Concrete Waterproofing: How to Choose the Right System Based on the Type of Structure

Waterproofing a concrete structure is not just a matter of choosing a product that “doesn’t let water through.” The right system must take into account where the water is coming from, whether it is under pressure, whether movement or cracking is expected in the structure, whether it is a new construction or a renovation, and what other requirements the waterproofing will need to meet over the long term.

An underground wall exposed to pressurized water requires a different solution than a balcony with movement in its details, a water tank that must come into contact with drinking water, or an industrial structure subjected to water, oil, or chemicals. Furthermore, for underground structures, it is often not just the concrete surface area that matters, but also construction joints, penetrations, connections, and any necessary radon protection.

That is why it makes sense to choose a waterproofing system. Comprehensive protection, detail solutions, substrate preparation, and any necessary repairs to cracks or leaks must be designed so that the individual components work together.

Quick Answer: How to Choose Waterproofing for Concrete?

Concrete waterproofing is selected based on the type of structure, the direction and pressure of the water, expected movement and cracks, the condition of the substrate, and other requirements —such as radon, chemical resistance, or contact with drinking water. For cohesive mineral substrates, cement-based or polymer-cement-based screeds can be used depending on the load; for details where movement is expected, flexible systems; for new construction, pre-applied membranes or waterproofing integrated directly into the structure; and for construction joints, penetrations, or active leaks, separate sealing details. There is no universal waterproofing solution for all structures.

First the water, then the material

Before selecting a specific waterproofing solution, it is first necessary to describe the actual loads on the structure. The same wet spot on a surface can result from rainwater, pressurized groundwater, a defective construction joint, a leaky penetration, or condensation. Each of these situations requires a different design approach.

Where does the water come from?

Water can exert pressure on a structure from the surface—such as rain, splashing water, or process water—from the surrounding soil—such as soil moisture or groundwater—from the inside—as in the case of tanks and pools—or locally through a crack, construction joint, expansion joint, or penetration. In practice, two or more of these pathways often occur simultaneously. In waterproofing, it is also important to distinguish between positive and negative pressure. On the positive side, water acts on the waterproofing toward the substrate. Under negative pressure, on the other hand, water penetrates the structure from the back side and attempts to push the surface layer away from the substrate. Not every system is suitable for both conditions.

Is water just moisture, or does it exert hydrostatic pressure?

Ground moisture, occasional rainwater, and constant water pressure represent different types of loads. In the case of pressurized water, the design must focus not only on the surface itself but also on construction joints, penetrations, connections, and any cracks. Very often, the weak point in waterproofing is a detail, not the surface.

Is the structure stable, or is movement expected?

Mineral and crystalline systems behave differently than permanently flexible screeds or membranes. If movement is expected at a specific location, it is necessary to ensure that the system can safely accommodate that movement or, if necessary, structurally transfer the crack into a joint. Elasticity is therefore not a universal advantage, but a property that must be suited to the specific location.

Is this a new construction project or a retrofit?

In new construction, waterproofing can be incorporated into the design even before concrete placement—for example, using a preventive membrane, waterproof concrete, and appropriate admixtures as specified in the design, along with a system for sealing construction joints. For existing structures, the design is based on the accessibility of the surface, the condition of the concrete, active leaks, and the possibility of working from the positive or negative side.

What other requirements must the system meet?

Depending on the structure, other factors may also be critical, such as contact with drinking water, a barrier against radon or other gases, resistance to oils and chemical exposure, frost resistance, the possibility of additional cladding or coating, and the desired speed at which the structure can be returned to service.

