How to build a new house around an old one: step-by-step instructions. How to attach a foundation to an existing one How to build a house on an old foundation

Increasing the usable space in a private property by adding new premises that stand on their own foundation begins with solving the problem of how to connect the foundation to the house so as not to harm both structures. The construction of additional structures usually begins after several seasonal cycles, during which financial resources have been accumulated, a desire has appeared for a new round of site development, and the standing buildings have begun to shrink normally in the ground. Building codes provide the answer to how to connect two foundations to each other, taking into account mutual influence.

Connection requirements

It is necessary to determine how to connect the new foundation of the extension with a residential building at the design stage, taking into account already existing factors. These include the following incoming conditions:

type and design indicators of the foundation of the existing building;
characteristics of underlying soils;
time elapsed since the previous construction (the main shrinkage occurs in 1 - 2 years);
commensurability of the weight load of 2 structures that need to be combined.

Full requirements for the calculation are contained in the set of rules SP 50-101-2004, which was developed in development of the regulatory rules contained in SNiP 2.02.01-83*, SNiP 3.02.01-87.

In any case, the help of experienced professionals is not superfluous, since mistakes can be costly later.

The result of linking the base and attached building structures with different values of base shrinkage is shown in this video

The construction of a new building begins depending on the season. In the spring, it is not recommended to start laying next to existing foundations, since at this time of year the soils are in the most loose and water-logged state. The settlement value of a new extension on heaving soil may be much greater than the calculated value in the project and may be uneven around the perimeter. At the same time, there is a risk of movement of the undermined old support due to the high groundwater level in combination with possible precipitation (rain or snow).

Before starting work, it is necessary to take into account that any new foundation (MZLF, piles, pillars, slab) will certainly give rise to settlement, even if it is made identical to the existing support.

Shrinkage

In construction, there are established settlement standards for various structures, the foundations of which are designed and manufactured in accordance with current state standards.

You can find out the standard and make a forecast for the design of your individual home using data from the reference tables:

When comparing calculated indicators, a new support unit is attached to the foundation of the old building at a given depth, taking into account its own settlement after a certain time.

The upper marks of monolithic strip foundations of combined buildings are made according to calculation, and not according to level, as in this photo.

It is the possibility of displacement relative to each other that determines what kind of connection between two foundations can be made. The following types of connections are used:

Rigid bond (concrete with reinforcement).
Separate installation (installation of an expansion joint taking into account the mutual influence of the supports).

The possibility of a rigid connection into a single structure is significantly influenced by the geological factors of the site - in case of mobile or heterogeneous soils, for buildings with a large support area, it is necessary to make intermittent foundations (sometimes with different widths of the tape).

Start of independent construction of a new extension module to residential building is permissible if the following requirements are met: issue permits for the installation of a new structure, maintain distances no closer than the minimum permissible to nearby buildings and communications, ensure independent settlement of all structures in relation to each other.

Combining foundations

It is best to attach a new room to the existing foundation of the house using a rigid coupling. In this case (if all conditions are correctly taken into account), it is possible to connect the above-ground surfaces into a single whole without the expectation that gaps and distortions will appear between the elements and the floor level. But such a design solution is limited to sites with non-heaving soils that have high load-bearing characteristics.

In practice, this method is used for low-rise buildings, provided that the extension being built is functionally connected by one roof to the building that is already in use.

Another condition for unification is the same type of foundation. If the strip base of a residential building turns out to be insufficiently wide, then it needs to be strengthened.

Such work includes connecting the reinforcement of an old support with a new frame or laying connecting anchors by drilling, followed by filling the belt with branded concrete. The reinforcement belt prepared for applying the solution is shown in this photo.

The connection of buildings consisting of several floors is carried out according to a more complex scheme, involving the construction of covering walls with dividing seams on each side, as shown in the drawing.

The rigid type of connection is chosen for cases when the problem of how to connect an old established foundation with a new building is considered, for buried strip foundations. The extension is also designed with a monolithic reinforced concrete structure.

Strip foundations

For a permanent premises attached to a house, having a commensurate weight of the used building materials, a stable support of large area and load-bearing capacity is required. This request corresponds in most cases to a strip foundation.

