How to Read an SBS Membrane TDS: Key Parameters Explained

Quick Answer: The Six Numbers That Decide Whether a TDS Is Trustworthy

Six parameters on an SBS membrane TDS decide project performance: soluble content, tensile strength, elongation, low-temperature flexibility, heat resistance and watertightness. The two you should check first are low-temperature flexibility (Type I -20°C / Type II -25°C) and soluble content (≥2,100 g/m² for 3mm, ≥2,900 for 4mm, ≥3,500 for 5mm under GB/T 18242) — they determine climate suitability and material honesty. Then confirm tensile strength, heat resistance and watertightness against your project specification, and always verify which standard edition the values reference (current edition: GB/T 18242-2025, effective 1 May 2026).

Why Reading a TDS Is a Procurement Skill, Not a Paperwork Formality

A technical data sheet is the only document where the supplier commits numbers — price lists and brochures do not. For a B2B buyer, the TDS serves three jobs:

1. Specification alignment. It tells you whether the offered membrane meets your tender’s grade (Type I / II), thickness and reinforcement requirements.
2. Quality verification. At goods-in inspection, the delivered rolls must match the TDS values — the declared numbers are your benchmark.
3. Fair comparison. Comparing two quotations means comparing two TDS documents parameter by parameter, not two prices.

Buyers who skip this step discover the difference between a 2,100 g/m² membrane and a 2,900 g/m² membrane only after installation. That difference is measurable — in service life.

The Six Parameters That Decide Performance

Parameter	What It Tells You	GB/T 18242 Requirement (Type II, PY)
Soluble content	How much bitumen compound is in the membrane (material honesty)	3mm ≥2,100 / 4mm ≥2,900 / 5mm ≥3,500 g/m²
Tensile strength	Resistance to substrate cracking and movement	≥800 N/50mm (PY Type II)
Elongation at peak	Ability to stretch with structural movement	≥40% (PY Type II)
Low-temperature flexibility	Cold-climate suitability	-25°C, no crack (Type II)
Heat resistance	Resistance to flow on hot roofs	105°C, slip ≤2mm (Type II)
Watertightness	Impermeability under water pressure	0.3 MPa / 30 min

Soluble Content — The Material-Honesty Number

Soluble content (g/m²) is the weight of the SBS-modified bitumen compound per square meter of membrane. It is the closest single indicator of whether the factory used enough material:

• 3mm requires ≥2,100 g/m², 4mm ≥2,900 g/m², 5mm ≥3,500 g/m² (GB/T 18242).
• A membrane with too-low soluble content has less waterproofing compound — faster aging, weaker puncture resistance, shorter service life.
• How to use it: compare the declared value against the requirement for the nominal thickness. A 4mm membrane declared at 2,300 g/m² is below spec, whatever the price.

Tensile Strength & Elongation — The Crack-Bridging Pair

Tensile strength (N/50mm) measures the pulling force a 50mm-wide specimen withstands before failure; elongation (%) measures how far it stretches. Together they describe crack-bridging ability:

• Type II polyester (PY) reinforcement: tensile ≥800 N/50mm, elongation ≥40%.
• Type I PY: ≥500 N/50mm, elongation ≥30%; fiberglass (G) grades carry lower tensile requirements (≥350-500 N/50mm) because glass felt prioritizes dimensional stability over stretch.
• How to use it: for substrates with expected movement (tunnels, foundations, large roofs), prefer high tensile + high elongation — the membrane must stretch with the structure without tearing.
• Composite (PYG) grades sit higher again: Type II PYG requires ≥900 N/50mm peak tensile with a second-peak requirement of ≥800 N/50mm — specified for heavy-load projects under the legacy classification.

Low-Temperature Flexibility — The Climate Decision

Tested at -20°C (Type I) or -25°C (Type II) with no cracking, this parameter decides where the membrane can be used:

• Type II (-25°C) is the specification for cold-climate regions, high-altitude sites and projects with demanding warranty terms.
• This is the parameter where SBS separates itself from APP (which typically reaches -15°C) — see our SBS vs APP comparison.

Heat Resistance — The Hot-Roof Limit

Declared as temperature with a slip limit: Type I 90°C, Type II 105°C, slip ≤2mm. It describes how the membrane behaves when the roof surface heats up in summer. For dark granulated roofs in hot climates, verify the declared temperature against expected surface temperatures — this is also a key difference between Type I and II grades (see our Type I vs Type II guide).

Watertightness — The Non-Negotiable

Tested at 0.3 MPa for 30 minutes (Type I PY and both Type II grades; 0.2 MPa for Type I fiberglass) with no water penetration. This is the parameter that must simply pass — there is no partial credit.

Seam Peel Strength — The System’s Weakest Point

Lap seams are the most common failure location in installed systems. Seam peel strength ≥1.5 N/mm confirms the seam can resist peeling forces; it is only meaningful when installation follows the approved lap procedure (see our installation guide).