Basic Types of Concrete Waterproofing and When They Make Sense

Solution Type	When is it used?	What to Watch Out For	Examples of BETOSAN
Flexible cement/polymer-cement screed	Full-surface insulation on a cohesive mineral substrate; hydraulic engineering, reservoirs, wet areas, and select layers beneath tile coverings.	Substrate, corners, joints and penetrations, water pressure, layer thickness, and any relevant reports.	WATERFIN PV, WATERFIN 1K flex
Crystalline Waterproofing	Concrete structures in which water penetration is limited by the pores and capillaries of the concrete or by an adjacent mineral layer.	Movable joints and larger active cracks are addressed separately.	XYPEX, WATERFIX XP, MONOCRETE MONOMIX XP
Permanently elastic polymer-based skim coat	Surfaces and details that require high flexibility and the ability to respond to movement.	Compatibility with the substrate and subsequent layers; actual range of motion.	WODAFLEX TH / LQ
Preventive Membrane	New sub-structures where waterproofing can be incorporated into the structure before concrete is poured.	Strip joints, corners, penetrations, construction joints, and membrane protection.	PROOFEX ENGAGE
Sealing Joints and Penetrations	Construction joints, expansion joints, penetrations, and structural interfaces.	A flat trowel alone may not be sufficient to address a movable or structurally significant detail.	BENTOSTOP, ARMOBET TP, WATERFIN TP / STS / STP, SUPERFIX XP
Localized Seepage Control	Active localized seepage or a crack prior to subsequent repair.	Stopping the water flow quickly does not automatically resolve the underlying cause.	WATERFIX rapid / injection system tailored to the situation

Flexible cement-based and polymer-cement-based screeds: versatile only at first glance

A surface waterproofing coating is a common choice because it is applied directly to a prepared mineral substrate and allows for the creation of a continuous layer. However, when it comes to concrete structures, it is not enough to simply know that the material is “waterproof.” The key factors are, in particular, adhesion, flexibility, the specified system thickness, the method of connection to the membranes at corners and joints, and other properties specified for the particular application.

WATERFIN PV is a two-component, permanently flexible polymer-cement sealing slurry designed for waterproofing concrete and reinforced concrete elements. BETOSAN recommends it, among other applications, for hydraulic engineering structures, water supply systems, swimming pools, reservoirs, and as a sealing layer under ceramic tiles. It also comes with certification for contact with drinking water and as a barrier against radon and methane.

WATERFIN 1K flex is listed in the BETOSAN product catalog as a single-component, flexible waterproofing coating and anti-carbonation coating. For a specific application, it is therefore always necessary to consult the current technical data sheet and verify the function the coating is intended to perform within the overall system.

Crystalline Waterproofing: When It’s an Advantage to Use It with Concrete

Crystalline waterproofing does not function like a conventional elastic membrane on the surface. Its active chemical components react with moisture and the products of cement hydration to form an insoluble crystalline structure within the pores and capillaries of the concrete. This limits the penetration of water through the concrete’s structure. XYPEX states that the system becomes an integral part of the concrete matrix and is also designed for structures exposed to hydrostatic pressure.

This principle is used, for example, in tanks, underground structures, tunnels, foundations, parking structures, and other structures exposed to water. BETOSAN is also publishing a protocol for contact with drinking water for XYPEX CONCENTRATE and documentation related to radon for XYPEX ADMIX C-1000.

XYPEX is one option, not a universal solution for every structure. The selection of crystalline waterproofing must take into account the condition of the concrete and, in particular, movement joints and active cracks, which require separate solutions. Therefore, during the design phase, it is necessary to separate the overall waterproofing of the concrete from the details that must safely accommodate movement.

Waterproofing mortars with a crystallizing additive

WATERFIX XP is a single-component waterproofing mortar for concrete substrates containing XYPEX ADMIX C-1000. MONOCRETE MONOMIX XP is a fine-grained concrete containing this additive, which BETOSAN markets for horizontal waterproofing layers and repairs to leaking concrete and reinforced concrete structures.

