Bathhouse foundation
A bathhouse is an integral attribute of any garden or summer cottage. This outbuilding is a source of pride for the owners. It’s not for nothing that immediately after building a house, the first thing they do is build a bathhouse. Despite the simple technology, building a bathhouse often raises many questions for inexperienced self-taught builders. A significant part of them concerns the construction of a load-bearing foundation, for example, how to properly make a foundation for a bathhouse made of foam blocks, or which foundation is better for a log bathhouse.
Technical and operational features of the bathhouse
To understand which foundation for a bathhouse is better, you should consider the operating features of this specific room. Among the technical and operational features of the bathhouse, the following should be noted.
Small dimensions and weight of the structure. Due to this, the depth of the foundation for the bathhouse can be insignificant. The load-bearing capacity of light foundations will be sufficient to support the weight of the building. The most economical choice from this point of view is a columnar-supported or shallowly buried strip base.
Due to the low cost of construction, its foundation should also be inexpensive. Massive and expensive supporting structures in this case will unjustifiably increase the total estimated cost of construction.
Frequency of heating the room. Due to irregular heating, all bathhouse structures go through many freeze-thaw cycles per year. The foundation of a building is no exception: frequent alternation of negative and positive periods can cause its premature destruction, therefore, to increase its service life, it is recommended to take care of the thermal insulation of the foundation base.
High humidity indoors necessitates high-quality waterproofing and drainage. The fact is that water, penetrating into small pores and cracks of concrete structures while using the bathhouse, remains there. When the room cools down and the temperature sets below zero, the water freezes, and, having turned into ice, it increases in volume, expanding microcracks and pores. Thus, over and over again, moisture leads to inevitable destruction of the foundation.
Effective multi-layer moisture insulation and wastewater disposal system will solve this problem. The foundation in the form of a monolithic slab best copes with the flow of “waste” water. In this case, the base slab simultaneously plays the role of a subfloor.
Other selection factors
In addition to the operational features of the baths, the following factors influence the choice of load-bearing base design:
- Weight and size characteristics of the building.
- Geological characteristics of the soil.
- Complexity and cost of technology.
Weight and dimensions of the bath
It is quite clear that the more massive the building, the more solid the foundation it needs. The weight of the bath depends on its size and the characteristics of the material from which it is made. For example, the foundation for a 6x6 m bathhouse, made of brick or stone, should be many times stronger than the foundation for a 4x4 log bathhouse.
Considering that the density of building bricks is several times higher than the density of wood (1500 kg/m3 versus 500 kg/m3), the weight of a building made from these materials with the same dimensions will differ by 3 times.
And if the foundation for a log bathhouse can be as light as possible, then the load-bearing foundation for a brick building must be quite solid.
Columnar foundation for a bathhouse
Calculation of the bearing capacity of the foundation
To get a reliable foundation, you need an accurate calculation of the mass of the building and the bearing capacity of the foundation. First of all, you should calculate the mass of the bathhouse by adding up the approximate weight of all structural materials from the foundation to the roof. The resulting number needs to be increased by 10 - 15%: this is the mass of interior decoration, water heating equipment, snow load on the roof, etc.
The next step is to calculate the supporting area of the foundation. To find the area of a slab foundation, simply multiply its length and width. It is somewhat more difficult to calculate the support area for a strip foundation. For example, you should calculate the foundation for a 4x6 m bathhouse: take the design width of the tape (30 cm) and multiply it by its length (the perimeter of the building is 20 m). It turns out 0.3 m x 20 m = 6 sq. m.
Next, the total mass of the structure is divided by the supporting area of the base, the result is an indicator of the specific pressure of the bath on the ground in kg/sq. see. Knowing the composition of the soil on the site, you can use the tables of building regulations and determine whether a given foundation is suitable for the future building.
If the developer does not trust his engineering skills, specialists from the construction company can make the necessary calculations. After all, errors in calculating the bearing capacity of the foundation can result in big troubles - from uneven subsidence of the building into the ground to the destruction of the foundation, and then the structure.
Geological characteristics of the soil
The bearing capacity of the soil directly depends on its composition. Rocky soils consisting of large fragments of stones and dense sandstones are considered the strongest. Such soils practically do not produce sediment and are not subject to the forces of frost heaving.
Frost heaving is a destructive effect that occurs on soils with high moisture content in winter. As a result of the transformation of water into ice, its volume increases significantly, and the moisture-saturated soil begins to bulge upward in the form of mounds and even small mounds.
On rocky and sandstone soils, you can build absolutely any type of foundation, of your choice - from a shallow-buried strip to a monolithic slab.
Clay and swampy soils have the weakest bearing capacity. In the first case, this is due to the property of clay to accumulate water, as a result of which clay soils are very heaving. Swampy soils, in addition to their tendency to heave, are themselves very weak. A building built on swampy soil risks sooner or later going underground, slowly subsiding down to the dense subsoil layers.
Foundations for weak soils
The susceptibility of soils to heaving is also influenced by the level of groundwater - the higher the level, the more saturated the soil is with moisture. In this case, the best solution would be to build a foundation on piles or in the form of a monolithic slab. In the first case, piles are used as supports, buried into the ground down to solid soil or below the freezing level of the soil.
Foundation on stilts for a bathhouse If the depth of the foundation for the bathhouse is below this mark, it will not be afraid of the destructive forces of frost heaving. Piles can be driven into the ground either by impact (driving) method - using hammers, or by the pile-screw method, when they are screwed into the ground using pile driving mechanisms.
A slab foundation for a bathhouse is one of the most attractive options. Making a foundation in the form of a monolithic slab is quite simple - just level the pouring area, pour a sand and gravel cushion, lay a reinforcing frame and fence the perimeter with board formwork.
In addition, the foundation slab has a large support area. The coefficient of specific pressure on the ground of a bathhouse built on a monolithic slab will be very small, which makes it possible to avoid subsidence of the building on soft soils.
Shallow burial creates the so-called “floating” effect: the base does not have a rigid connection with the ground and, when it swells, can rise without problems and fall again in the spring.
The rigid design of the monolithic slab allows the structure located on it to endure such cycles of raising and lowering without consequences.
Light foundations
Separately, we should consider examples of lightweight bases for baths. These include columnar-support and shallow-buried strip options, and they are intended for construction on dense, non-heaving soils.
