1930s20% of homes here
Cavity walls become standard, generally with clay tile or slate roofs, cast-iron rainwater goods and suspended timber ground floors. Bay-fronted semis dominate.
What we usually find. Wall-tie corrosion and bridged cavities are the usual structural concerns, and sub-floor ventilation is often obstructed by later paths, patios or extensions, which brings damp and timber decay to the ground floor. Original roof coverings are typically at the end of their life.
Worth knowing. Cavity wall insulation retrofitted into this stock can cause damp on exposed elevations if the wall was not suitable. Establishing whether the cavity was filled, and when, is worthwhile.
Pre-190019.7% of homes here
Normally solid walls of brick or stone with no cavity, lime mortar, timber suspended floors and lath-and-plaster internally. Any damp-proof course is either slate or absent altogether.
What we usually find. Damp at low level is the most frequent finding, usually where a slate damp-proof course has been bridged by raised ground or by later solid floors and cement render. Chimney stacks, roof coverings and rainwater goods are often at or beyond the end of their serviceable lives, and earlier repointing in cement rather than lime can trap moisture and spall the brick face.
Worth knowing. Solid walls cannot be treated like cavity walls. Injected chemical courses and internal tanking frequently move the problem rather than resolve it, so the cause matters more than the last remedy applied.
1965–198218.7% of homes here
Cavity walls with insulation increasingly built in, flat-roofed elements such as garages, dormers and rear additions, and a broader range of manufactured materials.
What we usually find. Flat roofs of this era are frequently on their second or third covering and are a common source of water ingress. Textured coatings applied before the mid-1980s may contain asbestos, as may some cement products, soffits and floor tiles.
Worth knowing. Asbestos-containing materials are usually safe if undisturbed and in good order, but they matter a great deal if you intend to remove ceilings, take down a garage or open up the layout.
These are tendencies of the local stock, not findings on any particular house. A well-maintained Victorian terrace can be in better order than a neglected 1990s semi, which is the entire reason a survey is done on the building in front of you rather than on its postcode.