Alexey Leontiev, General Director of Leontiev and Partners, shares advice on building a house on an old foundation or strengthening an existing one with the readers of the magazine.
To build your house on it or not to take risks and lay a new one? Yes, these questions cannot be called simple for an unprepared developer, because even professional builders cannot always immediately give the right advice.
Let's try to figure out what activities need to be completed in order to make the right decision.
When building a modern cottage, depending on the actual engineering and geological conditions of the site and the design of the foundation, the cost of the “zero cycle” can reach 30% of the cost of the “box” of the house.
It would seem that in the case of using the existing foundation, the savings are obvious. But do not forget about a fairly large risk. After all, it is unknown how professional the workers who built the foundation were, whether high-quality materials were used, whether the necessary preparation for the foundation was carried out, whether the base of the foundation is below the freezing depth, etc.
Often there is no design and executive documentation.
To minimize the risk, it is necessary to inspect the foundation by a specialized company. It is not worth saving on such a survey. The costs required to repair and maintain a home built on an unsafe foundation are many times greater than the cost of inspection services.
The purpose of the survey is to establish the technical condition of foundation structures and soils at the base of foundations, and to answer the following questions:
1. Can the existing foundations ensure normal operating conditions for the facility in the future or is it necessary to reconstruct, strengthen, etc.?
2. Which structural elements of the foundation can be preserved and which ones must be dismantled and restored?
3. How to eliminate the identified deformations of the foundation?
4. Is it possible to make an extension to an existing foundation and how to avoid possible deformations when constructing new foundations near existing ones?
Depending on the actual conditions of the construction site, other questions may be asked during the survey.
Based on the results of the examination, specialists will make a conclusion about the possibility of using the old foundation and, if necessary, offer recommendations for strengthening it.
What to do if strengthening is still necessary?
In the context of individual development, the following methods are most often used:
1. Expansion of foundations. The essence of this method is to increase the size of the base of the foundations.
The technology for carrying out such work is approximately the following: first, the soil is torn off from all sides of the foundation to the base level. If necessary, vertical fastening of the pit walls is installed, its width on one side at the level of the base is up to 1 m. After this, the exposed side faces of the foundation are thoroughly cleaned of soil and notches are made on them for better adhesion of the concrete to the foundation material. The base for expansion is carefully prepared by compacting crushed stone into the ground. After installing the formwork and installing the reinforcement, concreting is carried out.
2. Restoration of prefabricated foundations. In prefabricated foundations, for example, from the frequently used FBS foundation blocks, the joints often fail. Such foundations can be restored either by resinization or cementation: prepared repair resins and solutions are injected into cracks and seams using a hydraulic pump.
3. Strengthening foundations by injection. This method is often used when the site has a rubble foundation with delaminations, but with a preserved configuration. Holes are drilled in the foundation at a distance of 50–100 cm from each other; wash them with water until it is completely clear; injectors are buried into the foundation, which are placed in a checkerboard pattern in increments of 50–100 cm, and the solution is injected under pressure; the injection process is completed when the absorption of the solution by the foundation structure ceases.
4. Replacement of foundation sections. The method is used when it is necessary to replace a section of an existing foundation. At the same time, work can be carried out in increments, in sections of 4–5 m. In the adjacent section, work is resumed no earlier than 7 days after the completion of work on the previous one.
5. Strengthening foundations with piles. This method is carried out by installing piles along the contour of the foundation. In the conditions of cottage construction, it is advisable to use bored piles. They are constructed using the following technology: holes are drilled into the foundation soil with a manual or mechanical drill to the required depth. Casing pipes are installed in the wells (asbestos-cement pipes can be used), which act as permanent formwork. Reinforcement is inserted into the pipe and concreting is carried out. After installing the piles, they are combined with a grillage.
When examining foundations, it is often discovered that the waterproofing is either broken or simply missing. In this case, it is necessary to carry out a set of measures to restore or install waterproofing.
So, now you know how to approach the issue of using an old foundation for new construction. Having completed all the necessary measures, weighed all the risks and made the necessary economic calculations, you will be able to make the right decision.
"Landowner of the North-West"
No. 4(22), 2007
Building a house even on a free plot is not the easiest thing. It’s even more difficult if there are buildings on the land plot that you no longer need, and in their place you want to build a new cottage or townhouse. Today we will figure out how to build a house on a plot that is still occupied by another building.