How to Read a TDS in Five Steps

1. Check the grade first. Find Type I / II and the reinforcement (PY / G / PYG) — every other value must be read against these.
2. Verify the standard edition. Values declared under GB 18242-2008 (historical) differ from GB/T 18242-2025 (current, effective 1 May 2026). Require current-edition values for new orders.
3. Match thickness to values. Soluble content and some requirements change with nominal thickness — compare the value against the requirement for your ordered thickness, not the highest number on the sheet.
4. Look for ”≥” values that matter. The minimums (≥) are commitments; single-point “typical” values are informative only. If the sheet lists no standard reference, ask why.
5. Keep the TDS for goods-in inspection. The delivered membrane should match the declared values — the TDS is your receiving checklist.

Common Traps When Comparing TDS Documents

1. Mixing standard systems. GB values, ASTM (e.g. D6164) and EN values are not interchangeable — compare within the same system.
2. Comparing typical values as minimums. “Typical 900 N” is not a guarantee; the “≥800” minimum is the commitment.
3. Ignoring reinforcement and surface. Tensile requirements differ between PY and G; granule-surfaced sheets add weight and alter some values. Read the whole configuration row.
4. Using an outdated standard. GB 18242-2008-based TDS documents are still circulating; the current edition is GB/T 18242-2025.
5. Skipping the mass-gain / oil-bleeding checks. Mass gain after water immersion (≤1.0% PE/S, ≤2.0% granule) and oil bleeding (≤2 sheets) catch poorly formulated compounds that other numbers miss.

Checklist: What to Send Your Supplier

To receive a comparable, verifiable TDS, request these five items together:

1. Performance grade (Type I / Type II)
2. Reinforcement (polyester PY / fiberglass G / composite PYG)
3. Thickness (3mm / 4mm / 5mm) — to check thickness-matched soluble content
4. Surface finish (PE film / sand / mineral granules / aluminum foil)
5. Standard edition and test method (confirm values under GB/T 18242-2025)

A supplier that answers all five with a dated, referenced TDS is telling you how they control quality. One that sends a brochure instead is telling you something else.

Once the specification is confirmed, the next procurement question is quantity — see how many rolls and m² fit per container in our SBS container loading guide.

Frequently Asked Questions

What is the most important parameter on an SBS membrane TDS?

For most projects, the two parameters that matter most are low-temperature flexibility (which determines climate suitability, -20°C for Type I or -25°C for Type II) and soluble content (which determines how much bitumen compound is in the membrane, ≥2,100 g/m² for 3mm, ≥2,900 for 4mm and ≥3,500 for 5mm under GB/T 18242). Check these two first, then confirm tensile strength and watertightness against your project requirements.

What does soluble content mean in SBS membrane?

Soluble content is the weight of the SBS-modified bitumen compound per square meter of membrane (g/m²). Under GB/T 18242 it must be at least 2,100 g/m² for 3mm, 2,900 g/m² for 4mm and 3,500 g/m² for 5mm. It is the closest single indicator of material honesty: a membrane with too-low soluble content has less waterproofing compound, shorter service life and higher risk of premature aging. Always compare the declared value against the requirement for the nominal thickness.

What is the difference between Type I and Type II SBS membrane?

Type I and Type II are performance grades defined by GB/T 18242. Type II is the higher grade: heat resistance 105°C versus 90°C, low-temperature flexibility -25°C versus -20°C, and higher tensile requirements (≥800 N/50mm versus ≥500 N/50mm for polyester reinforcement). Choose Type II for cold climates, demanding civil engineering and projects requiring extended service life; Type I is adequate for moderate-climate general waterproofing.

What does tensile strength ≥800 N/50mm mean on an SBS membrane TDS?

It means a 50mm-wide test specimen must withstand at least 800 N of pulling force before failure. This value applies to Type II with polyester (PY) reinforcement under GB/T 18242, and it tells you how well the membrane resists substrate cracking and structural movement. Higher tensile strength and elongation together mean better crack-bridging performance. Compare the value with the reinforcement type — fiberglass (G) grades have lower tensile requirements than polyester (PY).

Why does a TDS list both GB 18242-2008 and GB/T 18242-2025?

GB 18242-2008 is the previous edition of the standard; GB/T 18242-2025 is the current one, effective 1 May 2026. GB/T 18242-2025 supersedes the previous edition and is the applicable reference for new orders. When reviewing a TDS, check which standard edition the values are declared against — and for new orders, require the supplier to confirm values under the current GB/T 18242-2025.

For the full specification matrix — reinforcement, surface and grade combinations — see our SBS Waterproofing Membrane product page. For grade selection logic, see the SBS Membrane Type I vs Type II Guide.