o Reflect building changes from major historic periods or
o Are examples of exceptional craftsmanship or design.
4.10.1 Window Surveys. Maintenance decisions should start
with a window survey that records the condition of every window
in the building. A window schedule listing all the parts of each
unit, with space for notes on existing conditions and repair
instructions, is helpful here. Start at the top of the
historic-building maintenance treatment sequence, and do not take
the next step unless it is necessary. Do simple maintenance
first; repair as needed; replace damaged or missing parts in-
kind; replace the entire unit in-kind only if it cannot be
repaired. Do not give up too soon on the idea of repairing
wooden or metal window sashes.
If a window must be replaced, make sure that the replacement
matches the original exactly. (See Figures 4-18 and 4-19.)
Custom-built or stock replacement windows suitable for most 19th
and 20th century buildings are readily available commercially
from specialty window companies. Good millwork shops can
duplicate parts, such as muntins or bottom rails, which can be
placed in the old sash. Consult the SHPO for help in finding
replacement sources in your area. When selecting replacements,
pay special attention to:
Pattern of openings and their sizes;
Proportions of the frame and sash;
Configuration of the window panes and muntin profiles;
Type of wood;
Characteristics of the glass; and
Associated details such as hardware, arched tops, hoods.
or other decorative elements.
Although reproduction handmade glass is commercially
available, existing old glass that shows manufacturing
irregularities such as bull's eyes, bubbles, and glass "streaks,"
or discoloration caused by age, should be protected during the
repair process and reused if practicable. Decorative colored or
stained glass and beveled glass is especially important for
Replace only as much of the historic material as is
necessary. If the lower sash is decayed and the upper sash is
sound, replace only the lower sash. If the sill is rotten, but
the head and jambs are sound, replace only the sill.