Foundation for a two-story house: calculation of depth, thickness

The foundation in construction is the basis for a strong and durable house, resistant to weather and seismic conditions. The durability of the entire structure depends on the features of its execution, materials and quality of materials. Next, various types of foundations will be considered, recommendations regarding calculations for installation, depth and width. Recommendations will be given, thanks to which the client will be able to decide which type of foundation is right for him.

Types

Foundations may differ in the materials used for their construction, depth, as well as the method of execution. It is according to the method of execution that they are divided into types:

• The columnar type is almost universal, it justifies itself well as the basis for any panel houses or townhouses. The installation of pillars takes place in special pre-drilled holes, which are made around the entire perimeter of the building. The distance between the supports is calculated individually. For supports, natural log materials, natural stone and artificial components (pipes or reinforced concrete stepchildren) are used.
  

• The pile foundation differs from the column foundation in the length of the elements and the principle of operation. In a columnar house, the mass of the house falls on the sole, and in a pile, on the side surface. The pile is good because it allows you to exclude the deformation of various parts of the building due to the uniform distribution of the load of the entire structure, and this prevents its deformation. Such a foundation can be of two types: hanging or retaining.
  

  In the first type, piles are driven directly into the ground, where the load is concentrated: corners, wall intersections. The length of such piles can be several meters. This is due to the fact that the main load is transferred to the lateral part of the support. 2. The retaining type of foundation is installed at a shallow depth, but at shorter intervals than the hanging one. Whether it is worth making a pile foundation for a two-story house is determined by several parameters. The main parameter is the type of soil, the second is the material of the house.

• Strip foundation – the most convenient type for the construction of small houses. For its installation, a block type of bookmark or a solid concrete tape is used. This design is simple and not subject to destruction. Base blocks can be filled or lightweight (hollow), depending on the requirements of the whole structure. Its advantage is that aerated concrete houses built on such a foundation are durable and resistant to soil movement. In addition, the strip foundation can be installed at a minimum depth, which makes the construction independent of geodetic indicators.
  

• The monolithic slab is characterized by seismic resistance. This is a one-piece platform with a large area, the height of which is calculated relative to the conditions of the area of ​​​​the future construction. This type of foundation is the most resistant to soil displacement and the most costly in terms of concrete consumption.
  

The choice of a specific type of foundation for a two-story house depends on the wishes of the client, the characteristics of the area and the architectural plan. But at the same time, there are recommendations regarding the choice of the best option, in terms of durability, ease of installation and saving the budget.

Which is better

The optimal choice of foundation for low-rise construction consists in a detailed analysis of many indicators of the object, as well as the features of the area where the house will be installed.

Pile and columnar structures are used for construction, but they have not proven themselves enough in terms of practicality and durability. A monolithic slab is relevant for the construction of both one-story and two-story houses, which are built on landslide soils or in zones of movement of the earth’s crust.

In areas with stable seismic activity, a monoplate is a very costly method. Practice shows that for a two-story brick house, tape technology is the best choice. And also the installation of foam block houses on a strip foundation is gaining great popularity, since it has a number of advantages:

• resistance to various deformations (cracks, tears, shedding);
• ease of installation and ease of maintenance;
• high bearing capacity and operation;
• variety of layouts.

The listed advantages are possible only if the installation technology is observed.

Foundation calculation

Calculations are made according to certain formulas, the material and features of the house are taken into account, as well as a number of geodetic factors. The dimensions of the foundation for a house made of brick, cinder block or concrete will differ, since the masses of materials are different and exert different pressure on the ground.

simple calculation

Without taking into account additional individual features, the installation depth of the foundation can be calculated using the standard formula, where 0,8 meters must be multiplied by the number of expected floors – a total of 1,6 meters.

The thickness of the foundation in the classic version is equal to the estimated thickness of the bearing walls plus 15 cm. However, it is worth knowing some parameters that can change this indicator:

• looseness of the soil;
• sole area;
• total weight of the structure.

Exact Calculation

For a more accurate calculation of its depth, you need to know:

• Type of soil (sandy, clay, sandy loam).
  

  

• Soil freezing point. It must be known so that deep freezing of loose and moisture-filled soil does not destroy the foundation. However, if the building is being built on fairly dry land or slightly heaving, this indicator does not matter.
  

  

• Height of aquifers. In a situation where the aquifer is located close to each other, its depth should be minimal for the purpose of waterproofing.
• Accommodation in the house.

The depth of freezing of the soil of your zone is taken as the basis. To this value you need to add 150 mm if the house is wooden or 350 mm when it is brick.