Expose the entire depth of the existing tape. You need to dig a trench in parts (1.5 m - 2 m), not along the entire length at the same time, since the exposed part loses lateral support, which can lead to its deformation. An old building can be further strengthened with inclined supports.
Drill holes along the side of the connection corresponding in size to the Ø of the reinforcement. In the middle of the tape, holes are drilled in a checkerboard pattern with a depth of about 0.75 of the width of the foundation itself, in the corners - 0.5 m. Reinforcement is driven into the middle holes, in which longitudinal slots are made with an inserted wedging liner for strong fastening in the hole. Reinforcement Ø 14 mm, having a periodic profile, is driven into the corner holes. The output of rods must be at least 0.3 - 0.4 m.
The frame of the new foundation is knitted and welded to the released reinforcement.
Fill with concrete mortar.

If there is access to the subfloor for work, the holes for pin-type tension elements can be made through with flat plates fixing the rods.

Rigid connections of tapes in the form of an open contour (U-shaped) are made in the same way, but the reinforcement is placed in rows with smaller spacing. If the connection side is long in the open strip, you can make several additional support points different from the monolith, as can be seen in the photo.

If there is a need to change the depth of support on the soil of the foundation being added, it is filled with ledges, the height of which varies in steps of no more than 0.5 m. The first ledge is located at a distance of about 1 m from the old foundation. The connection is made with a reinforced concrete strip of the same thickness as the existing foundation of the house.

Each option for rigid connection of foundations has its own characteristics for specific cases, which it is advisable to entrust to professionals to consider and calculate.

Plates

It is possible to ensure the rigidity of the connection between the slab foundations of the house and the extension provided that they are sufficiently thick, about 0.4 m, and also if there is a protrusion of the old slab beyond the boundaries of the supporting walls of the building. Such protrusions are usually left during the construction of cottages made of aerated concrete. The outlet dimensions must be at least 0.3 m. This will make it possible to clean reinforcing mesh slabs and make a welded connection with the frame of the new extension.

The connection of monolithic bases is carried out according to the following scheme:

The slab of the old house, which has already settled, in this case not only becomes one with the new fill, but also receives additional reinforcement along the vertical connection cement mortars due to the gravy under it in 0.2 m - 0.3 m.

Separate supports

If there is a large discrepancy in the weight of the old and new structures, the degree of shrinkage of these structures will differ significantly in magnitude. In such cases, it is not recommended to make a rigid connection for the foundations - it is necessary to choose separate construction of the supporting elements. It is possible to attach other types of foundation to the existing foundation and to do this use the principle of connection through an expansion joint.

The weight of the ceilings and walls of the extension should be distributed over its own support area, without creating tearing forces for the main foundation of the building.

Depending on the operating conditions, the expansion joint can be:

sedimentary;
temperature;
seismic.

The sedimentary option (in the absence of other significant influences) has a width of 1 - 2 cm. According to the conditions of the mutual influence of the supports, attachment to the load-bearing wall of an old house can be carried out with a deformation gap reaching 0.2 - 0.4 m, filled with elastic, moisture-proof material.

Frame wooden extensions are successfully operated on a pile foundation with a metal grillage, as in this photo.

Light verandas or summer kitchens can be built on screw piles, even if there are already several nearby buildings around. This is especially convenient if the site is located on a slope, slope or with uneven occurrence of hard supporting rocks.

At the design stage, the external design of expansion joints that visually separate the facade is envisaged in an open or hidden form, for example, hiding the gap with a subvertical drainpipe. On the façade side, they are usually covered with strips of a special flashing and sealed with low-strength decorative material, which will not prevent the outer walls of buildings from moving relative to each other with possible uneven settlement. Under the roof deck, gaps are bridged using a compensation device.

An extension to a house, installed on separate supports, is a much less labor-intensive process than installing a rigid link, requires significantly less time and financial costs, and can also be done with your own hands without ordering special equipment

A far-sighted solution is to provide for the possibility of an extension at the design stage of the main building of a private house. This will greatly simplify subsequent work and will contain ready-made constructive solutions, planned uniform settlement over the entire laying area and will ensure the reliability of the foundation.

Houses are not an easy task, even if the plot of land allocated for construction is vacant, or if the land plot already contains construction projects that the owner does not need. In this case, building a house is complicated by the need to resolve legal issues and overcome a number of technical obstacles.

