• Description

Care should be taken when cutting vertical and horizontal chases in walls if the structural stability is to be maintained. The depth of any chase shown is limited as listed below. A chase is a recess, cut or built in a wall, inside which small service pipes are run and then covered with plaster or walling.

Chases in walls


Care should be taken when cutting vertical and horizontal chases in walls if the structural stability is to be maintained. The depth of any chase shown is limited as listed below. A chase is a recess, cut or built in a wall, inside which small service pipes are run and then covered with plaster or walling.

Chases in walls

Limit on the depth of chases
A. Vertical chases, indicated B on the above diagram, should not be deeper than 1/3 rd of the wall thickness or, in a cavity wall, 1/3 rd of the thickness of the relevant leaf.
B. Horizontal chases, indicated C on the above diagram, should not be deeper than 1/6 th of the wall thickness or, in a cavity wall, 1/6 th of the thickness of the relevant leaf.
C. Chases should not be so positioned as to impair the stability of the wall. Back to back chases are not permitted.
D. For hollow or cellular blocks maintain a residual thickness of 15mm between the chase and the void unless otherwise recommended by the manufacturer.

Where acoustic performance is required, it is preferable that there are no chases or recesses in a masonry separating wall. However, there will be situations when this is not possible, in which case the chases or recesses on each side of the wall should not be located back to back.