TECHNICAL SOLUTIONS > WATERPROOFING > Waterproofing of basements > Waterproofing of basements against water under pressure

Waterproofing of basements against water under pressure


Basements of buildings, in order to be useable and viable, require effective protection against moisture and water under pressure.  When the underground water level around the basement is above the level of the basement floor, the basement must be prepared as a watertight basin, which will constantly be found in water and will be consistently subjected to hydrostatic pressure.

Such a sealing layer must:

  • Seal effectively, even in cases of high hydrostatic pressure.

  • Be long lasting, because potential damage would lead to immediate flooding of the basement, and because its repairing or rebuilding would require significant work and expenses.



In these cases, waterproofing from the interior of the basement is usually recommended, in order to create a continuous and watertight basin.

It is always of primary importance that the supporting elements are properly designed so that they are able to bear the water's hydrostatic pressure. The application of AQUAMAT cement-based brushable sealing slurry is recommended since it has the advantage of being applicable to internal walls and basement floor. It forms a strong bond to the substrate and withstands negative pressure from water.

Thus, AQUAMAT's bonding layer:

  • Creates a continuous, strong, closed and watertight basin to the entire basement. It may be applied both in new buildings and in old ones when a waterproofing issue arises.

  • Allows transpiration and ensures the viability and utilization of the basement.

  • Offers effective waterproofing even under high hydrostatic pressure.

  • Is long-lasting because of its inorganic substance.

In case of a new building, the addition of PLASTIPROOF waterproofing admixture into concrete during the concreting of the basement's structural elements, in a proportion of 0,2-0,5% of the cement weight, is recommended.



Preliminary work - temporary construction of a pumping saft

  1. A pumping saft is dug, as near as possible to the center of the basement's ground plan, and as deep as possible, in order to lower the water table below the level of the waterproofing works.

  2. The water is pumped out in order to keep its level constantly below the level of the waterproofing works.

  3. A drainage layer is prepared in the foundations by placing geotextile first, and then  2-4 cm gravel.

  4. It is proposed that the gravel layer is covered with a polyethylene sheet, in order to prevent fine-grained material from entering, during the concreting of the basement's slab.
    Alternatively, instead of polyethylene and gross concrete, DELTA-MS membrane can be used to cover the gravel, followed directly by the concreting of the basement's slab.

  5. At the same time, the saft is formed by placing perforated (holes with a diameter of 1 cm) cement pipes with a diameter of 40-50 cm, surrounded by a layer of gravel and geotextile, which will function as a filter, impeding the entrance of extraneous materials into the saft.

  6. In case of a basement of an existing construction, after setting the pipes in their place, the floor is concreted around their perimeter, so that the continuity of concrete slab and pipe.
    In this case, the bonding between the old and new concrete is enhanced by the application of a bonding layer reinforced with ADIPLAST polymer latex (cement : sand : ADIPLAST : water = 1 : 1 : 0,5 : 0,5 parts by volume).


Substrate preparation

  1. Cone-shaped holes are opened at any leaking points, they are broadened in the opposite direction from the water flow, and they are sealed with the rapid-setting AQUAFIX cement.
    Often, when leaking points are sealed, new ones appear, because the water finds the next easy way out. Since it is unknown how long the continuous sealing of new leaks can go on, small discharge pipes are placed along the open holes, which are sealed around them.  The discharge pipes can be directed to the pumping saft in order to drain the gathering water.

  2. Any remaining grease, deshuttering agents, loose particles etc. are cleaned thoroughly from the concrete surface.

  3. Cavities in the concrete are cleaned also from loose particles, gravel etc.

  4. Distance-pieces and form wires are cut at a depth of approx. 3 cm.

  5. Any existing construction joints are opened in a V-shape along their entire length tat a depth of approx. 3cm.

  6. The surface of the above areas is thoroughly dampened and DUROCRET polymer modified cement mortar is applied, or a cement mortar reinforced with ADIPLAST polymer latex. Alternatively, when fast work is required, RAPICRET fast-setting patching mortar can be used.
    DUROCRET consumption: 25 kg for a surface of 30-40 m2 (indicative consumption for a usual concrete wall surface).

  7. Intersections of the floor and vertical elements (walls, supports etc.) should be dampened and sealed over its entire length with DUROCRET polymer modified cement mortar or with a cement mortar reinforced with ADIPLAST polymer latex. (formation of a triangular groove with side length of approx. 5-6cm). When fast work is required, RAPICRET fast-setting patching mortar for sealing can be used instead.
    Consumption of DUROCRET:  1,9-2,7 kg/m of groove length.

  8. The entire substrate surface is dampened well, without leaving any water puddles.


Application of AQUAMAT

  1. The content of one bag of AQUAMAT (25kg) is gradually added into 8,25 kg of water under continuous stirring, until a uniform brushable slurry is formed. A low-revolution mixer (300 rpm) can be used for mixing.

  2. 3-4 layers of AQUAMAT are applied to the internal walls, and then to the basement floor. AQUAMAT should be applied at the walls for at least 50 cm above the water level. Each layer should dry before applying the next one. To avoid cracking of the material, each layer's thickness should not be more than 1 mm.
    Consumption: 3-4 kg/m2in total.

  3. For surfaces that may show hairline cracks because of expansion and contraction, or on construction joints, as well as at points where pipes or other metal elements penetrate the concrete, the use of AQUAMAT-ELASTIC elastic brushable sealing slurry is recommended.


Finishing - full-formation of the pumping saft
After the waterproofing of the basement is finished, there is no further need to pump out water; therefore, the presence of a pumping saft is no longer necessary. However, it is recommended that the saft is maintained, in order to confront possible future damage to the waterproofing, for example, during later electrical, mechanical, or plumbing work in the basement.

In such cases, if the saft has been maintained, a quick pump-out and immediate lowering of the water table can be done if needed, in order to avoid flooding of the basement and the probable ruin of any valuable items located there.

The saft should extend above the basement floor until the highest observed level of the water table plus a safety margin of at least 50 cm, because according to the principle of communicating vessels, after the pumping-out stops, the water level inside the saft will rise to the same height as the water level around the basement.

In order for the pumping saft to obtain its final form, the following work must be done:

  1. As many additional pipes as needed are placed until the saft reaches the desired height. These pipes are bonded to each other with a cement mortar reinforced with ADIPLAST polymer latex.

  2. Intersections of the floor with the overhang of the saft should be sealed along its perimeter with DUROCRET polymer modified cement mortar, or with a cement mortar reinforced with ADIPLAST polymer latex. (formation of a triangular groove with side length of approx. 5-6 cm).

  3. The floor waterproofing is extended to the entire height of the saft overhang by brushing 3-4 layers of AQUAMAT along its perimeter, up to its upper limit. Each layer should dry before applying the next one.

  4. 3 days after the waterproofing is applied, during which AQUAMAT has acquired significant strength, the discharge pipes are removed from the points of water discharge. Subsequently, sealing with AQUAFIX and brushing over locally with AQUAMAT follows.

  5. It is recommended that pumping out of water should continue for about 7 days after the waterproofing is finished, until the strength of the AQUAMAT's membrane has developed sufficiently.

  6. It is recommended that AQUAMAT membrane on the basement floor is covered with mortar flooring, tiling, etc. in order to protect it from possible damage caused while the area is used.



  • The ambient temperature, during the application, should be at least + 50C.

  • Consult the instructions for safe use and precautions written on the products packaging.