Quite often there is a situation when, instead of an old house or cottage, it becomes necessary to build a new one. In particular, a house with a plot can be inherited, and you may be faced with a solution to the problem - stay in the old house with stove heating or build new home with all the attributes of civilization inherent in modern construction - running water, a full-fledged heating system and gas.

If old house does not fit into the idea of comfortable ideal housing, it would be more reasonable to take up the issue of building a new one. However, a number of questions immediately arise before the developer: is it worth reconstructing or is it better to demolish? Is it possible to leave the old foundation? Is a demolition permit required in this case? How to coordinate a new building with the BTI?

First of all, before building a new house, it is necessary to understand the condition of the foundation of the old building, for the examination of which you need to invite specialists. The assessment of the old foundation is carried out according to several parameters - optimally withstand loads, compliance with the parameters of the planned house, soil properties, technical condition already existing foundation. A high-quality monolithic reinforced concrete foundation, even if its service life exceeds thirty years, does not require reconstruction in most cases and is suitable for the construction of a new house.

However, often houses that were built thirty years ago are on dilapidated foundations. According to expert reports, construction houses at that time it was carried out mainly using standard methods, which were far from modern ones. Plus, high-quality concrete was in short supply and most technologies low-rise construction was not followed. In order for a competent specialist to say for sure whether the foundation of an old house will be “livable” or not, it is necessary to conduct a minimal study of it.

Of course, the services of this specialist will cost the future developer a certain amount, but if the result is successful, the developer will be able to save on the construction of a new foundation.

If a decision is made to build a new house on the site of an old one, it is necessary to check the land documentation. Even if you plan to build a house in the same place, there is a possibility of getting into trouble with the law, because land plots and houses built or purchased before the nineties were often not registered. According to experts, from the legal side, it is possible to build a house on the site of an old one only when the land is recognized as the property of the developer. Even if the land and object were inherited or donated, there should be no problems with registering the site.

According to experts, before building a house, many people prefer not to obtain an official demolition permit, and carry out demolition and construction under the guise of reconstruction or major repairs. The reason for this is the complex points in the design of some issues, which are related, in particular, to the communications connected to the old house and the subsequent requirements of utility services for their reconnection.

Register the construction of a house on the site of the old one as “major” repair“or “reconstruction” is possible, but it is necessary to deal with the assigned tasks step by step and very carefully. It is advisable to replace the concepts only within a strictly limited framework, without exceeding the parameters of permitted construction established by law.

For most developers, all the requirements and instructions are too complex, so they completely demolish the old buildings along with the foundation and build a new house on this site, applying for a regular building permit.

Demolition clearance is another step that needs to be addressed before preparing for construction. The peculiarity of this procedure is that first you need to carry out the actual demolition and only after that, in order to draw up an act, contact the BTI.

The demolition of an old house from the technical side should be carried out as follows - the building must be demolished down to ground level, otherwise, demolishing the foundation can cost the developer a pretty penny. The need to dismantle the underground part arises only when the construction of a house will be carried out on the site of the old one.

I join you, because I myself took up such a reconstruction. During reconstruction, they really say, there is less running around while it’s still in progress.
Reconstruction is a change in the parameters of capital construction projects, their parts (height, number of floors (hereinafter referred to as the number of floors), area, production capacity indicators, volume) and the quality of engineering and technical support.
Obtain a construction permit from the local government for the purpose of reconstructing the individual housing construction project. It is issued upon application and attached documents of title to the land plot, an urban planning plan for the land plot, a diagram of the planning organization of the land plot indicating the location of the individual housing construction project (Part 9 of Article 51 of the Town Planning Code)
Implementation of preparation project documentation When reconstructing an object, individual housing construction is not required.
After obtaining a building permit for the purpose of reconstructing a residential building from the authority local government it is necessary to contact the organization for technical inventory (for example, the Federal BTI) at the location of the residential building in order to carry out its technical inventory, certification and technical registration. (This organization must provide title documents for a residential building and land plot, cadastral passport of the land plot, building permit, urban planning plan of the land plot, planning organization diagram of the land plot indicating the location of the individual housing construction project).
To register an individual housing construction project with the production of technical and cadastral passports for such an object, obtaining permission to put the object into operation is not required; the decision on the completion of the construction of such an object falls within the competence of the OTI, which carries out technical inventory, certification and technical registration of the object.
Based on the results of the technical inventory of the reconstructed facility, a technical passport is drawn up. Based on the results of technical registration, a cadastral passport of the real estate property is issued, which allows you to re-register the ownership of the residential building reconstructed by him on this land plot in the Unified State Register of Rights to Real Estate and Transactions with It.
Construction - erection of a new one... This means that it will be necessary to obtain permission to demolish the old building, liquidate the ownership of the old (demolished) building, and then again apply for a building permit, with all the consequences...
I personally contacted the architecture department with a question - reconstruction or construction, If there reside? I was surprised by the answer - “building permit!”
In general, I have submitted an application for a town planning plan and am waiting.

