The basements buried below the first floor are the most hydraulically vulnerable parts of buildings. The materials used to make basements are negatively affected not only by surface water, but also by groundwater in the soil.
Since any materials used to build basements have a porous structure, they let moisture through. It has a negative effect on both building structures and objects and finishing materials located inside basements.
To cut off water from the buried basement walls, their external hydraulic insulation is done at the construction stage. If the external waterproofing does not perform its functions, the basement premises are waterproofed from the inside.
Materials for making basements
Since the type of waterproofing used depends on the materials used to make the basement, it is rational to consider their main types. So, basements are made from:
- Filled reinforced concrete. This is the main type of basements of multi-story cottages, having the highest strength.
- FBS. These are solid foundation blocks (sometimes called building or wall blocks) made of reinforced concrete. They are also often used in the construction of basements, which require high strength to hold the walls of multi-story buildings. During installation, the blocks are laid on cement mortar, leaving fairly wide seams.
- FBP. Porous foundation blocks are small-piece materials for building basements designed for light loads. They are made from pure concrete or concrete with added fillers (cinder blocks, expanded clay blocks, ash blocks). Blocks are most often used to make underground cellars, laying them on cement mortar or adhesive mixtures for tiles.
- Rubble stone. Making basements from rubble stone is rational in mountainous areas, where it is available in abundance. To construct walls, formwork is used, which is filled with stones mixed with liquid cement-sand mortar.
- Brick. When making recessed basement walls, bricks with low water permeability are used. These are red, clinker brick, iron ore and semi-iron ore.
It should be noted that the use of any piece building materials in the construction of basement walls, although it may be cheaper than poured concrete monolith, creates big problems with their waterproofing. It is quite difficult to lay any waterproofing materials on uneven surfaces with numerous seams.
The need to seal the walls of basements
Since basement walls made of any building materials have a porous structure and allow moisture to pass through well, it is very important to perform their external waterproofing at the construction stage. Hydraulic protection:
- Prevents walls from getting wet, thereby increasing their service life.
- Protects the reinforcement of concrete structures from corrosion.
- Eliminates moisture on interior walls. This will improve the indoor microclimate, prevent mold and mildew, and preserve the finish and interior items.
- Prevents wetting of the masonry located on top of the basement walls.
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Materials for waterproofing basement walls
All building materials for hydraulic insulation of basement walls can be divided into two main groups ─ for external and internal use.
Outside
It should be noted that external waterproofing does not have high requirements for environmental friendliness and adhesion to the base ─ it experiences direct pressure from underground waters, pressing the waterproofing against the walls. For external insulation of basement walls, the following are most often used:
- Fused, glued onto mastic or its own adhesive side bitumen (polymer-bitumen) rolls.
- Bitumen or polymer-modified polymer-bitumen mastics.
- Liquid rubbers, which are one of the varieties of mastic waterproofing.
- Polymer membranes made of polyvinyl chlorides (PVC) or thermoplastic polyolefins (TPO).
- Bentonite mats or layers of regular clay.
- Cords made of foamed polyethylene rubber together with polyurethane sealants, mounting foams for sealing wide joints between massive FBS blocks.
It should be noted that none of the listed types of waterproofing materials, with the exception of bentonite and ordinary clays, can be laid qualitatively on the uneven surface of walls made of wall blocks, rubble stone or brick. The base will have to be leveled with cement plaster mortar, which will significantly increase the cost and complexity of the work.
However, if you add hydrophobic water-repellent materials (liquid glass, latex) or similar factory-made substances to the plaster, you can simultaneously obtain hydraulic protection for the walls, even if they are leveled.
From the inside
Unlike materials for external use, waterproofing of walls inside the basement must have high adhesion to the base and be environmentally friendly. These requirements are fully met by:
- Deep penetration cement compositions designed for hydraulic protection of concrete foundations.
- Cement mixtures with elastic additives, designed for sealing dynamically moving structures, cracks and joints.
- Cement compositions with hydrophobic additives that work effectively on cement-sand plasters.
It is worth noting that any cement compositions are applied to damp surfaces with open pores without preliminary priming.
- Polymer mastics. Mastics on acrylic, latex, polyurethane bases ─ this is turnkey basement waterproofing . After preliminary priming of the bases with the appropriate primer, mastics have the highest adhesion to any mineral wall materials. Due to this, they are able to effectively resist the back pressure of groundwater.
- Injection waterproofing. Injection of liquid waterproofing materials and micro cements into the structure of basement walls allows:
- Seal cracks, expansion joints and construction joints.
- Create curtains from moisture movement through wall capillaries.
