How to fill the foundation under the fireplace. Building a foundation for a fireplace

The base for the "decorative firebox" is mounted using various technologies. But if a fireplace is installed in a wooden house, then the issue of building a foundation for it requires special consideration, since many of the typical “projects” implemented in other houses are simply not suitable for such ones. Before getting acquainted in detail with all the features of this work, it is necessary to learn a number of rules regarding wooden buildings.

First

Fireplace DO NOT install directly on the floor or ceiling (with rare exceptions). A common mistake is “if I take care of the fire safety measures, then nothing will happen.” It's not so much about the "combustibility" of the log house, but about the strength of the structural elements. Even a small fireplace, given the materials used, has a large mass. Will the "flooring" of the floor withstand?

Second

Compliance with the dimensions of the firebox and the room. A large fireplace installed in a small room will literally "dry" it. And what low humidity is fraught with, and not only for the health of households, but also for the service life of things and materials, no need to explain. For example, excessive shrinkage of wood leads to its deformation, including in the form of twisting. At the joints, at the joints (fastenings) of a different type, this will not be reflected in the best way.

Third

In a room according to the principle "where it is more convenient and more beautiful" it is impossible. It is a source of an open flame, and even a small draft can initiate the ignition of a seemingly completely burnt fuel. What if the owners leave? Therefore, there is a ban on the installation of such "home fires" opposite the openings of windows and doors (after all, no one will constantly fill the firebox with water, just in case).

Fourth

Of all the known types of fireplaces, given the flammability of wood, a free-standing design is acceptable for a wooden house. But the expediency of recommendations for the arrangement of "hearths" attached to the wall or built into it is highly doubtful. Especially if it means "with your own hands", and even without proper experience. For example, how to properly mount a chimney (which gets very hot) in a wooden wall? More than enough questions and more.

On a note! It does not make sense to describe in detail any one technology, since it is not a fact that it will interest the reader. The author considers it more appropriate to highlight the general stages of work, and “what and how” to do specifically can be decided based on local conditions.

Features of the installation of the foundation

Place

Something has already been said about this. It remains to clarify a few points:

The base for the fireplace must be separate. It is forbidden to use part of the foundation of the house itself for these purposes. This is due to the difference in load and further shrinkage of structures.
Between the walls of the foundations (buildings and furnaces) there must be a gap (minimum 50 mm), which is filled with loose mass (as a rule, ASG). This provides a "decoupling" of the bases, so the shrinkage of one does not affect the other.

Depth

As for all types of foundations - taking into account the depth of soil freezing. In some cases, it is possible to mount a slab-type base (if groundwater comes close to the surface, if the soil is classified as problematic - clay, sandstone and a number of others).

The rule regarding depth can be neglected if, for example, the area of \u200b\u200bthe house is significant, it is, and the owners permanently live in the building (that is, it is heated all season). This ensures that the soil under the building itself does not freeze as much. It turns out that there are several options, but the meaning is clear - to prevent the fireplace from sinking.

Base area

It must protrude beyond the perimeter of the firebox by at least 50 mm on all sides.

foundation type

the mass of the fireplace;
soil characteristics;
the convenience of earthworks (this is true for an already inhabited house).

Tape foundation

It makes sense to erect a monolithic (for example, reinforced concrete) under a massive fireplace. It is better to use this option - block.

A cheaper technology is to fill the prepared trench with natural stone, crushed stone or pebbles of large fractions, and on top - laying bricks (the figure explains everything well).

Explanation: floor level (1), brickwork (2), cut-off waterproofing (3).

Columnar foundation

There are also many nuances here. Which material to choose? Probably, such an option, as in the figure, is too expensive, and laborious.

Upper: pos.5 - cut-off waterproofing.

