There are three main reasons why building materials in old buildings,
particularly Mortars, should be correctly identified:
1. To allow
for the correct selection of new or replacement mortars. Correct
identification of materials, their compatibility, durability and
aesthetics are all-important in the selection of new and replacement
mortars and renders. Incorrect selection can lead to number of serious
problems, which inevitably may cause failure of the mortar. The
more common problems associated with a poorly identified mortar
are: · Inability to adhere to background. · Presence of high salt
levels. · Differential thermal movement and flexibility. · Inability
to breathe. Careful and informed selection of the components of
the new mortar is vital in conservation where the new and old need
to be visually compatible, in 'patch pointing' for example.
2. To examine
the archeological value of the mortar. The identification of the
components of the mortar in a historic structure allows us to record
various periods in a buildings development. It can also reveal the
introduction of new and imported materials to the building at different
stages of its life.
3. To identify
problems with previously attempted repair work. Previous repair
or replacement work may have been inappropriate. It is not uncommon
for misguided repair work to actually be the cause of the problem.
Mortars may fail for no apparent reason. Identification of the exact
reason for failure is important, particularly if removal and reapplication
of a mortar is being considered.