Columnar bases
Columnar foundations are the simplest types of foundation. They are columns located around the perimeter of the building. Such supports can be made from a wide variety of materials: brick, cinder blocks, cast iron, steel and asbestos cement pipes, and also cast from monolithic concrete. The support pillars are located either on a shallow concrete pedestal base (brick and cinder block options), or buried in the ground and filled with concrete (tubular options).
At the top, the supports can be connected to each other by a metal, concrete or wooden beam - a grillage, which serves to impart rigidity to the structure. The pillars are located at a distance of 1 - 1.5 m from each other.
For small buildings such as a bathhouse, the pillars can be placed exclusively in the corners of the building. This will significantly reduce the overall size of the foundation for the bathhouse, reducing the time and financial costs of its construction.
Tape foundations
Strip foundation is the most common type of load-bearing foundation. It is used in the construction of multi-story skyscrapers and light utility buildings. Depending on the depth of the base, tape foundations are divided into three types:
- Recessed.
- Medium depth.
- Shallow.
Recessed strip foundations are used on difficult soils, when it is necessary to deepen the foundation below the soil freezing level, or when the project requires a basement or ground floor to be located under the building. In this case, the buried tape simultaneously plays the role of walls for the basement.
Medium-depth foundations are used on strong and medium-strong soils, when it is necessary to build a foundation for a fairly massive building - a brick or two-story timber-framed residential building.
The shallowly buried tape serves to simplify the construction of the foundation as much as possible. Such a foundation is considered if the depth of its laying does not exceed 0.5 m. In fact, the strip base can be deepened into the ground by only 10 - 15 cm, which is quite enough for small log bathhouses. This allows you to minimize the volume of excavation work and the consumption of concrete solution - the shallow foundation technology allows you to save on estimated costs and time and effort.
Foam concrete bath
Foam block foundation A relatively new building material that is gaining popularity in low-rise construction today is foam block. In recent years, many buildings, both residential buildings and outbuildings, have been built from foam concrete.
The popularity of foam block construction is explained by a number of advantages of this material. First of all, this is its lightness, high thermal insulation qualities and ease of construction. Building a bathhouse from foam blocks with your own hands is quite accessible to anyone who is more or less familiar with the construction business. However, this material has one serious drawback - it is very hygroscopic. That is, it has the ability to absorb and accumulate moisture from the surrounding air.
In this regard, the construction of a bathhouse made of foam blocks is accompanied by a number of nuances. Both internal and external foam concrete walls must be well protected from water and steam. The lower rows of blocks should be protected from rain and ground moisture. To do this, you should make the foundation high enough - up to 50 cm, so that splashes from rain jets do not fall on the wall.
In addition, a waterproofing layer should be installed between the foundation and the first row of foam concrete blocks. Failure to comply with the above conditions will lead to premature destruction of foam block structures, therefore, before deciding to build a bathhouse from foam blocks, you should carefully calculate all the pros and cons of such a design.
Having become familiar with the technologies for constructing foundations for bathhouses and the criteria for their selection, any owner of a suburban area will be able to build a reliable foundation for his bathhouse with his own hands. The main thing is to make the correct calculation and comply with the requirements of building regulations.
The foundation is the most expensive part of any structure, so It’s worth knowing in which cases you will have to shell out and in which you can save, using a fortunate combination of circumstances: strong soil, low soil water, shallow freezing depth. After all, there are significantly different in cost.
On what foundation is it better to place a bathhouse? Types of foundations
Let's consider all the options that are available. Each has its own area of application.
Tape
One of the most common foundations, which combines the possibility of installation on heaving soils with a moderate cost(it is lower than that of a slab and higher than that of a columnar one). It got its name because it is a concrete “ribbon” with the same rectangular or trapezoidal cross-section, stretching along the perimeter of the building and inside - under the partitions. The width of the tape is usually 10-15 cm wider than the thickness of the future wall. According to the manufacturing method, strip foundations are divided into monolithic and block.
By laying depth - shallow and full laying depth. This is worth explaining: according to the rules, the full depth of the foundation is equal to the depth of soil freezing plus 20 cm. But for light structures, even with a large freezing depth, you can use a shallow foundation, which (conditionally) is 20 cm deeper than the fertile layer, and is practically the same height as the base to the edge 50-70 cm (if the soil freezes 3 meters deep, this is really a small thing).
Monolithic
Such a foundation is obtained by pouring liquid concrete into the formwork. To give it more rigidity it must be reinforced with a frame made of reinforcement, which is placed inside the formwork.
A monolithic foundation can be used both for heavy buildings, for example, made of brick (at full depth), and for light ones.
IMPORTANT! A feature of this type of foundation is the need for strict adherence to technological requirements: from the device to the temperature regime and subsequent maintenance.
If everything is done correctly, then such a foundation can withstand even uneven shrinkage, which occurs when there is different soil at different angles of the structure.
Blocky
Ready-made reinforced concrete blocks are used to create a block or prefabricated strip foundation. They are laid in trenches and secured with mortar and reinforcement. The first to be laid are pillow blocks in the shape of a rectangle or trapezoid. The following rows of blocks are placed on them (with bandaging, that is, with displacement of the seams). Their joints must be reinforced.
IMPORTANT! Pillow blocks do not need to be used when building a bathhouse.
If the factory structures do not fit into the allotted space, they are either cut, or the remaining small space is filled with concrete or brickwork is made there.
The blocks require careful fitting, but the actual construction of them speeds up the process. Besides, such a foundation can be laid even in winter.
It is suitable for both heavy and light baths. But all block ones have one drawback: they poorly resist lateral soil pressure, therefore, they need additional protection - a wider blind area, etc.
In addition to the above, there are other types of strip foundations: rubble, rubble concrete, brick. Butovoy is not afraid of either heaving soils or groundwater. But it is the most difficult to build. Brick is suitable only for dry soils, and in this case you can choose a cheaper option.
Columnar
With this type of foundation, the load from the walls falls on pillars dug in at key points, which include:
- building corners;
- crossing walls in other places;
- places of high load.
In addition, the pillars are evenly distributed in the remaining space. A so that the pressure on the ground from each pillar is less, they are usually expanded towards the bottom. According to the rules, the distance between two adjacent pillars should not exceed 3 meters (in practice it is less).
