Mitigation Assessment Team Report
Hurricane Katrina in the Gulf Coast
Building Performance Observations, Recommendations, and Technical Guidance
FEMA 549 / July 2006 

Appendix J. Historic Buildings Pre- and Post-Disaster Mitigation

J.1 Pre-Event Mitigation

Throughout the region, old buildings can be further weakened from storms, which 
can have a long-term toll beyond the immediate wreckage. The use of pre-hazard 
mitigation techniques can benefit building owners and the community in various 
ways and to varying degrees.

Natural hazards such as hurricanes do not have to result in a natural disaster. 
There are proven design and construction techniques that can reduce or eliminate 
the threat of damage to buildings from these natural hazards and these 
techniques should be applied to all historic properties. However, some of the 
most vulnerable historic buildings are those that stand empty, waiting for 
restoration. Mothballing, which means to stabilize and temporarily protect a 
building from further deterioration, when undertaken before the next hurricane 
or other natural disaster strikes, can significantly reduce the likelihood of 
damage.

J.1.1 Mothballing

Mothballing is simply undertaking efforts to stabilize a historic structure to 
prevent further deterioration, although it can apply to any vacant structure 
deemed worth saving. During a major storm event like Hurricane Katrina, the 
deterioration and/or destruction of vacant and neglected buildings can be 
intensified.

J.1.1.1 Mothballing (Background)

Standing empty, a building is subject to progressive deterioration such as roof 
leaks; malfunctioning roof drainage such as internal drains or gutters and 
downspouts becoming non-functional; windows deteriorating to the point where 
many do not keep the elements out; trees growing along the foundation lines; and 
surface runoff flowing into basement windows. The first step in a program of 
historic preservation and adaptive reuse, meaning to change the functional use 
of a building from its original intent, is to arrest this deterioration, make 
the building sound, and mothball it until plans for its future use can be 
determined. Each vacant property of historic or potential historic value needs a 
mothballing plan. 

J.1.1.2 Mothballing Plan (Application)

The first step toward mothballing is to obtain a listing and evaluation of 
historical or potentially historical buildings that the State Historic 
Preservation Office (SHPO) is considering for mothballing.

In mothballing a building, keeping it sound and dry, and arresting progressive 
deterioration while an adaptive reuse and historic preservation plan is being 
developed is imperative. The following steps should form a part of any pre-event 
mitigation plan. 

To mitigate water intrusion issues: 

- Roofs: Inspect and perform temporary repairs as needed. If the roof has 
deteriorated to the point where re-roofing is necessary, either install a 
permanent roof if funding permits, or install a temporary roof. Perform followup 
yearly inspections.

- Gutters, downspouts, and drains: Gutters and roof drains should be cleared of 
debris. Repair sections of gutter that are missing or damaged. Repair missing 
and damaged downspouts and reconnect to the storm drainage system, if 
available. 

- Flashing and trim: Missing or damaged flashing should be repaired or replaced.

- Doors and windows: Exterior openings such as doors, windows, and louvers must 
also be minimally restored. Missing shutters should be replaced and all shutters 
closed and secured. Wood windows and other wood components suffering from rot, 
damage, or missing glass panes should be replaced. Glazing compound that has 
deteriorated to the point where the weather is no longer being excluded at the 
perimeters of the glass panes should be repaired. Operating hardware such as 
handles, locks, and latches should be replaced if missing or nonfunctional. 
Sealants between the window perimeters and the surrounding surfaces that have 
deteriorated to the point where the weather is no longer being excluded should 
be replaced. Missing doors, including hardware, should be replaced to keep wind 
and rain out. As a less expensive alternative, windows could be boarded (either 
all windows or only missing windows) until implementation of an adaptive reuse.

- Wood siding and trim: Wood siding and trim needs to be reattached where loose 
to prevent further loss from wind. Wood should be painted to protect it from the 
elements.

- Wood flooring: It could be worthwhile to remove the occasional floorboard to 
allow for expansion to occur from swelling, without causing permanent damage to 
the boards if there is a potential for flooding.

