Chapter 5 case study 1: walls below ground
Here we see two of the common methods adopted fro froming walls below ground. The filled cavity uses two leaves of block or brick below ground, with the cavity filled using weak concrete. In contrast the ‘trenchblock’ alternative uses a single, wide concrete block. The wall below ground is solid in this case. It is quite unusual for expensive clay bricks to be used below ground; instead, concrete bricks or blocks are used.
The walls below ground are formed here using foundation blocks. The concrete bricks used for the courses immediately above the foundation blocks allow the brick courses to be brought to ground level without the risk of exposing the foundation blocks, which would be unsightly. One course of blocks is the same height as three courses of bricks. A small amount of overhang is allowed when constructing external walls, and this can be seen below. The allowance of overhang permits the use of a slightly narrower block, which has economic benefits.
The walls below ground level must be durable enough to survive in the hostile conditions that arise as a result of high moisture levels, as seen here. In order to resist the passage of moisture to the interior of the building an impervious damp-proof course is installed. The ensure that there is a continuous barrier to moisture the DPC is lapped with the damp-proof membrane that is included in the ground floor construction.
The construction of houses on sloping sites can create several problems. One way of dealing with these is to create a level section on which to build. Here we can see that the house is built on a level pocket that has been excavated from the sloping ground. In order to cope with the heavy loads from the ground above the building a robust retaining wall has been formed to the rear of the house.