The safety of a private house or any other building in many cases is determined by the reliability and strength of the foundation. During the long-term operation of a building, even a well-built foundation can gradually collapse. This is evidenced by the appearance of numerous cracks on the load-bearing walls, their subsidence, the distortion of window and door openings of the house, and changes in the geometrically correct shapes of the corners. When identifying the first signs of a violation of the integrity of the building, it is necessary to immediately begin strengthening the foundation. However, even in the early stages of its destruction it is not always possible to do simple preventive repairs. Quite often, the nature of the deformations forces one to resort to a radical reconstruction of the old foundation, which involves either its complete replacement or the construction of a new underground structure around the perimeter of the house.

Causes of foundation deformations

Restoring the foundation of a structure is impossible without identifying the reasons that led to the loss of the bearing capacity of the foundation. Otherwise, the forces spent on reconstruction and material resources may not only not give the desired result, but also aggravate difficult situation. Among the variety of factors that most often lead to the destruction of the foundation, experts note the following:

errors in the initial design, inaccuracies in calculating permissible loads, non-compliance with technology and construction rules;
disruption of the normal operation of the building due to redevelopment, increase in number of storeys or construction of additional extensions;
the use of low quality building materials, or materials not intended for its construction;
ground vibrations near railway tracks, highways or multi-storey buildings under construction nearby;
rising groundwater levels;
incorrectly selected calculated depth of soil freezing;
a change in the ecological situation, provoking a change in the composition of the soil, as a result of which the foundation is exposed to dissolved in groundwater chemically aggressive substances;
loss of soil bearing capacity caused by regular flooding with melt and groundwater, heavy precipitation, and breakthrough of communications.

It should be noted that strip foundations are most often subject to destructive deformations, while slab foundations are much more stable.

Thorough Analysis possible reasons destruction of the old foundation will help determine the most suitable methods for eliminating them. However, it would not be a bad idea to have a preliminary consultation with relevant specialists on the problem that has arisen. If the examination shows that the deformation of the foundation is critical along the entire perimeter of the house, then most likely it will be necessary to make a new foundation around the old one.

Basic ways to restore the foundation of a house

First of all, it is worth noting that such work is quite labor-intensive, requiring a lot of time and significant financial investments. It is better to schedule them during the warm season, when the amount of precipitation is minimal.

Today, there are several ways to build a new foundation without destroying the old one. Their choice depends not only on the reasons that led to the work, but also on the state in which the foundation being reconstructed is located. In practice they use:

creation of an additional monolithic reinforced concrete belt around the foundation of the house;
pouring a new foundation under the base of the old foundation;
the use of piles with the transfer of the entire house to newly erected supports.

Since each of the restoration methods has its own methodology and sequence of work, we will consider each of them in more detail.

Construction of a monolithic reinforced concrete belt around the house

This method restoring an old foundation is the most common, as it does not require the use of special tools or the use of construction equipment. All work can be done independently. The essence of the method is to erect a reinforcing reinforced concrete belt around a dilapidated strip base on the outside of the house.

The new foundation should be laid slightly deeper than the old one, and its width should be at least one meter.

