Private domestic construction rarely uses a slab foundation. However, throughout the world it is used very extensively for the construction of a wide variety of buildings. The properties of such a foundation make it suitable for a wide variety of climatic zones. Of course, in addition to significant advantages, there are some disadvantages. But more about everything ...
- Advantages and disadvantages ↓
- Description ↓
- Scope of application ↓
- Styling technology ↓
- Types of slabs for the foundation ↓
- Composition ↓
- Layer description ↓
- Reviews ↓
The concept of slab foundation means a slab of reinforced concrete. It is installed under the entire area of construction. In this case, the plate can be installed both at the level of the earth's surface, and buried in the ground. The purpose of the slab foundation is to distribute the load over a larger area, which prevents the deformation of the erected objects during ground movements.
The thickness of the reinforced concrete slab for the slab foundation can vary from 20 to 40 cm. Laying slabs involves preparing the soil and arranging a “cushion” of sand.
Advantages and disadvantages
The most important advantage of the slab foundation is its large footprint, which significantly reduces the pressure exerted on the ground. As a result, uneven building settlement and wall deformation are eliminated.
Among other advantages, the following can be noted:
- ease of installation;
- safety and long-term guarantees of durability;
- opposition to both ground and ground waters;
- ground movement prevention;
- probability of arrangement of the basement;
- use of the slab as the basis of the floor of the first floor.
A significant minus of the slab foundation is its cost, higher in comparison with other options. However, they are justified due to the guaranteed reliability of the slab foundation against negative environmental conditions.
There are two types of slab foundations: classic and floating:
- Classic foundation located below the usual level of freezing of the soil. This allows you to complete the construction. basement or basement.
- Floating type of slab foundation laid to a depth of 70-90 cm from the surface of the earth, which excludes the possibility of building inland.
The following types of slab foundations are also distinguished:
- Usual. Its laying is possible when digging a conventional foundation pit, which is then rammed and leveled. In this case, the minimum thickness of the "pillow" should be at least 15 cm.
- Solid (monolithic), or insulated. A similar foundation is most often used in cold climatic zones.
- The foundation of a solid grid plate. It is used mainly for the construction of large objects.
Scope of application
The use of a slab foundation is considered the best option when building houses from a wide variety of materials, both light and heavy. Its device is allowed on any kind of soil, from sandy to peaty. The slab perfectly aligns the vertical and horizontal displacements of the earth. Not afraid of such a foundation and groundwater, which have a rather big impact on it.
Due to the high cost of concrete and metal, slab foundations are rarely used for the construction of objects with a large building area. Most often they are used in the construction of small buildings. It is effective to use slabs as a foundation on soils subject to excessive activity and heaving, as well as in regions with high soil moisture or high groundwater levels.
In private construction, a slab foundation can be combined with buildings of any materials. It can be frame houses, houses from timber or SIP panelsbrick or aerated concrete.
At the initial stage of laying the foundation plate, it is necessary to study the soil at the site of the proposed construction of the object. This procedure is necessary to determine the thickness of the “sand cushion”. Only then is the final draft drawn up.
Installation of the slab foundation takes place in the following order:
- The upper soil layer is removed, the pit is rummaged. Its depth should exceed the depth of freezing of the soil. The bottom of the pit is leveled and rammed.
- A sandy “pillow” is laid, which is also leveled and tamped.
- Mounted waterproofing and drainage system.
- Around the perimeter of the future building formwork exposed.
- Further, also around the perimeter, reinforcement is installed (even fiberglass), reinforcement is performed.
- Concrete pouring begins. At the same time, the concrete mass is poured in layers, 15 cm each. If ready-made slabs are used as the foundation, then a concrete screed is made on top of them.
- Vibration of the hardened concrete is carried out, which provides additional strength.
