Does the house need a basement?
The basement is the above-ground part of the foundation. This is a rather complex unit where the vertical (basement, walls) and horizontal (floors and ceilings) structures of the house converge and adjoin each other. Correct device, waterproofing and insulation of the base - the necessary conditions for the construction of a durable, economical and heat-saving house. The figure below clearly shows what will happen if the house has a very low base.
A base with a height of at least 20 cm protects the walls from moisture (in the picture on the left). Low base and the absence of a base leads to moisture in the wall of the house (in the picture in the center and on the right).
The height of the base of a private house must be at least 20 cm. With a low base, there is a high risk of the house wall becoming wet. The walls will be moistened by splashes when raindrops hit the ground, when snowdrifts melt, or from capillary suction of moisture directly from the ground.
Damp walls lose their heat-saving properties. Water freezing in the walls gradually destroys them. Dirt, dampness, fungus and mold appear on the walls outside and inside the house.
To protect the walls of the house from moisture coming from the ground, two lines of defense are created:
- Increase the height of the base in order to remove the walls of the house as far as possible from the ground, the source of moisture.
- Arrange waterproofing of the walls of the house and the basement in danger zone exposure to moisture.
A high base increases the cost of building a house. Therefore, depending on the design of the walls and foundation of the house, they try to find a reasonable compromise between the size of the base and the level of waterproofing. Be sure to install a horizontal layer of rolled waterproofing between the base and the wall of the house.
In some cases, which are discussed below, it is necessary to do additional waterproofing of the walls of the house.
For a private house, it is recommended to make a sinking base. In a sinking plinth, the outer surface of the wall protrudes beyond the border of the plinth by approximately 50 mm. The water falling on the surface of the wall flows down and falls from the wall past the base onto the blind area. This solution prevents water flowing down the wall from reaching the horizontal waterproofing and flowing along it into the wall. For better water drainage, a drip line is fixed along the lower edge of the wall.
It should be noted that in addition to the moisture-proof function, the base plays a certain role in the architectural appearance of the house. A house on a high base looks more solid and impressive, and finishing the base can highlight the beauty of the floors of the house.
The correct basement of a house with single-layer external walls.
The height of the basement of a house with single-layer external walls must be at least 50 cm (in the figure on the left). Or for a base with a height of less than 50 cm, but not lower than 20 cm, additional waterproofing of the walls is required. (in the picture on the right).
The outer surface of single-layer walls is less protected from moisture than that of multi-layer walls. Therefore, it is recommended that the basement of a house with single-layer external walls be at least 50 cm high.
If the base of a single-layer wall is below 50 cm, then additional waterproofing is installed in two places:
- In the wall, above the first or second layer of masonry made of aerated concrete or porous ceramic blocks, another layer of roll waterproofing is laid.
- The outer surface of the wall, in the area of the lower rows of masonry, is protected from water by a layer of vertical waterproofing. To do this, it is enough to use hydrophobic primers and waterproof plasters when finishing the wall. It is better, but more expensive, to line the base and lower part of the walls with a material with low water absorption, for example, basement siding, clinker tiles.
The design of the plinth for a single-layer wall of a house with a basement or a house on a slab foundation can be found here.
Dimensions of the basement of a house with two-layer external walls.
Minimum height plinth for a two-layer wall insulated with polystyrene foam 20 cm. For a wall insulated with mineral wool, at least 30 cm is recommended. (in the left picture). A low base will lead to moisture exterior finishing and soaking mineral wool insulation (in the picture on the right).
In a two-layer wall, with plaster over insulation, the polymer insulation does not absorb moisture and serves as an additional barrier to water, protecting the wall from moisture.
Mineral wool insulation for external walls, as a rule, has a hydrophobic (water-repellent) impregnation. However, they are able to absorb some moisture. For walls with mineral wool insulation, the height of the plinth should be increased - the height of the plinth is recommended to be at least 30 cm.
A low base leads to moisture and rapid destruction of the outer wall finish. As in the case of a single-layer wall, with a plinth height of less than 50 cm, the exterior finishing in the lower part of a two-layer wall must be additionally protected from moisture by vertical waterproofing. The role of the drip line in a two-layer wall is usually played by the starting strip, on which the bottom row of insulation boards is installed.