Lower: pos. 3 - leveling layer; pos. 4 - reinforced concrete jumper (slab),

A more economical foundation is made of metal pipes, into which a solution is poured. If it is being built during the construction of a house, then ready-made reinforced concrete blocks can be used. The floor is a reinforced concrete slab.

brick monolith

Here is one option, although given the complexity of the work and the cost of materials, not everyone will choose it.

materials

A few clarifications:

For masonry, it is recommended to prepare a lime mortar. He is considered the best for this job. Preparation - dilute lime in water in a ratio of 1 to 3. The mass is brought to the desired consistency by adding sand.
All buried parts of the base must be protected from liquid (vertical waterproofing). Most often, it is equipped by coating the surfaces with greasy clay, diluted to a state of thick sour cream. As a rule, this is enough for a fireplace, especially if the foundation of the house is a tape monolith.
Even in the process of preparing the pit, clay is placed on the bottom and compacted. Thus, the first layer of cut-off waterproofing is obtained, which protects the "cushion" under the masonry.

On a note! If the ceiling of the 1st floor of a wooden structure is made of a reinforced concrete slab (there is such an engineering solution), then the fireplace can be mounted directly on it.

The foundation for a fireplace is one of the most important parts of a device for heating a summer house or a private house. Professionals say that the foundation for the fireplace should begin in parallel with the construction of the building, otherwise the construction process is much more complicated. Of course, it happens that the fireplace is purely decorative in interior design. In this case, the foundation may not be needed. But in the case of the construction of a full-fledged structure in the medieval style, one cannot do without a strong foundation.

As a rule, the base under the fireplace is built from concrete mortar, buta or brick, which can withstand a humid environment. We must not forget that a gap must be left between the main foundation of the house and the base of the fireplace, which should be more than 5 mm (sand is poured and compacted into it). It is strictly forbidden to connect these two structural elements due to uneven settlement. This can lead to distortion and cracks. In addition, the sole area should be larger than the bottom of the furnace (protrude 100 - 150 mm from all sides). The technology for this type of foundation is identical to the construction of foundations for other structures.

The best option would be to include a fireplace device in the scope of work at the design stage of the house.

Then, during the construction of the main foundation, the foundation for the furnace is laid. The device of the fireplace foundation after the completion of the construction of the house will result in a pretty penny, because it will be necessary to open the ceilings and the floor. Without a sole, the construction will be unreliable (no one is safe from ground subsidence).

Starting construction, it should be remembered that the foundation for the fireplace and the walls experience different loads. This circumstance determines the need for their separate construction (different degree of load - different shrinkage). When installing a fireplace-type stove in an already finished building, it is necessary to carefully choose the installation site. In addition to considering general issues (heating efficiency, design, etc.), attention should be paid to the ease of installation of the structure. Moreover, the place for the fireplace should not violate the integrity of the load-bearing walls. Changing the design solution causes additional difficulties and entails material costs.

The following requirements are imposed on the design of the sole under the furnace:

ideally, the depth of the foundation pit should be more than 0.5 m (depending on the soil);
the area of the foundation must be greater than the area of \u200b\u200bthe base of the fireplace;
the depth of laying depends on the index of soil freezing. It must be at least 20 cm larger.

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Stages of self-construction

When building a foundation, consider the types of soil.

At the first stage, information about the soils contained on the site should be found. When the soil is represented by clay deposits, it should be taken into account that at high humidity the structure may tilt due to a weak ability to withstand heavy loads. When the soil is mostly sand, the pressure generated by the structure will cause shrinkage. When the soil is represented by rocks or it is supposed to use the fireplace in continuous mode, you can not think about the depth of freezing. Constant operation will not allow the soil to freeze.

After carrying out the analysis of the soil, they begin to prepare the necessary materials. Here you can get by with a simple set of materials:

gravel;
gravel;
previously used broken brick;
sand;
cement.

Concrete acts as a binder, which can be made by hand, taking sand and cement in a ratio of 6 to 1.

The pit is digging. To do this, you must first mark the territory. The bottom surface must be compacted, making it as even as possible.

The laying of the foundation begins:

1 layer. 0.2 - 0.25 m of crushed stone or fine gravel. All this is filled with a solution;
2 layer. Large stones in solution with gaps of 4-6 cm. The remaining gaps are covered with gravel or gravel.

Broken bricks for building foundations can be found at old abandoned construction sites.

