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|beyond maintenance/painting: repair and replacement
Treating Paint Problems in Historic Buildings
Justification for Paint
Exterior paint is constantly deteriorating through the processes
of weathering, but in a program of regular maintenance
assuming all other building systems are functioning properly
surfaces can be cleaned, lightly scraped, and hand sanded
in preparation for a new finish coat. Unfortunately, these are
ideal conditions. More often, complex maintenance problems are
inherited by owners of historic buildings, including areas of
paint that have failed (4) beyond the point of mere cleaning,
scraping, and hand sanding (although much so-called "paint
failure" is attributable to interior or exterior moisture
problems or surface preparation and application
mistakes with previous coats).
Although paint problems are by no means unique to historic buildings,
treating multiple layers of hardened, brittle paint on complex,
ornamental and possibly fragile exterior wood surfaces
necessarily requires an extremely cautious approach. In the case
of recent construction, this level of concern is not needed because
the wood is generally less detailed and, in addition, retention
of the sequence of paint layers as a partial record of the building's
history is not an issue.
When historic buildings are involved, however, a special set
of problems arises varying in complexity depending upon
their age, architectural style, historical importance, and physical
soundness of the wood which must be carefully evaluated
so that decisions can be made that are sensitive to the longevity
of the resource.
At the outset of this Brief, it must be emphasized that
removing paint from historic buildings with the exception
of cleaning, light scraping, and hand sanding as part of routine
maintenance should be avoided unless absolutely essential.
Once conditions warranting removal have been identified the general
approach should be to remove paint to the next sound layer using
the gentlest means possible, then to repaint (see figure 2).
Practically speaking as well, paint can adhere just as effectively
to existing paint as to bare wood, providing the previous coats
of paint are also adhering uniformly and tightly to the wood and
the surface is properly prepared for repainting cleaned
of dirt and chalk and dulled by sanding. But, if painted exterior
wood surfaces display continuous patterns of deep cracks or if
they are extensively blistering and peeling so that bare wood
is visible, then the old paint should be completely removed before
repainting. The only other justification for removing all previous
layers of paint is if doors, shutters, or windows have literally
been "painted shut," or if new wood is being
pieced-in adjacent to old painted wood and a smooth transition
is desired (see figure 3).
(4) For purposes of the Brief, this includes any area
of painted exterior woodwork displaying signs of peeling, cracking,
or alligatoring to bare wood. See descriptions of these and other
paint surface conditions as well as recommended treatments.