Selecting
an Appropriate Level of Treatment
The treatments that follow this section in chart format are divided into levels based on the degree of moisture problems. Level I covers preservation
maintenance; Level II focuses on repair using historically compatible materials
and essentially mitigating damaging moisture conditions; and Level III
discusses replacement and alteration of materials that permit continued
use in a chronically moist environment. It is important to begin with Level
I and work through to a manageable treatment as part of the control of
moisture problems. Buildings in serious decay will require treatments in
Level II, and difficult or unusual site conditions may require more aggressive
treatments in Level III. Caution should always be exercised when selecting
a treatment. The treatments listed are a guide and not intended to be recommendations
for specific projects as the key is always proper diagnosis.
Start with the repair of any obvious deficiencies using sound preservation
maintenance. If moisture cannot be managed by maintenance alone, it is
important to reduce it by mitigating problems before deteriorated
historic materials are replaced. Treatments should not remove materials
that can be preserved; should not involve extensive excavation unless there
is a documented need; and should not include coating buildings with waterproof
sealers that can exacerbate an existing problem. Some alteration
to historic materials, structural systems, mechanical systems, windows,
or finishes may be needed when excessive site moisture cannot be controlled
by drainage systems, or in areas prone to floods. These changes, however,
should, be sensitive to preserving those materials, features, and finishes
that convey the historic character of the building and site.
Level I Preservation
Maintenance
Exterior: Apply cyclical maintenance procedures to eliminate rain
and moisture infiltration.
 Installing ventilating fans can improve damp conditions or reduce cooling loads. Photo: NPS files. |
Roofing/guttering: Make weather-tight and operational; inspect
and clean gutters as necessary depending on number of nearby trees, but
at least twice a year; inspect roofing at least once a year, preferably
spring; replace missing or damaged roofing shingles, slates, or tiles;
repair flashing; repair or replace cracked downspouts.
Walls: Repair damaged surface materials; repoint masonry
with appropriately formulated mortar; prime and repaint wooden, metal,
or masonry elements or surfaces; remove efflorescence from masonry with
non-metallic bristle brushes.
Window and door openings: Eliminate cracks or open joints;
caulk or repoint around openings or steps; repair or reset weatherstripping;
check flashing; repaint, as necessary.
Ground: Apply regular maintenance procedures to eliminate standing
water and vegetative threats to building/site.
Grade: Eliminate low spots around building foundations; clean
out existing downspout boots twice a year or add extension to leaders to
carry moisture away from foundation; do a hose test to verify that surface
drains are functioning; reduce moisture used to clean steps and walks;
eliminate the use of chlorides to melt ice which can increase freeze/thaw
spalling of masonry; check operation of irrigation systems, hose bib leaks,
and clearance of air conditioning condensate drain outlets.
"Controlling Unwanted Moisture" an Historic Preservation Brief