Height and waterproofing of the plinth for a three-layer wall.
In a three-layer wall, water may appear at the border of insulation and cladding. For protection, drainage holes and additional vertical waterproofing.
In a three-layer wall with brick cladding or with a ventilated facade, water may appear at the border between the insulation and the cladding. Water appears when water vapor condenses, as a result of the vapor permeability of the wall material, or enters from the outer surface of the cladding when it is moistened, for example, by slanting rain. Emergency soaking is also possible for various defects in cladding, roofing, etc.
For the reasons stated above, water can appear at the boundary of the insulation and cladding, both in walls with and without a ventilated gap. Both in walls with polymer insulation and in walls with mineral wool insulation.
Drops of water flow down and collect on horizontal waterproofing base The design of the cladding should allow water to drain out of the gap. To do this, for example, in brick cladding, part of the vertical joints of the lower row of masonry is not filled with mortar. Drainage holes in the masonry are left every 0.8 - 1 m. Water through these holes has the opportunity to drain out without accumulating on the horizontal waterproofing of the base.
If there is between the insulation and brick cladding ventilated gap, the same holes serve for air entry into the ventilated gap. To prevent water from the horizontal waterproofing of the base from leaking into the house, it is recommended to additionally install vertical waterproofing between the insulation and the wall to a height of approximately 15 cm.
Insulation of the basement of the house.
Developers usually always pay enough attention to insulating the external walls and floors of the first floor of the house, but often neglect to eliminate the cold bridges in the basement through which heat escapes from the house.
In the basement of the house, a cold bridge may appear through the base and load-bearing part of the wall, bypassing the insulation of the wall and floor.
When building a house on heaving soils, base and underground part of the foundation to a depth of at least 0.5 - 1 m. It is recommended to insulate the outside with a layer of insulation. This insulation option is for different designs the wall is shown in the pictures above.
In a single-layer wall, the floor is raised to the level of the second or third row of masonry. The vertical waterproofing of the base is raised to the same level. 2 - waterproofing; 4-5 - plaster on mesh; 8 - finishing; 9 - floor on the ground.
Insulation of the base and foundation allows you to eliminate or reduce the depth of soil freezing in the basement space with wooden or concrete floors on the ground, as well as under the base of the foundation. This reduces the impact of frost heaving forces on the house structure.
If we supplement the vertical thermal insulation of the foundation with a horizontal thermal insulation skirt, we will get the design of a thermally insulated foundation - the best for a private house. In addition, the thermal insulation of the base eliminates the cold bridge through the base and the load-bearing part of the wall, bypassing the thermal insulation of the floor and wall.
If the soils on the site are not heaving or slightly heaving, then the task of combating the forces of frost heaving is not worth it. In this case, it is only necessary to get rid of the cold bridge through the base and load-bearing part of the wall.
To eliminate the cold bridge in a house with single-layer walls without basement insulation, it is necessary to raise the floor to the level of the second or third row of masonry blocks outer wall. This is sufficient, since the material of a single-layer wall has low thermal conductivity.
The load-bearing part of two- or three-layer walls is usually made of material with high thermal conductivity. To eliminate the cold bridge in two- or three-layer walls, you can cover it with insulation only top part base, approximately 0.5 m below floor level. This will increase the length of the heat flow path along the base. If the basement space under the house is not heated, then the basement is covered with thermal insulation on both sides.
In multi-layer walls, to eliminate the cold bridge, cover one outer or both sides of the base with thermal insulation (for houses with an unheated basement or floors on the ground).
For multilayer walls, another way to combat the cold bridge is used. The lower rows of masonry of the load-bearing part of the wall are made of wall material with low thermal conductivity. The floor level is raised in the same way as for a single-layer wall.
For insulating the base and underground part of the foundation, extruded polystyrene foam slabs (penoplex, etc.) are best suited.
It is convenient to insulate strip foundations. Design of pile foundations with bored (including TISE) or screw piles more suitable for a cold base. Insulation of such foundations is quite problematic and expensive. The basement space of houses with pile foundations is usually not insulated. design basement floor and the floors of the first floor of a house on a pile foundation are chosen taking this circumstance into account.
Before starting construction, any building structure, it is necessary to develop a competent and detailed project for the future structure.
