House waterproofing and groundwater disposal

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We consider the fight against groundwater to be one of the most difficult engineering tasks. Passive methods are not always able to solve the problem, but in some cases, waterproofing alone is sufficient. Its correct device, materials and key features will be discussed in today’s review..

House waterproofing and groundwater disposal

Features of the structure of the soil

To properly deal with the flow of water into the basement, you need to have an idea of ​​how it gets there. Most plinths and normally buried foundations rest on soil layers below the first water-resistant layer of dense clay. Accordingly, almost always the top water is located somewhere at the level of the walls. Sometimes higher, sometimes lower, but one way or another, groundwater adjoins the vertical plane of concrete.

The water-resistant layer is extremely rarely strictly horizontal. Its plane can be inclined and even curved. Accordingly, water inflow is most pronounced in the upper part of the slope, to a lesser extent on the lateral sides and is practically absent from below. When excavating the soil, the slope of the waterproof layer is quite simple to determine by the cut.

Destruction of the foundation from groundwater“Verkhovodka” water penetrates through the soil to the concrete surface of the foundation and provokes the onset of a number of destructive processes. 1. Verkhovodka. 2. Top layer of soil. 3. The first waterproof layer of clay. 4. The foundation. 5. Blind area. 6. Concrete or sand preparation under the foundation (in the presence of a large volume of groundwater, it is subject to erosion). 7. “Pie” Rough floor of the basement of the building. 8. Consequences of exposure to water – washing out of the binder, cracks.

In accordance with the direction of the flow of groundwater, their pressure on the walls of the basement and the required degree of hydrophobization of the latter are determined. A decision may also be made on the need for a monolithic pairing of the basement floor and one or more walls, the admissibility of casting the foundation in several stages. The latter is of key importance: the so-called “cold” joints are the main path for water seepage. Therefore, if the filling cannot be performed in one stage, the seam must be located above the groundwater level..

Types of waterproofing

To exclude the penetration of water through concrete, waterproofing is used, which differs in functionality, method of application and used hydrophobic material.

Foundation waterproofingA simple scheme for waterproofing the foundation to protect against the effects of groundwater and “top water”. 1. Verkhovodka. 2. Top layer of soil. 3. The first waterproof layer of clay. 4. Drainage. 5. Foundation. 6. Blind area. 7. Continuous waterproofing of the foundation, complemented by a clay lock on the outside in contact with groundwater. 8. “Pie” subfloor basement of the building.

In a constructive sense, there are vertical and horizontal waterproofing for walls and floors, respectively. And if the device of the first type is performed, as a rule, after the completion of concrete work, then the floor is isolated mainly during their implementation, arranging a water-repellent screen immediately along the layer of concrete preparation before pouring the main floor slab.

Actually, some types of concrete may not require waterproofing at all. These include:

  • low permeability concrete grades from W2 to W20 according to GOST 26633;
  • mixtures prepared independently with the inclusion of hydrophobizing modifiers (zinc and calcium stearates, sodium oleate, aluminosilicates).

Of the characteristics of concrete for determining water absorption, density / porosity and the presence of through capillary cracks are of primary importance. This, in turn, depends on the ratio of water and cement in the mixture when pouring it. Actually, for the high hydrophobicity of concrete, not only the preparation recipe is important, but also the observance of the technology of pouring and compaction of the mixture.

Protection of the concrete foundation from the effects of groundwaterThe addition of a water repellant almost completely suppresses the property of concrete to saturate with excess moisture

Almost all modern waterproofing materials are based on the properties of a certain group of chemical compounds that absolutely do not absorb moisture. These include bitumen, rubber and synthetic polymer resins. They are applied in a continuous layer and create a barrier that prevents moisture from seeping into the concrete mass, thereby increasing the service life of the structure.

For the correct performance of its functions, the waterproof layer must not only maintain hydrophobicity, but also its integrity throughout the entire service life. Unfortunately, most polymeric materials do not tolerate cyclic temperature changes and building settlement very well, because of them the hydro-barrier cracks and peels off from the base..

Foundation waterproofingThe waterproofing layer must not only be continuous and resistant to water, but also have mechanical strength, elasticity

In some cases, such disadvantages are eliminated by modifying the chemical composition, in others, a fastening reinforcement is added to the waterproofing layer – fiberglass, carbon canvas or fiberglass. It is precisely because of the need to ensure the strengthening of the structure of waterproofing that several types of it have been developed: coating, roll, penetrating, screen and combined.