Widening the base can significantly reduce the load on the ground, preventing further subsidence of the walls of the building. The work is performed in the following sequence:

a trench is dug along the foundation walls, almost end-to-end, along the entire perimeter of the house;
at the bottom of the excavation a drainage cushion is placed from a layer of sand and gravel, which is then covered with a layer of waterproofing material;
the old base is thoroughly cleaned of contaminants, damaged areas are repaired and, if necessary, the surface is treated with an antifungal compound;
in the dilapidated foundation, grooves are drilled in increments of 25-30 cm, into which sections of metal rods are then placed, required to connect the old structure with the reinforcement frame assembled and laid at the bottom of the dug trench;
On the outside of the future foundation, a lumber formwork is constructed, the individual parts of which are pressed tightly against each other. To prevent concrete mortar from seeping through, experts recommend using plastic film in problem areas;
Thick consistency concrete is poured into the prepared formwork with the reinforcement cage laid. At the same time it is controlled uniform distribution solution that does not allow the formation of voids.

All work on the reconstruction of the foundation must be carried out in a short time so that the old foundation remains open for minimum quantity time. After the concrete reaches its design strength, the support of the house, widened in this way, will additionally strengthen the external walls of the building.

New concrete foundation under the old house foundation

In cases where the foundation loses its bearing capacity, which may occur as a result of the washing out of individual soil layers by groundwater, a slightly different restoration method will be required. It involves pouring concrete under the base of the foundation along the entire perimeter of the house. This method allows not only to expand the supporting area, but also to increase the depth of the old foundation structure, as a result of which the new foundation will be based on more dense soil. The procedure for carrying out the work is slightly different from the above. It consists of the following steps:

from the external corners of the foundation of the house, as well as in the places where the internal walls of the building meet the external ones, digging is carried out to the calculated depth;
a sand and gravel cushion is poured under the exposed supports and the assembled reinforcement frame is laid;
formwork is constructed from the outer edges of the pit;
Concrete is poured at angles and backfilled.

After the concrete has gained sufficient strength, a trench is torn off in the areas between the restored corner supports, along the foundation walls. It is buried below the level of the old foundation, in such a way that it is possible to dig under the existing foundation.

Attention! Digging a trench must be carried out in several stages, in separate segments no more than 2 meters long. To prevent the walls of the building from collapsing, sections must alternate!

Next, concreting is done in the exposed areas by pouring a ready-made solution of cement-sand mixture under the base. The poured concrete must be carefully compacted, ensuring that it fills the available space under the old foundation of the house as tightly as possible.

To ensure the strength of the new foundation, its individual segments are connected into a single structure. For this purpose, the reinforcement frame of the corner parts of the house is assembled in such a way that small outlets of metal reinforcement remain outside the formwork being constructed, to which the assembled frames of other intermediate elements are then tied. Then the formwork is constructed in a similar way, and the structure is filled with concrete. Before backfilling, the solution must be left for several days to set.

New screw pile foundation

In case of partial or complete destruction of the foundation, pile technologies for its restoration are widely used to preserve the rest of the building. The most innovative is the use screw piles as new supports. The main advantage of this method of constructing a new foundation is the speed of installation, since it does not require quite a long time for the concrete to gain the required strength. Restoring the foundation using screw piles is most preferable on swampy or loose soils. However, to carry out such work, the involvement of a construction team and the availability of special tools will be required.

When replacing an old foundation, it is advisable to use pile technologies for wooden houses or light frame buildings.

The construction of a new foundation is carried out in the following sequence:

Support piles are screwed in around the entire perimeter of the house in increments of up to one and a half meters and buried in the ground below the freezing line. The distance from the boundary of the external walls of the building to the supports should be no more than 1 m. The main thing is to ensure ease of use;
the building box is gradually raised to the required height using jacks and placed on temporary supports;
metal beams or channels are attached to the heads of screw piles by welding, connecting them into a single structure;
Using jacks, the structure is lowered onto the constructed grillage.

Before starting work, you should decide on the type and required quantity screw piles. The calculation is made on the basis of studies of the soil, the area of the building, the weight of the house itself, useful and temporary loads. The most difficult stage is the process of raising the structure, which must be entrusted only to professionals in this field. Independent work may not only not give the desired result, but also lead to rather disastrous consequences.

The cost of constructing such a foundation is relatively high. It largely depends on the quality of the screw piles used and the wages of hired workers. However, large expenses will be justified by a significant extension of the life of the house for more than a dozen years.