The tops of the pillars are connected by a grillage, which makes it possible to lay walls made of block material. But The main function of the grillage is to provide stability to the pillar foundation.
The material used for pillars is:
- brick;
- stone;
- asbestos cement pipes;
- concrete.
In the past, wood was often used, but it has a short lifespan (except larch). If you make poles from wood, they need to be impregnated with an antiseptic and waterproofed with bitumen mastic, however, waterproofing is recommended for poles made of any material.
Column foundations are recommended for lightweight buildings. Heaving soils are not a problem for it, nor are high groundwater levels, but this type of foundation has one big drawback: it does not hold the load well during horizontal expansion or soil shift. Transverse pressure during frost heaving can topple poles directly in the ground. The grillage partially helps against this. We strongly recommend a geological survey of the site to avoid unnecessary expenses in the future.
Based on their depth, columnar foundations are also divided into shallow and full depth. Small ones go into the ground only 40-50 cm, while complete burial is the depth of soil freezing plus 15-20 cm.
Pile
Outwardly, it is similar to a columnar one, but the main elements are not pillars, but piles. The depth of immersion of piles can be from 3 to 20 meters. Their tops are connected into a single structure using a grillage.
The main reason for constructing a pile foundation is unstable soil or soil. These can be “quicksands” or deep peat areas. In addition, piles are used when the building site has a pronounced relief - piles make it possible to obtain a level foundation for the building at any height difference. The weight of the building does not matter much - the piles can withstand heavy buildings.
Let's consider two types of pile foundations: pile-screw and bored (here only briefly). In addition to screw metal piles, there are also reinforced concrete and combined ones.
Screw
The end of the metal pipe is equipped with a screw blade, with the help of which the pile is first screwed into the ground and then fixed in it. Herself the pipe must be coated with good paint with high adhesion, which will serve as anti-corrosion protection.
To drive a pile into the ground, you need a special technique that allows you to control the depth and verticality of the plunge. On the one hand, this increases the cost of the foundation, on the other hand, it reduces production time.
IMPORTANT! Don’t buy cheap pipes, because the price goes down only due to the quality. (But expensive pipes and work together can cost as much as a slab floating foundation. Take the average ones.)
Bored
The principle of a bored foundation is simple:
- wells are drilled in the ground;
- they contain a frame made of reinforcement;
- into the well.
The drill for drilling wells can be not only mechanized, but also manual. After this, the walls of the well are strengthened using a casing pipe (if the soil is loose).
Useful video
Sometimes piles are drilled and filled using special equipment, and sometimes some are made with their own hands, as in the video below:
Concrete is poured in stages: after each meter, the concrete must be compacted. To do this, you can use either a mechanical tamper or a vibrator.
Slab
Another name for this variety is monolithic and floating. This is the most expensive type of foundation because it is a concrete slab with a thickness of 10 to 50 cm or more, which is poured directly on the site onto a sand and gravel bed.
Such a slab rises along with the ground, preventing deformation and destruction of the building. If you add stiffening ribs to the structure, it will more successfully withstand horizontal displacements.
The main indications for the construction of a slab foundation will be the same quicksand and peat bogs as for a pile foundation. Therefore, it is possible to choose a more cost-effective solution. And here For stable and non-heaving soils, such a foundation is simply a waste of money.
IMPORTANT! A slab foundation is not suitable for areas with large elevation differences. (The only solution here is a pile solution).
As for the weight of the bathhouse, it is not critical for a slab foundation; it will support a house of up to 3 floors.
The advantages of a slab foundation include indifference even to high groundwater. Only concrete must be sulfate resistant.
Well, we have looked at every possible foundation for a bathhouse, which one is better - you will learn from the following chapters. But first, watch this video with a conversation about choosing a foundation. It’s a little tedious, but at the same time necessary - so that later you don’t have to spend money on alterations.
Which foundation is best for a bathhouse depends on the soil
While we were looking at the types of foundations, you have already become acquainted with some recommendations for different types of soil. Let's put this knowledge in order.
Gristly
This is the name of the soil located on a rocky base and consisting of sand and pebbles.
It is ideal for construction because water does not erode it, it is filtered through it, and deep freezing does not occur. The soil itself is quite strong; it contains few subsidence rocks, so it can withstand heavy loads.
On such soil you can build the cheapest columnar foundation. Other types are also possible, but it is unnecessary to use them.
Sandy
Water does not stay in it, so groundwater usually lies deeper. In winter, sandy soil freezes no deeper than a meter. It is also good for construction. But it is worth taking into account that when moistened it becomes very compacted, there is a lot of subsidence rock in it, and this is fraught with soil displacements both vertically and horizontally.
Both reinforced columnar and strip block foundations can be laid on sand.
Rocky
A rock without cracks is the strongest foundation, which makes a foundation as such unnecessary. If we are talking about rock fragments, then in this case it is still worth making a foundation with a minimum laying depth.
Such soil practically does not freeze, it is not characterized by heaving, and there are almost no subsidence rocks in it. Any foundation can be made, but a strip foundation with insignificant depth is more advantageous. It will be quite inexpensive.
Clayey
Clays are able to absorb and retain water, while swelling greatly. And when they dry, their volume decreases and they crack badly.
When moisture in the soil turns into ice in winter, this increases its volume, causing the soil to swell—to move both vertically and horizontally.
At the same time, heaving also occurs unevenly - some areas rise higher, others lower. And this has an extremely negative impact on the foundation and structure.
Heaving is neutralized by excavating the soil and replacing it with a sand-gravel mixture, on top of which it is usually done either strip or slab foundations.
Peaty
Peaty soils are considered unfavorable for construction. They contain many organic impurities and are highly compressible. In addition, peat bogs are usually saturated with moisture. The soil is unstable and not every foundation is suitable for it.
If the peat layer is small, then the optimal solution would be to remove the peat layer and replace it with sand and gravel. But when the peat layer is too large, you have to erect a building either on pile or slab foundations.
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In addition to the type of soil, you should be interested in: the depth of its freezing(it can be found in the tables of geologists) and groundwater height Location on.
And here is a useful video about the types of foundations and the rules for calculating their depth depending on the soil. It will answer the question which foundation is best for a bathhouse.