Types of slabs for the foundation
The slab foundation differs in the types of plates used:
- for small buildings, a monolithic slab is used, characterized by the simplicity of the pouring technology and the small depth of the bookmark;
- for industrial and high-rise buildings foundation plate with stiffeners is usedassembled from individual plates firmly bonded to each other, or a completely monolithic design is used;
- for the construction of ultra-stable structures, especially in areas with increased seismic activity, it is used box construction, assembled from prefabricated or monolithic concrete boxes, rigidly fastened to each other.
The parameters of the slab foundation are selected based on the construction technology. Basically, the thickness of the plate is 30-40 cm. despite the fact that precast slabs are often used, a monolithic slab is considered more reliable, providing greater rigidity and reliability of the finished foundation.
Of the finished plates for the slab foundation, the following types are used:
- Slabs for shallow foundation. They are installed over the entire area of the building and most evenly distribute the load on the ground. Such plates are recommended for houses made of logs, beams and a variety of wall blocks.
- The Finnish plate is not very thick, however, it is very durable and has excellent thermal characteristics. It is most often used for frame houses and for buildings with underfloor heating.
- Floating ribbed slabs are great for variable soils. They protect the building from subsidence, destruction and cracking. The only drawback of such plates is their higher price.
- A warm stove, in other words, a Scandinavian or insulated Swedish stove, can be installed on any soil, because it does not allow the soil to heave, and the heat-insulating layer prevents freezing of the soil. Suitable for use as a ground floor floor and for the arrangement of underfloor heating.
- Floor slabs are often used in construction to equip a slab foundation, this improves the reliability of the finished structure.
- Road slabs can be used as an alternative to concrete pouring. At the same time, time costs are significantly reduced, since it is not necessary to completely fill the slab, it is enough to perform a concrete screed.
To increase the strength of the building, it is recommended to make the slab foundation slightly wider than the main building. Extra meter - two will not play a significant difference in costs, and reliability will increase significantly.
The composition of the slab foundation completely depends on the characteristics of the future building. In case of material selection errors, it will be impossible to correct them after pouring. Concrete grade is selected depending on the purpose of the building and weather conditions:
- for one-story auxiliary buildings (garage, summer house, outbuildings), concrete of the M50 brand can be used, provided that the screed is made of stronger concrete;
- if in winter the temperature drops to -20 degrees, then it is better to use a frost-resistant concrete grade F-75;
- For permanently operated residential buildings, you should choose durable M200 concrete with increased water resistance (at least 95%).
If the entire volume of concrete cannot be poured in one day, then work can be continued no later than 12 hours later. Otherwise, it is necessary to wait 1-2 weeks until the poured layer is completely dry and only then continue pouring, this will prevent the formation of cracks due to uneven drying of the concrete.
If we describe the slab foundation in layers, then it looks like this (from bottom to top):
- Priming. Before laying the foundation, a foundation pit of the required depth is dug, and its bottom is carefully leveled and compacted.
- Sandy "pillow". Sand is poured on the ground. At the same time, every 10 cm it spills with water and condenses.
- Geotextile. A drainage pipe is laid on it.
- Rubble. It is necessary to prevent the soil from clogging the holes of the drainage pipe.
- Concrete screed. Prevents damage to waterproofing.
- Waterproofing. Its installation is necessary, since concrete absorbs moisture well and cracks can form when it freezes.
- Extruded polystyrene foam, e.g. Penoplex. Required for additional foundation insulationespecially in cold climates.
- Protective layer made of plastic film.
- Reinforced concrete slab.
“The slab foundation was the solution to my problem. I inherited a small piece of land and wanted to build a summer house there. However, I was stopped by the fact that groundwater is a meter underground. But with the use of slabs, this has become insignificant. ”
Igor Sabelnikov, Voronezh
“As a former builder, I can argue that the slab foundation is the best solution. It does not sag, excellent thermal and waterproofing. A building with such a foundation will be super stable. ”
Vadim Reshetov, Saratov
"Hello. I used the slab foundation when building a house on the advice of Western relatives, although I originally planned to use the usual tape. Taking advantage of the advice, I did not regret it, I am sure of the strength of the building, and used the concrete slab as the floor of the basement floor. ”
Grigory Maltsev, Tomsk