More than half of the owners country houses sooner or later they are faced with the need to expand the area of their home. Naturally, this is easiest to do at the design stage of the building, but at this time, as always, the limited construction budget does not allow for a larger area. What should you do if you have received a residential building and want to build an extension to it? It is recommended to start with the most important stage - connecting a new foundation for an extension to the old one. Let's figure out what kind of foundation to pour for an extension, and how to properly combine the base of the house and the foundation of the attached module.

The need to join two foundations

Home owners often have a need to increase their living space. A convenient and practical option for expanding real estate is to add block modules, such as a veranda. Such premises are open, so time can be spent here only during the warm season.

Before constructing the module, it is necessary to take into account that an extension to the house is possible only if a list of conditions is met: obtaining the appropriate permits for the construction of new structures, maintaining all permissible distances to neighboring houses and plots, ensuring independent settlement of all elements of the house relative to each other.

Like any construction process, the construction of a veranda should begin with the development of a project. This module near the house must be positioned in such a way that you can get from it into the main room, so it is customary to build a veranda at the end of the house or near the main entrance.

Despite the simplicity of the design, the extension must be completed efficiently and competently, and one of the first problems that arises with this is the installation of a foundation for the building. The best solution when constructing a foundation for an extension next to a house is considered to be combining foundations. Otherwise, cracks may appear in the walls, subsidence of the floor and other troubles may begin.

Features of connecting the old and new foundation

To understand how to properly build a foundation for an extension, you should find out how the foundation under the house is made and what it is like. If the foundation is strip, then you need to know its width; if it is columnar, then the overall dimensions of the pillars, as well as its depth. Experts strongly advise against building a foundation for the extension, which is distinguishable from the foundation of the house. Thus, if your house is located on a monolithic reinforced concrete strip, it is better not to save money and not build a columnar foundation for the extension.

The point is that different types foundations interact with soils differently; accordingly, their shrinkage is different. Therefore, in order not to want to take risks, it is better to bet on the same grounds. The depth of the foundation of the extension must match the depth of the foundation for the house - this avoids distortions. Measuring the depth is quite simple. To measure the width, take a metal rod and bend it at a right angle.

After this, hold the bent part horizontally in your hand and thread it under the foundation. Turn it so that the hook hooks on the opposite side. Next, make a mark on the rod and remove it. You can use the serif to measure the width of the base. In addition, the foundation for the block module must be connected to the existing one, because otherwise the new walls will move away from the old building after some time. And this provokes the formation of cracks and distortions.

An important point that you need to pay attention to if you are going to connect the foundations together is that in the spring there will be a decrease in the bearing capacity of the soil. As a result, its humidity increases. A building built on a new foundation will experience additional shrinkage in the spring.

Considering the fact that old and new buildings may have a significant difference in weight, it is worth understanding that subsidence of the foundations will occur unevenly. Therefore, to connect the foundations between them, you should wait one season before work and provide for a technological gap. Such a gap, as a rule, is a gap that has a size of approximately 20 - 40 centimeters, in which pieces of reinforcing bars are placed that protrude from the foundations.

To expand the foundation, ordinary concrete mortar or reinforced concrete is used. So that the old and new parts of the foundation are firmly connected to each other and form monolithic structure, before pouring a new foundation with concrete, it is necessary to strengthen the foundations: weld the reinforcement of these parts of the foundation or drill reinforcing bars into the old foundation.

Methods for connecting two foundations

The connection of two foundations can be carried out based on one of two solutions: constructing the foundation of the extension separately or rigidly combining it with the foundation of a residential building. When choosing a specific solution, it is recommended to start from the heaviness of the attached module and quality indicators soil on the site. If it is uniform, and the built house has not undergone significant shrinkage over time, you can combine the foundation of the building and the base of the extension into a single structure. Otherwise, you should think about building a separate foundation, which will be in contact with the base of the house through an expansion joint.

Rigid connection between the base of the house and the extension

When building a house with your own hands, the most difficult thing is to make a full-fledged rigid connection to create a single residential building-extension structure. As a rule, such a solution is relevant for a situation where the site has slightly heaving or non-heaving soil (when the settlement of the new foundation can be predicted), as well as in the case where it is planned to build a two- or more-story extension with a house under one roof. After the work is completed, a single design will be obtained.

