In a restoration project, research of documents and physical
investigation of the building usually will establish the roof's
history. Documentary research should include"
- any original plans or building specifications,
- early insurance surveys,
- newspaper descriptions, or
- the personal papers and files of people who owned or were
involved in the history of the building
- old photographs of the building might provide evidence of
Along with a thorough understanding of any written history of
the building, a physical investigation of the roofing and
its structure may reveal information about the roof's construction
history. Starting with an overall impression of the structure,
are there any changes in the roof slope, its configuration, or
roofing materials? Perhaps there are obvious patches or changes
in patterning of exterior brickwork where a gable roof was changed
to a gambrel, or where a whole upper story was added. Perhaps
there are obvious stylistic changes in the roof line, dormers,
or ornamentation. These observations could help one understand
any important alteration, and could help establish the direction
of further investigation.
Because most roofs are physically out of the range of careful
scrutiny, the "principle of least effort" has probably
limited the extent and quality of previous patching or replacing,
and usually considerable evidence of an earlier roof surface remains.
Sometimes the older roof will be found as an underlayment
of the current exposed roof. Original roofing may still be intact
in awkward places under later features on a roof.
Often if there is any unfinished attic space, remnants of
roofing may have been dropped and left when the roof was being
built or repaired. If the configuration of the roof has been changed,
some of the original material might still be in place under the
existing roof. Sometimes whole sections of the roof and roof
framing will have been left intact under the higher roof.
The profile and/or flashing of the earlier roof may be apparent
on the interior of the walls at the level of the alteration. If
the sheathing or lathing appears to have survived changes in the
roofing surface, they may contain evidence of the roofing systems.
These may appear either as dirt marks, which provide "shadows"
of a roofing material, or as nails broken or driven down into
the wood,.rather than pulled out during previous alterations or
repairs. Wooden headers in the roof framing may indicate that
earlier chimneys or skylights have been removed. Any metal ornamentation
that might have existed may be indicated by anchors or unusual
markings along the ridge or at other edges of the roof. This primary
evidence is essential for a full understanding of the roof's history.
Caution should be taken in dating early "fabric" on
the evidence of a single item, as recycling of materials is not
a mid-20th-century innovation. Carpenters have been reusing materials,
sheathing, and framing members in the interest of economy for
centuries. Therefore, any analysis of the materials found, such
as nails or sawmarks on the wood, requires an accurate
knowledge of the history of local building practices before any
final conclusion can be accurately reached. It is helpful to establish
a sequence of construction history for the roof and roofing materials;
any historic fabric or pertinent evidence in the roof should be
photographed, measured, and recorded for future reference.
During the repair work, useful evidence might unexpectedly appear.
It is essential that records be kept of any type of work
on a historic building, before, during, and after the project.
Photographs are generally the easiest and fastest method, and
should include overall views and details at the gutters, flashing,
dormers, chimneys, valleys, ridges, and eaves. All photographs
should be immediately labeled to insure accurate identification
at a later date. Any patterning or design on the roofing deserves
particular attention. For example, slate roofs are often decorative
and have subtle changes in size, color, and texture, such as a
gradually decreasing coursing length from the eave to the peak.
If not carefully noted before a project begins, there may be problems
in replacing the surface.