable for most types of soils and buildings. High bearing capacity, as well as uniform distribution of loads from the building to the soil base, is one of the main advantages. And also, durability, subject to high-quality work on hydro-thermal insulation. It is also suitable for the construction of houses with a basement.
In construction, the following types of strip foundations are most often used:
Monolithic foundation – consists of a solid layer of concrete and reinforcement, which is interconnected along the contour.
Prefabricated foundation – mounted on the principle of tape, they are only made up of FSB blocks.
The tiled foundation is a solid, monolithic slab over the entire area of \u200b\u200bthe building, which does not require much penetration into the ground. It is considered the most durable and reliable. It is also called “floating” because of the ability to maintain integrity when the ground is displaced, preventing damage to structural elements.
Important! For a strip foundation, a sand and gravel cushion is required, which redistributes the load from the house to the ground, and serves as a “shock absorber” during frost heaving. Suitable for unstable, loose soils or clays with a large freezing depth.
Pillar foundation – built for small, light buildings. Baths, sheds, garages and temporary buildings, as well as for terraces, gazebos. awnings and verandas. In some cases, it is possible to use for frame houses.
The foundation of this type consists of supports with a small recess in the ground no more than 1.5 m, mainly 0.5-0.7 m. Support pillars are installed at all corners of the building and in places of load-bearing walls and partitions. If the structure exceeds the length of 3-3.5 meters, then additional pillars are installed.
Such a foundation is also used in conditions of frost heaving.
The material for the construction of this type of foundation is concrete, brick, concrete blocks and rubble stone.
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Selection of foundation according to the type of soil | LLC “Gestion Group”
To build a foundation for a house, it is necessary to carefully examine the soil and study its characteristics. The choice of foundation will depend on the nature of the soil on the site.
Different types of soil have different bearing capacities. The bearing capacity of the soil determines how many years the house will stand without being exposed to groundwater, frost heaving, shrinkage and deformation.
The foundation for the house is chosen according to the following criteria:
- type and size of the building;
- soil characteristics;
- groundwater level;
- degree of frosty heaving.
All types of soils are divided into the following groups:
- Stony and rocky;
- Loams and sandy loams;
- swampy soil.
- 1 General characteristics of soils
- 2 Basic types and brief characteristics of foundations
General characteristics of soils
containing soil elements. These soils are not subject to heaving, as there is no water in them. Rocky and stony foundations do not change their properties and are considered ideal for laying the foundation.
Cartilaginous soil includes a mixture of stones, clay and sand. Any kind of foundation on cartilaginous soils will stand for more than a decade, it is not exposed to water.
Sandy Soil consists of granular sand that is permeable to water and compacted during construction. The foundation on coarse-grained sand does not freeze. The depth of freezing of sandy soil reaches 1 meter.
Clay soils contain a lot of moisture, are subject to soaking and severe heaving. In the cold season, clay freezes by 1.5 meters. The foundation on such soil, without replacing the soil and installing a sand cushion, will quickly collapse.
Loams and sandy loams consist of sand and clay. The soil freezes, retains moisture and becomes very wet if the clay part predominates.
Peat soils are abundantly saturated with water. The groundwater level is very high. Peat bogs lie on drained swamps. The soil is easily pressed through and is able to tighten the foundation.
Swampy soil refers to heterogeneous soil, which consists of peat, sandstone and clay. Such soil has different density and different water saturation.
When building a foundation on swampy soil, a geological study of the soil should be made. The information obtained will help you choose the right foundation.
Depending on the type of soil, the depth of its freezing can reach 2 meters. The more the soil is saturated with water, the more it freezes and swells in the cold season.
- Reinforced concrete.
- Reinforced concrete
Basic types and brief characteristics of foundations
Column foundation is the cheapest and easiest to erect foundation. This type of foundation is erected under light frame houses made of wooden material. The presence of a cellar and a basement on such a foundation is not provided.
The construction of the columnar foundation consists of pits that are drilled on the site. A reinforcing cage is installed in the resulting pits and a concrete solution is poured to the level of the base. To bring the pillars above ground level, formwork is installed and pillars of the required height are cast. Posts are placed in the corners and at a width of 1.5 – 2 meters from each other.
Recently, TISE technology is used for columnar base.
Its meaning lies in the fact that the pits are expanded to the bottom, and then reinforced and poured with concrete. This technique is used to strengthen the bearing capacity of the pillars.
Installation of a columnar foundation takes place on light soils that are not subject to heaving and shifts. The use of pillars on an unstable foundation will lead to loosening and destruction of the foundation.
A columnar foundation with a grillage is made according to the same technology as a classic columnar foundation, but additionally strengthened by bandaging.
Bandaging will complicate the process of laying the foundation, but will allow building a building from heavy materials (concrete, brick).
A grillage is installed with a slight penetration into the ground on a sand cushion and a single reinforcement of the pillars and the grillage is carried out.
The deep strip foundation is the most reliable.
Its laying is carried out at a depth below the level of soil freezing.
This foundation is erected if it is planned to build a basement. A deep foundation is used on any soil due to its high reliability and holding a building of any weight.
Shallow strip foundation is a monolithic reinforced concrete structure (at least in terms of ground level) and a brick superstructure. The depth of the tape is 50-70 cm, sometimes less. A sand cushion 20-30 cm thick is arranged under the tape. With good moisture insulation, it is possible to equip at least a subfloor, and sometimes a cellar inside the foundation perimeter.
Such a foundation makes it possible to use concrete hollow slabs as floors and to erect any low-rise building. But such a base on clay or sandy soil will crack and settle unevenly.
Monolithic foundation is the only possible type of foundation on peatlands and unstable ground. The construction of such a foundation practically does not require any excavation, except for filling a sand cushion 20-30 cm. Then a monolithic slab is cast on the cushion to fit the size of the house or a little more. The house, as it were, floats on such a foundation and the state of the soil has little effect on its stability. A monolithic slab on such soils does not collapse and is not subject to heaving.
Such a foundation is very inexpensive precisely due to the exclusion of earthworks. The only restrictions are that the site should not have a strong slope, because the pillow will slowly slide off. In addition, you will have to forget about the basement and cellar.
If a basement is still needed, then they do it like this: a foundation pit is dug to the required depth. At the bottom of the pit, a pillow of sand and gravel is arranged and a monolithic slab is cast. On the slab, they are erected from blocks or by monolithic concreting of the basement walls. From the outside, they are carefully waterproofed.