Foundation construction technology requires strict adherence to verticality and horizontality of all sides. This will help to avoid the effect of side loads and the sole will only experience the loads exerted by the weight of the fireplace. Side loads can lead to uneven subsidence of the soil and deformation or displacement of the foundation.

Concrete should be laid below the floor level by 0.15 m. Subsequently, it will need to be leveled with a screed and the first layer of the fireplace ordering should be laid. The base of the masonry, as a rule, is made in two rows with a waterproofing device. The waterproofing layer is laid in two rows. The result should be a structure that is flush with the subfloor. The lower part of the fuel chamber is placed on top of the brickwork - the fireplace table.

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Concrete sole under the fireplace

The rubble concrete is perfect for the foundation for the furnace. One of the most important stages of work is the preparation of formwork. Formwork sheets are pre-coated with bitumen, upholstered with roofing felt or roofing felt. Such measures are necessary so that the milk (cement) does not seep into the pillow. The foundation for the fireplace is poured in layers.

For the construction of the foundation, you need to use a stone with a diameter of at least 15 cm.

1st layer - large stones with a diameter of less than 15 cm. The stones are not laid tightly. Crushed stone is poured into the remaining gaps.
A solution of sand and cement is poured onto this resulting layer, 1 part of cement is poured into 3 parts of sand. It is better not to make a large amount of the solution, only the required amount consumed per day.
After that, a concrete mortar is prepared. It is prepared in the following proportions: for 1 part of water, 1 part of cement. The result should be a suspension that resembles cream in density. The solution must be laid in layers, and experts advise doing one row per day. Of course, if specialized equipment is involved in the work, for example, a concrete mixer or a mixer, then all the work can be done in one sitting.

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Reinforced concrete slab as a base

In order to make a concrete foundation for a fireplace, you will need:

Portland cement;
sand;
crushed stone;
rebar for reinforcement;
formwork boards;
waterproofing materials.

Stages of work.

Be sure to reinforce the foundation so that it does not crack in the future.

Preparation for concreting. The pit is digging. A reinforcing mesh with a mesh size of 100 - 150 mm is laid in it.
The pit is filled with a mortar made from 1 part of cement and 4 parts of gravel and sand. It is better to divide the filling into two stages. The concrete will harden in about 2 days.
When work is carried out in the hot season, in order to avoid the harmful effects of sunlight, the concrete is covered with roofing material.
It is possible to improve the quality characteristics of concrete by wetting the surface with water after dismantling the formwork. It is recommended to dismantle formwork sheets after 5-7 days in summer and after 10-14 days in winter.
If the concrete turned out to be defective, additional waterproofing measures are carried out. To do this, use special formulations, the ingredients of which depend on the quantitative index of groundwater. In the event of a complete absence of groundwater in the soil, waterproofing can be done with sifted sand and cement, that is, make a sand-cement mortar in a ratio of 1 to 1, or 2 to 1.
At the last stage, the pit is covered with non-porous soil.

Vladimir

Good afternoon Tell me what foundation you need under a brick fireplace measuring 120 x 63 cm in a 2-story house? The size of the foundation is 150 x 100 cm, I believe. The soil is clayey, dry, the freezing depth is 130 cm, although it really does not freeze more than 80 cm in Samara. And what should be the depth and reinforcement scheme? Thanks for the answer.

Answer to the question

Location of the fireplace on the first floor

For an accurate calculation of the dimensions of the foundation, it is necessary to indicate the dimensions of the room, then it is possible to calculate the dimensions of the portal of the firebox (furnace hole). In addition, the calculation of the dimensions of the chimney pipe is performed, also based on the size of the furnace opening. You have already given the intermediate dimensions of a brick fireplace.

This is not all the original data. First of all: will an open or closed fireplace be installed indoors, its height, is the firebox open to one, two, three sides or a completely open fireplace? Corner or wall? There is no area of the room, the height of the rooms on the first and second floors, the height of the fireplace chimney above the roof, the material of the chimney. The height of the outer part of the pipe also depends on its distance from the roof ridge.