Which foundation is better for a bathhouse, depending on the type of building
| Bath type | What kind of foundation can I place it on? |
| Log house, timber | You can use any, but it’s more economical to use a columnar or shallow belt, if the soil allows. |
| Frame, panel | The structure is lightweight and does not require a solid foundation. Again, if the soil allows (it will not overturn the pillars), we can recommend a columnar foundation. Any other will also do, but will be less profitable. |
| Foam block | Another lightweight design. The conditions are the same as for the frame one. |
| Cinder block | Relatively heavy material, but the columnar foundation will support it. Tape is also recommended. The rest depend on circumstances. |
| Brick | The heaviest of wall materials. We exclude columnar. Tape is considered optimal. The use of the rest depends on the properties of the soil and other factors. For more details, see the link above, the same as for cinder block. |
This table suggests that wall material is a factor that simply cannot be considered separately from the properties of the soil.
IMPORTANT! To the weight of the structure you also need to add the snow load characteristic of your region.
The heavier the structure, the more thoroughly the foundation has to be made, the more expensive it is, but lightweight structures put little pressure on the ground, so highly heaving soils can push out a structure made of light material.
You can combat frost heaving by either replacing the soil under the bathhouse with drainage soil, or by making a wide blind area (more than 1 meter) around it and discharging precipitation through gutters away from the bathhouse.
conclusions
So, we have considered all the factors that determine on which foundation it is better to place a bathhouse..
First conclusion from what was said: you need to have an understanding of the geology and hydrology of your site. You may have already done research while building your home. As a last resort, ask your neighbors - this will not give accurate information about the strata on your site, but you will get an idea of the dominant soil in the area.
Conclusion two: the results of geo- and hydrostudies, calculation of the load on the foundation almost always leave us with a choice. For example, even before building the foundation, you can try to improve the soil - drain water, reduce heaving. Is this advisable? Find out the prices and decide.
Conclusion three: it is worth soberly assessing the service life of the bathhouse and comparing it with the theoretical service life of a particular foundation. A slab bathhouse, for example, promises to last for 200 years—what kind of bathhouse can last that long?
In contact with
Before carrying out technical work on installing the foundation for a bathhouse, you need to carry out geological survey.
Depending on the identification of the exact type of soil, its load-bearing properties, the possibility of changing quantitative parameters as a result of tectonic changes, the best material for the foundation is determined, and most importantly, its depth is calculated. Correct calculation of the burial depth, in some cases, will save the foundation and walls of the bathhouse from subsidence, cracks, distortion, and deformation.
Fine and dusty sandy soils contribute to strong shrinkage of the bathhouse foundation. To reduce or level out this process, the depth of the foundation can be significantly increased. Instead of the planned 50 cm depth, it would be advisable to increase it to 70-100 cm. With increasing foundation depth, the compression resistance increases proportionally. This value in fine sands is approximately two times lower than in coarse sands. In order to make up for the missing load-bearing capacity, the depth of the foundation is doubled.
Gravelly and coarse sandy soils are quite reliable in terms of load-bearing qualities. Sandy soils are not heaving, so regardless of the amount of precipitation per year or the depth of freezing, you can choose any type of foundation for a bathhouse. Coarse sandy soils exhibit insignificant shrinkage compared to fine ones. On them it will be easy to build a shallow foundation, ranging in size from 20 to 50 cm.
Sandy soil does not retain water, which means it is a light soil. A pile or columnar foundation can be built on it. The depth of the pillars is approximately 1.5 m.
Rocky soils have the best load-bearing qualities of all other types of soil. They practically do not shrink, supporting the weight of fairly large-scale structures. Rocky soils are not heaving because they do not retain water in their pores. The depth of soil freezing will not be taken into account when building the foundation. There is no excess moisture in the soil, so they will not expand due to the conversion of water into ice. On rocky soils, foundations can be installed more economically.
Rocky terrain acts as an unshakable foundation for a building, so shallow or shallow foundations (less than 20 cm) are always built there.
Clay soils, unlike most others, have a finely porous structure. The main disadvantage of clay soils is their ability to swell. The proximity of groundwater and abundant rainfall contribute to the rapid accumulation of water in the pores of the soil. With the onset of sub-zero temperatures, water turns into ice. The density of water, after turning into ice, increases, which leads to an expansion of the volume of the entire soil. Changes in soil volume place additional load on the foundation, causing its deformation, cracking, distortion, and lifting of the bathhouse building.
Calculations for deepening the foundation on clay soils are being carried out taking into account freezing depth. It is necessary to build the foundation below the soil freezing level, then the loads will be exerted only on the side walls of the foundation, eliminating pressure on the base of the foundation. For example, the depth of soil freezing is 1.5 m, which means the foundation lies at a distance of 1.6 m. The high level of groundwater will not allow the necessary deepening of the foundation.
The base of the foundation is at an indentation of no lower than 0.5-1 m. Sufficient distance will be required in case of capillary rise of water in the soil and in case of an unexpected increase in water level due to heavy floods or prolonged downpours. To drain excess water from the ground, a drainage system is installed around the foundation. They dig a trench deeper than the base of the foundation. They lay the foundation around the perimeter with a pipe and lead it into the inspection well. Water will not accumulate and freeze in the pores of the soil, and excess water will also be automatically drained in the event of a strong rise in the groundwater level.
When installing a drainage system, the depth of the foundation can be changed, taking into account the load-bearing properties of the soil and non-tectonic parameters, which are also important for calculating the depth of the foundation for a bathhouse.
The depth depends on the type of foundation
Columnar foundation formed by horizontal pillars located along the contour of the walls of the bathhouse. The main advantage is considered to be high wear resistance, suitability for many types of soil and cost-effectiveness. Its versatility deserves attention. Depending on the material for the walls of the bathhouse, you can use concrete, wooden, or brick pillars. The standard length of pillars is from 2 m. It is laid at 1-1.5 m. There is a shallow columnar foundation, occupying a height of only 50-70 cm. It is laid at 40-60 cm.
Pile foundation preparing for construction by drilling wells. It is laid in several ways. The easiest way is to pour concrete mixture into pre-dug wells using a hand drill. Wooden and steel piles are laid. The main advantage of a pile foundation is that the foundation lies below the soil freezing level. A team of workers will be able to install the piles in just 1-2 days. The burial depth is determined for each structure, the maximum is more than five meters.
