SBS modified bitumen membrane is a premium waterproofing sheet produced by blending styrene-butadiene-styrene elastomeric polymer with penetration-grade bitumen. The polymer converts standard bitumen into an elastic, rubber-like material with outstanding cold-temperature flexibility and crack-bridging capability — making SBS membranes the preferred choice for cold climates, green roofs, tunnels, and structures subject to movement.
RAHA Gilsonite Co. supplies the raw materials behind membrane manufacturing: gilsonite as a hardness and compatibility modifier, and oxidized bitumen grades as the base binder. This page explains SBS membrane technology, where gilsonite fits into the formulation, and how SBS compares with APP.
What is SBS Modification?
Styrene-butadiene-styrene is a thermoplastic elastomer. Blended into bitumen at 12–15% by weight, it forms a continuous polymer network throughout the binder, giving the finished membrane properties that unmodified bitumen cannot reach:
- Remains flexible at temperatures as low as −20 °C
- High elongation at break — up to 150%
- Excellent crack-bridging and movement accommodation
- Elastic memory — recovers original dimensions after stretching
- Compatible with self-adhesive application systems
Why elasticity matters. Roof and below-grade structures move — thermally, seasonally, and through settlement. An unmodified bitumen membrane transmits that movement as cracking. SBS absorbs it and returns to shape, which is why SBS membranes dominate in cold and high-movement applications.
Technical Specifications
| Property | Typical Value | Test Method |
|---|---|---|
| Softening point | 110–130 °C | ASTM D36 |
| Cold flexibility | −20 to −25 °C | EN 1109 |
| Tensile strength (L/T) | ≥ 700 / 500 N per 50 mm | EN 12311-1 |
| Elongation at break | ≥ 100% | EN 12311-1 |
| Heat resistance | 110 °C | EN 1110 |
| Water impermeability | Pass at 200 kPa | EN 1928 |
| Thickness | 3–5 mm | EN 1849-1 |
| Carrier | Polyester / fiberglass / composite | — |
Gilsonite in SBS Membrane Compounds
Gilsonite — natural asphaltite — is used in bituminous membrane formulations as a hardness and softening-point modifier. Its role in an SBS compound differs from its role in oxidized or APP membranes, and understanding that difference matters for formulation.
What gilsonite contributes
- Raises softening point without requiring additional air-blowing of the base bitumen
- Improves filler compatibility and dispersion in the compound
- Increases stiffness and surface hardness of the finished sheet
- Reduces polymer load — part of the stiffening effect otherwise requiring more polymer
- Enhances adhesion to substrates and between layers
Dosage considerations in SBS compounds
Gilsonite is used more sparingly in SBS membranes than in oxidized or APP membranes. The reason is straightforward: the entire purpose of SBS modification is low-temperature elasticity, and gilsonite is a stiffening agent. Excessive dosage raises the softening point at the cost of the cold flexibility the membrane was formulated to deliver.
Practical guidance. In SBS compounds, gilsonite is typically used at low dosage as a supporting modifier rather than a primary one. Always validate cold flexibility (EN 1109) on trial batches before committing to a production formulation — the trade-off between softening point and low-temperature performance is the controlling variable.
For the complete material data behind formulation work, see gilsonite specification, chemical characterization, and technical advantages of gilsonite.
Base Bitumen Grades Used in Membrane Production
The base binder beneath the polymer determines much of the finished membrane’s thermal behaviour. Membrane manufacturers typically work with oxidized bitumen grades selected for softening point:
| Grade | Softening Point | Typical Membrane Use |
|---|---|---|
| Oxidized Bitumen 115/15 | 110–120 °C | High-temperature membrane compounds |
| Oxidized Bitumen 105/35 | 100–110 °C | General membrane and sheet production |
| Oxidized Bitumen 90/40 | 85–95 °C | Softer compounds, cold-climate blends |
| Oxidized Bitumen 90/10 | 85–95 °C | Harder, lower-penetration applications |
Related reading: gilsonite and bitumen · gilsonite in construction
Key Applications
Cold climate roofing
SBS membranes are the standard choice where thermal cycling and freeze-thaw movement would crack conventional bitumen sheets — Scandinavia, Canada, Russia, Central Asia, high-altitude construction, and cold storage facilities.
Green and vegetated roofs
Root-resistant SBS grades serve as the primary waterproofing layer in green roof assemblies: extensive roofs with sedum and grass, intensive roofs with shrubs and trees, and biodiverse or brown roofs.
Tunnel and underground waterproofing
Elasticity and crack-bridging make SBS membranes well suited to tunnel lining — road and rail tunnels, metro and subway structures, and underground car parks.
Below-grade and foundation waterproofing
Self-adhesive SBS grades provide reliable below-grade protection for basement walls and floors, foundation slabs, and elevator pits.
Bridge decks and infrastructure
SBS membranes provide elastic waterproofing for bridge structures subject to dynamic loading and continuous thermal movement.
SBS vs APP — When to Choose Each
| Criterion | Choose SBS | Choose APP |
|---|---|---|
| Climate | Cold / temperate | Hot / temperate |
| Flexibility required | High movement | Low to moderate |
| Installation | Torch or self-adhesive | Torch-applied |
| Below-grade | Excellent | Good |
| Green roof | Preferred | Acceptable |
| UV exposure | Covered / protected | Exposed |
| Gilsonite dosage | Low — supporting role | Higher — stiffening is desirable |
For the APP side of the comparison, see APP membrane.
Advantages of SBS Membrane
- Outstanding cold flexibility — remains workable to −20 °C
- High elongation — up to 150% at break
- Elastic memory — returns to original shape after deformation
- Crack-bridging — accommodates structural movement and settlement
- Self-adhesive options for flame-free installation zones
- Root-resistant grades certified for green roof applications
- Long service life — 25 to 30 years with correct installation
- Versatile across roofing, below-grade, and civil applications
Quality Standards
| Standard | Scope |
|---|---|
| EN 13707 | Reinforced bitumen sheets for roof waterproofing |
| ASTM D6163 | SBS modified bituminous sheet materials |
| EN 1928 | Water impermeability |
| EN 1109 | Flexibility at low temperature |
| EN 1110 | Heat resistance |
| EN 12311-1 | Tensile properties |
| FLL Guidelines | Root resistance certification for green roofs |
Frequently Asked Questions
Yes, but at lower dosage than in oxidized or APP membranes. Gilsonite raises softening point and surface hardness, while SBS modification exists to deliver low-temperature elasticity. The two work against each other above a certain dosage, so cold flexibility must be verified on trial batches.
SBS uses an elastomeric polymer that gives the membrane elastic recovery and cold flexibility. APP uses a plastomeric polymer that gives higher heat resistance and better UV tolerance. SBS suits cold climates and moving structures; APP suits hot climates and exposed roofs.
Membrane producers typically use oxidized grades selected by softening point — 115/15 for high-temperature compounds, 105/35 for general production, and softer grades such as 90/40 for cold-climate blends.
Twenty-five to thirty years with correct installation and appropriate surface protection. Service life depends heavily on UV exposure — SBS membranes should be covered or protected rather than left fully exposed.
RAHA Gilsonite Co. supplies the raw materials used in membrane manufacturing — gilsonite as a modifier and oxidized bitumen grades as the base binder. Contact us with your formulation requirements for specification sheets and pricing.
Raw Materials for Membrane Production
Gilsonite and oxidized bitumen grades supplied from Dubai and Ankara offices. Specification sheets, samples, and quotations available on request.
Related pages: What is Gilsonite? · Oxidized Bitumen Grades · Gilsonite in Construction · Gilsonite Price