Building a house even on a free plot is not the easiest thing. It’s even more difficult if there are buildings on the land plot that you no longer need, and in their place you want to build a new cottage or townhouse. Today we will figure out how to build a house on a plot that is still occupied by another building.
The situation described above is far from hypothetical; a very specific example can be given. A family with three children inherited a plot of land with a house built around 1979. It would seem that this is freedom, you can do whatever you want. But, upon reflection, the couple came to the conclusion that everything is not so simple. First, what to do with an old house? It is, of course, theoretically possible to live in it: there is stove heating and electricity. But I want it better! So that there is gas, running water, a civilized heating system for the premises. And the house should be two-story, so that each family member has his own room.
The old house by no means fit into the image of an ideal family nest. Therefore, the new owners decided, it must be demolished. And put a new one in the vacant place. New questions immediately arose: demolish it completely or leave the foundation? Do I need to obtain a demolition permit? Is the old foundation suitable for a two-story new house? How then to coordinate the new construction with the BTI? We asked real estate market experts about all this.
Down to the ground and then
First of all, you need to think about what problems might arise if you leave the old foundation and build a new building on it. Yulia Severinenko, general director of the ZemAktiv company, believes that it is necessary to first conduct an inspection of the old foundation. This is done by specialists who will evaluate the technical condition of the existing foundation, the properties of the soil at its base, and the suitability of the structure for future loads. As a rule, if it is, for example, a monolithic reinforced concrete foundation, which was made correctly at one time, it will be possible to erect a new structure on it from any material.
True, if the foundation was poured back in Soviet times, then it is unlikely to be in decent condition. “In 1979, no one made foundations using modern technologies. High-grade concrete was in short supply, and few people followed the technology in low-rise construction. Based on a foundation that has been standing for 30 years, you can almost immediately tell whether it will stand for another 100 years, or whether it has already practically “died,” says Alexander Dubovenko, development director of GOOD WOOD.
Therefore, the owner of an old house needs to decide whether to spend money on an examination of the condition of the foundation.
In addition, in any case, you need to check the documents for the land, even if you are going to build a house on the site of the old one, without changing the development plan, because, as practice shows, land plots and houses acquired or built before the 90s were often not registered. “From a legal point of view, it is possible to build a new house on an old foundation if the land is owned and the permitted use of the land plot involves the construction of a house,” explains Alexander Sergeev, legal adviser to the Volzhskie Dachi Management Company.
However, if the object was transferred by inheritance or as a gift, then problems with registration of ownership, and therefore with the disposal of this property should not arise.
Demolition or reconstruction?
Experts note that obtaining a demolition permit depends on many factors, in particular, on the nature of the supplied communications and the requirements of utility services when reconnecting them. “Therefore, in order to simplify approvals, owners often demolish a house and build a new one under the guise of reconstructing the property, or use similar schemes,” says Yulia Severinenko.
Irina Bashilova, head of the legal department of the Volzhskie Dachi Management Company, believes that it is quite possible to register the construction of a new house on an old foundation as a “major repair” or “reconstruction” of the previous house, but you need to be very careful about the process. “The substitution of concepts will be advisable only if we are talking about “major repairs” or “reconstruction” that do not affect the structural and other characteristics of the reliability and safety of a capital construction project and (or) its parts and do not exceed the maximum parameters of permitted construction, reconstruction established by urban planning regulations. Only in this case, in accordance with Art. 51 of the Town Planning Code of the Russian Federation, there will be no need to first obtain a construction permit, and after the construction of a residential building, a permit to put the facility into operation,” the expert warns.
Therefore, it seems that it is better to completely demolish the old house along with the foundation in order to build a new cottage on the vacant plot. By the way, the majority of Sobstvennik readers think the same thing: according to the results of our survey, 36% of respondents would prefer this option.
Demolish, cannot be pardoned!
Now let's see what needs to be done to properly formalize the demolition of the structure. Alexander Sergeev emphasizes that the owner of the house has every right to dispose of his property, including destroying it, and if the house is registered in the cadastral register, then it will need to be removed from this register.
But first you need to carry out the actual demolition, and then contact the BTI authorities to draw up a house inspection report. “Based on the inspection report, the BTI will cancel the record of the existence of the house. After this, you need to contact the Rosreestr department with an application to make a record of the cessation of the existence of the old house,” explains Maria Bondarevskaya, a lawyer at the law firm Yukov, Khrenov and Partners.
As for the technical features of demolition, it is necessary to demolish the house itself, as well as the basement part of the foundation to ground level, since dismantling the underground part will be very expensive. “For example, you will have to drill out piles laid several meters deep, or tear up a foundation pit in order to remove concrete that was once poured,” says Yulia Severinenko.
