Waterproofing: penetrating, cementitious, membranes, polyurea

What is waterproofing?

Waterproofing protects structures and premises against water penetration. For concrete, this means more than a dry basement: water seeping through cracks and joints leaches lime out of the concrete, carries chlorides and sulphates to the reinforcement and, when it freezes, destroys the surface layer. That is why the codes also treat waterproofing as part of corrosion protection: under ShNK 2.03.11-24, the waterproofing provided for in the design must at the same time protect structures exposed to an aggressive environment against corrosion.

The job is done not by a single material but by a system: waterproofing of the surface, sealing of joints, pipe penetrations and junctions, protection of the layer during backfilling and in service and, where necessary, drainage. Water almost always gets in through a weak point — a joint, a pipe penetration, a corner or a crack — so the details are worked out before the material for the walls and slabs is chosen.

Waterproofing is selected according to the water, the structure and the working conditions, not the name of a material. Describe your project, and we will select the system, the joint solutions and the material quantities. Protective coatings engineering →

What kind of water you are dealing with

Capillary moisture rises from the ground through the pores of concrete and masonry: damp patches and efflorescence at the base of walls, flaking plaster and paint.
Non-pressurised water — rain and meltwater, perched groundwater, water on roofs, terraces and balconies and in wet rooms. It runs off the surface and does not exert constant pressure on the structure.
Water under pressure — groundwater above the foundation base, water in tanks, swimming pools and channels. The pressure increases with depth: every 10 m of water head corresponds to about 1 bar.
Aggressive water — saline and sulphate-bearing groundwater, wastewater, chlorinated swimming pool water. Here the waterproofing also protects the concrete against corrosion, and its resistance is checked for the specific medium.

The groundwater level changes with the seasons and over the years — because of irrigation, leaks from utility networks and development on neighbouring plots. ShNK 2.03.11-24 requires the side surfaces of below-ground structures in contact with aggressive groundwater or soil to be protected, taking into account that over the service life the water level may rise and its aggressiveness may increase. Designing waterproofing for a “dry excavation” is a common and costly mistake.

Positive and negative side

The positive side is the side the water pushes against: the outer face of a basement wall, the inner face of a tank. The water presses the waterproofing against the concrete, and the structure behind it stays dry. The negative side is the opposite side, for example the inner face of a basement when the water is outside. Here the pressure tends to tear the layer off the substrate, and the concrete behind it stays wet. Not all materials work on the negative side, and manufacturers state the permissible pressure for it separately: for the polymer-modified cementitious coating Fosroc Nitocote CM210, it is 7 bar on the positive side and 3 bar on the negative side, while for the flexible Mapelastic Foundation the negative pressure is limited to 1.5 atm.

In new construction, while the excavation is open, the positive side is waterproofed and the joint details are cast in. In a building in service there is usually no access from outside, and the choice narrows to penetrating compounds, cementitious coatings rated for negative pressure, and injection.

Main types of waterproofing

Type	How it works	Where it is appropriate	Limitations
Penetrating (crystalline)	active components penetrate the pores of damp concrete and form insoluble crystals; available as a coating and as an admixture for the concrete mix	basements and tanks from either side, manholes, piles, new cast-in-situ concrete	works only on concrete with open pores and needs moisture to crystallise; does not bridge moving cracks and joints
Rigid and flexible cementitious coatings	a polymer-modified cementitious layer a few millimetres thick; flexible products bridge cracks in the substrate	foundations, wet rooms, balconies and terraces under tiles, swimming pools, tanks	reinforcement needed at corners and joints; rigid products crack together with the substrate
Liquid-applied membranes	polyurethane and bitumen-polymer compounds form a seamless elastic film	roofs, terraces, foundations, bridge decks under asphalt	sensitive to substrate moisture; many need protection from UV light or during backfilling
Polyurea	a two-component mix is sprayed with a high-pressure rig and cures within seconds	bridges and car parks, roofs, tanks and channels, large areas on tight schedules	requires equipment, a trained crew and a primer; aromatic grades yellow in light
Joint waterproofing	waterstops, swelling profiles and sealants, injection hoses, tapes bonded with epoxy adhesive	construction and movement joints, pipe penetrations, junctions	the detail is resolved at the time of concreting; an installation error can later be corrected only by injection
Injection	resins, gels and rapid-setting mortars are injected into cracks and joints and behind the structure	active leaks, repair of basements, tunnels and manholes in service	foam stops water only temporarily; permanent sealing is carried out with a separate material

Roll and sheet membranes — PVC, TPO, bitumen-polymer sheets — and bentonite mats are not yet included in the catalogue: their selection, layout and junction details are almost always worked out in the design for the specific excavation. If the design calls for them, we will select the material and accessories on request.