Permanently Flexible Systems: When a Component Needs to Move

For structures subject to movement, wider joints, or details where a rigid mineral layer is not suitable, the system’s high flexibility can be a decisive factor. In BETOSAN’s technical documentation, WODAFLEX TH and WODAFLEX LQ are listed as permanently highly flexible waterproofing coatings based on MS polymers—the TH variant for vertical surfaces and suspended ceilings, and LQ for horizontal surfaces. BETOSAN has also published a protocol for the WODAFLEX system regarding a barrier against methane penetration; this specific property must be documented for the specific product or system.

Flexibility alone does not solve the problems of a non-cohesive substrate, active seepage, or a poorly designed construction joint. Before application, it is necessary to assess the substrate and the detail as a whole.

Preventive membranes: waterproofing installed prior to concrete placement

For new substructures, waterproofing can be installed even before concrete is poured. PROOFEX ENGAGE is a membrane system consisting of a grid structure bonded to a polyethylene/polypropylene membrane. Fresh concrete mechanically anchors itself to the structure, creating a strong bond. The manufacturer specifies it for protecting structures against water, water vapor, gases, and aggressive substances in the soil.

The advantage of this approach is that the waterproofing layer is integrated into the design of the substructure. As with other membranes, however, the details are crucial: strip joints, corners, penetrations, construction joints, and connections to other parts of the system.

Joints, penetrations, and cracks: the weakest point is often in the details

The surface of a concrete wall may be flawless, yet the structure still leaks. Water often enters through a break in the concrete pour, around pipes or anchor elements, or through a crack or expansion joint. For this reason, the waterproofing system specifically addresses construction joints between pouring stages, expansion and movement joints, pipe and cable penetrations, wall-to-floor interfaces, localized voids, and active or inactive cracks.

For these details, BETOSAN offers, for example, BENTOSTOP bentonite tapes and sealants, ARMOBET TP sealing sheets, WATERFIN elastic strips, and SUPERFIX XP expansion mortars. However, the design selection is not based solely on joint width—the decisive factors are whether the joint is a construction joint or an expansion joint, whether movement is expected, and how water affects it.

How to Choose Waterproofing Based on the Type of Building

Foundations, Basements, and Underground Structures

When it comes to the foundation, it is necessary to distinguish between ground moisture, seepage, and constant hydrostatic pressure. At the same time, it is necessary to address construction joints, penetrations, and any requirement for a radon barrier. For new construction, a preventive membrane, an integral concrete solution, and a systematic joint sealing system can be combined. For existing structures, the choice depends on whether the approach is from the positive or negative side, the condition of the substrate, and the nature of the seepage. If the system is also intended to serve as a radon barrier, it is necessary to use a specific product or composition for which relevant technical documentation exists.

Water Tanks, Reservoirs, and Structures for Drinking Water

For a tank, the requirement that it “not leak” is not sufficient. The structure is constantly subjected to water pressure, and for drinking water, materials with appropriate certification for the specific application must be used. BETOSAN publishes, for example, test reports for WATERFIN PV, XYPEX CONCENTRATE, DENSOFIX XP, and other selected products. Joints, penetrations, and any chemical or technological stresses are addressed separately.

Balconies, Loggias, and Terraces

On balconies and loggias, waterproofing must contend with temperature changes, rainwater, movement of components, slope, and connections to railings, doors, or metal flashing. Simply installing new tiles or locally repainting the underside of the slab does not address the cause of the leak. A suitable solution must take into account the specific construction, slope, details, and type of final surface finish.

Roofs and Roof Details

For concrete roofs and roof details, it is not only the waterproofing of the surface that matters, but also the slope, connections to parapets and drains, penetrations, expansion joints, and the method of protecting the waterproofing layer. A suitable system must be compatible with the roof structure, expected movement, and adjacent layers. Solutions designed for a tank or substructure cannot be applied to a roof detail without evaluating the specific roof structure.

Swimming Pools, Showers, and Wet Areas

For structures under tile coverings, it is important to have continuous, full-surface insulation and proper sealing at corners, joints, and penetrations. WATERFIN PV BETOSAN is also recommended as a waterproofing layer under ceramic tiles in bathrooms, swimming pools, and water tanks.

