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Purpose and standards

A vapour control layer (also known as a vapour barrier) is used to reduce the moisture vapour that passes through the external walls due to the difference in internal and external temperatures and pressures. Vapour control layers are a thin material that is fitted on internal side of the insulation between the plasterboard and studwork.

All vapour control layers must conform to I.S.EN1931:200 and EN12572:2001. All vapour control materials should come with an approval certificate or under EN13788 must be specified by condensation risk analysis. 500 gauge polythene sheeting with a vapour resistance of 250MNs/g is a common form of vapour control layer.

Installation

The vapour control layer must not be fitted until the studwork moisture content has dropped below 18%. The vapour control layer should be fixed to the timber studwork by austenitic stainless steel