Let's calculate the dimensions of the foundation, based on the fact that the fireplace is open, wall-mounted, the fireplace chimney is also lined with bricks, the height of the first floor is 2.8 m, the height of the second is 2.5 m, the height of the attic at the place where the pipe passes is 1.7 m , the height of the pipe above the ridge is 1 m. If you have other sizes, then you can do the recalculation yourself.

Placing a fireplace on a separate foundation

Typically, the width and height of the fireplace have a ratio of 2: 3. This means that the height of the fireplace should be about 60 cm, and its volume is 0.45 cubic meters. m. For such a fireplace, approximately 55o pieces are needed. brick (red + fireclay). The height of the pipe is 8 m. In one row of the pipe, 5 bricks are laid, 14 rows are laid in 1 m. This means that 580 bricks are needed per pipe. If we add to this more bricks for raising the fireplace above the floor level, fluff and otters, we get a total number of bricks over 1200 pieces. The weight of the oven brick, taking into account the mortar, is 4 kg. This means that the total weight of the fireplace will be approximately 5 tons.

For such a fireplace weight in sandy-clay soil, it is recommended to do depth from 0.75 to 1 m. If you live permanently in your house, we will assume that the soil under the house will not freeze. If the residence is not permanent, seasonal, then the depth of the foundation should be taken more than the depth of soil freezing. We take the depth of the foundation equal to 90 cm. Then the weight of the foundation itself, based on the fact that the specific gravity of concrete is 2400 - 2500 kg / cu. m, equal to 3.3 tons. The total weight of the fireplace and foundation will be about 8.3 tons. The actual load on the ground with your base area of 1.5 square meters. m will be equal to 8300/15000=0.55 kg/sq. cm. This is below the allowable load, which for sandy-clay soils is 1 - 1.5 kg / sq. cm.

Foundation device with viscous reinforcement

Now about the order of pouring the foundation and the reinforcement scheme. At the bottom of the pit under the foundation of the fireplace, pour 20 cm of sand, spill it with water, carefully compact it, that is, make a sand cushion. Check its horizontalness with a level. Then pour a 10-centimeter layer of rubble. You also check it for horizontality in order to properly lay the reinforcing mesh in the future. On it you knit (with steel wire) a mesh of reinforcement with a diameter of 12 - 15 mm, you can weld the mesh. Take a grid step of about 15 cm. Pour all this with concrete mix and periodically tamp carefully. The concrete mixture must be poured at regular intervals in order to obtain a homogeneous concrete slab.

The height of the foundation should be two rows of brickwork below the finished floor level. Carefully level the top of the foundation. Complete drying of the concrete mixture is 28 days. Only after this interval can you start laying a brick fireplace. Before laying the first row of bricks, waterproofing of two layers of roofing material should be laid on the concrete foundation.

Good luck to you!

Fireplaces and stoves made of bricks are tall and massive structures assembled from a large number of small parts. The foundations on which they are erected must withstand the appropriate load and ensure an even, strictly vertical position of the heating device without distortions, otherwise cracks will inevitably appear over time, increasing the risk of fire, worsening the characteristics of the heating system, or making the operation of the stove (fireplace) completely impossible.

The foundation of a heating device is no different from the foundation of any structure. It is better if the owners think about building a stove or fireplace even before the construction of the house begins. In this case, the foundations for the walls and for the fireplace can be built at the same time, which will make it possible to do without costly measures for the dismantling of floors and ceilings in the future.

The foundation for the walls and the foundation for the fireplace carry different loads, they have different shrinkage during operation, so they should never be arranged as one. Between the foundation of the heating device and any other, a gap of 5 cm wide covered with sand must be arranged.

When installing a fireplace in a finished building, choosing a place for it is a responsible procedure. It is necessary to consider not only the expected design advantages of the room and the heating efficiency, but also to ensure that when installing the chimney and foundation, it is not necessary to dismantle the supporting structures, which is difficult, expensive and fundamentally not always possible.

The dimensions of the foundation plane for the fireplace must be at least 5 cm larger than the dimensions of the fireplace table. The minimum depth is 50 cm. In reality, it can be more, as it depends on the condition of the soil.