Its mandatory component will be data regarding the characteristics of the base.
The project must contain information about the depth of the underground part, overall dimensions soles, materials used.
The height of the foundation above ground level is also important parameter. Many developers are trying to save money on it.
A significant portion of the capital is spent on the construction of the foundation. total amount construction. Each individual developer strives to reduce these costs as much as possible.
And if, by calculating the width and depth of the base, we obtain the mandatory parameters that must be followed when carrying out construction work.
When constructing the above-ground part, you can use more affordable building materials and vary the height within certain limits.
What affects the height of the foundation
It should be understood that the extent to which the structure will be exposed to external climatic influences: temperature fluctuations and humidity depends on the above-ground part of the foundation.
To solve the issue related to its height, it is necessary to understand why the base should be raised above the ground level:
- The above-ground part serves as a basement covering. It is clear that a solid structure will have more best characteristics than a two-part structure;
- The walls of the house receive additional protection from moisture. Even with a blind area, they are constantly moistened. Creating an intermediate layer reduces this effect. The height of the foundation above the ground should not be less than 200 mm;
- Sometimes this parameter is affected by the presence of a basement. Then this value is determined based on the design documentation data;
- For pile and columnar foundations, the level of the above-ground foundation also cannot be less than 200 mm. This is necessary so that the heaving soil does not affect the building structure. If there is a slope, this distance can be greater;
- When making calculations, it should be taken into account that the house may shrink due to the characteristics of the soil and the impact of pressure from the building structure;
- Sometimes, by increasing the height of the foundation above ground level, it is possible to avoid the destruction of the walls of the structure. This is especially true for wooden buildings, for example, baths. In such situations, at the stage of design work provide for a high base, or use other building materials when constructing the base.
How do the parameters of the foundation compare?
As an example, let’s look at how the parameters of the foundation are calculated when building an individual house.
Practice shows that the ratio of the height of the above-ground base to the width is 1:4.
The structure of the classic does not imply the presence of a base. As a rule, the height of the foundation above ground level does not exceed the underground part, but the opposite option occurs quite often.
If the soil at the construction site has standard specifications, usually the height and depth are the same and do not exceed 0.5 m.
Building up the base
Both the foundation and plinth structures have four various surfaces– top, bottom, internal and external. Each one must have an absolutely even surface.
An uneven base can subsequently lead to deformation of the entire building structure. How to remove unevenness and, if necessary, increase the height of the foundation?
Most often, raising the base is done using solid bricks. It is used to strengthen and build up the base part to required sizes. Reinforced mesh is used to strengthen the masonry.
When tying brickwork use cement mortar. When constructing frame or wooden buildings used to strengthen the base solid brick. Cinder block houses are reinforced with concrete.
How to level the base
The following methods are used to level the base:
- Correction of significant defects formed on the foundation covering is carried out by manufacturing a new formwork structure and pouring concrete mortar;
- For small irregularities, the foundation base with outside covered with bricks;
- Instead, you can use a chain-link mesh. First, it must be securely fixed and then covered with a layer of plaster;
- The existence of small irregularities located on the inner surface can be neglected. They will not be noticeable under a layer of thermal insulation coating;
- To obtain a perfectly flat top surface, it is most convenient to use brickwork.
Level of the above-ground part of the base for a wooden structure
For wooden structure Having a sufficient foundation height is especially important. This will prevent the process of rotting of the lower part of the structure.
To make such a base, brick, concrete, metal or wood can be used. It is imperative to carry out high-quality waterproofing using coating or roll materials.
When choosing optimal height the base must take into account the climatic features of the area in which the building site is located.
In standard situations, the level of the above-ground part should be 10 cm higher than the height of the snow cover.
The foundation must be protected from moisture not only from the bottom, but also from the sides. For this you can use ceramic tiles or clinker.
If the foundation of the house is located high enough, its thermal insulation properties will improve and the operating time will increase.
conclusions
With a higher foundation location, it is better preserved Bottom part building structure. Optimal level above the ground surface is 0.4 m.
It should be remembered that it is necessary to carry out hydro- and thermal insulation works. This will protect the foundation from moisture and prevent destruction of the reinforcement frame.
The video shows which foundation height above ground level is best to choose:
The foundation is the basis of any wooden structure. It takes on the main load during operation and protects the house from negative impacts. groundwater.
