A weather-tight roof is basic in the preservation of a structure,
regardless of its age, size, or design. In the system that allows
a building to work as a shelter, the roof sheds the rain, shades
from the sun, and buffers the weather.
During some periods in the history of architecture, the roof imparts
much of the architectural character. It defines the style and
contributes to the building's aesthetics. The hipped roofs of
Georgian architecture, the turrets of Queen Anne, the Mansard
roofs, and the graceful slopes of the Shingle Style and Bungalow
designs are examples of the use of roofing as a major design feature.
But no matter how decorative the patterning or how compelling
the form, the roof is a highly vulnerable element of a shelter
that will inevitably fail. A poor roof will permit the accelerated
deterioration of historic building materials-- masonry, wood,
plaster, paint--and will cause general disintegration of the basic
structure. Furthermore, there is an urgency involved in repairing
a leaky roof since such repair costs will quickly become prohibitive.
Although such action is desirable as soon as a failure is discovered,
temporary patching methods should be carefully chosen to prevent
inadvertent damage to sound or historic roofing materials and
related features. Before any repair work is performed, the historic
value of the materials used on the roof should be understood.
Then a complete internal and external inspection of the roof should
be planned to determine all the causes of failure and to identify
the alternatives for repair or replacement of the roofing.
Clay Tile: European settlers used clay tile for roofing as early
as the mid-17th century; many pantiles (S-curved tiles), as well
as flat roofing tiles, were used in Jamestown, Virginia. In some
cities such as New York and Boston, clay was popularly used as
a precaution against such fires as those that engulfed London in
1666 and scorched Boston in 1679.
 Repairs on this pantile roof were made with new tiles held in place with metal hangers. Photo: NPS files. |
Tiles roofs found in the mid-18th century Moravian settlements
in Pennsylvania closely resembled those found in Germany. Typically,
the tiles were 1415" long, 67" wide with a curved butt.
A lug on the back allowed the tiles to hang on the lathing without
nails or pegs. The tile surface was usually scored with finger
marks to promote drainage. In the Southwest, the tile roofs of
the Spanish missionaries (mission tiles) were first manufactured
(ca. 1780) at the Mission San Antonio de Padua in California.
These semicircular tiles were made by molding clay over sections
of logs, and they were generally 22" long and tapered in
width.
The plain or flat rectangular tiles most commonly used from the
17th through the beginning of the 19th century measured about
10" by 6" by 1/2," and had two holes at one end for
a nail or peg fastener. Sometimes mortar was applied between the
courses to secure the tiles in a heavy wind.
In the mid-19th century, tile roofs were often replaced by sheet-metal
roofs, which were lighter and easier to install and maintain.
However, by the turn of the century, the Romanesque Revival and
Mission style buildings created a new demand and popularity for
this picturesque roofing material.
"Roofing" an Historic Preservation Brief