Let us first calculate the depth of a one-story house. We take the freezing depth in the Moscow region with fine sand soil. It is 1,34 m. The house will be brick, so add another 35 cm and get 1,69 m.

There is a relationship between the depth of the foundation and the temperature in the room. This dependence is expressed in coefficients and is given in the table. According to it, the higher the temperature in the house, the less deep you need to do.

We will have a floor on logs on the ground with a temperature of at least 20. From here we get 1,69 * 0,6≈1 meter. It is enough to deepen the foundation by 1 meter.

Now for the two-story. The mass of the house will be almost 2 times greater, so it must be stronger. According to the rule written above, the depth should be 1,6 meters. And this is below the freezing point, which is quite satisfactory.

Installation of strip foundation

When choosing the basis for a two-story house, it is recommended to take into account the complexity of installation and material costs. The most convenient, economical and durable option is the tape type. Before installation, it is necessary to calculate the width of the base, as well as the thickness, which directly depends on the material used. Reinforced concrete has the smallest width, then concrete, and the widest base must be made for natural stone, which is due to the weight of the material.

Deepening depends on the type of material of the future structure and correlation with the freezing point of the soil. The height of the foundation varies from the individual needs of the customer and his preferences. If there is a threat of flooding naturally the height must be increased.

There are standard standards that offer a height of 35-40 cm for wood, and 20 cm for brick and aerated concrete. In addition, it is recommended to add another 10 cm to the height of the snow cover, which is the most typical for the construction site.

The main stages of installation of the strip foundation:

• a preliminary drawing is made;
• trench marking and digging;
• laying the pillow, moisturizing it, and tamping;
• reinforcement is made;
• formwork device;
  

  

• pouring concrete;
• drying.

Reinforcement is the main stage in the strip base, since it is the reinforcement frame that creates a strong structure. Usually rods with a diameter of 12–16 mm are used. The interval between the bars is about 30 cm and may vary depending on the individual indicators of the building.

Filling must be carried out in one or a maximum of two stages in order to maintain the solidity of the structure. With manual mixing or using a private concrete mixer, this is difficult to achieve, so it is better to resort to factory concrete. After the final pouring, a high level of insulation must be ensured. The pillow can be made of sand, gravel, their mixture or concrete, which justifies the density of the soil.

Errors in the construction of foundations

Mistakes made during construction can lead to the complete destruction of the building. For those who want to strengthen the foundation on their own, seek to save money or want to hire a team of specialists, while not understanding anything in construction, the most common mistakes when pouring the foundation will be listed below.

By choosing construction according to a standard project, the customer usually saves time and money on the development of unique drawings. But at the same time, keep in mind that there is no data on the type of soil, its freezing, the horizon of groundwater. All indicators are directly related to the installation depth of the main structure, which must be calculated immediately. This is the first technically possible mistake, the following bad ideas during construction are also possible:

• Savings on material. Usually leads to the rapid appearance of cracks, after which the entire foundation will begin to crumble. A cheap brand of concrete for the foundation of a two-story house is not suitable, since the base made of it, having collapsed, entails the destruction of the walls and the entire structure.
• Wall laying and installation of any load-bearing structures earlier than 4 weeks after pouring the base. Without waiting for the concrete to fully set, the construction of the entire box of the house takes place on a movable base, which ultimately leads to its destruction literally immediately after construction is completed.
• Lay a concrete strip around the entire perimeter of the same width and thickness, without taking into account the internal features of the house. This creates an uneven load, and, accordingly, different shrinkage at various points in the building. The thickness at each specific point should be calculated depending on the thickness of the walls, their location and purpose in the supporting structure.
  

  

• The use of boards from unfitted boards for formwork leads to the fact that liquid flows out of the concrete through the cracks. Subsequently, this leads to the delamination of concrete, a decrease in its strength and further destruction of the house.
• Replacing the factory fill with a batch manually stretches the time and the canvas itself becomes heterogeneous. A strong foundation requires a one-time pour, which ensures its homogeneity and increases the strength. The occurrence of air voids, which leads to the destruction of the foundation, occurs due to poor compaction of the concrete mixture.
• Reinforcement and piles are the supporting frame for the foundation, so its thickness, grade and metal should be selected in accordance with the requirements of the architectural project, without saving.

A common mistake in construction is a careless attitude to the season and climatic conditions. In winter, it is imperative to use specialized plasticizers (anti-frost), and in summer, cover the concrete with polyethylene and moisten with water twice a day to maintain the strength of the material.

Work in construction can be done independently, for complex tasks, professional mixing of mortar and calculations, you should contact professionals. The base must be made of the highest quality materials, in the required quantities. Savings are possible in decoration or design, and so that the house does not collapse, maximum attention must be paid to the installation of the foundation.