- Use micro cements to strengthen and restore damaged masonry.
- Eliminate leaks.
- Repair damaged PVC membrane insulation from the inside.
Waterproofing of basement walls
As noted above, hydraulic insulation of basement walls is always carried out from the outside at the stage of building construction. If external waterproofing does not perform its functions and the walls inside the premises get wet, internal waterproofing is done to combat this negative phenomenon.
Vertical waterproofing of walls
When performing vertical waterproofing of walls using various materials, the following requirements must be met:
- Bituminous mastics and rolls are laid on a pre-prepared and level base, primed with a bituminous primer.
- The moisture content of the base for the bitumen primer on solvents should not exceed 4% if a water-emulsion composition is used; the permissible wetting of the walls is no more than 8%.
- Any polymer mastics are also applied to a base coated with an appropriate primer.
- To create high adhesion of cement waterproofing compounds to the base, they try to prepare the surface with open pores.
- All cement mixtures are applied to pre-moistened surfaces.
- Bitumen and polymer-bitumen rolls are fused onto vertical walls in two layers, overlapping all seams. When laying them, side overlaps of 100 mm, end overlaps of 150 mm and a gap between adjacent sheets of at least 500 mm are observed.
Horizontal waterproofing of walls
Horizontal waterproofing of basement walls means cutting off capillary moisture in the foundation from the wall masonry located on it. Cutoff waterproofing is carried out using two main methods:
- At the construction stage, strips of bitumen rolls are laid on top of the foundation walls. TechnoNIKOL Corporation produces cut-off waterproofing of 200, 400 and 600 mm width especially for these purposes.
- If the cut-off waterproofing has been damaged during operation and the wall masonry on the foundation gets wet, one of the main methods of its restoration is injection. Injection work consists of the following sequence of operations:
- Two rows of holes are drilled at an angle at the top of the foundation walls under the brickwork.
- After blowing with compressed air from a compressor, tubular injectors are inserted into them – driven plastic ones for brick walls and expanding metal packers for concrete.
- Using special injection pumps, superfluid acrylate gels are pumped into the wall structure.
Technology of waterproofing internal and external basement walls
The easiest way to waterproof walls from the inside and outside is to use mastics. These materials can be applied independently by coating, using brushes or fur rollers.
Waterproofing of basement walls from the outside
For external waterproofing works, it is practical to use bitumen and bitumen-polymer mastics on solvents (Technomast (TechnoNIKOL No. 21), TechnoNIKOL No. 24 (MGTN)) and water-based (TechnoNIKOL No. 31).
Before carrying out work on the base, all cracks are sealed and loose areas are removed from it, after which the surface is leveled. Particular attention is paid to removing protruding ridges left after removing the formwork sheets. Depending on the humidity, the surface is primed with the following primers using a fur roller or sprayer:
- up to 5% ─ TechnoNIKOL No. 1;
- up to 10% ─ TechnoNIKOL No. 4;
- moistened base without surface moisture and frost ─ TechnoNIKOL No. 8.
After the primer has dried (determined by the absence of a print on a white napkin), further work on applying mastics is carried out in the following sequence:
- The mastic is mixed in a bucket with a mixer with a special attachment and applied to the surface from the bottom up using a brush, spatula or brush.
- The areas around utility inputs, weak areas and corners are reinforced with fiberglass mesh, pressing it into the mastic layer.
- After the first layer has dried (check for the absence of an imprint on the napkin), a second and, if necessary, a third mastic coating is applied across it.
Waterproofing basement walls from the inside
For internal waterproofing of walls, it is practical to use polymer mastic waterproofing, which has high adhesion to the base. One of the best representatives of this class are polyurethane mastics of Greek production Hyperdesmo Classic, Hyperdesmo System, which are applied to the walls in the following order:
- The prepared base without peeling areas and with sealed cracks is covered with a two-component primer Primer Universal 2K 4060 using a roller or brush. The primer can be applied to both dry and damp walls.
- After the primer has dried (approximately 12 hours), the surface of the walls is covered with Hyperdesmo mastic, using a wide brush or fur roller for this purpose.
- A second layer of mastic of a contrasting color is applied perpendicularly to the dried waterproofing to visually control the completeness of the surface coverage.
Conclusion
Waterproofing of basement walls is carried out at the stage of their construction, using a wide range of mastic, roll, membrane and other materials.
If the external protection is damaged, the basement walls can be waterproofed from the inside. For these purposes, materials with the highest adhesion to mineral walls are used, which include cement compositions and polymer mastics.
If repairs or strengthening of damaged walls are required, injection waterproofing made of resins, gels and micro cements is used.
