Introduction
A cautionary approach to paint removal is included in the guidelines to the Secretary of the Interior Standards for Rehabilitation.
Removing paints down to bare wood surfaces using harsh methods
can permanently damage those surfaces; therefore such methods
are not recommended. Also, total removal obliterates evidence
of the historical paints and their sequence and architectural
context.
This Brief expands on that advice for the architect, building
manager, contractor, or homeowner by identifying and describing
common types of paint surface conditions and failures, then recommending
appropriate treatments for preparing exterior wood surfaces for
repainting to assure the best adhesion and greatest durability
of the new paint.
Although the Brief focuses on responsible methods
of "paint removal," several paint surface conditions
will be described which do not require any paint removal, and
still others which can be successfully handled by limited paint
removal. In all cases, the information is intended to address
the concerns related to exterior wood. It will also be generally
assumed that, because houses built before 1950 involve one or
more layers of lead-based paint, the majority of conditions warranting
paint removal will mean dealing with this toxic substance along
with the dangers of the paint removal tools and chemical strippers
themselves.
 The paint on this exterior decorative feature is sound. Photo: NPS files. |
Paint applied to exterior wood must withstand yearly extremes
of both temperature and humidity. While never expected to be more
than a temporary physical shield--requiring reapplication every
58 years--its importance should not be minimized. Because one
of the main causes of wood deterioration is moisture penetration,
a primary purpose for painting wood is to exclude such moisture,
thereby slowing deterioration not only of a building's exterior
siding and decorative features but, ultimately, its underlying
structural members. Another important purpose for painting wood
is, of course, to define and accent architectural features and
to improve appearance.
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
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).
 When the protective and decorative paint finish was removed and an inappropriate clear finish applied, the exterior character of the building was altered. Photo: NPS files. |
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.
"Exterior Paint Problems" an Historic Preservation Brief