In these cases, the expert believes, it is better to shift the new foundation a little so that it does not coincide with the old one. If it is important that the new house stands on the same wall-to-wall construction site, the underground part will also have to be dismantled. But it's extremely expensive.
After demolition, the site will need to be prepared for new construction. “It is necessary to remove construction waste, plan the territory of a new construction site, equip an entrance to the site (for construction equipment), install temporary structures (cabins) for storing materials, tools, accommodation for builders, carry out engineering preparation (providing the site with electricity, water, sanitary cabins)” , - advises Dmitry Yazykov, construction director of the Zagorodny Project company.
Most often, people who inherit a house receive it in such a condition that there is only one thing left to do - tear down the old walls and build new ones in their place. Sometimes the following situation occurs: when building a house on an undeveloped plot, most of the money is spent on supplying all communications to the home (water, electricity, gas) and processing official documents.
This problem can be easily avoided if you purchase a plot (or a house for demolition) with communications already installed. In addition, in the real estate market you can always come across a couple of advertisements of this nature (it happens that people have already laid the foundation and carried out communications, but then a force majeure situation occurred, and then the house, or rather its “beginning,” was urgently put up for sale). The main thing is not to miss this opportunity.
It’s good when you can bring heavy equipment to the demolition site, but sometimes this is not possible. In such cases, demolition must be done manually. A short video tutorial will tell you how to do it correctly.
You can determine whether a foundation needs repairs by taking just one look at it. The fact that the days of the foundation of the house are already numbered is indicated by the skew of the building, cracks on the walls and subsidence of the house. It is impossible to insure a building against such deformations, because over time the foundation materials deteriorate. Therefore, one day the time comes when the owners of a wooden house have to decide what type of repair to do - partial or complete.
Conditions for partial and major repairs
In order to find out the extent of damage to the foundation and determine the necessary measures to restore it, you need to carefully study the current state of the foundation and identify characteristic defects that may affect the strength and integrity of the building or its individual elements.
If cracks appear on the foundation, then you need to think about the need to repair it.
The foundation is restored in fragments if it has sunk lower but has not begun to collapse. Complete repairs are resorted to when cracks and other damage are detected.
The decision on what basis to replace a completely damaged structure is made taking into account the type of soil, the terrain and the type of foundation originally created.
If the foundation of the house has sunk into the ground, it’s time to repair it
With a strip base, they often proceed as follows: the destroyed areas are dismantled and the structure is reinforced along the entire perimeter. In case of serious destruction of the foundation strip, it is decided to completely replace it.
If there are serious defects in the strip foundation of a house, it makes sense to think about its complete replacement.
Repair of a columnar foundation is almost always carried out completely: all the old supports of the building are replaced with new ones. To do this, the house is raised to the height of the pillars using jacks. New reliable supports are fixed on reinforced concrete “pillows”.
The columnar foundation is most often completely replaced with a new one
A foundation made of wood, which has already been slightly damaged by fungus, is usually replaced with a strip or columnar structure. To do this, the building is raised to a certain level and concrete blocks or bricks are placed under it.
Strengthening the foundation of a wooden house
When repairing the foundation, it makes sense to immediately strengthen it. This can be done if you are confident in the stability of the soil, which is below the foundation level of your house. Strengthening the structure under the building may also be required in the case where it is planned to add another floor to the house, but there is a suspicion that the previously installed foundation will not withstand the increased load.
You can strengthen the foundation in two ways, depending on the load it has to withstand.
Instructions for strengthening the strip structure
To make the foundation more durable, perform the following work:
- A trench is dug along the perimeter of the base. The hole must be wide, otherwise it will be inconvenient to work. In addition, we must take into account that the new foundation will become stronger.
- The soil is removed from the excavated foundation. To do this, use a metal brush.
The trench must be wide enough to make it comfortable to work in.
- Holes are made in the old base with a drill. It is important that their diameter exceeds the thickness of the purchased reinforcing bars by no more than 1 mm. In this case, the metal elements will be installed securely and without gaps.
- Reinforcement rods are inserted into the drilled holes using a hammer. They will help connect the new base to the old one.
Reinforcing bars are driven into the drilled holes, to which the vertical grid is attached.
- Further metal elements are welded to the hammered rods, forming a reinforced belt. It is better to solder the reinforcement with already installed rods only in a few places. For the most part, it is wiser to tie metal elements with wire to avoid deformation of the reinforcing belt during pouring and hardening of concrete.
