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Moravian College • Preservation Master Plan
biological growth also trap moisture within the
masonry and contribute to deterioration.
Ivy was a historic feature on some of Moravian
College’s buildings and has an appealing visual
impression. Over time, however, ivy and other
clinging vines growing directly on masonry walls
saturate them with moisture; the tendrils work their
way into cracks and mortar joints, which erodes
mortar and causes spalling during freeze-thaw
cycles. Attempts to remove established ivy often
results in damaged masonry surfaces and pitting.
Ivy, therefore, should be cut off at the base, left to
die off completely, and then removed gently by
hand. Subsequently, it is recommended that ivy not
be allowed to become established again. Vegetation
may be grown up masonry walls through the use of
trellises mounted several inches away from the face
of the wall, the proper selection of non-clinging
vines, and careful maintenance to ensure that the
vegetation does not get out of control.
Should ivy be permitted to grow on walls, it should
be periodically removed as noted above to allow
for inspection and repair of masonry walls. On a
yearly basis, ivy on walls should be trimmed back
from windows, door opening, roof eaves, and any
wood features.
Shrubs and trees in close proximity to masonry
walls trap moisture and prevent walls from drying
out properly. Likewise, tree limbs that extend over
roofs deposit debris that clogs or damages gutters
and downspouts.
Structural Stress
Masonry wall cracks are problematic because
they indicate building movement or deterioration
of internal structural members and provide
opportunities for moisture penetration and
further deterioration. Cracking may be caused by
settlement, structural failure, freezing moisture
within the wall, or corroded metal reinforcements.
Cracking along the mortar joints or through
masonry units is an indication that the masonry is
in motion. Bulging, leaning, or disrupted masonry
units indicate an advanced state of deterioration.
If cracks or disrupted masonry are observed in
a masonry wall, a structural engineer should be
consulted to determine the cause and appropriate
remedial treatments. The majority of structural
problems can be prevented through proper
inspection and preventative maintenance. It is
important to identify ongoing deterioration, such
as water infiltration and poor site drainage, before
it leads to structural problems.
Improper Maintenance Treatments
Improper maintenance treatments, such as aggressive
cleaning, use of deicing salts, waterproofing
coatings, inappropriate sealant installation,
and hard pointing and bedding mortars, can
accelerate or directly cause masonry deterioration.
Sandblasting, harsh chemical cleaning, and other
abrasive cleaning methods inevitably damage the
exterior surface of the masonry. This damages the
hard, protective surfaces of brick and limestone
masonry. By roughening the surface of all types
of masonry, such cleaning methods increase the
potential for reactions with acid rain and biological
growth.
Traditional sodium, calcium, and magnesium
chloride based deicing salts can damage entryway
and foundation masonry, as well as doors and door
frames. The salts are then absorbed into the masonry.
As the masonry dries, salts form deep within or on
the surface of the masonry causing internal stresses
and damage. Alternative deicing materials have
proven to be effective while reducing their effects
on the environment. Alternative deicing materials
include sand, cat litter, or chemical deicers, such as
calcium magnesium acetate.
Waterproofing coatings, synthetic stucco, and
exterior insulation should not be installed over
historic masonry because they create interior
condensation that damages the wall’s integrity.
Masonry buildings must be allowed to breathe by
allowing water vapor from the building interior to
migrate through the wall and evaporate outside.
Masonry walls should only be insulated from
interior surfaces using a proper vapor barrier.
The exterior walls of historic buildings should not
be insulated if it means removal of intact historic
interior finishes. Additionally, such barriers
inevitably fail when applied over historic masonry
and allow water into the wall, often trapping it in,
exacerbating all of the problems associated with
water infiltration.
Sealant should only be installed in masonry units
located on wash surfaces, such as coping units,
projecting water table and belt courses, and steps.
Sealant should never be installed on vertical wall
surfaces. Sealant will trap water within the masonry
wall, forcing the water back into the masonry units.
John Milner Associates • October 2009 • Chapter 9 • Building Guidelines • 286