Waterproofing the strip foundation of a residential building is necessary to prevent moisture from concrete and reinforcing elements included in the foundation structure from sedimentary and groundwater. Wet concrete provokes the destruction of the foundation when the frozen water expands in the capillaries of the concrete tape and leads to corrosion of steel reinforcement, reducing the strength properties of the base of the house. The owners of individual buildings are able to independently correctly perform the work on arranging the waterproofing of the foundation of their home, having certain knowledge in this area.
The destructive effect of moisture on the foundation of a building occurs when water interacts with the materials of the foundation structure. The porous structure of concrete, saturated with capillaries, contributes to the constant absorption of moisture from the environment and groundwater. In order to make the tape base of a residential building as protected as possible from a humid environment, it is necessary, in accordance with (formerly SNiP 2.03.11-85), to ensure its hydroprotection by methods of primary and secondary corrosion protection (clauses 4.5, 4.6 and 4.7). Foundation waterproofing belongs to the category of secondary protection, based on the use of protective coatings or treatment with special compounds.
Scheme of waterproofing strip foundation.
Builders with their own hands or with the involvement of specialized organizations carry out activities for applying waterproofing materials to the foundation, taking into account external factors affecting the foundation of the house:
- Atmospheric precipitation and melt water;
- groundwater.
To guarantee the protection of the foundation from the penetration of sedimentary and melt water, it is enough to make a high-quality blind area around the perimeter of the entire building. To implement hydroprotection from ground moisture, it is necessary to take into account a set of initial data, among which the main ones are:
- Type of groundwater near the building;
- The depth of occurrence of groundwater passing near the construction;
- Heterogeneity of soils in the construction area;
- Purpose and planned operation of the house.
Let us consider how these factors influence the choice of the foundation waterproofing method.
groundwater type
Groundwater has a direct impact on the formation of the groundwater level (GWL) in the area of the construction site and on the degree of soil moisture near the foundation. The diagram below shows the distribution pattern of the two main types of groundwater in soil:
- Verkhovodki are local foci of water formation that have a seasonal nature of existence. Verkhovodka lies near the earth's surface, is formed and exists only during high humidity of the environment, disappearing during dry periods;
- Groundwater lying near the surface of the earth and having a territorial regional distribution. The groundwater level is characterized by susceptibility to seasonal fluctuations.
As mentioned above, to protect against perched water, it is enough to make a good blind area and storm water. Protection from groundwater will depend on the depth of their occurrence. This dependency is discussed below.
Groundwater depth
“Recommendations for the design of waterproofing of underground parts of buildings and structures” of the Central Research Institute of Industrial Buildings, M., 1996 (amended in 2009), determined that waterproofing of structures must be carried out above the maximum GWL by at least 0.5 m (p. 1.8 and 1.9). Since the average value of fluctuations in the level of HW in many regions of the Russian Federation, according to the results of geological surveys, is taken within 1.0 m, then in order to guarantee the protection of the foundation from ground moisture, it is recommended to adhere to this indicator as a reference point when choosing a waterproofing of the base of the building, depending on the depth of HW . In particular:
- At the groundwater level, less than 1 m below the base of the foundation, it is necessary to waterproof the foundation;
- If the GWL is deeper than the foundation by more than 1 m, the hydroprotection can be omitted.
It is necessary to take into account the possibility of increasing GWL as a result of infrastructure development in the region. As well as the maximum GWL for past seasons.
With a high level of GW exceeding the lower level of the foundation sole, in addition to waterproofing, it is necessary to additionally make local drainage to remove moisture from the foundation, as prescribed by "Design and installation of foundations and foundations of buildings and structures" (Chapter 11).
Soil heterogeneity
The heterogeneity of soils with different chemical composition leads to chemical aggression of groundwater in relation to concrete in the foundation, up to its destruction (concrete corrosion). The use of special corrosion-resistant concrete of the W4 grade is required when pouring the foundation and high-reliability hydraulic protection from materials resistant to aggressive environments.
Purpose and planned operation of the house
In the presence of basements equipped with their own hands for functional purposes such as a gym, workshop, etc. increased requirements are imposed on the reliability of waterproofing in order to prevent the deterioration of the microclimate in these rooms.
Properly equipped waterproofing of the strip foundation of a residential building requires compliance with three basic principles for constructing a waterproofing system for the foundations of buildings of any purpose:
- Continuity of each waterproofing layer along the entire perimeter of the waterproofing;
- Installing a waterproofing layer only on the side exposed to moisture, i.e. foundation waterproofing should be carried out outside, but in no case inside the basement;
- Preliminary special preparation of the outer surface of the foundation for the subsequent application of waterproofing material.