How the system is chosen

1. Water and pressure

Where the water comes from, whether it is under pressure, whether it is present all the time or seasonally, and how aggressive it is. This determines whether a single layer is enough or whether back-up protection at the joints, drainage and a design calculation are needed. Each material has its own permissible pressure: the manufacturer recommends the SikaSwell A swelling profile for up to 2 bar and Mapei Idrostop for up to 5 atm, while Fosroc Supercast PVC waterstops are rated for a head of up to 100 m.

2. The structure and its movement

Rigid materials — penetrating and conventional polymer-modified cementitious ones — work as long as the substrate does not crack or move. Where there are shrinkage and thermal cracks, vibration and temperature fluctuations — roofs, terraces, bridges, thin-walled tanks — flexible materials are chosen, and moving joints are dealt with by separate details.

3. What goes on top of the waterproofing

Backfill, tiles laid in adhesive, a screed, mastic asphalt on a bridge, an exposed roof in the sun, pedestrian and vehicle traffic, water in a tank. For each case, the material’s suitability must be confirmed in its data sheet: a class to EN 14891 for use under tiles, UV resistance, compatibility with hot asphalt, abrasion resistance.

4. Drinking water and aggressive media

Drinking water tanks require materials with hygiene documents. Foreign approvals, for example to NSF/ANSI/CAN 61 in North America, confirm the properties of the material but do not replace the documents required in the country of use. For wastewater, saline groundwater and process solutions, resistance to the specific medium is confirmed by our questionnaire: substance, concentration, temperature and regime.

5. Application conditions

Air and substrate temperature, the moisture content of the concrete, the dew point, heat and wind, the time available before backfilling or filling. Cementitious products need a water-saturated substrate and moist curing; reactive resins and polyurea need a dry substrate that is warmer than the dew point — by at least 3 °C according to the data sheets of the polyurea products in the catalogue.

Codes and standards

ShNK 2.03.11-24 “Protection of Building Structures of Buildings and Facilities against Corrosion” — Uzbek code, in force since 28 February 2025, replacing KMK 2.03.11-96. The requirements that matter for waterproofing are: to seal concrete construction joints with hydroactive profiled cords and waterstops when the concrete is placed; to protect the external side surfaces of the below-ground parts of buildings — basement walls and enclosing structures — against aggressive groundwater with brush-applied (mastic) or bonded sheet insulation, or with coatings; to provide waterproofing under the base layer of ground-bearing floors regardless of whether groundwater is present and of its level; and to ensure a bond strength of protective coatings to concrete of at least 1.0 MPa.
EN 1504-2 — surface protection systems for concrete: hydrophobic impregnation, impregnation and coating. Many cementitious coatings, membranes and polyurea products are marked to this standard.
EN 1504-5 — concrete injection products: force-transmitting (F), ductile (D) and swelling (S) filling of cracks, voids and interstices. Preliminary injection to stop water temporarily and the filling of voids outside the structure are not covered by the standard.
EN 14891 — liquid-applied waterproofing beneath ceramic tiling bonded with adhesives: polymer-modified cementitious mortars, dispersions and reaction resin coatings for external wall and floor finishes and for swimming pools.
EN 15814 — polymer-modified bituminous thick coatings for waterproofing below-ground structures.
EN 12390-8 — the method for determining the depth of penetration of water under pressure into hardened concrete; manufacturers of penetrating compounds and admixtures use it to demonstrate the effect of the treatment.
NSF/ANSI/CAN 61 — the North American standard on the health effects of materials and products in contact with drinking water.

