The installation of electrical, gas, water or other services in the walls of a building is generally permitted by the Building Regulations 2010. However, removal of material from a wall for the installation of services can weaken the wall and may lead to structural movement of the wall and/or building. Therefore, the designer and installer of building services must take account of the requirement not to impair the stability of the walls where such services are to be installed within a wall. To reduce the risk of structural movement of a wall and/or building, chases in walls for the installation of services should not be positioned in such a way as to impair the stability of the wall. Furthermore, ADA recommends for particular walls that the dimensions of chases are restricted. The restrictions given in paragraph 2C30 of ADA are illustrated in Fig 1. They apply to walls constructed of masonry units, such as bricks or blocks, forming part of a residential building of up to three storeys, where such walls are parapet1 or extend to the full storey height and the walls are: The restrictions on dimensions of chases apply equally to parapet walls, external and internal load-bearing wal...