Screw foundation got its name due to its manufacturing technology. Screw piles resemble the shape of a screw and, thanks to special blades, are easily screwed into the ground. Building a foundation on screw piles has many advantages. For such a foundation you do not need to dig a trench or even level the ground. Suitable for all types of soil, except rocky. Service life more than 100 years. Disadvantages include average load-bearing qualities.
The piles are installed in a certain order. The distance between the piles should not be less than 3 m. The piles lie at least 1.5 m deep into the ground. The maximum depth of the pile foundation is 2.4-2.6 m, since the longest pile length is 3 m. If the required depth is greater, than indicated, piles can be built up using reinforced concrete.
Slab foundation consists of a monolithic reinforced concrete slab. Its minimum thickness is only 15 cm.
A shallow foundation is laid 30-40 cm deep into the ground.
Floating foundations- a type of slab shallow foundation. It differs from other foundations in the presence of stiffening ribs - dense placement of reinforcement along the entire perimeter of the slab.
The peculiarity of the floating slab is the ability to move. Unlike other types of foundation, a floating slab does not compete with the pushing forces of the soil, but moves slightly as they rise in the cold season, due to their lowering with the arrival of spring.
A floating foundation will be an excellent way out of a difficult situation related to soil characteristics. When there is close groundwater and a high level of soil freezing, a floating foundation is built on the surface. The minimum deepening of the foundation is only 40 cm.
Depth of strip foundation for bathhouse
Classic strip foundation depth consists of a twenty-centimeter, well-compacted sand cushion. Above is a foundation 60 cm high: 40 cm lies in the ground, and the remaining 20 cm extends to the surface. Since the strip foundation has become the most popular, universal option for bathhouse foundations, the correct calculation of its depth needs to be studied in more detail.
First of all, they start from soil properties. Frequently encountered problems associated with the structure of the soil when designing a foundation affect the depth of its construction. The risk of cracks arises when erected on rocky soil. In this case, a shallow or non-buried foundation is used. Soil prone to swelling requires the foundation to be sunk deeply below the freezing level. The possibility of foundation failure is characteristic of fine sandy soils. When building a foundation on such soil, a deep foundation is designed to increase compression resistance.
Other parameters affecting the depth of the foundation
Foundation depth depends on the material, from which the walls for the bath are made. A stone bathhouse requires from 1 m, preferably from 1.5 m. A bathhouse made of logs or timber also needs a foundation of at least 1 m. Laying cinder block walls is 1.5 times lighter than brick, so the foundation can be laid from 0.5 m. Aerated concrete and foam concrete blocks need foundation with a depth of 40 cm.
Significant influence The depth of the foundation for a bathhouse is influenced by the type of soil, type of foundation, materials for making walls and foundations.
Having compared all the factors that influence the depth of its occurrence, having determined the required depth for a specific foundation, you can proceed to the stage of its construction.
The construction of a bathhouse must begin with the development of a project, which requires taking into account the results of preliminary engineering surveys, calculating the optimal dimensions, selecting materials and designating the location of the structure, and determining which foundation is best for the bathhouse.
Design features of the bathhouse
The bathhouse is an auxiliary outbuilding and has a number of design features. In particular, when building a bathhouse, the issues of water supply, sewerage, power supply and heating should be taken into account. You should also take into account the mode of operation of the bathhouse - year-round or seasonal. A summer bathhouse requires lower costs for its construction and operation, and for year-round use of the bathhouse it is necessary to pay special attention to the thermal insulation of the building, as well as protecting the water supply and sewerage from freezing.
The material used to build a bathhouse is timber, logs, brick, stone or foam block. For a summer bath it is permissible to use a frame base with lumber covering the walls. Internal partitions can be made of timber, thin logs, boards or fibreboards. When installing a bathhouse, special attention should be paid to fire safety rules and waterproofing of wooden walls. Another extremely important point is the organization of proper ventilation to remove fuel combustion products in the furnace.
Based on the size of the bathhouse, the weight of the walls and stove, location, soil quality and climatic characteristics of the region, the foundation for the bathhouse is laid. Which foundation is better, cheaper and easier to make is determined during the development of the project, carrying out engineering surveys and drawing up estimates.
You can determine on which foundation it is better to place a bathhouse after deciding on the size of the building and the material for its manufacture. Particular attention is required to checking the quality of the soil, determining the groundwater level and freezing depth. The depth of foundation laying, in addition to soil density, is also determined by the groundwater level and the depth of freezing of the ground in winter.
Depending on these parameters, the foundation depth can range from 50 cm with dense soil, low groundwater levels and shallow freezing depth, to 100 cm or more with large freezing depths and high groundwater levels. The groundwater level and freezing depth can be determined by laying a test pit in summer and winter. To prevent swelling of the foundation, the foundation is laid below the freezing depth of the soil.
Rules for choosing a foundation for a bath
You can choose which foundation is best for a timber bathhouse after drawing up the project. For example, for a small bathhouse, the walls of which are made of medium-thick beams, you can use a pile or columnar foundation. If thick, heavy beams are used, strip concrete foundations can be made. The foundation for a log bathhouse can be of the same type. What is the best material to use for its manufacture is determined during the costing process.
Which foundation is best for a foam block bathhouse is also not difficult to determine. In this case, you can use a combined structure, including elements of pile and strip foundations. A strip foundation is used for the external load-bearing wall of the bathhouse, and piles or load-bearing columns can be used for the internal partitions. In addition, strip foundations, with relatively low labor costs for their manufacture and the required material, can also be used for baths made of brick or stone.
The easiest to manufacture is a shallow strip foundation for a bathhouse.. Which material is best to choose for the foundation strip is determined by the density, type of soil and the presence of nearby groundwater. The optimal depth for most buildings made of timber, logs, brick or foam concrete is about 30-50 cm.
Pile foundations
If the soil base at the site where the bathhouse is being built is soft, wet and prone to crumbling, then a deeper foundation may be required. In this case, you can use metal screw piles, which are steel pipes with cutting blades at the end.
When installed, such a pile is aligned vertically along a plumb line and screwed into the ground until it stops in a dense or rocky layer located below the freezing level. The distance between the piles is selected based on the size of the bathhouse. Piles are installed at the corners of the building and at support points with maximum load. After installation, the piles are cut to a height of 20-30 cm and filled with concrete, having previously inserted into them fastening threaded rods with a diameter of 15-20 mm and a length of 40-50 cm, onto which the support beam will subsequently be attached using a nut.