Sections of the guide

Penetrating waterproofing — crystalline compounds for concrete surfaces, admixtures for the concrete mix, rapid-setting mortars for leaks.
Cementitious waterproofing — rigid and flexible polymer-modified cementitious compounds for foundations, wet rooms, balconies and swimming pools.
Liquid-applied membranes — cold-applied polyurethane and bitumen-polymer membranes for roofs, terraces, foundations and bridges.
Polyurea — hot-applied spray membranes for bridges, car parks, roofs, tanks and channels.
Joint waterproofing — waterstops, swelling profiles and sealants, injection hoses and tapes for construction and movement joints.
Injection waterproofing — polyurethane resins and foams, acrylate gels and hydraulic mortars for stopping leaks.
Hydraulic plugs — rapid-setting compounds for stopping active leaks through cracks, joints and service penetrations.
Tanks, swimming pools and treatment plants — linings for drinking water, wastewater and swimming pools, sealants for joints under water.

Common mistakes

The main surface has been carefully waterproofed, but construction joints, pipe penetrations and junctions have been left “for later” — and that is exactly where the water gets through.
A rigid material where the structure cracks and moves: on a roof or terrace, in a thin-walled tank, over a movement joint.
A material designed only for the positive side has been applied on the negative side — water pressure from the concrete pushes the coating off.
A coating applied to a dusty, over-dry or weak substrate, without repairing blowholes and cracks and without rounding off corners.
Backfilling the excavation without protecting the waterproofing — stones and machinery damage the layer.
Temporarily stopping a leak with foam has been taken for a permanent repair.
A drinking water tank has been lined with a material without hygiene documents, or filled before the end of the curing period.

How to request a selection

To get an accurate proposal first time, please send us:

what is to be waterproofed: foundation and basement, roof or terrace, wet rooms, tank, swimming pool, channel, manhole; new construction or repair;
the water: groundwater, rainwater, process water or drinking water; the groundwater level, the pressure, a chemical analysis of the water, if available;
the structure: concrete or masonry, cracks, construction and movement joints, pipe penetrations;
access: whether work is possible from outside, whether there are leaks, what downtime is acceptable;
what will go on top of the waterproofing: backfill, tiles, screed, asphalt, an exposed surface;
the season of the works, areas, joint lengths, the schedule and the design requirements, if there is a design.

Based on this information, we will propose 1–3 system options from different manufacturers, explain the differences between them and obtain the current technical data sheets from the manufacturers.

About supply

We supply waterproofing materials across Uzbekistan and to neighbouring Central Asian countries and put together a complete system — the main material, primers, tapes and meshes, profiles and sealants for joints, injection resins. We select and calculate the system for your project and, where needed, organise the works through partner contractors. The catalogue includes materials from Sika, Mapei, Fosroc, Xypex, Penetron and Teknos; the data in the cards are taken from the manufacturers’ technical data sheets, and the source is given in each card.

Frequently asked questions

Can a basement be waterproofed from the inside?

Yes, if there is no access from outside. From the inside, penetrating compounds and cementitious coatings rated for negative pressure are used, and active leaks are first stopped by injection or with a rapid-setting mortar.

Which is more reliable: penetrating waterproofing or a membrane?

They are different tools. A penetrating compound densifies the concrete itself and works from either side, but does not bridge moving cracks and joints. A membrane bridges cracks, but must form a continuous layer on the positive side and needs protection. On critical below-ground structures, the two are combined and supplemented with separate solutions for the joints.

How many coats are needed, and how thick?

This is set by the material’s data sheet and the design: for most of the cementitious products in the catalogue, two coats with a total thickness of about 2 mm; for polyurea, at least 1.5–2 mm.

When can the excavation be backfilled or the tank filled?

According to the times in the technical data sheet: cementitious products need moist curing and time to gain strength, reactive ones need full cure. For example, according to the Xypex Concentrate data sheet, tanks are filled no earlier than 12 days after application, and the Fosroc Nitoseal MS600 sealant is cured for 21 days at a temperature of 7 °C or above before contact with drinking water.

Related sections: concrete repair — restoring deteriorated concrete before waterproofing, crack injection to restore monolithic integrity, protective coatings and impregnations for concrete, coatings for steel tanks and chemical protection — for acids, alkalis and aggressive effluents.

Need waterproofing selected or a supply quotation? Call us or message us on WhatsApp/Telegram: +998 94 094 52 27.