- Masonry walls: Secure masonry veneers into the faade if they are in danger of 
falling out; concentrate on those whose deterioration allows water or vermin 
entry, or where pieces are in danger of falling and causing injury. Execute a 
regimen of selective tuck pointing of deteriorated mortar at selected areas of 
the building faade.

- Additions and alterations: Building elements that have been installed 
relatively recently and are not historically significant but are, however, 
structurally sound and mostly weather-tight, should remain, with some nominal 
repairs for the purpose of mothballing. Upon execution of an adaptive reuse or 
restoration, the disposition of these elements can be determined.

- Hazardous material: It should be noted that some historic buildings may 
contain asbestos or lead-based paints; proper handling of these hazardous 
materials will need to be observed during both demolition and restoration.
J.1.1.3 Site Corrections and Miscellaneous Issues

- In places where ground slope against the building faade is either flat or 
toward the building, increase the grade immediately adjacent to the faade to 
achieve positive drainage away from the building. In some areas, existing 
masonry and concrete window wells around basement windows will need to be built 
up to retain the extra height of the earth.

- On tree-covered sites, remove all insignificant trees within 20 feet of a 
structure to minimize potential damage from wind-fallen trees. In addition, tree 
growth close to foundations can weaken the structure because the root growth 
along the foundation line can undermine the footings.

- Clear site drainage systems of sediment and debris in inlets and pipes.

J.1.2 Priorities and Permutations

Recommendations described previously should be given priority. When taken 
together, they comprise a comprehensive mothballing plan for arresting ongoing 
deterioration. It is understood, however, that all of the funds needed to 
implement this comprehensive plan are not necessarily available. With this in 
mind, it is necessary to consider a plan whereby those items of greatest need 
are given highest priority and implemented first, with other items of lesser 
need implemented second, third, fourth, etc. The schedule of items implemented 
would have to match the flow of available funds, in a phased approach. High 
priority should be given to items that will correct progressive deterioration 
that is most advanced and is occurring at the greatest speed, or will affect 
components of historic significance, with highest priority given to those items 
with the highest cost-effectiveness. Lower priority should be given to items 
that will correct less advanced or slower progressive deterioration, assuming 
that these can wait some finite time period until funds become available.

J.1.2.1 Objectives

The objectives of a Condition Assessment and Mothballing Report are to visually 
assess the general condition of the facility and its building systems, assess 
the nature and cause of progressive deterioration, and develop a mothballing 
plan for making the building sound and watertight for the near future, while a 
plan of adaptive reuse is developed.

J.1.2.2 Scope

To accomplish these objectives, the Scope of Work should include the following 
tasks:

1 Review available documentation, such as drawings, previous reports, histories, 
Web sites, and/or reports of building code violations.
2. Interview site management or maintenance personnel knowledgeable of the 
physical characteristics, maintenance, and repair of the property.
3. Conduct a walk-through survey of the property to obtain information on 
material systems and components in order to provide a brief description, 
identifying observable physical deficiencies, and to obtain information needed 
to develop the mothballing plan.
4. Prepare Opinions of Probable Costs to remedy observed physical deficiencies, 
and implement the mothballing plan.
5. Prepare the report, documenting the findings and results of the preceding 
tasks.

J.2 Post-Event Mitigation

The primary damage to historic buildings in a flood disaster is from immersion 
of building materials in floodwaters, the moving force of which can cause 
structural collapse. Storm and sanitary sewer backup during flooding is a major 
cause of damage to buildings. In addition, floods may also cause a fire due to 
ruptured utility lines; growth of mold and mildew; and swelling, warping, and 
disintegration of materials due to prolonged presence of moisture. 
Following a wind event such as a hurricane, inspect and make repairs as needed 
to prevent water entry and to mitigate potential life-safety problems.

J.2.1 First Steps

The most important single step is to air out wet buildings, open doors and 
windows, remove airtight coverings such as aluminum and vinyl siding, and run 
fans. In refurbishing flooded buildings, it is vital to reinstate the drainage 
systems to remove water from the structure and foundations. This includes ground 
drainage, surface drainage, and basements, with the use of sumps, if necessary.