FACTORS AFFECTING THE SIZE OF THE FOUNDATION
The foundation consists of a basement and an underground part, the dimensions of which depend on several factors:
1. Type of soil and its changes in autumn-spring period. To the foundation laid on capricious sandy or marshy soils, there are special requirements.
2. Level of soil freezing and availability of groundwater. The base must lie below these points and requires high-quality waterproofing and insulation.
3. Weight and number of floors wooden house.
4. Tasks of the basement and plinth.
VALUE OF BASE
The above-ground part of the foundation performs several functions:
Prevents getting wet internal floors;
· Compensates for soil shrinkage;
· Protects the cladding of the house from contamination;
· Promotes high-quality ventilation of the underground;
· Increases the thermal insulation characteristics of the building;
· Considered an architectural decoration.
The height of the plinth plays a huge role especially for wooden houses, since rotting of the lower rows complicates the repair work and reduces the service life of the building.
The standard height is approximately 30-40 cm. But experts advise equipping the ground part of the foundation of a wooden house to a height of 60-80 cm. clay soils this value can reach 80-90 cm, and 50 cm is enough for sandy ones.
TAPE BASE
A common foundation option for a wooden house. The monolithic structure allows you to equip usable area plinth at moderate construction costs.
In areas with severe winters and soil freezing to an impressive depth, the underground part of the strip foundation can reach 1.5 meters. The height of the base depends on several conditions (for example, the presence of a boiler room or basement). The firebox requires special responsibility, so the height of the ground part is characterized by safe use and proper placement of equipment.
Regardless of the quality of the soil and terrain conditions for wooden buildings It is recommended to build plinths of sufficient height. Wood is a very capricious material, therefore, the higher the house is raised above the ground, the longer it will last.
The optimal size of a strip foundation is about two meters, which means that the ground part is 50 cm.
CLASSIFICATION OF THE PINTER FOR STRIP FOUNDATION
The above-ground part is divided into two types:
1. Monolithic. The base is made in the form of a continuous (indivisible) concrete sheet.
2. Masonry. First, the lower part of the foundation is poured (to the soil level), and then the base is laid out (made of brick or other material). A less reliable option that requires additional cladding.
PLATE BASE
According to building regulations, the monolithic slab should rise above the ground surface by at least 20 cm. But for regions with unregulated snow cover levels, this parameter should be increased to 40 cm.
A monolithic slab is considered the most reliable type of foundation. Its underground part should be buried below the soil freezing level. The strength of the slab does not depend on potential ground movements, but in case of probable seismic shifts, its height must be increased. The total thickness of the foundation depends on the weight of the wooden house, its number of storeys, area and type of soil.
PILE FOUNDATION
Arranging a plinth on a pile foundation is accompanied by certain difficulties. Its dimensions depend on the height of the ground section of the piles. The base can be hinged or made on a tape.
The design of the hinged version consists of a wooden or iron sheathing fixed around the entire perimeter. After arrangement, it must be sheathed with any facing material.
The second option is more complex and expensive. The laying is done on a strip foundation. Its main advantage is the fairly high quality of thermal insulation.
BASE CONSTRUCTION
The ground section of the foundation can be made in several options:
· Sunken. Economical option plinth, typical for walls with a small thickness. Allows you to hide the protrusion using waterproofing material or a small layer of soil.
· Speaker. Requires more building materials. Provides reliable protection wooden house from cold air, but needs high-quality waterproofing and drainage.
· The base is flush with the wall. The most unfortunate and rarely used solution, requiring constant monitoring of the cut of the waterproofing layer.
MATERIALS
To build the above-ground part of the foundation, it is necessary to use durable materials - concrete, brick, different kinds stone In most cases, the base of a wooden house requires the installation of an armored belt. The number and thickness of reinforcing bars depend on the design of the building.
· For wooden houses, a base made of monolithic concrete. Its arrangement requires the installation of formwork and reinforcement cage.
· For a structure made of solid (not gas silicate!) brick, it is necessary to take material with high frost resistance.
· Using concrete blocks requires special skill. Between them there will certainly remain various voids, which must later be filled with cement mixture.