The reinforcement cage will firmly connect the old foundation with the reinforcing concrete structure
- The formwork is installed and filled with concrete. After waiting for the solution to harden, the structure of the boards is dismantled. The new foundation is left untouched for several days so that it becomes even stronger.
Formwork is installed around the reinforcement frame and concrete is poured into it. After the reinforcing layer has hardened, the formwork is removed
- The created base is covered with waterproofing material. An asphalt strip is created around the foundation at an angle.
Thanks to the reinforcement, the weight of a wooden building is distributed over a larger area. This method allows you to stop subsidence and destruction of the house.
Video: how to strengthen a strip foundation
Replacing the foundation under a timber building
The method for replacing the base depends on its type.
Replacement of strip foundation
Overhaul of the base in the form of a tape is carried out in stages:
- In order to reduce pressure on the foundation, furniture is removed from the house, floors are dismantled, and the stove is dismantled. Only heating equipment located on a separate concrete platform is not subject to dismantling.
- The building is raised slightly. If the house is small, then its level in relation to the ground is changed using a kind of lever for lifting weights - a beam measuring 8x8 cm, placed at the corner of the building. A log will serve as a support for it. For heavy construction, it is better to choose thicker lumber. The wooden structure is raised by applying pressure to the timber.
The house is raised on jacks and temporary supports are placed under it.
- A trench is dug around the house or only in areas where the wooden building needs to be raised.
- A jack is placed under the old foundation. There may be several mechanisms for raising a building. The number of jacks is determined by their load capacity and the weight of the house. The mechanisms can only be installed in areas where there is no damage.
- Using a jack, the house is slowly raised to the desired level. It is important that it rises evenly above the ground. Since there is a risk of unsuccessful installation of the jack, it is advisable to play it safe - place wooden wedges between the structure and the base pad.
The house is raised evenly on several jacks. For insurance, wooden blocks are placed under the load-bearing beams.
- The lower crown of a raised wooden structure is tied together with a steel hoop or hammered in with strong boards. This technique will protect the overloaded lower beams of the house from damage.
- The house is freed from its former foundation right down to the surface of the earth. If you are not ready to spend a lot on repairing the base, then you can partially disassemble the structure - remove only the damaged areas.
A hammer drill is used to destroy the old foundation.
- A cushion of sand-cement mixture is made under the reconstructed base of the house. Supports made of concrete or bricks are placed at the corners of the building. Instead, you can use piles. Thanks to the installation of supports, the size of which must correspond to the height of the foundation being constructed, in the future the foundation will be able to withstand increased pressure.
- Construct a reinforcing belt necessary to strengthen the base. Elements of a metal structure are connected not by welding, but by wire.
- Formwork is made from boards. The finished structure is filled with concrete mortar.
Formwork with a reinforcing frame inside is reinforced with side supports and filled with concrete
- After 3 days, the concrete hardens, so the formwork is removed, but no further work is carried out yet, waiting for the foundation to strengthen.
- A few days after dismantling the formwork, the new base is covered with a waterproofing sheet, for example, roofing felt.
A few days after the formwork is removed, the foundation is covered with waterproofing material
- The house is lowered, acting as slowly as during the raising of the building. The front side of the base is covered with waterproofing and facing materials. A blind area is made around the house, which will not allow rainwater to seep into the foundation.
Video: how to repair a strip concrete base
Repair of support pillars
To replace a columnar foundation, proceed as follows:
If it is necessary to replace just a few pillars, they act differently: they make tunnels in the area where they are located, and pipes are immersed in them and filled with concrete. Old supports are dismantled after the solution has hardened.
Video: replacing a columnar foundation with your own hands
Converting a rubble or brick foundation into a monolith
Since the brick foundation is characterized by increased fragility, it is more advisable to replace it with a concrete foundation.
To build a concrete foundation in place of a brick or rubble foundation, perform the following steps:
Video: brick foundation repair
Repairing the foundation of a wooden house with your own hands
The wooden foundation is mainly made of pine or larch. A wooden structure always requires complete replacement, since over time it becomes completely covered with fungus and rots. Replacing old elements of such a base with new ones is carried out as follows:
The damaged foundation of a dilapidated wooden house can be put in order. To do this, you need to obtain the necessary knowledge and choose a repair or replacement technology. You can do the reconstruction of the foundation of a house yourself, if you have the desire and at least a little experience in construction work.
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