Similarly, a pile foundation is made from asbestos-cement pipes with a diameter of about 20-30 cm. The pipes are installed in vertically drilled wells at least 2 m deep and filled with concrete. Before pouring concrete, 3-4 reinforcement bars and a fastening threaded rod are installed in the pipes. The number of pipes is determined by the size of the bathhouse and the load on the foundation. The disadvantages of pile foundations include their weak resistance to horizontal soil movements.
Massive foundation
If the soil at the site where the bathhouse is being built is very weak and prone to swelling and movement, then a solid reinforced concrete slab 20-40 cm thick is used as the foundation for construction. When pouring a solid foundation, you should dig a pit, level and compact its base. A cushion of sand and gravel about 10-30 cm thick is poured onto the bottom of the pit, onto which a reinforcement frame is laid and the concrete mixture is poured.
When making a solid foundation, before pouring concrete, it is necessary to first install drain and water pipes. Concrete for solid, pile or strip foundations is made from high grade cement, which ensures heat resistance and water resistance of the foundation. You can reliably find out which cement is best for the foundation of a bathhouse using a reference book on building materials, where, in addition to the brand of cement, its operational characteristics are also indicated.
As a rule, for the production of cement mortar and concrete for foundations in construction practice, grade 150 or 200 cement is used.
The choice of location for a bathhouse directly depends on the conditions of water supply and sewerage. A convenient place to build a bathhouse will be a flat area with a slight elevation relative to the outbuilding at a distance of 15-30 m from an artificial or natural reservoir. Regardless of the type of foundation, the site must be carefully marked and leveled, having previously assessed the density of the soil.
After preliminary marking and leveling of the site, you can determine on which foundation it is better to build a bathhouse. If the soil is strong enough with a low level of groundwater, then the choice of foundation type is determined only by the material used to make the walls of the building and their weight. In this case, it is necessary to take into account the weight of the roof and seasonal snow load.
To level and pre-mark the site for the construction of a bathhouse, the following tools may be required:
- marking pegs;
- marking cord or wire;
- theodolite;
- rail;
- shovels and bayonet shovels;
- ax or chainsaw;
- roulette.
Making the foundation
After preliminary marking, planning and leveling of the site for the foundation, you can begin laying the foundation. Let's consider the process of manufacturing a strip foundation with a shallow laying depth, as the most common and suitable for constructing bathhouse walls from any material.
A strip foundation with shallow depth is a concrete strip about 30 cm wide, going into the ground to a depth of 30 - 50 cm, the upper edge of which is 15-20 cm above the ground surface, forming the basement part of the structure.
The following tools are required to carry out the work:
- marking pegs;
- measuring cord or wire;
- building level;
- plumb line;
- bayonet and shovel;
- hammer;
- saw a hacksaw for wood;
- hacksaw saw;
- pliers;
- construction vibrator;
- concrete mixer.
A trench is dug on the site marked for construction using pegs and a cord. Its depth is 0.5 m, width - about 30 cm. The bottom of the trench is covered with a layer of sand 10 cm thick and compacted. A layer of gravel (10 cm) is poured on top of the sand cushion and compacted so that the sand and gravel form a single mixture.
According to the plan, drain and water pipes are laid in special recesses, as well as, if necessary, pipes for electrical wiring. To organize the drainage, a drain well is usually used, located at a distance of 3-5 m from the wall of the bathhouse. Drain pipes are laid with a slope towards the drain well to organize gravity flow of water. Where the pipe passes through the concrete strip of the foundation, several layers of waterproofing material are wound onto the surface of the pipe so as not to damage the surface of the pipe during the process of pouring concrete into the formwork.
Along the edges of the trench, formwork is installed from boards 20 cm wide, forming the upper basement part of the foundation. The boards are secured with spacers and pegs driven into the ground. In the corners of the boards, they are additionally fastened with nails or binding wire. The verticality of the trench walls and the location of the formwork is checked with a plumb line, the horizontal position of the edge of the formwork is corrected using a building level.
2-3 contours of reinforcement with a diameter of 10-15 mm are laid in a prepared trench with installed formwork. Vertical sections of reinforcement are connected to horizontal rods using knitting wire. The fastening spacing of vertical rods should not exceed 0.5 m. The ends of horizontal reinforcing rods should not be located in the corners of the building; for this purpose, during installation, the reinforcement is bent so that the ends of the rods are no closer than 0.5 m from the corner of the building.
The formwork rods are laid so that they do not protrude from the concrete. Otherwise, the reinforcement will be subject to corrosion, which may cause the integrity of the foundation strip to be damaged under load during its operation.
After completing the installation and checking the strength of the reinforcement, concrete is poured into the trench, from which air bubbles are removed using a construction vibrator. The surface of the concrete is leveled and covered with waterproofing material to protect it from atmospheric moisture and direct rays of the sun. 10-14 days after the concrete has completely hardened, the formwork can be removed and the construction of the walls of the bathhouse can begin.
If the internal partitions of the bathhouse are light, there is no need to use a strip foundation as their support. To reduce labor costs and save material at the intersection points of internal partitions, columnar foundation elements can be used. To make load-bearing support columns for the internal partitions of the bathhouse, you can use baked brick or concrete. The size of foundation pillars made of brick is usually 0.5x0.5 m, of concrete - 0.6x0.6 m.
If a large stove-heater is used to heat a bathhouse, then to install it it is necessary to make a separate foundation, which can be made in the form of a solid concrete slab or a combined structure can be made in the form of buried brick pillars, the space between which is also laid with bricks on cement mortar.
Building a bathhouse is a less complicated task than building a private house, for example, but still requires skills and a professional approach. So, initially, having chosen a convenient place, you need to make a foundation for a small bathhouse. The question becomes about the choice of material from which it will have to be built in the future. If the walls are made from lightweight foam blocks, the same preparation is needed; when constructing walls from expanded clay concrete blocks, the base is made completely differently. If construction is carried out using a log house, you can get by with arranging a foundation made of sleepers, timber or car tires.
The monolithic option is taken into account only when constructing a heavy structure. Let’s take a closer look at where and what kind of foundation for a bathhouse is better to build with your own hands and how long it will take to dry.
