Waterproofing Foundation and Retaining Wall Surfaces with Flexobit High-Elasticity Bituminous Membranes
Long-Lasting Waterproofing Beneath Foundation Slabs
After the lean concrete (blinding concrete) has been poured, the surface should be leveled using a mechanical trowel to achieve a smooth finish. Before waterproofing installation, the substrate must be completely dry.
The bituminous membrane used should have the following characteristics:
- SBS-modified with high elasticity
- Homogeneous thickness of 5 mm
- Filler-free composition
- Three-dimensional formability for detailed applications
Membrane Features
The membrane provides several important performance benefits:
- Up to 1600% elongation in all directions
- Retains flexibility even at temperatures as low as –25°C
- Full adhesion to the substrate through its PE film-coated bottom surface
- Sanded top surface that improves seam bonding performance
- Self-healing capability under appropriate conditions
Installation Method
For foundation slab waterproofing, a loose-laid installation method is recommended:
- Longitudinal overlaps: 10 cm
- Transverse overlaps: 15 cm
- During installation, the torch flame should not directly melt the membrane across the entire surface
- Heat should be applied only at overlap joints to ensure proper seam bonding
This method provides excellent performance against structural settlement and movement while maintaining reliable waterproofing protection.
Fully Bonded Waterproofing on Retaining Walls
After the retaining wall concrete has been cast and cured, proper surface preparation becomes essential for successful waterproofing performance.
The following defects and contaminants must be completely removed or repaired:
- Rust
- Oil and grease
- Loose particles
- Cold joints
- Segregation areas
All imperfections should be repaired using a suitable repair mortar. Tie-rod holes should be filled to a depth of approximately 5–10 cm, and a 3–5 cm fillet (cant strip) should be formed at the foundation-to-wall transition.
Primer Application
- Apply a cold-applied bitumen-based primer to the concrete surface.
- Recommended consumption: minimum 0.400 kg/m²
- Allow the primer to dry completely before membrane installation.
Membrane Installation
- A fully bonded application method should be used on retaining wall surfaces.
- Longitudinal overlaps: 10 cm
- Transverse overlaps: 15 cm
- The membrane should be firmly bonded across the entire surface to ensure continuous waterproof protection.
Conclusion
This application method, using highly elastic SBS-modified bituminous membranes, provides long-lasting, comprehensive, and durable waterproofing for both foundation slabs and retaining wall surfaces.
Thanks to their ability to maintain flexibility even under low-temperature conditions, these advanced waterproofing membranes meet the requirements of modern construction projects while delivering performance in line with European waterproofing standards.
Key Benefits
✔ Up to 1600% elongation capability
✔ Flexibility maintained at –25°C
✔ Excellent waterproofing performance against groundwater and hydrostatic pressure
✔ Self-healing characteristics
✔ Strong seam bonding through sanded surface technology
✔ Long-term durability in demanding environmental conditions
✔ Suitable for complex structural details due to three-dimensional formability