To the beginning
The same problem can be solved in another way. So, as shown in Figure 7. Here the heaving forces do not act on the base of the foundation. This is achieved by the fact that the support is located below the level of soil freezing. However, there remains the danger of pressure on the foundation of the lateral grip forces. How to get rid of them can be seen in Figure 8. In this case, the lateral adhesion force is practically equal to the load created by the weight of the building, since there is non-porous soil around the foundation (in this case, coarse sand).
To reduce the effect of lateral adhesion forces on the foundation, its side walls are coated with greases. A layer of grease isolates the foundation from the soil, and the heaving effect does not occur. The treated surface must be covered with a thick plastic wrap, isoplast, roofing material. And this coating is securely fixed to the foundation. Otherwise, the grease will mix with the soil, and then, as they say, start all over again. Also, care should be taken that the grease is not absorbed into the foundation material. For this, the walls of the foundation must be painted with waterproof enamels before applying the lubricant.
It should be noted that after the foundation supports have been installed, they must not be left unloaded, since they can be displaced under the action of lateral adhesion forces. In an extreme case, around the foundation it is necessary to arrange a reliable heat-insulating coating of sawdust, slag, expanded clay and other materials that can protect the soil from freezing. In order to avoid the action of lateral adhesion forces, a shallow foundation must not be built on a frozen base.
But what to do if cracks or distortions still appear in the house or building? How can these destructive forces from swelling of the soil eliminate or at least slow down their action? The first step is to install reliable metal tightening strips or corners on the cracks (Figure 9). This is often very helpful.
I have been observing a multi-storey residential building with cracks in the walls for several years. It is on them that the tightening strips are installed. And I must say that over the years the cracks have not widened at all. The installation of the tie strips is perhaps the most radical attempt to prevent the walls and foundations from collapsing. Other measures mainly serve to weaken the action of the heaving forces as much as possible.
You can, for example, pour soil around the house (Figure 10). Or dig a ditch around the house 1.2-1.5 meters wide and up to 0.8 meters deep and replace the heaving soil with gravel or coarse sand (Figure 11). Practice proves that such a replacement can reduce the freezing depth to 40 centimeters.
In addition, it is possible to lay a heat-insulating gasket about two meters wide from a mixture of slag and coarse-grained sand to a depth of 20-40 centimeters (Figure 12). The layer of this mixture should be at least 20 centimeters, and it is laid on top of the same gravel and coarse sand 20-30 centimeters thick. It turns out, as it were, the reinforcement of the lower layer by the upper one. This makes it possible to reduce the freezing depth by 0.5-0.7 meters.
It is even desirable to build around the house a so-called "vegetable" protection against deep freezing of the soil. To do this, the thickest layer of turf is laid around the house and bushes are planted. They will retain and accumulate snow around them, thereby forming a thermal cushion, which significantly reduces the depth of soil freezing in comparison with snow-free areas.
Just remember that you cannot shovel snow from the house in winter. Except, of course, the tracks to it. They are small enough, and therefore do not have a significant effect on the freezing of the surrounding soil.
To lower the groundwater, drainage ditches are very useful. They are dug out on both sides of the house in the direction of the general lowering of the site. Or sent to drainage wells, which are located as far from the house as possible. At the bottom of the ditches, pieces of asbestos-cement pipes or other available drainage materials are laid. For example, various construction waste, broken bricks, crushed stone, small stones. After that, the ditch is covered with earth.
Of course, the most reliable of all is a properly arranged, buried foundation, laid below the level of freezing of the soil. This is a very reliable foundation that can withstand almost any deformation movement of the soil. However, its device is associated with a large volume of work, and, consequently, with a high cost. That is not always affordable for a summer resident.
But in any case, when constructing a foundation in heaving soils, both a substantiated technical solution and its impeccable practical implementation are required. Only then will it be possible to avoid the destructive phenomena associated with the deformation of the swollen soil.
Therefore, when starting construction on heaving soil, one must always remember this.
Alexander Nosov, jack of all trades
Let's see what a shallow strip foundation is?
This foundation is a subspecies of tape and can be either monolithic or prefabricated.
Its main difference is that the base of the foundation is located above the freezing point of the soil. The shallow belt is mounted on sand and gravel preparation at a depth of only a few tens of centimeters
Such foundations attract with their price, which is several times lower than their counterparts, buried to a depth of 2 meters. However, this also causes its main drawback. If heaving of soils occurs under the foundation, this will lead to a violation of its geometry and integrity. The walls of the house will suffer the same fate.
Due to the shallow depth of the foundation, as well as the small amount of excavation and concrete work, the shallow strip foundation is simple and quick to install. However, in most cases, the surface location requires the adoption of measures against heaving of the soil, such as insulation and drainage. It is also possible to build such a foundation with a complete replacement of heaving soils under it with non-heaving soils to the depth of freezing
A shallow foundation shows itself perfectly in warm areas where the soil does not freeze, or on non-porous soils (rock, hard clay, sand). In areas with freezing soil, a shallow foundation requires mandatory drainage, as well as insulation and the presence of an insulated blind area. Thermal insulation prevents the soil under the foundation from freezing and pushing it up.