Industrial and chemically contaminated structures

In industrial settings, water may not be the only major concern. Surfaces may come into contact with oils, solvents, petroleum products, or other chemicals. In such cases, it is necessary to verify the chemical resistance of a specific material for the given medium and operating conditions. The selection must be based on the specific operating conditions, not merely on the general designation “chemically resistant.”

Decision-Making Guide: Which Principle Makes Sense in a Typical Situation

A typical situation	What Is the Deciding Factor?	An appropriate principle	Examples of BETOSAN
New underground structure before concrete placement	Preventing water ingress from the outside and connecting details.	Waterproofing membrane + joint system solution.	PROOFEX ENGAGE + Compatible Sealing Elements
Existing concrete wall with widespread seepage	Cohesive mineral subgrade, direction of water pressure, condition of cracks, and accessible side.	Mineral or crystal system, depending on the situation.	XYPEX / WATERFIX XP as specified
Tank or Reservoir	Constant contact with water, specific details, and, if applicable, a requirement for drinking water.	A comprehensive system + separate solutions for joints and penetrations.	WATERFIN PV or XYPEX, as specified in the design and protocols
A vertical surface with expected movement	High flexibility; suitable for vertical surfaces and suspended ceilings.	A permanently flexible skim coat system for vertical surfaces and suspended ceilings.	WODAFLEX TH
A horizontal surface with expected movement	Flexibility on a horizontal surface.	A permanently flexible trowel.	WODAFLEX LQ
Construction joint in the new concrete pour	Waterproofing details are already included in the design.	Bentonite / system sealing element or sheet.	BENTOSTOP or ARMOBET TP
Local active seepage	Quickly shut off the water supply prior to any repairs and determine the cause.	Fast-setting topical material or injection.	WATERFIX rapid / grouting
Radon Requirement	The proven anti-radon function of a specific system.	Do not automatically apply this property to every waterproofing layer.	WATERFIN PV or XYPEX ADMIX, as specified in the protocols

Positive and Negative Water Pressure: Why It Matters

If the waterproofing is applied from the side where the water is coming from, the water pushes it toward the substrate. From the perspective of layer adhesion, this is generally a more favorable situation. However, in renovation projects, the exterior side is often inaccessible, and waterproofing is performed from the inside. The water then acts from the back side and creates negative pressure.

Rule of thumb: Under negative pressure, you cannot automatically use the same trowel as on the positive side. It is necessary to verify adhesion, the condition of the substrate, water pressure, and whether the specific material or system is designed for such conditions. For example, the manufacturer specifies that XYPEX CONCENTRATE can be applied to both the positive and negative sides of a concrete surface.

Why the “most flexible” waterproofing isn’t automatically the best

Flexibility is essential for details involving movement, but for a solid mineral structure, a system that is compatible with concrete and works directly within its structure may be advantageous. Conversely, a rigid mineral layer may not be suitable for a detail where repeated movement is expected. At the same time, the waterproofing system must be compatible with the substrate, water loads, structural movement, traffic, and the overlying layers.

The preparation of the concrete subfloor determines the final result

Even high-quality waterproofing cannot function effectively over the long term on loose, contaminated, or improperly prepared concrete. Typically, it is necessary to remove loose concrete and old layers with insufficient adhesion, remove dust, grease, and other separating substances, repair cavities and rough irregularities, address active leaks before applying the waterproofing over the entire surface, and treat construction joints, corners, and penetrations in accordance with the system specifications. The current technical data sheet for the specific product is always decisive.