Site preparation and territory marking
Construction begins with markings. You will need a few tools: 10 wooden stakes, a hammer, a tape measure 15 meters long, a construction cord of 25 m, or a fishing line, a hydraulic level of 20 m. Let's take a regular foundation made of expanded clay concrete blocks. Such a foundation for a bathhouse can be built with your own hands in a couple of days and does not require a huge investment of funds. Let's take the standard option.
We calculate the width of small pits. We take into account the insulation and piping of the foundation blocks of the bath: 200 mm is the width of the block, and 400 mm is the length. The height of the base part is approximately 600 mm, 3 blocks. It turns out that the pits for development will be: 450 x 450 mm, with a depth of 0.8 meters - this is the standard width and depth for the usual construction of a block base made of expanded clay concrete blocks. Now let's move on to developing pits.
Development of soil for a bathhouse
To make the foundation of a bathhouse with your own hands you will need: a bayonet shovel, a scoop, a pick in case of the presence of stones, an ax for snags, and a cart for removing soil. Having dug to the specified depth, we clearly level all the edges. A foundation for the firebox (sauna stove) should also be provided. We must not forget that the installation of a firebox inside a building requires the preparation of a concrete pad. This is done before the main monolith is poured, after calculations a cushion is made, and then the support pits are poured under the expanded clay concrete blocks.
Pillow for a stove or firebox
Dig a pit 1200 x 1200 mm to a depth of 600 mm. This depth was not chosen by chance; 300 mm is sprinkled with sand. The pillow is compacted using a hand tamper. The following steps follow:
- A layer of waterproofing material is laid on the bottom so that there is a reserve and the edges protrude outside the pit.
- Place the frame (formwork) at the required height and pour a 200 mm concrete slab.
- Insulation is carried out with 50 mm polystyrene foam slabs, placing it directly on fresh concrete.
- Then pour a finishing layer of screed, 50-150 mm. The insulation under the heating element is ready.
After concrete work on the installation of a load-bearing cushion, it is necessary to lay a network of water supply and sewerage pipes and carry out their complete insulation.
Tip: The base for the firebox should not come into contact with the main foundation, since it tends to expand when heated. The gap is filled with sand after concrete work and dismantling of the upper formwork.
Networks and drain
Laying pipes for water supply networks for drainage in the bathhouse Let's move on to laying pipes for water supply networks. Calculation of the diameter and length of water supply networks is carried out in advance, before all concrete work is carried out. Separate trenches are dug under the water supply pipes to the pipe outlet points. The installation of water supply networks requires special skills and knowledge, but you can prepare trenches yourself. According to the technology, the pipes are laid on a bed of crushed stone. The bottom of the ditches is filled with gravel, the standard layer thickness is 80-100 mm. The ends of the pipes are brought out 100 mm above the floor level, in the right place and closed with plugs.
Subsequently, after all the concrete work and the construction of walls from sleepers, all pipes and internal networks are installed. The depth of laying pipes in the ground on the outside of the room is 1200 mm, and on the inside 600 mm. The installation of networks can be carried out simultaneously with the drainage by laying the pipes together.
The cushion for laying pipes and networks must be compacted. The slope for laying sewer pipes, the height of the inlet and outlet openings, and the drainage angle are measured. Before making the entire foundation for the bathhouse, take care of the wastewater drain. Prepare a hole or pit and drain there. The optimal distance between the bathhouse and the drain is 6-10 meters, otherwise the log house will become damp.
Foundation insulation
The foundation for a frame bath can freeze, therefore, it is insulated from the outside with various materials. Insulation is carried out before pouring concrete. Sheet material made of polystyrene foam or polystyrene is used; they are optimally suited for these purposes. Sheets with a thickness of 50 - 80 mm are used, with a size of 600 x 1000 or 1000 x 1000 mm.
They are fastened on the outside of the pits (along the outer edge), between the reinforcement frame and the ground. The space is then completely filled with concrete to the required height. The insulation is of high quality and monolithic, durable. Expanded polystyrene does not absorb moisture. The service life of such materials is 25−30 years.
There is another option for carrying out external insulation by filling all the supports for the bathhouse with expanded clay around the perimeter: after all the concrete work, develop cavities around each concrete base and pour a cushion of expanded clay. Such insulation will require additional costs for excavating the soil and installing waterproofing.
Reinforcement
Now let’s try to figure out how to make full reinforcement and pour concrete pillars under the bathhouse with our own hands, and consider how to arrange masonry from expanded clay concrete blocks. You can start knitting an armored belt right on the site. This will also require marking and calculation. A simple way to knit a spatial frame:
- Draw two parallel lines, and then lay reinforcement cut to size along them and tie them together like a ladder. The edges of the transverse rods must extend 30 mm beyond the edge of the main trolls and rods. All workpieces are measured in advance and a preliminary calculation is made on the length and height of the workpieces as much as required.
- Having installed the blanks in all the holes, they are tied together with knitting wire. First, the lower crossbars are knitted for ease of movement. Then the upper rods are attached.
If the holes are narrow, then the blanks are knitted completely. Then they are installed in the pits entirely, tying only the corners. Carry out reinforcement only with viscous reinforcement; the use of welding equipment is unacceptable.
Foundation for heavy materials made of expanded clay concrete blocks and foam blocks
It is possible to make a reliable foundation for an ordinary bathhouse with your own hands only if you do not violate the basic construction technologies. The frame is tied, the concrete is being prepared. The calculation of materials is carried out as follows: for the total cubic capacity of the foundation, take the ratio of materials: 12% cement, 25% sand, 45% crushed stone, the rest water and clay. For expanded clay concrete compositions, the filler (crushed stone) is divided equally with expanded clay.
The composition will be warm, but it requires the use of waterproofing materials. Before building a foundation for a bathhouse from such material, calculate the weight of the entire structure. It is suitable for a lightweight structure made of foam blocks, but for expanded clay concrete materials it must be strengthened. It is necessary to change the depth of the foundation, pour it 0.5 meters deeper, this applies to each monolithic pillar.
DIY block laying
Scheme of a columnar foundation made of blocks for a bathhouse The foundation in this case consists of expanded clay concrete blocks standing on concrete pillars. To begin with, we mark the directions for the blocks by driving 4 pegs along the outer perimeter of the future bathhouse. Pull and level the cord to the height of approximately the first block. If you made basement formwork when pouring concrete, the masonry is carried out according to its dimensions, placing the blocks on concrete pads.
