Client: NHBC Location: West Yorkshire
These are timber framed houses built of a flat raft foundation slab. The original detail at the external wall around the block is failing and allows rain entering the cavity to drain directly onto the raft slab due to inadequate waterproofing.
The first proposal was to install an Aco channel around the rear and side elevations of the three plots but this was an insufficient solution.
Walker Builders then proposed to open up the base of the external walls and install a liquid waterproof tanking to form a continuous cavity tray along the base of the wall. This was applied to the face of the timber frame and down the front edge of the raft foundation. Although it was recommended to the client to carry this detail through the French doors & front door openings and install stop ends to the party walls, the client felt it unnecessary.
Walker Builders carried out further investigations whilst working on the project, reported our findings to the Client, this resulted in the proposed additional work being done.
The solution was to carry the continuous waterproof tanking detail around the whole perimeter of the three plots, below all door openings and install the stop ends originally recommended to ensure no water could track in or around the back of the cavity. Also installed is a French drain below ground at the base of the raft edge, connected to the surface water drainage to stop water rising at the base and entering the cavity during a rainwater surge.