David Rawlins - Chartered Surveryors

External walls

The walls of period houses tend to behave in a different manner than those of modern construction, and therefore require different methods of repair. “Modern” housing, where the walls are of cavity construction, incorporate impervious membranes and other materials specifically designed to stop moisture entering the inside of the building. Older walls of solid construction are constructed of porous materials, which are not designed to prevent moisture entering the structure. Rather, moisture will inevitably enter the material. Traditionally, the moisture would then evaporate out from the wall. ANY impervious material added to such wall can alter or restrict such evaporation. With the introduction of Portland cements in the 1850`s, which were found to harden much quicker than the traditional lime mortars, there has been a gradual replacement of lime with cement rich mortars. This has increased in recent years due to the loss of craftsmen.