Damp walls in basements or ground floors are a common problem in German homes. Waterproofing mortar is often used, especially for basement waterproofing and in the basement area, to protect these critical areas from moisture and water damage. But is it really the best choice? In this comprehensive guide, you'll learn everything about waterproofing mortar and why there's a significantly better alternative.

What are 1C and 2C sealing slurries?

Sealing slurry is a waterproofing material used to seal structures. It typically consists of a mixture of:

• Cement as a binding agent
• Sand as filler
• Plastic additives for adhesion and elasticity
• Additional additives depending on the manufacturer

There are various products in the field of sealing slurries, the main distinction being between 1C and 2C sealing slurries. The main difference lies in their composition and therefore in their technical properties and areas of application:

1-component sealing slurry (one-component)

• Composition: Powdery, is mixed with water
• Binder: Cement-based
• Flexibility: Low to barely flexible → only suitable on dimensionally stable, crack-free substrates
• Area of application: Exterior basement walls (not at risk of cracking), interior areas without strong stresses
• Processing: Simple because only water is added

2-component sealing slurry (two-component)

• Composition: Powder (cementitious) + liquid polymer dispersion
• Binder: Cement + plastic binder
• Flexibility: Highly flexible, crack-bridging (even at sub-zero temperatures)
• Area of application: Substrates with possible cracking, balconies, terraces, pools, negative water impact
• Processing: Two components must be mixed

With 2-component sealing slurries, a powder component is mixed with a liquid component to produce the sealing compound. Correct processing and adherence to the reaction time of the liquid component are decisive for the result.

Sealing slurry is a waterproofing compound, also known as waterproofing mortar. It is often used as a surface solution for moisture problems, both indoors and outdoors. Typical packaging units are bags containing 25 kg, for example. The required quantity and consumption per square meter depend on the layer thickness and the specific application and should be carefully calculated.

The principle of waterproofing slurry is based on a surface seal of the affected areas. It is applied in multiple layers to ensure reliable waterproofing. The most important properties of waterproofing slurries are their watertightness, flexibility, and resistance to various environmental influences. However, this method presents fundamental problems, which we will examine in more detail later in this article.

Sealing slurry inside vs. outside: The areas of application

Sealing slurry inside

Sealing slurry is often used indoors for surface waterproofing in cases of moisture problems such as rising damp in basements or bathrooms. Typical applications include plastered surfaces and use under tiles, for example, as moisture protection in bathrooms or other wet rooms.

Exterior sealing slurry

Outdoors, waterproofing slurry is often used to protect against moisture penetration on baseboards, terraces, or components in contact with the ground. Typical applications include baseboards, balcony waterproofing, floor waterproofing, and swimming pools, where a reliable moisture barrier is particularly important.

The fundamental problem with both applications: sealing slurry only treats the surface, not the actual cause of the moisture.

Properties and problems of sealing slurry

Waterproofing slurry is often advertised as a versatile product for waterproofing indoor and outdoor structures. It is used in numerous applications, such as waterproofing basements, patios, baseboard areas, or wet rooms such as showers and swimming pools. Thanks to its special composition, the waterproofing slurry adheres to a variety of substrates, including concrete, masonry, plaster, and even mineral soils.

One advertised advantage of waterproofing mortar is its elasticity: It's supposed to bridge movements and cracks in the substrate. However, this seemingly positive property leads to a dangerous misconception: it doesn't stop moisture, but merely redirects it. While application may seem simple for DIYers, the results are rarely consistently satisfactory.

Although waterproofing mortar is advertised as weather- and frost-resistant, it cannot solve the underlying problem: the cause of the moisture remains. Instead of long-term value preservation, it often results in consequential damage due to moisture buildup in the masonry.

The processing of sealing slurry

The application of sealing slurry typically takes place in several steps:

1. Preparation and cleaning of the surface, paying particular attention to the strength, evenness and cleanliness of the substrate.
2. Mix the material according to the manufacturer's instructions
3. Apply in several layers
4. Post-treatment for curing

For an even and professional finish, we recommend using a smoothing trowel to smooth the applied layers.

Make sure to use the correct amount of sealing slurry and calculate the consumption according to the manufacturer's instructions.

Technical data and information on sealing slurries

The technical properties of the waterproofing slurry can vary slightly depending on the product and manufacturer, but some key figures are typical: The bulk density is usually around 1.14 g/cm³, and the recommended wet layer thickness is approximately 3.0 mm per layer. For optimal application, the temperature should be above +5°C, and the product must be protected from direct sunlight and frost during curing.

