SBS-Modified 5 mm Waterproofing Membrane for Foundations and Retaining Walls
Foundations and retaining walls are among the most critical structural elements of any building. Water infiltration in these areas can significantly reduce the service life of a structure. For this reason, SBS (Styrene-Butadiene-Styrene) polymer-modified, 5 mm homogeneous thickness, reinforcement-free, highly elastic bituminous membranes provide long-term protection against groundwater and hydrostatic pressure.
1. Waterproofing Beneath Foundation Slabs
After the lean concrete (blinding concrete) has been poured:
- The surface should be leveled using mechanical troweling.
- The substrate must be completely dry and clean.
Recommended Membrane Properties
The waterproofing membrane should have the following characteristics:
- SBS-modified bitumen formulation
- 5 mm homogeneous thickness
- Reinforcement-free construction
- No filler materials
- Up to 1600% elongation in all directions
- Maintains elasticity at temperatures as low as –25°C
- PE film on the bottom surface for full adhesion to the substrate
- Sanded top surface to improve seam bonding performance
- Self-healing capability
- Three-dimensional formability for detailing applications
Application Method (Under Foundation Slabs)
- Loose-laid installation method
- Longitudinal overlaps: 10 cm
- Transverse overlaps: 15 cm
- Torch flame should be applied only at overlap joints
- Bitumen should be heated and bonded without direct ignition
This application method provides optimum performance against potential settlement and structural movements beneath the foundation.
2. Waterproofing on Retaining Wall Concrete Surfaces
After the retaining wall concrete has been cast and fully cured:
Surface Preparation
- Remove oil, dust, dirt, rust, and other contaminants.
- Repair honeycombs, segregation areas, and cold joints using suitable repair mortar.
- Seal tie-rod holes to a depth of approximately 5–10 cm.
- Create a 3–5 cm fillet (cant strip) at the foundation-to-wall junction.
Primer Application
- Apply a cold-applied bituminous primer at approximately 0.400 kg/m².
- Allow the primer to dry completely before membrane installation.
Membrane Installation
- Fully bonded application method
- Longitudinal overlaps: 10 cm
- Transverse overlaps: 15 cm
- Apply torch heat carefully without igniting the bitumen
- Ensure complete and uniform adhesion across the entire surface
This method provides maximum adhesion and waterproofing performance on vertical retaining wall surfaces.
Advantages
The key advantages of this waterproofing system include:
✔ Excellent resistance to hydrostatic water pressure
✔ Up to 1600% elongation without cracking during settlement or structural movement
✔ Maintains flexibility at temperatures down to –25°C
✔ Three-dimensional formability at foundation-wall junctions and complex details
✔ Self-healing capability for enhanced durability
✔ Full adhesion through the PE film bottom layer
✔ Strong seam performance thanks to the sanded top surface
Frequently Asked Questions (FAQ)
Which membrane should be used for foundation waterproofing?
SBS-modified membranes with a homogeneous 5 mm thickness, reinforcement-free structure, and high elasticity are recommended for superior waterproofing performance.
Is full bonding mandatory on retaining wall surfaces?
Yes. Fully bonded installation on vertical surfaces provides the highest level of adhesion and waterproofing protection.
Why is primer application necessary?
Primer improves membrane adhesion and ensures complete bonding, especially on vertical and inclined surfaces.
How should membrane overlaps be installed?
Longitudinal overlaps should be 10 cm, and transverse overlaps should be 15 cm. Overlaps should be heat-bonded using a torch without igniting the bitumen.