Carnton SH cover - MTSU Center for Historic Preservation

FLOOD DAMAGE ASSESSMENT
for the
CARNTON PLANTATION SPRINGHOUSE
Franklin, Tennessee
May 2010
FLOOD DAMAGE ASSESSMENT
for the
CARNTON PLANTATION SPRINGHOUSE
Prepared for
Jennifer Esler, CEO, Battle of Franklin Trust
by
Michael Thomas Gavin, Preservation Specialist
A Professional Services Project of the
Tennessee Civil War National Heritage Area
May 2010
The Tennessee Civil War National Heritage Area (TCWNHA) is a statewide program
dedicated to the interpretation and preservation of Tennessee’s Civil War and
Reconstruction legacies. Partially funded by the National Park Service, the TCWNHA
is one of several projects administered by the Center for Historic Preservation at
Middle Tennessee State University.
Background: This visit was made on May 6, 2010, by Dr. C. Van West and Michael T.
Gavin of the Heritage Area at the request of Jennifer Esler, CEO, Battle of Franklin
Trust. East of the main house at Carnton and down a steep grassy slope sits a twostory springhouse. The brick structure was built atop a bubbling clear water spring to
preserve the water source from impurities and to stockpile perishable foodstuffs in
troughs and on shelves inside.
This springhouse, or dairy, served as a larder where the plantation’s milk, eggs, and
butter were kept so they stayed cool and sweet. Brick buildings were high in thermal
mass and retained the cool temperature emitted by the 55 degree water for long periods
of time, making them ideal for storing dairy products.
The rectangular c.1840s structure, constructed with hand-made brick molded and fired
nearby, was placed over the source of a strong spring and rests on a low roughly hewn
limestone foundation.
The springhouse has a gable-front cantilevered roof facing west, and is covered with
split wooden shingles. Horizontal lapped wooden siding closes in the gable ends.
The items to be kept cool were placed upon flat rocks, troughs, or shelves in the lower
level. This room was accessible by a low wooden door on the south side. For some
reason, the bricks in the south wall were laid in Flemish bond.
Barred wooden frames were set into the bases of the other three walls (which are laid in
American common bond) to provide ventilation. Brick jack arches support the walls
above the vents. A short set of steps led up to a small porch at the front (west) of the
building.
A four-panel wooden door provides access to the upper room, and 2” by 12” wooden
joists support the tongue-and-groove boards of the second floor.
Description
On the first weekend in May 2010, record rainfall caused widespread flash flooding in
the greater Nashville area. The water came up quickly and inundated many places that
had never before been under water. One of these locations was the site of the Carnton
springhouse, where the water level rose higher than its walls and eventually lifted the
roof right off of the building. Although the high water receded and set the roof back
down on the structure almost exactly where it had been originally, considerable damage
to the historic springhouse has occurred as a result of the storm.
As the water continued to rise, powerful currents swirled around the building. The
lateral loads created by the water’s action (push-pull effect) were more than the old
brick walls could withstand. The ebb and flow of the flood waters washed away the top
fifteen courses of the east wall and caused severe damage to the lower part of the east
side of the north wall.
The hydraulic pressure created a large V-shaped fissure in the wall which now
threatens the structural integrity of the northeast corner. The wall has begun to bulge at
the affected area and the situation needs to be addressed as soon as possible before
this corner collapses.
In addition, the high water saturated the historic mortar, weakening it and even
dissolving small portions at different places in the walls.
The traditional mortar mixture of sand, clay, and lime, while water-resistant, was never
intended to be used below water for extended periods. Nineteenth-century masons
knew that hydraulic mortars must be used for underwater applications, but they
obviously did not envision a situation occurring at the Carnton springhouse where the
use was required.
The roof of the structure appears to be sound, although the east gable framing and
siding is missing. The front steps and porch, made of modern materials, lie nearby after
being separated from the structure by the action of the flood waters.
After the Water Recedes
No other "element" is as destructive to buildings as water. After a building has been
saturated and once the floodwaters recede, it is important that the drying process begin
immediately. Most of the damaging effects of water, such as rot, rust, and spalling, can
be minimized by reducing both interior and exterior moisture levels. This problem is
compounded by the nature of the springhouse, i.e., its primary function naturally
contributes to a high moisture level within the building. However, it is essential not to
attempt to dry old buildings out too quickly by the application of heat. The result can be
catastrophic: timber elements, including floors, doors and siding, may warp, twist or
split; salts will migrate through old stone and brickwork, causing them to blister, powder
and exfoliate; and many painted surfaces will peel and flake. The remedial work can be
much more damaging than the flood itself. The best general advice is to dry the
building down gently and slowly, first through natural ventilation, and, if necessary, with
the aid of dehumidifiers and very low background heat. It is also useful to monitor the
relative humidity within the property to ensure that moderate levels are maintained.
Slow and gentle drying can take several months, but it is better than destroying
irreplaceable historic fabric by acting in haste. The enclosed portions of the building,
particularly the wall cavities, may retain water for long periods of time which can cause
problems during subsequent restoration.
Once the floodwaters recede, any remaining mud, dirt, and flood debris should be
rinsed from all surfaces with fresh water as soon as possible. It is safer and easier to
remove the mud while it is still wet. Do not wait until the material is dry. Beware of
concealed hazards such as nails or broken glass hidden in silt or pooled water. Step
carefully because floodwaters deposit a coating of mud, which can be very slippery
underfoot. Make sure that all electricity is turned off before cleaning with water.
