SikaTop® Seal-125 | Two-Component Semi-Flexible Cementitious Waterproofing Material

Choosing the right waterproofing product is a critical step for surfaces exposed to continuous water and moisture. SikaTop® Seal-125 provides a reliable waterproofing solution for both new construction projects and renovation applications with its two-component cement-based formulation reinforced with liquid polymers and special additives.

Thanks to its semi-flexible structure, it offers excellent compatibility and adhesion with mineral-based substrates.

Product Description

SikaTop® Seal-125 consists of two components:

Component A: Liquid polymer and special additives
Component B: Portland cement, selected aggregates, and additives

When the two components are mixed together, they form a semi-flexible waterproofing mortar that creates a water-resistant barrier on the surface.

The product has been tested for contact with drinking water according to the BS 6920:2000 standard and has a verification dated 22.08.2016.

Application Areas

SikaTop® Seal-125 can be used in indoor and outdoor applications, including:

Waterproofing of concrete, cement-based plaster, brick, and block surfaces
Rigid waterproofing of foundation walls in new construction and renovation projects
Waterproofing of foundations and basement areas
Sealing of inactive fine cracks in concrete structures
Filling pores and surface voids
Protective coating against freeze-thaw cycles and the corrosive effects of de-icing salts

Key Advantages

SikaTop® Seal-125 offers several important benefits:

Semi-flexible cement-based structure with excellent adhesion to mineral surfaces
Two-component system for controlled consistency and reliable performance
Easy application by brush or spray
Smooth and uniform finishing with notched trowel application
Protective layer against freeze and salt damage
Tested suitability for contact with drinking water
Wide usage range in foundations, basements, facade substructures, and renovation projects

Technical Properties (Summary)

Components

Component A: Liquid polymer + additives
Component B: Portland cement + selected aggregates

Packaging

33 kg set
- 8 kg Component A
- 25 kg Component B

Density

Powder density: ~1.320 kg/L
Fresh mortar density: ~1.70 kg/L

Mixing Ratio

Flowable consistency: 1:3 (A:B by weight)
Plastic consistency: 1:3.5

Consumption

Approximately 1.7 kg/m²/mm

Layer Thickness

Minimum: 0.75 mm
Maximum: 1.75 mm

Application Temperature

+8 °C to +30 °C

Curing Time

3–5 days with suitable curing conditions

Shelf Life

12 months under proper storage conditions

Surface Preparation

The surface must be properly prepared before application.

Remove oil, dirt, weak particles, and cement residues.
Concrete surfaces should have a minimum tensile adhesion strength of 1.0 N/mm².
After mechanical preparation, the surface must be in SSD condition (Saturated Surface Dry).
Pores and voids should be cleaned with compressed air.

Proper surface preparation is essential for achieving maximum waterproofing performance.

Mixing Instructions

A low-speed mixer (maximum 500 rpm) should be used.

Mix for approximately 3 minutes until a homogeneous, lump-free consistency is achieved.
Free-fall mixers should not be used.

For Flowable Consistency:

Pour half of Component A into the mixing container.
Add Component B and mix thoroughly.
Add the remaining Component A and continue mixing until the desired consistency is achieved.

For Plastic Consistency:

For a smoother surface finish, the amount of Component A can be reduced by approximately 10%.

Application Method

Flowable Consistency (Brush/Spray Application)

Apply onto an SSD surface in one direction.
Apply the second coat perpendicular to the first coat after the initial layer has hardened.

Plastic Consistency (Notched Trowel Application)

Suitable for applications requiring a smooth and even surface finish.
The second coat should be applied after the first layer has sufficiently set.
Surface void filling can be performed using a trowel.

Curing

After application, the surface should be properly cured for at least 3–5 days.

Proper curing helps reduce cracking risks and improves the final durability and waterproofing performance.

Limitations

It is not a decorative coating material.
Avoid application under direct sunlight and strong wind conditions.
Do not add extra water to the mixture.
Maximum layer thickness must not be exceeded.
A minimum of two coats is generally recommended, achieving a total thickness of approximately 1.5–2.0 mm.
Protect the applied surface from frost and rain.
It is not designed as a walkable surface. If necessary, it should be covered with a suitable protective screed or coating.

Conclusion

SikaTop® Seal-125 provides a durable and reliable waterproofing solution for foundations, basements, and facade substructures thanks to its semi-flexible structure, easy application properties, and resistance against freeze-thaw and salt effects.

When professionally applied, it delivers high performance in both new construction projects and renovation applications.

Frequently Asked Questions (FAQ)

Where is SikaTop® Seal-125 used?

It is used for waterproofing concrete, plastered surfaces, bricks, and blocks, as well as foundations and basement areas. It also provides protection against freeze-thaw and salt damage.

How is it applied?

It can be applied by brush or spray in flowable consistency, or by notched trowel in plastic consistency. Application must always be performed on an SSD surface.

What is the consumption rate and application thickness?

The consumption rate is approximately 1.7 kg/m²/mm. Each coat should be applied between 0.75 mm and 1.75 mm thickness.

How many coats are required?

A minimum of two coats is generally recommended. Three coats may be applied in areas exposed to higher water pressure.

Is curing required?

Yes. A curing period of 3–5 days is required to achieve optimum strength and performance.

Can it be walked on after application?

No. If a walkable surface is required, an additional protective layer should be applied.