HEAT AND WATER INSULATION
High-quality heat and waterproofing are mandatory steps for arranging the basement of a wooden house. Insulation must be done with porous materials with minimal water absorption. Suitable for waterproofing bitumen mastics or rolled materials.
The height of the base and the features of its arrangement depend on many parameters. But under any conditions, the minimum level of the ground part should not be less than 20 cm. This will help protect the house from flooding and increase the “life” of the lower wooden crowns.
Always before purchasing materials and starting construction of a building, a plan is created. When designing, it is especially important to choose the right type of foundation, materials for its manufacture and the desired height. Next, we will dwell on the last question in more detail and consider what the height of the foundation can be, the requirements of SNiP and why there should be a certain height for different structures.
Why is the height of the base given so much attention?
The requirements of SNiP quite clearly regulate the requirements for the foundation. It performs the task of supporting the entire structure and if constructed incorrectly, the latter will not be able to guarantee safe conditions for people during operation. In addition, the foundation is constantly affected by destructive factors, and especially in its outer part: winds, rains, snow masses, sun, etc. Therefore, it must not only protect the structure from subsidence, but also raise the wall material two-story house or any other structure to a safe height. Let's take a closer look:
- It’s great to use a raised base as a plinth. In any case, there must be an elevation of the walls above ground level regulated by SNiP. The advantages of using a plinth combined with a foundation are obvious - the structure of the structure will be more holistic and stable.
- Some SNiP of certain materials require their distance from the aggressive influence of the earth: moisture, precipitation, etc. Otherwise, the lower layers of the walls may be destroyed, which can harm the entire building (especially in the case of a two-story house). As for the exact requirements, the base should be 10 cm higher than the calculated level of the maximum possible snow mass in winter period. Simply put, if a lot of snow falls, then the foundation should not be hidden under it. As for exactly strip base, then the minimum height of the foundation above the ground is 30 cm.
- In some cases, the elevated base is a continuation of the basement walls of a two-story house. Similar to the plinth analogy, joint construction will provide many advantages.
- It is possible to create a high base as a measure to combat shrinkage, which is typical for some soils. Experienced planners always take into account all the features of the land at the site where the future building will be located.
- Elevations within the range of 20-30 cm are typical for a pile foundation, as well as in cases of constructing a one- or two-story wooden house - the tree does not tolerate exposure to moisture.
Please note that even reliable waterproofing of the walls on the base side will not protect them from moisture and the only way out is to make the base with a sufficient height to protect it from moisture.
Height of strip base
It must be taken into account that the entire height of the foundation consists of 2 parts: underground and aboveground. If you listen to the recommendations of experts, then it is optimal when it rises 40 cm from the ground. This indicator can also be influenced by the amount of precipitation and the material for laying the walls. For example, when using structural aerated concrete, a significantly lower elevation is required than in the case of cinder block.
If there are no special requirements for height requirements, then SNiP documentation should be taken into account when determining the depth. It indicates the freezing levels of the main types of soil and the recommended base heights in each situation:
- The soil is slightly heaving: freezing is 300-350 cm - recommended foundation depth is 150 cm, 250 cm - 100 cm, 150 cm - 75 cm, 100 cm - 50 cm.
- Non-heaving: more than 300 cm - 100 cm, up to 300 cm - 75 cm, 200 cm - 50 cm.
Also, when determining the depth, the groundwater level is taken into account.
Determining the height of a monolithic base
It is worth considering some points:
- SNiP rules regulate the minimum height of such a base at 20 cm. To be more precise, this is exactly what the height of the base should be. But in regions with uneven rainfall, this figure in the case of building a two-story wooden house is increased to 40 cm - this allows you to protect the tree from moisture.
- Also, in cases where the soil freezes to 1 m, the base should be installed deeper.
- To the benefits monolithic slab we can attribute its complete insusceptibility to displacements of soil masses. But in the case of construction in areas with characteristic seismic activity, the width of the foundation should be increased.
General results
- The minimum height of the strip base is 30 cm above ground level;
- It’s great if the foundation performs the task of the base;
- The wall material should be protected as much as possible from moisture;
- It is necessary to make such a foundation that at maximum precipitation it is 10 cm higher than the snow.
Approach the design correctly and it does not matter whether the construction of a two-story house, bathhouse or utility room will be carried out. A well-chosen foundation height above the ground will extend the life of the structure for a long time.