The Most Common Mistakes in Concrete Waterproofing

Only the surface is addressed, not the details. Waterproofing can fail at a construction joint, corner, or penetration, even if the surface layer is flawless.
It is impossible to determine where the water is actually coming from. The material is applied to the wrong side, or water under pressure is mistaken for surface moisture.
A rigid mineral material is applied to the moving crack. Movement of the structure may cause the new layer to break again.
A flexible trowel is used on non-cohesive concrete. Its flexibility does not compensate for poor adhesion of the substrate.
Construction joints and expansion joints are often underestimated. A blanket waterproofing system cannot replace a properly designed waterproofing detail.
For drinking water or radon, a product without the appropriate documentation is selected. Water tightness and compliance with hygiene or radon standards are different requirements.
Products from different systems are combined at random. The individual layers may not be technologically compatible.
A properly installed layer will be damaged during subsequent work. In the case of substructures, it is also necessary to address the protection of the membrane or waterproofing layer during concrete pouring, installation, and backfilling.

Myths and Facts About Concrete Waterproofing

Claim	Verdict	What’s the reality?
“If the material is waterproof, it’s suitable for any construction project.”	Myth	The deciding factors include water pressure, structural movement, the substrate, details, and other requirements.
“The joints are finished with the same trowel as the surface.”	Myth	Construction joints, expansion joints, and movement joints often require a separate sealing detail.
“Crystalline waterproofing is always a substitute for a membrane.”	Myth	This is a different principle, and its suitability depends on the design and specific details.
“When it comes to drinking water, the specific product protocol is important.”	Fact	Use must be in accordance with the declaration and documentation for the specific material.
“A radon barrier is an inherent feature of every waterproofing system.”	Myth	This feature must be documented for a specific product or system.
“Good waterproofing starts with preparing the substrate.”	Fact	Non-cohesive or contaminated concrete can cause even high-quality layers to fail.

When It’s No Longer Enough to Choose a Product Based on the Overview

It is advisable to involve technical support or a structural engineer, particularly when the structure is subjected to constant water pressure, the positive side of the structure is inaccessible, there are active or moving cracks in the structure, or the structure is a water reservoir, tank, a wastewater treatment plant, or another industrial facility; contact with drinking water is required; radon-proof or gas-tight functionality is required; the structure is exposed to chemical stress; it is a large underground structure with numerous construction joints and penetrations; or previous waterproofing has failed and the cause is unclear.

BETOSAN Technical Support for the Design of Waterproofing Systems

At BETOSAN, we don’t view waterproofing as simply selecting a single product from a catalog. For more complex structures, it is necessary to assess the substrate, the source and pressure of water, joints, penetrations, structural movement, and the connection to other layers. Our product range includes flexible cementitious and polymer-based coatings, materials featuring XYPEX technology, membrane systems, bentonite components, sealing strips, materials for localized leaks, and specialized solutions for tanks and structures exposed to chemical stress. We therefore always recommend verifying the specific composition based on the actual site conditions and current technical data sheets.

Summary: Proper waterproofing depends on the structure, not the product name

When selecting a waterproofing system for concrete, it is necessary to proceed from the problem to the system. First, identify the source of the water and its pressure; then assess the movement of the structure, the condition of the substrate, joints, and penetrations; and only then select specific materials. The correct procedure includes: determining where the water is coming from and whether it is under pressure; identifying whether the positive or negative side is accessible; assessing cracks, joints, expansion joints, and penetrations; deciding on the principle (mineral, flexible, crystalline, or membrane); verifying additional requirements (drinking water, radon, chemicals, frost), designing the substrate preparation and all system details, and—for more complex structures—verifying the design with technical support.

The best waterproofing isn’t the one with the longest list of features. It’s a system that’s tailored to a specific structure and its actual load.

Do you need to design waterproofing for a concrete structure?

Are you working on a foundation, a tank, a leak, a balcony, a construction joint, or another concrete structure, and aren’t sure which system is right for you? Contact BETOSAN technical support. We’ll help you choose the right material solution based on the type of structure, water load, design details, and operational requirements.

Frequently Asked Questions

What is the best waterproofing material for concrete?

There is no single best waterproofing solution for all concrete structures. The choice depends on the source and pressure of the water, structural movement, the condition of the substrate, joints, the method of application, and other requirements, such as those related to radon or contact with drinking water.