Under the pressure of the foundation, sandy soils are compacted, as a result of which the foundation sags evenly in a short time. Clay soils are unreliable - their characteristics are largely dependent on humidity. Wet clay is not able to bear the load, foundations on clay soils sag and heel over the years, gradually increasing the deformation.

In winter, the soil freezes, which causes it to swell and move. Therefore, it is desirable that the depth of the foundation be below the freezing level of the soil by about 20 cm. This rule can be neglected if the building is built on reliable rocky or cartilaginous soil, or year-round operation of the house with constant heating in winter is expected, which will not allow the soil to freeze.

The foundation material is chosen by any that is available. Usually it is rubble stone, crushed stone and gravel, brick, including broken. To bind the foundation fillers, cement or lime-cement mortar is used. The ratio of cement and sand in the mortar for the foundation is enough to choose 1:6 (by volume).

The foundation pit is dug according to preliminary marking. The bottom of the pit is leveled without slope and compacted, the foundation is laid in layers. The first layer - small stone or crushed stone - is rammed, then poured with a layer of mortar 20-25 cm thick. Large stones are placed in the solution with a gap between them of 3-5 cm. The gaps between the stones are filled with small stone or crushed stone (crushed).

After filling the pit for the construction of the above-ground part of the foundation for the fireplace, formwork is made according to the size of the pit and the laying is continued in layers. Each layer is carefully leveled, the horizontal level is controlled by the level.

The sides of a properly arranged foundation are strictly vertical, the surface is horizontal. In this case, only the weight of the heating device, balanced by the pressure of the soil, acts on the foundation.

Additional forces that contribute to the destruction of the foundation arise if the foundation is located with an inclination, as well as during movements and subsidence of the soil.

The foundation for the fireplace is brought to a level below the floor by 14-15 cm. The surface is carefully and strictly horizontally leveled with cement mortar. After hardening, the upper part of the foundation is arranged on it, on which the fireplace will be directly installed. The upper part is laid out with two rows of bricks on cement mortar, between which two layers of waterproofing material are laid.

Ideally, the foundation ends strictly at the level of the finished floor. The base (table) of the fireplace is placed on the foundation, which is understood as the part of the structure located below the firebox.

fireplace base

For efficient heating, it is advisable to place under the firebox as low as possible. In practice, it can be installed at any height. The dimensions of the fireplace table are not fundamental, the main thing is that the fireplace body fits on it completely, along with the finish without overlaps on the sides. Usually the width of the table is wider than the portal of the fireplace by one brick on each side. The depth depends on the depth of the firebox. For small fireplaces, a base depth of 2.5 or 3 bricks is usually chosen.

Depending on the chosen design of the fireplace, an ash collector (ash pan) and an air channel through which air is supplied to the combustion zone can be placed in the base. Sometimes the air duct is led through the foundation to the basement, for example, if it is difficult to supply the volume of air required for combustion through the heated room. In the simplest case, when an ash collector and air channels are dispensed with, the thickness of the base of the fireplace can be as little as one row of bricks.

Consider the structure of a fireplace table measuring 5 × 2.5 bricks with a drawer for collecting ash. The first row is solid, consists of 25 bricks.

The second row is laid with dressing to the bricks of the first row, in the middle they leave space for the ash box.

The bricks of the central zone of the third row of the base of the fireplace form a firebox. Under lay out refractory fireclay bricks. The fireclay bricks of the front row of the hearth and the ordinary bricks of the upper row of the base adjacent to them are laid with a release of a quarter of a brick. This is done for ease of use, it will be possible to substitute a scoop under them when cleaning the firebox.

The part of the compartment for the ash collector, above which the grate will not be installed, is covered with steel strips 4 mm thick, the middle bricks of the front row of the hearth of the firebox are laid on them. In the bricks on which the grate will be installed, samples are made for the protrusions of the grate.

Under the considered version is laid out using cut parts of fireclay bricks. The general rule in this case is that only untouched, factory-fired edges should be turned towards the fire, brick cuts are less resistant to high temperatures.

About the device of the remaining elements of the fireplace - in the following articles.

We thank RETRO for their help in preparing the material. The company "RETRO" carries out the whole range of furnace works, is engaged in the manufacture, repair, restoration of stoves and fireplaces.

