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 o Roll Roofinq.
Do not use asphalt or roll roofing on historic
buildings except on flat roofs that are not visible
from ground level. Membrane roofing is acceptable as
a replacement on flat concealed roofs.
If roll roofing was added over the historic material
in an earlier rehabilitation, consider going back to
the historic material when reroofing.
4.8.2 Water Drainage. To keep excessive moisture out of the
building, maintain and repair flashing, gutters, and downspouts.
If the building does not have adequate flashing or gutter
systems, add them. Install them in a way that will preserve the
original appearance of the building.
4.9 EXTERIOR WALL SYSTEMS.
4.9.1 Masonry. In historic construction, stucco was usually
applied directly on top of masonry walls without an intervening
layer of lath. This makes the masonry more vulnerable to
moisture infiltration through rising damp or water running down
the wall. When repairing, consider adding expanded metal lath
between the masonry and stucco layer. Respect decorative aspects
of stone work. Do not remove or smooth over water tables, string
courses, or other projecting elements. In repairing brick walls,
be mindful of the original brick pattern and type of brick used.
Match replacement bricks to the original in size, color, and
texture. Repointed mortar joints should match the size, color,
and tooling of the original as closely as possible. In repairing
stone walls, match replacement stones to the original in size,
color, and type of stone. Be aware that stone that looks
identical to the original may have different weathering patterns.
4.9.2 Wood Frame. Most frame construction since the mid-19th
century has been balloon framing, except for large wooden
industrial buildings. Earlier historic framing was widely spaced
post-and-beam construction. Post-and-beam construction continued
much later in industrial buildings.
There are special problems of frame walls in historic
buildings, including rot and deterioration, lack of insulation,
structural failure, and deformation. Sills and other horizontal
surfaces where water can stand are a particular deterioration
problem.
o
Clapboards and Shingles. Repair board by board.
Do not
re-side the entire wall unless necessary.
o Stucco Over Wood or Metal Lath. Early 19th century stucco
was often placed directly over wood or solid brick walls
to improve waterproofing. 20th century stucco was
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