What is the difference between a waterproofing screed and a membrane?

The screed is applied directly to the prepared substrate to form a continuous layer. The membrane is a standalone strip or foil system. For new subgrade construction, the membrane can be installed before concrete placement; for screeds, the condition and preparation of the surface are critical.

When should crystalline waterproofing be used?

Crystalline waterproofing is appropriate for mineral concrete structures where water penetration through the concrete’s pores and capillaries needs to be limited. However, its suitability depends on the condition of the structure, and moving joints or active cracks require a separate solution.

Is it possible to waterproof concrete from the inside against water coming from the outside?

In some cases, yes, but this involves exposure to negative pressure. The specific system must be suitable for such a situation and must provide sufficient adhesion to the prepared substrate. Not just any surface coating can be used automatically.

How are construction joints in concrete handled?

Construction joints are sealed using system-specific sealing elements, such as bentonite tape, sealing sheets, flexible strips, or other components depending on the design. A waterproofing coating applied over the entire surface may not, on its own, provide a secure seal for the construction joint.

What type of waterproofing is suitable for a drinking water tank?

It is necessary to use a system designed for the specific load and, at the same time, materials with the appropriate certification for contact with drinking water. BETOSAN publishes the relevant test reports for selected products, such as WATERFIN PV or XYPEX CONCENTRATE.

Does every waterproofing solution also provide protection against radon?

No. Radon-proofing is not an inherent property of every waterproofing material. It is necessary to verify whether a specific product or system has this property, as documented by the relevant test report.

What should you do if water is actively seeping through concrete?

Active seepage usually needs to be contained locally first using a suitable quick-setting or injection solution, and then the cause must be identified and a permanent waterproofing system designed.

Does the concrete have to be dry before waterproofing?

It depends on the specific system. Some cement-based and crystalline materials are applied to a pre-moistened substrate, while other systems require a dry or specially prepared surface. The technical data sheet for the specific product is decisive.

Why does waterproofing most often fail?

Common causes include a poorly prepared substrate, unresolved joints and penetrations, an incorrectly determined direction or water pressure, the use of a rigid material on a moving part, or an inappropriate combination of layers.

Is more flexible waterproofing always better?

No. Flexibility is advantageous where movement is expected, but for massive mineral structures, a different principle may be more appropriate. The system must be suited to the structure and the loads as a whole.

How can I tell if I need a professional waterproofing design?

This specialized solution is particularly suitable for pressurized water, underground structures, tanks, structures with active cracks, applications requiring drinking water or radon protection, chemical exposure, and in any situation where previous waterproofing has failed.

Technical and Official Sources Used

BETOSAN – Technical Brochure on Methods for the Protection and Repair of Concrete Structures; WODAFLEX TH/LQ and WATERFIN. https://www.betosan.cz/wp-content/uploads/brozura_1504.pdf
BETOSAN / FOSROC – PROOFEX ENGAGE. https://betosan.cz/hydroizolace/proofex-engage/
BETOSAN – Waterproofing, product category. https://betosan.cz/produkty/hydroizolace/
BETOSAN – WATERFIN PV. https://betosan.cz/hydroizolace/waterfin-pv-bily/
BETOSAN – Reports: drinking water, radon, methane, and operational verification. https://betosan.cz/protokoly/
BETOSAN – WATERFIN 1K flex / Product information in the Waterproofing category. https://betosan.cz/produkty/hydroizolace/
XYPEX – C-Series Admix, official information from the manufacturer. https://www.xypex.com/product/admixtures/admix-c-series/
XYPEX – Concentrate, official information from the manufacturer. https://www.xypex.com/product/coatings/concentrate/
BETOSAN – WATERFIX XP. https://betosan.cz/hydroizolace/waterfix-xp/
BETOSAN – MONOCRETE MONOMIX XP. https://betosan.cz/hydroizolace/monocrete-monomix-xp/