External timber framed walls

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Insulation shall be correctly installed and provide suitable performance.

Insulation should be:

  • breathable, e.g. mineral wool (rock or glass), or
  • assessed in accordance with Technical Requirement R3 for use in timber frame wall panels.

Insulation should generally be placed within the stud void and cover the whole wall area between studs. No gaps should be left:

  • at corners
  • at junctions with partitions
  • against studs or rails
  • against noggings
  • behind service panels.

In England and Wales, account should be taken of Accredited Details.

Water and heating services within walls should be on the warm side of the insulation.

Where partial fill cavity insulation with a 50mm residual cavity is used, it should be assessed in accordance with Technical Requirement R3 as an integral part of the wall system.