Resist the temptation to start cleaning up right away. It is much better to assess the
damage and make a coherent plan of action first. Avoid using high pressure water on
historic materials and exercise extreme care when washing decorative features and
damaged or loosened elements. Silt and mud will accumulate not only on the floor, but
in wall cavities as well. To clean any remaining dirt and stains, use a standard nonsudsing household cleaning product as directed by the manufacturer. Special care
should be used when working on or around historic materials. After cleaning, use a
disinfectant to kill the germs, bacteria, and odor left by floodwaters. Keep in mind that
floodwaters and the remaining silt are contaminated by sewage and chemicals. Protect
your eyes, mouth, and hands, and wear a mask and rubber gloves when cleaning out
debris left by floodwaters. Use disinfectants to wash your hands before eating.
Salvaging Damaged Items
Do not throw away materials (e.g. loose decorative elements, furnishings, etc.)
indiscriminately, but salvage and retain as much as possible – even items thought to
be badly damaged. Cleaning and steady drying out, together with conservation or
repair may save them. If not, they may be used as models for new replica fixtures and
fittings or found as a match in salvage yards. Floodwaters can carry even heavy items
a long way which you may find on your property, and these may well be vital to the
restoration works of an upstream neighbor. Loose items that are missing from your
property may turn up farther downstream.
Foundation Erosion
Water currents can erode soil beneath foundation walls. Although this situation is
not common, when it does occur the building's foundation will be destabilized and
repairs will be necessary. The best evidence of structural destabilization is the
appearance of cracks in the foundation walls and in the brick courses above the
foundation. However, not all cracks that appear after a flood are indications of longterm instability. Some may result from temporary expansion of clay soil around the
foundation. When the soil returns to its natural water content, the cracks should shrink
or, at the very least, not expand further. Cracks from actual foundation erosion,
however, can be expected to worsen over time as the building settles slowly to its new
soil support. The best indicator of this type of structural problem is cracks that move.
Movement, particularly widening of cracks, is a sign of structural instability warranting
careful examination by a qualified structural engineer or architect.
Loss of Mortar
The foundations of most older and historic buildings are masonry. Stone and brick
foundation walls with soft lime mortar are very durable, although the lime mortar does
not hold up well to water erosion. After the building dries out, the mortar of the masonry
walls should be carefully inspected to ensure that it has not leeched from the joints and
made the walls unstable. If a significant amount of mortar has been lost, it can usually
be replaced without dismantling the wall. In many cases, a "loose" mortar can be
poured into the joints to fill the voids. Make sure that replacement mortar is not too hard
for the surrounding stone. If the foundation wall is constructed of limestone or other
relatively hard stone, a standard tuck-pointing mortar may be used (ASTM "Type N,"
which contains one part hydrated lime to one part white Portland cement and six parts
sand).
In walls constructed of brick masonry, there will likely be less leeching of mortar than if
the walls were constructed of stone. Nevertheless, these walls should be inspected for
missing mortar and re-pointed with a soft lime mortar mixture that contains at least two
parts hydrated lime to each part of white Portland cement and nine parts sand (known
as ASTM "Type 0" mortar), unless there is reason to suspect a more serious structural
problem created by the flooding. In many situations, impermeable, heavily-cementitious
mortar will exacerbate deterioration in flood situations by holding the moisture in the
masonry for longer and by causing salts to crystallize within the historic material. If this
should become a problem, the wholesale removal and replacement of hardened
Portland cement with weaker, porous, lime-based mortar will help the walls to dry out.
Summary
The damage to Carnton’s historic springhouse is not overwhelming and can be
reversed. An experienced restoration company would be able to stabilize the building,
repair the brick walls, reinstall the second floor, align the roof properly, and return the
structure to usability. Churches, schoolhouses, stores, banks, homes, courthouses, and
barns in river and coastal communities often bear watermarks on the walls where
owners pencil in the dates and levels of significant floods -- the 1937 Flood, the 1973
Flood, the Johnstown Flood. Yet many of these buildings have stood the test of time
and survived inundation. While floodwaters can cause significant damage to historic
buildings, they do not spell the end. With proper cleaning and drying out procedures,
followed by expert historic restoration, the only reminder of floodwaters in historic
structures should be a watermark and date on the wall.
Enclosed with this report is a guide entitled Before and After Disasters: Federal
Funding for Cultural Institutions, written and produced by Heritage Preservation in
partnership with the Federal Emergency Management Agency (FEMA) and the National
Endowment for the Arts (NEA) as a service to the American cultural community.
The Preservation Briefs series, published by the National Park Service, provide useful
technical information in dealing with the effects of floodwater damage to old or
historic buildings. Copies are available from:
Superintendent of Documents,
Government Printing Office,
Washington, D.C. 20402-9325.
Or download directly from:
http://www.nps.gov/history/hps/tps/briefs/presbhom.htm
Several titles are particularly relevant:
#1 The Cleaning and Waterproof Coating of Masonry Buildings
#2 Repointing Mortar Joints in Historic Brick Buildings
#6 Dangers of Abrasive Cleaning to Historic Buildings
Michael Thomas Gavin
Preservation Specialist
Tennessee Civil War National Heritage Area