skip to main page content :: Town & Regional Planning Home > Glossary Home > D >
Differential settlement / Tell tails / Drift
defects due to the uneven sinking of a building. In buildings on historic sites, this can
sometimes have an archaeoligical explanation,
as buried walls and pits can produce hard and
soft spots. York Minster is a famous example. Settlement can occur at a very early stage
in the life of a building and can be live or expended. There are a number of sophisticated
techniques for measuring rate of settlement ranging from tell tales to laser technology.
Tell tails are strips of a brittle material, usually
glass, carefully positioned and secured
at each end over cracks. If they fracture, movement is still live! Ideally, they should
always be dated.
Drift is the gradual displacement of the fabric of a structure caused
by the expansion and contraction which is the natural result of temperature change.