decorative effect. Patch historic plaster walls or, if
necessary, replace with new plaster over metal lath (but retain
old wood lath). Do not replace with wallboard, except for small
(See Figure 4-29;)
The patch is stepped
so that each new coat
of plaster laps over
Repair of Old Plaster.
Patch and retain old plaster rather than replacing with
modern wallboard. Keep the old wood lath in place when
possible and install metal lath between old lath and plaster.
Preservation Briefs 21, National Park Service)
4.17 NEW AND SUBSTITUTE MATERIALS. There are only two good
reasons to replace historic building elements or materials that
have been lost or damaged beyond repair: to match visually what
was there before and to prevent further damage to the feature or
the building. The best (and often the cheapest) way to do this
is to replace or repair with materials that are exactly like the
originals. Most of the time, closely matching materials are
available, although it may require research to locate them.