A DAMP WALL PROBLEM

Evening Star, Issue 21081, 19 April 1932, Page 2

A DAMP WALL PROBLEM

INVESTIGATION OF RESEARCH STATION The architect for a block of recently erected flats requested the assistance of the Building Research Station (England), in tracing the cause of dampness in a wall in one of the apartments on the ground floor. An inspection carried out at tho building by an officer of the Building Research Station showed that on one side of tho affected wall was a solid concrete floor finished with wood bearers and flooring, while on tho other side was a pipe duct with a hollow tile and concrete cover also finished with wood bearers and flooring. A sketch showing tho construction is appended. It was obvious from an inspection that the trouble was most probably due to the capillary rise of ground moisture at tho point where the concrete was in contact with the wall

above the damp-proof _ course: the arrows on the sketch indicate the manner it was thought that the moisture was rising. Jt was, perhaps, not generally realised that even a dense, wellmade concrete may not be a barrier to the capillary movement of moisture, although the amount actually transmitted may be small. The fact that one flat alone was affected may be the result of some peculiarity in the distribution of ground moisture on the site. In this connection it was observed that the corner of the building where the Hat was situated appeared to be at a rather lower level in relation to the general ground level than the rest of the building. To prevent the rise of moisture in the wails it Would be necessary to provide a vertical damp course. This might be "satisfactorily accomplished by cutting a chase in the concrete adjoining the wall to a depth sufficient to leave the full thickness of the dampproof course exposed, and filling up the chase with hot bitumen.

With .the construction carried out tho floor timbers were also liable to become saturated with moisture, a condition very liable to result in an outbreak of dry-rot, and it would be advisable to introduce some form of insulation between the timbers and the top surface of the concrete. A bitumen coating would probably provide satisfactory insulation from moisture,' but to be effective it would be necessary to ensure that tho layer of bitumen over the concrete was continuous.