Lay two blocks at a time, filling the seam with mortar. Lay the next row perpendicularly, the edge of the expanded clay block or foam block should touch the cord. Blocks are mainly used to raise the height of concrete foundations above the ground or when the site has a large slope. Lay the required height and leave it to dry. During laying, place studs between the blocks to secure the frame.
Construction of a supporting structure for lightweight materials
The weight of foam blocks is small, up to 24 kg, with dimensions of 200 x 300 x 600 mm, unlike expanded clay concrete. We calculate the foundation slab differently than for a pillar foundation. In this case, the entire structure will lie on the slab, transferring all loads to the ground evenly, making it stronger.
The construction of a slab (slab version of the foundation) is easier to do than the pillar version, but for a log building it will also work. Depth is not needed for a monolithic surface foundation 1-1.5 meters high; a 40-50 cm deepening into the ground along the entire plane or perimeter is enough, it depends on the configuration of the log house.
The height of the above-ground part of the concrete slab is 10−15 cm. When poured, a monolithic layer (slab) is obtained that carries the entire frame, evenly distributing the load from the building onto the ground. The slab option is suitable both for medium-weight buildings and for structures made of foam blocks, foam concrete blocks; on it you can build a bathhouse from sleepers, build a log house; there are many options for using slab technology, as many as are necessary for high-quality construction of buildings.
The slab foundation for the construction of walls made of foam blocks is arranged as follows:
- Markings are made for the slab, the building is taken in width and length, but with a margin of 800-100 mm. It would be correct to lay only a slab around the perimeter under the bathhouse, and fill everything inside with clay when finished.
- The soil is removed to a depth of 400 mm, the pit is filled with sand, 200 mm thick. For foam blocks this pillow is enough. Now we compact it around the perimeter, there should be no gaps. Although the frame is not heavy, the slab must work over the entire plane; the depth here is not as important as the uniform compaction of the soil and sand.
- Now the formwork is placed around the future foundation, the height of the board is selected according to the protruding part, in this case 150 mm.
- Cards are knitted from 12mm reinforcement, with a cell of 300x300, laid on a prepared site, having previously placed plastic distances, or spilled small nickels from the solution. After reinforcement, you can pour the solution. Such a foundation does not dry for long, 7-12 days.
Tip: In summer, sand dries quickly, so wet it with water before pouring concrete. .
Tire foundation
You can build a unique and at the same time strong foundation with your own hands from car tires. This is an economical option for a foundation for a wooden building made of logs or sleepers. The method for laying out the elements is as follows: markings are made for the contour of the bathhouse. Then the top layer of earth is removed along the entire perimeter, 15 cm deep and 50 cm wide. The space is filled with crushed stone and sand mixed in a 1:1 ratio. The pillow is compacted under the tires using a manual tamper.
The required number of tires is prepared, about 20-25 pieces of the same size and height (it all depends on the size of the tires and the bath). A perimeter of tires is laid out so that they lie tightly to each other.
Now we insert the threaded studs and tie them to the reinforcement threaded through the tires. We will attach a load-bearing structure made of sleepers and timber to them. The depth of the studs should be the entire thickness of the tires. The height of such anchors must be at least 250 mm so that the supporting beam for the log house or sleepers can be screwed on.
It is advisable to extend the reinforcement along the entire perimeter and diagonally, and then fill the tire space itself. Reinforcement can be carried out directly through the body of the tires by drilling holes and threading the reinforcement through the entire perimeter, so there is no need to tie the outside with a channel or angle.
You can make a set of blocks from tires and bury them directly into the ground. At the same time, the cost of construction will be significantly reduced; there is no need to cast a large slab to build a building from foam blocks or expanded clay concrete blocks. The construction of load-bearing elements from tires is one of the cheapest and simplest options, which is not inferior in quality to slab ones. This is an ideal foundation for a bathhouse made of timber, sleepers or for a solid wooden house (log house).
You can use a block version of the foundation made of tires, where the marking is carried out in the same way as in other cases, but you do not need any pipes, piles, concrete blocks, and expensive reinforcement.
A set of tires (4-5 pieces), placed on top of each other, will serve as a support for a log house or sleepers, instead of pipes and formwork. The construction time for such supports is minimal, the tire foundation dries quickly, since there is not a large volume of concrete in the ground, and within a couple of days further installation of a frame bathhouse or the construction of a wooden frame can be carried out.
Repair of wooden base
Sometimes the foundation for a bathhouse is prepared from thick timber, concreted directly into the ground, and sometimes a monolithic version is installed. You need to know some little things before you properly repair the foundation of a bathhouse or build a new foundation for a bathhouse with your own hands:
- For example, a wooden structure made from sleepers or a log frame is tightened from the outside with brackets in places where they settle. You can calculate how to tighten the frame, how many staples are needed. With other foundations it’s a little more complicated. You need to know how long it takes for the concrete itself to dry, and only then install the frame or beams. If the load-bearing blocks burst during installation and their height is small, you can add a reinforcing layer of concrete around the blocks, filling in all the cracks formed in the column.
- By deciding to make the foundation of the bathhouse yourself, you will not only save a lot of money, but also get a good experience. It’s not difficult to build a monolithic or any other foundation with your own hands; you just need to go through all the stages of construction one by one and not violate the technology.
- Make the correct calculations, markings for construction, soil development, reinforcement, and insulation. Do all necessary waterproofing work. It would be a good idea to consult with builders (developers) who have been building this type of foundation for a long time and have good experience.
Decide what material to build the foundation from, logs, sleepers, what the height of the building will be, how many sleepers or timber you need. Do you need a monolithic or concrete foundation for a log house, a wooden one made from sleepers, or a permanent foundation for a building made of foam blocks?
Knowing how to make a foundation for a bathhouse is not everything; you need to make preliminary calculations, and only then can you confidently begin its construction. It’s up to you to decide which foundation is best for a bathhouse, but it’s better to calculate how much materials you will need for this in advance and draw its structure. Having carried out a simple calculation, you can do everything perfectly, because you won’t need heavy equipment here, except perhaps a concrete mixer with a wooden chute and a concrete drain.