The “tape-to-tape” connection between two strip foundations with your own hands is carried out in this way:

First you need to dig out the foundation to the depth of the foundation of a residential building; the length of the trench should be about 1.5-2 meters. You should not dig up the entire side, but only part of it, while creating a sand cushion.
Drill holes in the base of the house that have a diameter equal to the diameter of the reinforcement. For the middle part of the tape, a hole is drilled to a depth of ¾ of the width strip foundation in a checkerboard pattern and for corner parts - by 0.5 meters.
In the holes that are drilled ¾ of the width of the tape, you need to drive reinforcement with a longitudinal slot into which a wedging insert, for example, made of wood, is inserted. Drive 14 mm reinforcement with a periodic profile into the holes made half a meter long.
Next, they are engaged in the formation of the frame of the future foundation, using the outlets of driven reinforcement as elements of the new foundation. To join the next parts of the base, releases are made that are 30-40 centimeters long, which are subsequently welded.

A rigid connection for an open contour is formed in a similar way, only the reinforcement is driven in slightly differently and more of it is used per unit area at the points of contact of the two bases.

A rigid “slab-to-slab” connection between a slab foundation and the base for an extension can be made provided that the foundation is thick (from 400 millimeters), or if there are slab protrusions at the base of the residential building from the base part. As a rule, such protrusions are left when constructing a foundation for a building made of aerated concrete. In this case, the base should protrude by at least 30 centimeters, which allows the slab reinforcement to be exposed and then welded to the frame of the new slab foundation.

If there is a large difference in the weight of the new and old buildings, for example, a light veranda is attached to the house, the level of their shrinkage will differ significantly. Therefore, it is not recommended to rigidly tie the foundations of these structures. In this case, you should pay attention to the construction of a separate foundation for the extension.

Separate base and expansion joint

The simplest and therefore most common option for laying a foundation for an extension is the construction of a separate foundation, which is located in close proximity to the base of the house. In this case, it is most reliable to work in a closed circuit, when you erect a full-fledged reinforced concrete grillage near the house. Between two foundations, waterproofing is carried out by laying sheets of roofing felt.

You can also use thermal insulation material or tow. The essence of the method is simple - to create a layer that allows the new base to play during settlement, without damaging the foundation of the house. When calculating the connection of foundations using an expansion joint, it is customary to focus on the indicators of the soil mixture, as well as the potential loads from the extension on the area under its base.

The calculation of the foundation is carried out in the same way as when constructing a deep or shallow strip foundation. Before making a foundation, you need to take into account an adjustment for future shrinkage, which is implemented by laying a new foundation slightly higher than the old one. The new structure will eventually settle to the depth of the foundation of the residential building. For the construction of a frame extension they use columnar foundation, thanks to the low weight of the structure.

Another option is to place the extension on a concrete pad. They are easily molded directly on site. Pre-impregnate the finished piles with mastic, waterproofing material or other impregnations for protection, after which they are installed in a mold and filled with concrete.

The pillars are spaced from each other at a distance of approximately 1 to 1.5 meters, depending on the overall dimensions and weight of the attached module. Determine the height at which you will place the floor, cut them to a certain size. Next, the building frame is attached to them. In just two days you can begin construction, which significantly reduces the work process.

Ideal option for connecting foundations

Already at the stage of building a house, you should think about the fact that after a certain time you will want to expand your home possessions. It is much easier to lay the foundation for an extension at this stage. This is the ideal foundation technology. This approach will allow you to create a rigid structure, and you will not have to think about expansion joints and other design solutions.

In the meantime, you can cover the area that is empty in the meantime with decking - temporary structures. This approach will do nothing to a well-waterproofed foundation. In addition, during this time the base will take the strongest position and reduce the risk of settlement during the construction of the above-ground part of the extension.

Thus, a situation often arises when an extension or a new building needs to be erected next to the house. When attaching a new foundation to an old one, it is necessary to give the new part time to harden well. Ideally, at least a year should pass from the stage of designing the foundation and laying it to erecting the walls. In this case, it is necessary to take into account such factors as the topography of the site, the type of soil, the weight of the structure and other features.