Identify, Retain and Preserve
Identifying, retaining, and preserving architectural
metal features such as columns, capitals, window hoods,
or stairways that are important in defining the overall
historic character of the building; and their finishes
and colors. Identification is also critical to differentiate
between metals prior to work. Each metal has unique
properties and thus requires different treatments.
During the overall rehabilitation of the New Market Theater in Portland, Oregon, the original cast iron features on the west facade were retained and preserved. Photo: George
McMath.
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Removing or radically changing architectural metal features
which are important in defining the overall historic
character of the building so that, as a result, the
character is diminished.
Removing a major portion of the historic architectural
metal from a facade instead of repairing or replacing
only the deteriorated metal, then reconstructing the
facade with new material in order to create a uniform,
or "improved" appearance.
Radically changing the type of finish or its historic
color or accent scheme
Protect and Maintain
Protecting and maintaining architectural metals from
corrosion by providing proper drainage so that water
does not stand on flat, horizontal surfaces or accumulate
in curved, decorative features.
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This cast iron decorative feature is in need
of cleaning and repainting, but its overall form and details are in good condition. Photo: Courtesy: New
York Landmarks Conservancy.
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Cleaning architectural metals, when appropriate,
to remove corrosion prior to repainting or applying
other appropriate protective coatings.
Identifying the particular type of metal prior to
any cleaning procedure and then testing to assure that
the gentlest cleaning method possible is selected or
determining that cleaning is inappropriate for the particular
metal.
Cleaning soft metals such as lead, tin, copper,
terneplate, and zinc with appropriate chemical methods
because their finishes can be easily abraded by blasting
methods.
Using the gentlest cleaning methods for cast iron,
wrought iron, and steel--hard metals--in order to remove
paint buildup and corrosion. If handscraping and wire
brushing have proven ineffective, low pressure grit
blasting may be used as long as it does not abrade or
damage the surface.
Applying appropriate paint or other coating systems
after cleaning in order to decrease the corrosion rate
of metals or alloys.
Repainting with colors that are appropriate to the
historic building or district.Applying an appropriate
protective coating such as lacquer to an architectural
metal feature such as a bronze door which is subject
to heavy pedestrian use.
Evaluating the overall condition of the architectural
metals to determine whether more than protection and
maintenance are required, that is, if repairs to features
will be necessary.
Failing to identify, evaluate, and treat the causes
of corrosion, such as moisture from leaking roofs or
gutters.
Placing incompatible metals together without providing
a reliable separation material. Such incompatibility
can result in galvanic corrosion of the less noble metal,
e.g., copper will corrode cast iron, steel, tin, and
aluminum
Exposing metals which were intended to be protected
from the environment.
Applying paint or other coatings to metals such as
copper, bronze, or stainless steel that were meant to
be exposed.
Using cleaning methods which alter or damage the historic
color, texture, and finish of the metal; or cleaning
when it is inappropriate for the metal.
Removing the patina of historic metal. The patina may
be a protective coating on some metals, such as bronze
or copper, as well as a significant historic finish.
Cleaning soft metals such as lead, tin, copper, terneplate,
and zinc with grit blasting which will abrade the surface
of the metal.
Failing to employ gentler methods prior to abrasively
cleaning cast iron, wrought iron or steel; or using
high pressure grit blasting.
Failing to re-apply protective coating systems to metals
or alloys that require them after cleaning so that accelerated
corrosion occurs.
Using new colors that are inappropriate to the historic
building or district.
Failing to assess pedestrian use or new access patterns
so that architectural metal features are subject to
damage by use or inappropriate maintenance such as salting
adjacent sidewalks.
Failing to undertake adequate measures to assure the
protection of architectural metal features.
Repair
Repairing architectural metal features by patching,
splicing, or otherwise reinforcing the metal following
recognized preservation methods. Repairs may also include
the limited replacement in kind--or with a compatible
substitute material--of those extensively deteriorated
or missing parts of features when there are surviving
prototypes such as porch balusters, column capitals
or bases; or porch cresting.
Replacing an entire architectural metal feature such
as a column or a balustrade when repair of the metal
and limited replacement of deteriorated or missing parts
are appropriate.
Using a substitute material for the replacement part
that does not convey the visual appearance of the surviving
parts of the architectural metal feature or that is
physically or chemically incompatible.
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In an effort to repair the stair railing, concrete
was poured around the wood spacer inside the railing
ceiling. Water penetrated the railing and reacted
with the concrete to accelerate the corrosion
of the iron. Photo: John G. Waite.
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Replace
Replacing in kind an entire architectural metal feature
that is too deteriorated to repair--if the overall form
and detailing are still evident--using the physical
evidence as a model to reproduce the feature. Examples
could include cast iron porch steps or steel sash windows.
If using the same kind of material is not technically
or economically feasible, then a compatible substitute
material may be considered.
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Fiberglass columns and aluminum capitals
were installed to replicate the ornamental
features on the east facade of the New Market
Theater in Portland, Oregon. Photo: William
J. Hawkins, III.
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Removing an architectural metal feature that is unrepairable
and not replacing it; or replacing it with a new architectural
metal feature that does not convey the same visual appearance.
The following work
is highlighted to indicate that it represents
the particularly complex technical or design aspects
of Rehabilitation projects and should only be
considered after the preservation concerns listed
above have been addressed.
Design for the Replacement of Missing Historic
Features
Designing and installing a new architectural metal
feature such as a metal cornice or cast iron capital
when the historic feature is completely missing.
It may be an accurate restoration using historical,
pictorial, and physical documentation; or be a
new design that is compatible with the size, scale,
material, and color of the historic building.
Creating a false historical appearance because
the replaced architectural metal feature is based
on insufficient historical, pictorial, and physical
documentation.
Introducing a new architectural metal feature
that is incompatible in size, scale, material,
and color.
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