The drying time of the sealing slurry is typically about 120 minutes; after 24 hours, the surface is walkable and can be further processed. When applying, it is important to follow the manufacturer's instructions.

To ensure safe use of the sealing slurry, ensure adequate ventilation in the work area and wear appropriate protective clothing to avoid skin, eye, or respiratory irritation. Always apply the sealant in accordance with the instructions on the product side and the safety data sheets.

The problem with sealing slurry: Why it is only a false solution

At first glance, waterproofing mortar seems like the ideal solution. It's inexpensive, easy to apply, and initially stops water from penetrating. However, there's a risk that improper application could cause cracks in the waterproofing mortar, which could compromise the waterproofing. But here lies the fundamental problem:

Sealing slurry only treats symptoms, not the cause

When you seal a damp wall with sealing mortar, the following happens:

• The water is stopped superficially
• However, the moisture remains in the wall
• The wall can no longer "breathe"
• The water seeks a new way upwards

The fatal ascent effect

In the case of rising damp, sealing mortar inside leads to a particularly problematic effect:

• They seal the lower part of the basement wall
• The moisture continues to rise until it can "breathe" again
• The problem shifts - often to the ground floor
• You have not solved the problem, but only postponed it

Long-term damage caused by sealing slurries

• Wall corrosion continues: The water remains in the wall and continues to destroy the mortar
• Salt efflorescence: Increased salt pollution due to impaired evaporation
• Damage to plaster: The sealing slurry can become detached or cracked, which particularly endangers plaster surfaces in the base area.
• Danger of mold: Moisture in the wall promotes mold growth

The better alternative: Isofin horizontal barrier

Instead of superficially "hiding" the problem, Isofin goes to the root of the problem and permanently eliminates the cause.

The advantages of Isofin over sealing slurry

Why Isofin is the better choice

• Real problem solution: Isofin combats rising damp where it originates – in the masonry itself.
• Wall remains breathable: The hydrophobic pores allow water vapor to pass through but prevent the penetration of liquid water.
• Long-lasting effect: With over 50 years of experience, Isofin is proven to offer long-lasting protection.
• No displacement of the problem: The water is stopped at the point of entry, not just blocked superficially.
• Maintaining the value of the property: Dry walls mean healthy building structure and maintaining the value.

Limited areas of application for sealing slurries

There are only a few situations where surface sealing such as sealing slurry can be useful:

• As a temporary measure until the complete renovation to ensure temporary moisture protection
• For very specific applications in the splash water area
• As a supplement to a real horizontal barrier

In all other cases, a professional, causal solution is the better choice.

How does Isofin® work?

Isofin® is a hydrophobic barrier system that impregnates masonry to repel water without clogging the pores. It works in a similar way to the impregnation of fabric or suede, repelling liquid water but allowing water vapor and air to pass through. Unlike leather, which has to be regularly re-impregnated, Isofin® guarantees this hydrophobic effect for at least 20 years, and often even longer.

Once hydrophobicized, the masonry permanently retains its water-repellent properties without the need for retreatment. This is also crucial for masonry to restore its natural function and thermal insulation. Contrary to popular belief, the distribution of the injection agent does not depend on its water solubility, but rather on its water insolubility, as well as its low surface tension and viscosity. These properties enable Isofin® to self-disperse and displace water in water-saturated masonry.

What is Isofin®?

Isofin is a purely organic, water-free, hydrophobic, polymer-based capillary water barrier that allows you to get your moisture problem under control and save money in the process. Isofin is effective against rising damp and laterally penetrating damp. It penetrates deep into the masonry and forms an invisible barrier that effectively repels non-pressing moisture. By simply inserting the Isofin bottles into pre-drilled holes, the product is distributed evenly and thus ensures complete protection. This not only preserves the building fabric of your home, but also increases your well-being through a dry and healthy indoor climate.

Frequently asked questions about surface sealing and Isofin

Conclusion: Invest in the right solution

At first glance, waterproofing mortar may seem like a simple and inexpensive solution. In reality, however, it's often just an expensive workaround that doesn't solve the underlying problem and can even worsen it.

With Isofin, you're investing in a proven, permanent solution that addresses the root cause of the problem. Your walls will be permanently dry, the building structure will be protected, and you'll save money in the long run.