We're building an extension and want to use Celotex CW3000 board insullation.
The wall will have a 100mm cavity, so what is the maximum thickness of board we can use. My feeling is 75mm is the maximum to leave a 25mm cavity, but I seen some comments about allowing a 50mm cavity to prevent bridging of the gap through low quality brickwork. Is this the case?
I should add that we are not using variable sized bricks (e.g. reclaimed) for the exterior leaf, but will be using Ibstock Marlborough bricks with the inner leaf made from 100mm hemelite blocks.
The wall will have a 100mm cavity, so what is the maximum thickness of board we can use. My feeling is 75mm is the maximum to leave a 25mm cavity, but I seen some comments about allowing a 50mm cavity to prevent bridging of the gap through low quality brickwork. Is this the case?
I should add that we are not using variable sized bricks (e.g. reclaimed) for the exterior leaf, but will be using Ibstock Marlborough bricks with the inner leaf made from 100mm hemelite blocks.