walls either by secondary joists bearing on to the walls or the principal beams bearing on to those walls. The party walls are a minimum of one brick thick, strengthened by the chimneybreast to provide lateral restraint to the walls. The face of the chimneybreast is generally only half a brick thick.
Depending on the circumstances, and the sequence of building, it is not unusual to find the front and back walls butting on to an original gable end of a previously built property, and not tied in. In other cases front and rear walls simply fly past the party walls and are not significantly connected.
These buildings were constructed quickly, with little or no foundations. They were built of flexible materials. The mortar took a significant time to set and the structures tended to settle down as they were built, retaining a degree of flexibility not found in later buildings of similar size. This flexibility has undoubtedly led to the long life of these buildings.
The structure of the buildings fails not because of vertical load but because of lack of lateral restraint, and sometimes lack of bonding within the thickness of the wall. Such failures are found particularly in higher-quality Georgian houses, where the outer skin of the face of the external walls was built with very thin mortar joints, built by the experienced bricklayer, while the inside face the brickwork was built with thick joints by the apprentice. Thus the walls were never bonded together because the joints were at different levels. This form of construction is described as snapped-header construction. Even when high-quality facing bricks were not used, there was a tendency for the outer face to be built by the experienced bricklayer, backed up by the apprentice.
Basements or lower-ground floors are always potentially a problem as far as damp-proof treatment is concerned. The modern style of living does not normally suit the form of construction.
Walls of soft bricks and lime mortar work because they breathe. Rain makes the wall wet or damp, and the wind dries the external face. The internal plaster also breathes and allows a small proportion of the damp to dry out within the atmosphere of the rooms. The basements or lower ground floors were constructed with pammets (floor bricks), covered by stone slabs. Both had open joints, allowing moisture to dry up through the floors. Walls were plastered with a hair-reinforced, lime-based plaster which also allowed the walls to breathe. Even where these conditions have prevailed for perhaps 150 years, I have seen original plaster in perfect condition. Air circulated within the rooms and a damp atmosphere seemed not to worry the occupiers.
In the early days of conservation restoration, pammet floors or stone floors were taken up, and floors were concreted, generally with a damp-proof course. The result was that the moisture was driven up the walls and the plaster came off. The walls were then rendered with a waterproof render, sometimes the full height of the room but mostly about one