Types of waterproofing strip foundation
According to clause 5.1.2 of the set of rules (formerly SNiP 2.03.11-85), waterproofing of the concrete structure is provided by:
- Lacquer and mastic coatings;
- Coating and plaster coatings;
- adhesive insulation;
- Impregnation of the surface layer of the structure or other surface treatment methods.
With regard to strip foundations, taking into account modern technologies for applying waterproofing, vertical waterproofing is divided according to the method of installation into the following types:
- Coating (painting);
- built-up;
- Plastering;
- Stick-on;
- injection;
- impregnating;
- Sprayable.
Coating (painting) waterproofing
Coating technology waterproofing is based on the use of bitumen and bitumen-polymer emulsions and mastics with the formation of waterproof films on the foundation surface.
Coating waterproofing protects the foundation from the penetration of capillary ground moisture in soils of low humidity when groundwater is removed 1.5-2 meters below the basement floor level. In the presence of hydrostatic head, it is allowed to use coating technology in the following versions:
- Bituminous mastic is used for pressure not higher than 2 m;
- Bitumen-polymer mastic - for a pressure of not more than 5 m.
Mastics are applied in 2-4 layers. The thickness of the coating hydroprotection depends on the depth of the strip base and is:
- 2 mm - for a base with a laying depth of up to 3 meters;
- 2-4 mm - for a foundation with a laying depth of 3 to 5 meters.
The advantages of coated bitumen protection are as follows:
- Relatively low cost;
- Lack of special requirements for the qualification of performers;
- High elasticity;
- Excellent adhesion.
Among the shortcomings, a short service life should be noted - already 6 years after the insulation loses its elasticity. The waterproofing layer is covered with cracks, which reduces the overall level of waterproofing. To increase the shelf life of the insulation, polymer additives are added to provide improved performance of the waterproofing coating.
The technology for applying mastic is simple. A special primer is applied to the previously prepared surface with a roller or brush, which ensures deep penetration into the foundation material. After the primer dries, bituminous mastic is applied in layers.
Fused and glued waterproofing
These technologies refer to the methods of waterproofing with rolled materials. They are used as independent measures for waterproofing, and as an addition to the do-it-yourself coating method. When using glued waterproofing, a traditional roofing material is used, which is fixed on the foundation surface treated with a bituminous primer.
With glued waterproofing, the thickness of the waterproofing layer reaches 5 mm. 2-3 layers are allowed.
Roofing felt can be fixed with special adhesive mastics in several layers with an overlap of 15-20 cm. Of modern materials, instead of roofing felt, rolled waterproofing materials are used - TechnoNIKOL, Technoelast and other materials for fusing on a polymer-based polyester, which increases the wear resistance of the coating. The service life of such waterproofing is 50 years.
Plaster waterproofing
Laying waterproofing with a plaster method is identical to do-it-yourself plastering of walls along lighthouses. For insulation, mixtures of moisture-resistant components such as polymer concrete and hydro concrete are used. The minimum thickness of the applied layer must be 20 mm.
The advantages of the plaster method include the cheapness of materials and ease of implementation.
Of the shortcomings, it should be noted:
- Average level of moisture resistance;
- Short service life, after 5 years cracks appear through which water can seep.
Injection waterproofing
The injection method of hydroprotection is based on pumping under pressure special polymer mixtures-injectors into the pores of the foundation. For injection technology, materials are produced on a mineral or polyurethane basis, which are close in density to ordinary water. If you use polyurethane-based compounds, then at least 1.5 liters will be required for waterproofing each square meter, while acrylic-based mixtures will require much less. Injection perforation is performed with conventional perforators or drills, the hole sizes (from 25 to 32 mm) are determined by the diameters of the injection packers and capsules. Upon completion of the injection process, the perforation is sealed with a cement-sand mixture of the usual composition.
Impregnation waterproofing
This technique is based on the impregnation of concrete with special organic binders that fill the concrete capillaries and form an antihygroscopic layer up to 30-40 mm deep in the concrete.
The technology of spraying a waterproofing material requires the use of a special spray gun. So far, the cost of materials is high, but their use is economically justified for waterproofing foundations of complex configuration, which are difficult to process in other ways.
Drainage as an auxiliary measure
The arrangement of drainage systems is designed to remove excess moisture from the foundation system of the building at a high level of groundwater. According to clause 11.1.15 of the set of rules, drainages are divided into general and local. Their use in combination with waterproofing allows you to protect the foundation from the penetrating effects of ground moisture.
Do-it-yourself waterproofing of a strip foundation is a complex technological process that requires a clear understanding of each stage of the entire event. Only in this case, a long period of trouble-free operation of the house will be ensured.
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