Light steel framed walls and floors

6.10

6.10.13Vapour control layers

Vapour control layers shall restrict the passage of vapour from within the home to the steel frame and be correctly installed.

Vapour control layers should be provided, unless a condensation risk analysis in accordance with BS 5250 shows it is not necessary. Where they are provided, vapour control layers should be:

  • 500g polyethylene sheet, vapour control plasterboard, or material assessed in accordance with Technical Requirement R3
  • fixed on the warm side of the wall insulation and frame
  • in accordance with the design
  • placed to cover the external wall, including base rails, head rails, studs, lintels and window reveals
  • overlaping the base rail
  • fully sealed and punctures made good.

Where polyethylene sheet is used:

  • each joint in the vapour control layer should be located on studs or noggings and lapped by 100mm minimum
  • double-sided tape or adhesive should be used as a temporary fixing before the wall board is fixed.

Where vapour control plasterboard is used:

  • joints between sheets should be positioned on studs or noggings
  • care should be taken not to displace the vapour control material when cutting vapour control plasterboard.