Over time, the owner of a private house or cottage may need to expand the total area of home ownership. The extension to the house is a full part of it. The construction of the extension begins with the construction of the foundation. Before you start pouring the foundation for the extension with your own hands, you need to go through several stages of building the foundation.
Choosing the type of foundation
The type of foundation is determined based on the total weight of the extension, the composition of the soil base, the depth of freezing and the level of groundwater. Consider the main types of foundation structures.
Strip foundation
According to the depth of laying, the foundations are divided into shallow and deep.
Shallow foundations are designed for houses made of light structures, in the absence of a threat of heaving of the soil. The shallow foundation is a monolithic reinforced concrete beam on a sand cushion with a continuous reinforced belt. When building such a foundation, a mandatory drainage device.
The sole of a deeply laid base is below the freezing depth in order to avoid the occurrence of deformations from heaving of the frozen soil.
The concrete strip foundation in its design can be monolithic, prefabricated and combined.
Tape monolith made of reinforced concrete is the most durable and reliable foundation.
The prefabricated base is erected from prefabricated reinforced concrete blocks, beams and slabs.
Combined structures are built from ready-made factory blocks and concrete. This type of foundation is used for a complex configuration of the house in terms of.
Pillar foundations
Columnar supports are brought under light extensions. Pillars are placed in all corners of the base plan, at the junction of load-bearing walls and at points of load concentration. The distance between the centers of the pillars is from 1.2 to 2 meters. Between the supports, a strapping (reinforced concrete or metal rand beams) is made from above, connecting the entire structure into a single support system.
The laying of pillars brings significant savings in materials compared to a tape monolith.
Pile foundations
Screw piles are sometimes used for outbuildings. Screw piles are metal pipes with large threads cut or with blades at the lower end. The process of installing supports is similar to screwing a screw into a tree.
The advantage of mounting such a base is a quick installation that does not require excavation and concrete work.
Bored piles
A reinforcing cage is inserted into the drilled holes in the ground and poured with concrete. Such supports are called bored piles.
The complexity and high cost of the work determine the feasibility of using bored piles on loose and flowing soils, where the installation of other foundations is impossible.
Slab foundations
The foundation slab is made in the form of a monolithic platform or from intersecting monolithic tapes. Such foundations are erected on all types of soils. A monolithic reinforced concrete slab is a structure with powerful spatial rigidity. On uneven, highly compressible soils, only this type of foundation is laid.
The advantage of a monolithic reinforced concrete slab is its versatility, reliability and independence from the level of groundwater.
Such a construction of the base on the ground with a slope of a height difference of more than one meter is not used.
Preparation for pouring the foundation
After the owner of the house has opted for one or another type of foundation, he does the axial marking of the base of the extension with his own hands. Then they carry out earthworks, the device of a sandy, crushed stone pillow. A waterproofing layer is laid on the pillow in the form of two layers of roofing material or one layer of a polymer film.
The width of the trenches and the outer boundary of the pit should be wider than the foundation as much as it would allow for the installation and dismantling of the formwork without hindrance.
Formwork can be made of wooden panels, metal panels and other materials. They carefully check whether the verticality of the formwork walls is maintained correctly, the reliability of fastening stops, clamps, spacers, ties and other fasteners. Correctly exposed formwork should not have gaps. Carefully look through all the connecting seams. If gaps wider than 4 mm are found, they are immediately closed.
Any leakage of concrete mixture from the formwork can significantly weaken the foundation. Properly executed geometry of the fence allows the difference in the length of the diagonals between the opposite corners of the formwork to be no more than 20-30 mm.
Before pouring concrete, check the integrity of the waterproofing surface. The internal space of the formwork is cleaned of debris and foreign objects. The installed reinforcement frame must not come into contact with the formwork surface. To do this, special clamps are installed at the points of conjugation of the reinforcement elements with the fence.
Preparation of concrete mix for pouring
In order to correctly fill the formwork, the developer needs to organize the process of preparing the concrete mix and its continuous supply to the unloading points. Watch the video on how to properly prepare the concrete mixture.
If an extension of small size will be built by hand, then, depending on the volume of concrete work, one or two concrete mixers can be installed. In the case of a very small size of the base, you can get by with a construction trough or any suitable container and improvised tools.
The owner of the house needs to know what brand of concrete he will prepare with his own hands. Therefore, it is necessary to prepare a supply of cement, sand, solid filler (crushed stone, gravel) and a container of water. Determine how many materials will be needed for one batch.
Pouring the foundation for an extension
Consider the process of pouring concrete into the formwork of a strip foundation for an extension with your own hands.
Filling should be done by at least three workers. Ready-mixed concrete is loaded into the formwork in layers 200 mm thick. Each layer is compacted with a hand vibrator or, in the absence of such, rammed with a piece of reinforcement or a similar device. They tamp until "cement milk" appears on the surface of the concrete. Under the influence of the vibrator, the concrete is evenly distributed over the entire volume of the formwork, allowing the air to escape. Watch the video on how to fill the foundation tape.
If we allow the presence of air sinuses in the body of concrete, then this will entail a loss in the bearing capacity of the foundation and the appearance of deep cracks in it.
Filling is carried out continuously and at one time. A break in work can be allowed, but not more than two hours.
Curing
Properly organized care of hardening concrete will not allow the monolith to lose its bearing capacity due to increased evaporation of moisture from the concrete surface or freezing of the base mass for the extension.
In the summer, concrete is covered with a moisture-proof material and periodically moistened.
In winter, measures are taken to heat both the side surfaces of the formwork and insulate the upper surface of the concrete.
Is it necessary to combine the foundations of the house and extensions
The owner of the house definitely needs to know what type of foundation his house has, what brand of concrete was used for pouring, what quality the soil foundation of his dwelling has. If the owner of the house is not the first, then he may not know anything about the condition of the foundation. Then, if possible, you need to dig a small hole in the place where the foundation is laid and analyze the nature of the foundation, the depth of its laying, the amount of its settlement for the entire period of operation of the building.
For example, a house stands on a reinforced concrete base of a tape type - shallow. The settlement for all the years of the existence of the structure is insignificant.
In this case, lay the foundation of the extension similar to the foundation of the house. At the junction of the bases, the ends of the old monolith are exposed and connected from the extension with the bare reinforcement of the old tape. The extension and the house will behave as a single integral structure.
When laying a stand-alone tape monolithic base, it is necessary to arrange expansion joints, both at the junction of both foundations, and along the entire transverse perimeter of the connection between the structures of the extension and the house.
Also come in the construction of foundations of other types.
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