Pros and cons of a shallow strip foundation:
* Low construction cost
* Possibility of self-production
* Not suitable for all types of soils, on heaving soils requires mandatory insulation
* Even with insulation, the soil under the house, left for the winter without heating, can freeze and damage the structure
* In most cases, low bearing capacity due to bearing on the upper weak soil layers
Shallow tape is suitable for not very heavy houses. These can be one or two-storey wooden or frame buildings, as well as houses made of foam blocks, wood concrete and similar materials. For the construction of heavy brick buildings with reinforced concrete floors, this foundation is not always suitable.
Conclusions. On bases with good load-bearing capacity, strip foundations are suitable for any home. If the groundwater is located high, then the foundation will require reliable waterproofing, and therefore will be more expensive.
For light houses, it is cheaper to make a pile foundation rather than a strip foundation. Shallow foundations are cheaper, but they are only suitable for houses with a low mass and require insulation on heaving soils. If you need a house with a basement, then tape is ideal.
Despite the fact that there are a large number of different foundations, a strip base is most often laid under private houses. It is easy enough to build it yourself, without the use of technology and with minimal knowledge in this area. Such a base will become a reliable support for a wooden, brick or stone structure on different types of soil, and step-by-step instructions will enable anyone to do all the work with their own hands, efficiently and without errors.
Diagrams of the device of unburied monolithic and precast-monolithic foundation slabs.
The design of a reinforced concrete monolithic slab refers to one of the options for the construction of a shallow or shallow foundation.
A shallow foundation is used for lightweight buildings, the installation of which is made of wood or foam concrete, small brick or frame buildings. It is advisable to use it on slightly heaving soil. A shallow foundation slab is laid about 50-70 cm deep.
Heavy houses with bulky floor slabs are built on buried foundations. This type of base is used on heaving soils, as well as in the case when it is planned to equip a basement or basement in the house, for example, for a utility room or garage. The foundation is deepened 20-30 cm deeper than the soil freezing mark. Dwelling on such a design, it should be understood that its device will entail a large consumption of materials and labor costs.
Diagram of the foundation slab device.
What is a monolithic slab? This is a slab of reinforced concrete, under which a cushion is laid from a layer of tamped rubble or sand 10-30 cm. The crushed stone cushion is placed on the mainland soil, in another way - the earth, which was not subjected to mechanical stress (loosening and digging).
Often a concrete slab is 20-40 cm thick. In addition to a monolithic slab, precast reinforced concrete from several slabs (for example, road slabs) is allowed. They provide for the installation of a concrete or cement leveling screed over the slabs.
However, a monolithic foundation, representing a device of one slab, is more reliable and durable in operation, since it has a high spatial rigidity, in comparison with a precast type foundation made of many slabs. In addition, the cost of the device and installation of a monolithic foundation on site is significantly cheaper than the purchase, delivery and installation using a crane of road slabs and the installation of a cement screed on top of them.
If you decide to attach a veranda to a wooden house, you can put a columnar foundation. To do it yourself, you need to find out at what depth and at what distance the supports are placed. The distance between the posts depends on the material from which the extension will be built. If these are light materials - wood or light frame construction - you can put them in 1.5 meter increments. For heavier ones, the distance should be from 1 meter.
Columnar foundation for the veranda - the pillars are made of bricks. This open veranda is attached to a wooden house. The house stands on a strip foundation. The foundations of the extension and the house are not connected
When choosing the depth of the posts, there are two approaches:
Let's go through the construction of a veranda in a wooden house with our own hands step by step. It should be noted that the extension to the house can be started only after its complete shrinkage. Log houses, or made of timber, sit down actively for three years, during this period it is better not to build an extension, otherwise the walls may be skewed. Experienced builders recommend, for those who do not wish to wait, to build a transitional structure of the veranda with the house, which allows the frame to play.
The rebuilding of the house must be reflected in the permits. To obtain these permits, you must contact the regional department of architecture and submit the documents:
It is advisable to start drawing up documents for a construction permit 3-4 months before the start of work. From the generalized experience of private developers, this is a lengthy procedure.
It is possible to build an extension without permits, but in this case, problems may arise when the house is inherited or you want to sell it. The reason lies in the change in the total area of the house, since the veranda is part of it, and the total area of the residential building is considered with it. The BTI department can consider this as an unauthorized decision to increase the area for housing. This is especially appreciated when the terrace is covered with heating.
No need to get carried away and make deviations in the dimensions of the terrace, which are indicated in the project. A simple check will easily find out, and a fine will follow with correcting the documentation. For what unauthorized developers can expect to join the veranda to the house, it is indicated in the law of the Russian Federation.
Bored foundation is one of the types of pile foundation. Its design is quite simple: boreholes are made in the ground with a depth of about 1.5 m.The exact value depends on the characteristics of the soil and the climatic zone.
Further, reinforcement is installed in the resulting wells and poured with concrete.
A bored foundation can be ordinary, where a bath is built directly on piles - this option is cheap and simple. But if you need a more reliable foundation, then in this case, preference is given to the pile-strip or pile-grillage foundation. It implies a rigid connection of individual piles with a concrete tape (grillage). The main advantage of such a foundation is that the load between the piles is distributed more evenly, which makes the structure reliable and durable.
The bored foundation is used for the construction of lightweight buildings, in particular, wooden and frame baths. If you strengthen the foundation with a grillage, then it will withstand higher loads.
The use of a bored base will also be relevant if construction is planned not on a flat surface, but on a site where there are strong differences in height.