House foundation height updated: February 26, 2018 by: zoomfund
Before erecting any building, every serious builder will draw up a competent and detailed design of the structure, including the foundation. The project must indicate all the necessary parameters of the foundation: the width of the foundation itself (this applies, first of all, to the strip foundation), the area of its base, the depth, the material used during construction and the height of the foundation above the ground. All this must be taken into account at the design stage.
But knowledge cannot be used without understanding its essence, even if confirmed by words experienced builders. And in order to do any task correctly, it is necessary to understand the reasons for precisely such parameters and requirements. Here we are going to deal with the last parameter of the house foundation listed in the listing. What should be the height of the foundation and why is it necessary to know this? Why are certain numbers indicated in recommendations and projects? What experience do builders rely on?
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Difficult choice of ideal
It is believed that the price of the foundation in the total estimate for the construction of a house is about 30%. Therefore, if there is an opportunity to save money, then most will definitely do it. And in the parameters of the foundation there is an obvious point where costs can be greatly reduced - this is its height above the ground. The fact is that if the depth depends on objective and obvious reasons to everyone, changing something there, in terms of economy, is fraught, then the distance from the ground to the wall simply attracts the thrifty. After all, in fact, what is above the ground is the above-ground part of the building, and there is a temptation to make it all from cheaper materials. After all, every cm of foundation in terms of cost is much more expensive than the same cm of walls, especially if the latter are made of cheap materials (wooden, panel, etc. buildings).
But such savings are a mistake, and it is better for the owner of the future home to carefully read the requirements for this part of the foundation and understand why they are needed in order to take a balanced approach to the issue of the height of a strip or other foundation.
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The height of the base above the ground, what is its role?
Having carefully studied the role of the foundation of the house, you can see that it experiences various unfavorable factors. This is especially noticeable at the boundary between the soil and the atmosphere. From this it can be seen that the parameters of a conventional strip, block and other foundation include not only such functions as providing reliable support for the entire structure, insulating the house from harmful factors from the ground (primarily moisture), but also the function of raising the walls and the residential level in general above all negative weather manifestations. Let's look at what this means point by point.
- A highly erected foundation in its upper part can be well used as the base of a building. The benefit here is obvious; a solid structure will have better characteristics than in the case where the foundation and base are clearly separated. This will affect both operational characteristics home, and on its integrity.
- A high strip or block foundation has the best characteristics for protecting the walls of a house from moisture. Even if you use protection for the lower part of the walls (waterproofing, blind area, etc.), it will still be constantly moistened under the influence of ground moisture or precipitation. A high base in this case will protect the house from moisture much more reliably. The upper boundary of the foundation should rise 10 centimeters above the level of snow that falls in the snowiest winters. But in any case, the upper limit of the strip base should be no less than 30 cm above ground level.
- The base, elevated above ground level, is sometimes part of the basements under the house, reflecting the design characteristics of the building. As in the case of the base, such a design of the house will have a good effect on its operation.
- An elevation of 20-30 cm is also typical for pile and columnar foundations. There, this measure was taken as part of the fight against unstable soils. Heaving soils with this design have less impact on the structure during seasonal movements. In some cases, due to the slope of the terrain, this height above ground level can be much greater.
- Very often it is a measure to combat the shrinkage of a structure. That is, taking into account the characteristics of the soil, builders add some additional height to the foundation in advance in anticipation of future subsidence of the house.
- During construction, materials that are extremely unstable to high humidity and other environmental influences, such as wood. In this case, builders can also use a high base to prevent the wood from coming into contact with the wet soil.
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Calculation of the height of the strip foundation
Let's look at calculating the parameters of its height for an average house. The practice of the modern construction industry shows that the height of the above-ground part of the base of a house should be related to its width as one to four. It's about about the classic shallow monolithic strip foundation, without basements and plinth, with the inter-foundation space filled with soil. That is, the height of the part of the foundation above the ground should be 4 times the width. In this case, the above-ground part cannot be larger than the underground, and the opposite situation will be quite normal. In our area, both parts of the foundation, as a rule, have the same height and depth characteristics and are about 45-50 cm. If the house has an underground floor, then the foundation must have vents for proper ventilation of underground spaces.