Is it realistic to do without drainage

The question of the possibility of deaf waterproofing of the basement without a drainage system is very vividly discussed. The simplest one-layer waterproofing with a layer of mastic or film eliminates the migration of moisture from the soil through the concrete. But if the water is not drained from the adjacent soil, it will be under pressure, and the slightest gap will be enough to flood the basement..

Violation of foundation waterproofingThe slightest violation of the waterproofing layer can lead to flooding of the basement, if drainage is not organized along the entire perimeter of the building

The issue of the arrangement of the drainage system is based on economic motives. Sometimes it is more profitable to invest in soil drainage, sometimes it is easier and cheaper to arrange a powerful hydro-barrier that will not require repair in the next 30–40 years. Only one thing can be said with certainty: the necessary technical means for waterproofing drainage exist, but they work properly only with a systematic approach and careful calculation, taking into account climatic and geomorphological conditions.

Drainage around the house to drain groundwater from the foundationDrainage effectively removes groundwater from the foundation, preventing the soil from becoming saturated with moisture

With a high GWL and a significant freezing depth, which is common practice for Russian builders, comprehensive protection of concrete from freezing / defrosting in a moisture-saturated state is required. The primary role in this matter is played by the correct arrangement of the blind area; you should also prepare for an increased volume of earthworks when digging a foundation pit for the basement. As a result, the technological trench between the earthen and the concrete wall should allow not only complete freedom of action in the installation of waterproofing, but also make it possible to install a water-cut-off lock around the entire perimeter of the concrete box.

How to insulate the floor

Upon completion of the excavation, the bottom of the pit is leveled, an incompressible gravel bed is arranged over the geotextile layer. Preparatory pouring is carried out without reinforcement with concrete grade 100, after three weeks of exposure it is covered with a layer of horizontal waterproofing.

Waterproofing the bottom of the foundation

Almost any material can be used here, from the simplest polyethylene films of 70–100 microns to the coating compounds. It is recommended to place a damping layer of one or two layers of roofing material with hot-soldered joints over the plaster..

After the waterproofing has hardened, the main floor slab is poured, and the basement walls are cast over the shield formwork. The floor slab performs both the main load-bearing and loading function, tightly squeezing the hydrophobic layer between two concrete blocks. The main concrete structure is made with reinforced double-row reinforcement with concrete grade no lower than 350, with water absorption and frost resistance, corresponding to the climatic conditions at the facility.

Foundation horizontal waterproofingWith increased requirements for strength and durability, multilayer horizontal waterproofing of the foundation base is used

Basement wall waterproofing technique

After removing the formwork from the concrete walls, a thorough analysis of the presence of casting defects and concrete shrinkage is carried out. All cold joints at the boundaries of the masses from different stages of casting must be cut from the outer and inner grooves at least 35 mm in each direction, after which a bentonite strip is laid in the groove and sealed with a cement-gravel mixture.

External waterproofing should not be expected to remain intact throughout its entire life. It would be much more correct to play it safe and combine insulation materials in several layers with different methods of their application, especially if drainage was not performed on the site.

Foundation waterproofingCoating waterproofing compounds form the basis of the protective barrier

To improve adhesion, the outside concrete walls are washed and primed, after which at least one layer of coating waterproofing is applied. It is the innermost barrier that prevents water from entering the concrete. Most likely, gaps will not appear in it over time, but provided that the material was used of high quality, and several more protective layers are arranged outside. In case of damage to the outer insulation, you can resort to the proven method of injection waterproofing of the foundation.

The main waterproofing layer is applied over the preparation layer. In the best way here, coating materials will show themselves with rolling of the reinforcing base in several alternating layers, or roll insulation, glued and docked in compliance with all installation rules. Its lower layer is poured onto a slab of concrete preparation about 25-30 cm for a tight adhesion to the floor insulation.

Foundation waterproofing and groundwater disposal

The durability of the main waterproofing can be increased by shielding. For a single screen, a hydraulic lock with a sloping outer wall is used: lightweight clay is simply poured into a technological trench, wetting it and strongly compacting it. This will not eliminate moisture penetration completely, but will reduce it to acceptable levels..

Foundation waterproofing and groundwater disposal

When installing a double screen, a layer of bentonite of 30–40 mm is applied on top of the main waterproofing, and then backfilling and tamping of light clay are carried out. In this case, it is very important to separate the dissimilar layers with geotextiles, and lay a layer of geocomposite on the outside of the protective screen.

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