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Strip foundation, how to calculate and fill the foundation correctly

Strip foundations are ideal for homes with heavy walls and tile floors. True, this type of foundation is the most material-intensive and requires a lot of labor, in comparison with other types of foundation. And yet it remains the most common and popular in individual construction. Why? This is primarily due to the simplicity of its construction and operational qualities. If done correctly, such a foundation will last for centuries. But what does it mean right? First of all, accurate calculation and observance of construction technology. This will be the focus of our article.

Content

How is the foundation laying depth calculated?

The depth of the bookmark, first of all, depends on the soil, the depth of its freezing and its moisture. The depth of the foundation also depends on the presence or absence of the basement in the project. For example, if you plan to build a small cottage without a basement, you can use a shallow strip foundation. It allows you to reduce the cost of the strip foundation by 3 times. It is also applicable on heaving soils, but for this a complex of land reclamation works will be required, with the required insulation of the foundation.

As already noted, for long-term construction, first of all, the properties of the soil are important:

he must have the appropriate bearing abilities;
he must not hold water.

If the soil has the appropriate properties, it is initially wonderful, if not, we will be forced to give these properties artificially. This is achieved by equipping the drainage system and adding material from such materials as crushed stone, pebbles or coarse sand. Having thus prepared the soil, we will eliminate its tendency to heave. After all, the main reason for the movement of the soil is the moisture that is contained in the ground.

It is generally accepted that the depth of the strip foundation of more than 2.5 meters is economically unjustified. And even then, this maximum value is allowed in houses with a basement. Accordingly, if the soil properties require deeper laying, another type of foundation is needed.

In practice, the following minimum laying depths of the strip foundation are allowed:

on clay soils at least 75 cm;
on sandy and loamy soils from 45cm;
rocky and rocky soil, including artificially prepared up to 45 cm.

Foundation Width Calculation

The main requirement for the width of the foundation is to provide acceptable pressure on the ground. And above all, it will depend on the properties of the latter. Those. the lower the bearing capacity of the soil, the wider the lower part of the foundation should be. In general, the construction of a strip foundation less than 30 cm wide is not allowed, this is the minimum value.

It should be noted that the foundation sole load should not be more than 70% of the nominal soil bearing capacity. The last parameter depends on the type of soil, the diagram below will help determine it.

Having determined the type of soil, you can determine its bearing capacity, the plate below will help us with this.

Now we need to calculate the load at home. To do this, we need to summarize the dead weight of the building, the snow and wind load and the approximate weight of furniture and equipment for the home. We multiply this value by a factor of 1.3.

The dead weight of the building will depend on the material, for example, 1 m * of a wall 380 mm thick of brick will exert a load of up to 750 kgf / m *. We multiply this value by the total wall area.

Next, you need to calculate the load of the floors. For example, 1 m * of reinforced concrete floor (basement or floor) has a load of 500 kgf / m *. This figure is multiplied by the total area of \u200b\u200ball the floors of the lady. Similarly, we calculate the load of the attic floor.

Snow and wind loads can be found on the nameplate below.

It is customary to take the weight of furniture and other equipment for a residential building according to the norms of SNiP, it is 195 kg / m *.

We summarize all the values \u200b\u200band multiply by 1.3 - we get the calculated load.

Next, you need to find out the total length of the tape and convert it to centimeters.

The width of the foundation is calculated as follows: the design load is divided by the length of the foundation and the value of the bearing capacity of the soil.

Foundation height

There are two options for calculating the height of the foundation. The easiest way is English, the ratio of the height to the depth of the bookmark is taken as 1: 1. Those. if the depth of the foundation is 60 cm, then the height can be up to 60 cm.

The second way to calculate the height: the width of the base of the foundation is multiplied by four.

The technology of laying the strip foundation

Consider the technology of laying a monolithic strip foundation for a house on a sandy pillow. The procedure is as follows:

digging trenches;
sanding;
laying waterproofing on a sand cushion (roofing material or reinforced plastic film);
formwork construction;
make reinforcement of the foundation;
pour concrete.

We will not analyze each step individually; instead, we will focus on the most important technological nuances:

all work on the construction of the foundation should begin immediately after excavation of the trenches, otherwise the edges will crumble and water may accumulate in the pit, which is not permissible;
soil that is prone to water accumulation or is easily compressed, must be removed, and instead gravel, coarse sand or a mixture of crushed stone and sand should be filled and compacted;
alignment of the trench is allowed only with coarse sand, but not as soil from the walls of the trench;
the thickness of the sand cushion should be at least 30 cm, or according to the BCH standards 29 85 3: 1, i.e. thickness three times the width of the foundation;
sand for the pillow needs to be moistened to the pit, otherwise we risk washing the bottom of the trench, which is fraught with deformation of the tape;
the thickness of the concrete from the sand cushion to the reinforcement should be at least 70 mm;
works on waterproofing the foundation begin no earlier than 3-5 days, during which time concrete gains 50% of its strength;
to simplify the drainage system, you can do with backfilling with such material as crushed stone, gravel or coarse sand (the width of the backfill should be at least 0.3 meters from the bottom of the foundation and increase in height by the amount of freezing of the earth);
backfilling of such sinuses occurs immediately after the waterproofing and thermal insulation of the foundation.