SBS-Modified High-Elongation Waterproofing Membrane for Foundations and Retaining Walls
Foundations and retaining walls are among the most critical parts of any structure. Even minor water infiltration in these areas can significantly reduce a building’s service life. For this reason, SBS-modified, 5 mm thick, reinforcement-free, three-dimensionally formable elastomeric bituminous membranes are widely used in foundation waterproofing applications.
The key advantages of these membranes include:
- Elongation of up to 1600%
- Maintains flexibility even at –25°C
- Self-healing capability
- Excellent adaptability to complex construction details
1. Waterproofing Application Beneath Foundation Slabs
After the lean concrete (blinding concrete) has been completed:
- The surface should be leveled using mechanical troweling.
- The substrate must be clean and completely dry.
Membrane Specifications
The waterproofing membrane used should have the following characteristics:
- SBS-modified bitumen formulation
- Homogeneous 5 mm thickness
- Filler-free composition
- Reinforcement-free structure
- PE film-coated bottom surface
- Sanded top surface
- Self-healing properties
- Three-dimensional formability
Application Method
- Loose-laid installation method
- Longitudinal overlaps: 10 cm
- Transverse overlaps: 15 cm
- The membrane should not be fully torch-bonded beneath the foundation slab
- Torch heat should be used only to seal overlap joints without igniting the bitumen
This application method provides maximum flexibility and waterproofing performance against foundation settlement and structural movement.
2. Waterproofing of Retaining Walls
Surface Preparation
- Remove oil, rust, dust, dirt, and loose particles from the surface.
- Repair honeycombs, segregation areas, and cold joints using structural repair mortar.
- Fill tie-rod holes to a depth of approximately 5–10 cm.
- Form a 3–5 cm fillet (cant strip) at the foundation-to-wall junction.
Primer Application
- Apply a cold-applied bituminous primer to the concrete surface at a minimum consumption of 0.400 kg/m².
- Allow the primer to dry completely before membrane installation.
Installation of Elastomeric Bituminous Membrane
- Use the fully bonded application method on retaining wall surfaces.
- Longitudinal overlaps: 10 cm
- Transverse overlaps: 15 cm
- Carefully heat and bond the membrane using a torch without burning the bitumen.
This process ensures long-term waterproofing performance and maximum water resistance on retaining wall structures.
Conclusion
SBS-modified elastomeric bituminous membranes provide reliable waterproofing performance thanks to their:
- High elasticity
- Resistance to low temperatures
- Self-healing capability
These properties make them an ideal solution even in challenging ground conditions. When properly installed, they significantly improve the long-term waterproofing performance and durability of a structure.
Frequently Asked Questions (FAQ)
Why is an SBS-modified 5 mm membrane preferred?
Its exceptional elongation capability (up to 1600%) and ability to maintain flexibility at temperatures as low as –25°C provide superior resistance to structural movement and settlement.
What is the difference between foundation slab and retaining wall applications?
A loose-laid installation method is used beneath foundation slabs, while a fully bonded application method is recommended for retaining walls.
Is primer application necessary?
Yes. Primer improves adhesion on retaining wall surfaces and helps ensure complete bonding of the membrane.
Why is a fillet (cant strip) installed at connection points?
A fillet allows the membrane to transition smoothly around corners without cracking or lifting, ensuring full contact with the substrate and improved waterproofing performance.