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Moravian College • Preservation Master Plan
1. Repointing of Mortar Joints – Ineffective,
inappropriate and sometimes damaging
repointing work was observed on almost every
historic building on campus. Before the College
proceeds with any more repointing projects, an
assessment of the mortars used in each historic
masonry building should be conducted by a
conservator or specialist. It is preferable that
this work occur simultaneously with the other
masonry testing and analysis outlined in this
section.
Figure 8-323. Foundation parging failure, 1457 Iron St. (JMA
2008).
Figure 8-324. Crumbling concrete steps, 1416-1418 Monocacy St.
(JMA 2008).
8.5 Overall Conditions –
Key Preservation Issues
The inventory of buildings at Moravian College
represents one of the most historically significant
small college campuses in the nation. This
impressive architectural legacy is orchestrated
through a masonry building tradition of brick
and stone. In conducting the assessment of
existing conditions for Moravian’s buildings, three
consistent preservation issues were noted. This
section outlines the key historic preservation issues
for the College to address, and recommendations
on how to do so.
Preservation Issue #1 – Masonry
It is imperative that the College adopt an appropriate
and consistent approach for maintaining brick and
stone masonry. The following conditions have been
observed and issues identified:
Original and early pointing mortars should
be analyzed on each historic building to
determine mortar composition, color, and joint
profile (tooling). Sand was almost always used
as an additive in historic mortars, however,
modern masonry or builder’s sand may not be
appropriate in color or grain size. For example,
in Memorial Hall the type of sand originally
used in the mortar has a very large grain size,
like tiny pebbles. Every effort should be made to
match the original mortar as closely as possible.
A repointing mortar that is compatible with the
original mortar will create a better bond and
weather tight seal without damaging stone or
brick masonry units. A properly repointed
historic masonry building is watertight and
does not require water-repellent or protective
coatings.
Also, mortars and masonry units should
be tested for the presence of corrosive salts,
moisture content, vapor permeability, and
compressive strength. Based on the resulting
analysis, a masonry specialist should develop
a mortar formula and method to be used for
repointing. It is likely that several different
formulas and tooling techniques will be
developed for the various historic buildings at
Moravian College.
A basic rule of thumb to follow is that a mortar
should never be harder than the masonry units
it is holding together. Portland cement, a major
ingredient in most commercial mortar mixes, is
a very hard, sticky, fast-drying substance that
generally has greater compressive strength and
less vapor permeability than most stone and
brick traditionally used in building construction.
Also, modern masonry cement doesn’t always
contain hydrated lime, the ingredient that
gives historic mortars their permeability and
elasticity. For these reasons, pre-mixed mortar
cement straight from the bag should never
John Milner Associates • October 2009 • Chapter 8 • Historic Buildings • 274