TS EN 13970

TS EN 13970 is the standard for flexible, reinforced bitumen sheets intended for use as water vapour control layers in buildings. In the building envelope, vapour control helps limit moisture migration into colder layers, reducing the risk of condensation within roof and wall assemblies; this makes the product category important to overall hygrothermal performance.

What a bitumen vapour control layer is

In general technical terms, a flexible sheet is a roll-based membrane, typically finished with a bitumen-based binder and reinforced to improve tensile strength and dimensional stability. The standard focuses on definitions and characteristics, so its value lies in identifying the product family and the properties used to describe it, rather than in prescribing a complete installation system.

What this standard provides

• Defines the product category used as a water vapour control layer in buildings.
• Addresses characteristics for flexible reinforced bitumen sheets.
• Provides common terminology for describing and identifying these products.
• Helps distinguish this membrane type from other bituminous waterproofing sheets used for different functions.

From a general construction perspective, vapour control layers are typically paired with insulation and other envelope layers to manage moisture movement through the assembly. Bitumen-based membranes are widely used where a durable, practical sheet material is needed, but correct product selection and detailing remain essential to performance. TS EN 13970 serves as a technical reference for defining and characterising this family of sheets.