If you decide to build a classic hearth in your house, then construction work must begin with the preparation of a solid foundation. A properly executed foundation for a fireplace is of great importance in the context of the further operation of the entire heating structure. At the same time, neglect of the fundamental building codes will irreversibly lead to deformations and subsidence of the fireplace in the first year of its use. Therefore, we will consider in detail the main recommendations of experts on pouring (laying) the foundation with their own hands under the fireplace.

Why do you need a separate foundation for the fireplace

In practice, there are cases when the owners of the house consider it unnecessary to equip a full-fledged foundation under the fireplace. Often people simply limit themselves to props in the basement, but then over the years they begin to notice that the masonry is gradually collapsing and the fireplace requires a separate foundation. The most reasonable solution is to lay the fireplace foundation in parallel with the implementation of the main foundation of the house. This will save money, time and labor resources. But it is a mistake to believe that it is possible to make these two foundations a single whole, because they are designed for different loads and, as a result, give a distinctive drawdown. That is why a bunch of foundation for a house and a fireplace base is strictly not recommended. Between the foundations there must be a gap of at least 50 mm, which is filled with compacted sand.

How to calculate the dimensions of the foundation

When calculating the dimensions of the future structure, one should start from the fact that the foundation for the fireplace should be larger than the fireplace itself, that is, protrude beyond its limits by about 100-150 mm. As for the depth of the foundation, it varies depending on the characteristics of the soil: its flowability, the likelihood of freezing, etc. The minimum depth is 0.5-0.6 m, for a two-story house it is approximately 0.8-1.0 m. The width of the foundation pit is determined by calculating the dimensions of the future structure plus 100-150 mm.

Leveling pad

Before pouring (laying) the foundation, it is necessary to prepare a leveling pad. To do this, you can take sand, which is compacted in layers by hand or using special equipment and, at the same time, is gradually wetted with water. Each of the layers should be regularly checked for level horizontality. The soil under the pillow is also subject to leveling and tamping. If the soil is heaving, the pillow is made of sand and gravel in a ratio of 4:6. The approximate height of the pillow is usually from 0.1 to 0.6 m and depends on the heaving of the soil.

The following materials are suitable as the basis for the foundation:

brick;
booth stone;
concrete.

Brick variant

If the walls of the pit hold the verticality of the form, do not crumble, are not exposed to close-lying groundwater, then waterproof brick-ironstone can be used to build the foundation. For bonding masonry, a cement-sand mortar with a ratio of components of 1: 3 is used. It is worth considering that in the winter months, freezing of the soil may occur, which sometimes leads to deformations of the brick foundation. It is desirable that the beginning of the masonry is located at a depth below 20 cm of the freezing level. This factor can be neglected if year-round living in the house is planned, provided that it is constantly heated, which minimizes the likelihood of soil freezing under the foundation.

Rubble concrete

If you decide to make a foundation of rubble stone, then tune in to the phased work. The formwork is made strictly vertical, the inner walls are coated with bitumen or upholstered with roofing material - so that the cement "milk" is not absorbed into the sand. The first layer is laid out from large stones with a diameter of about 15 cm. There should be a gap of about 20-30 mm between them, which is crushed with a fine fraction. The resulting structure is abundantly poured with a cement-sand mortar (1: 3). The final leveling of the first layer is carried out using a creamy mortar with a ratio of cement and sand of 1:1. The next layer is best done the next day.

ordinary concrete

For concrete, sand, Portland cement and gravel are taken under the foundation: 1 part cement to 4 parts sand and gravel mixture. Reinforcement with a cell of about 10-15 cm is also used. As a rule, pouring is carried out in two approaches. After the first layer, the reinforcement is compacted. This is followed by the second phase and, accordingly, the completion of work. Complete setting of concrete occurs only on the third day. In the summer, the formwork is stripped after 4-6 days, in winter - after 8-10.

Completion of work

When the base is ready, it is leveled horizontally using a cement-sand mortar (1: 2), as well as the mandatory waterproofing with two layers of roofing material. In this case, the upper level of the foundation should eventually be approximately 60-70 mm below the floor level.