J.2.2 Identification of Problem Areas

It is also important to identify areas in the structure where water and moisture 
are trapped, so that appropriate measures can be taken to allow drying and 
prevent decay to vulnerable materials, as well as minimize mold growth. Most 
historic buildings are inherently durable and are relatively resistant to 
flooding due to the use of materials such as cypress framing and lime or cement 
plaster. 

- Wood paneling: Immediately after the waters recede, any water trapped behind 
the paneling must be allowed to drain out. This can be done by drilling holes in 
the bottom of the panels. If there has been extensive saturation of paneling, it 
may be necessary to dismantle and dry the panels to avoid distortion.

- Wood floors: As wood becomes wet, it swells. When wood floors are saturated, 
they expand and buckle. After a flood, if the immersion has not been too 
prolonged, it may not be too late to prevent such damage. If the flooring does 
buckle, it will have to be taken up carefully and stacked, allowing each board 
to dry to its pre-flooded moisture content. If the boards have not buckled, but 
have cupped excessively, they will have to be replaced, although minor cupping 
may be acceptable. If the floor is not of great historic value, resand it to 
level the surface.

- Drainage: Backup and overflow of foul water and sewage systems are not an 
uncommon consequence of flooding.

J.2.3 Accelerated Drying

There are a number of measures that are commonly used after flooding. These 
measures improve drying and reduce the time required before refurbishment and 
reoccupancy can occur. These measures are laid out in order of priority.

1. Drain water clear of the structure and, if required, prevent further water 
penetration by the use of temporary roof and ground drainage systems. 
2. Remove all damp materials and debris from the structure, including all damp 
carpets, furnishings, and collapsed building materials. 
3. Demolish or remove all parts of the structure not to be retained or 
refurbished. Remove any damp plaster or drywall to expose the structure. 
4. Provide through-ventilation to all parts of the structure, including all 
structural cavities such as sub-floor voids and wall cavities. Prop doors and 
windows and partially open millwork to allow air circulation.
5. Identify all trapped moisture in the structure. Where possible, remove all 
impermeable finishes from trapped moisture areas.
6. Use heaters, dehumidifiers, fans, and other devices to facilitate drying. If 
heating and mechanical systems are online, running them will assist in 
expediting drying time.

J.2.4 Relocation of Historic Buildings 

Although consideration for relocation should be given to historical buildings 
that are located in an area prone to flooding from hurricanes, all properties 
that have sustained significant damage from a hurricane should be evaluated for 
possible relocation as part of the restoration process. Relocating a building to 
higher ground will reduce the risk of further damage from future hurricanes. 
Hotel Magnolia (see Figure J-1) underwent relocation after being badly damaged 
in 1969 from Hurricane Camille. As a result, the hotel experienced only minimal 
flooding. 

Figure J-1 caption. Built by John Holm in 1847, the Magnolia Hotel, badly 
damaged from Hurricane Camille in 1969, was moved 100 yards north and restored 
by the City of Biloxi in 1972. While the main structure remains intact, the wood 
railing and one wood stair to the second floor porch were damaged; the other 
wood stair was completely destroyed (Biloxi, Mississippi). [end of caption]

J.2.5 Elevating Historic Buildings

If for whatever reason a historic building is non-movable, consideration should 
be given to raising the building to a higher elevation, preferably above the 
flood level. Working with state and local preservation offices, successful 
designs can be achieved to preserve the aesthetic as well as the historical 
value of the property. An alternative consideration if the building cant be 
raised aesthetically is to raise the ground below the structure, effectively 
raising the building to a higher elevation.

J.2.6 Alternate Protection of Historic Buildings

An alternate to relocation or raising a historic structure is the construction 
of barriers such as floodwalls or berms or a combination of both. Floodwalls can 
be constructed around historic districts, protecting several buildings at one 
time.

J.2.7 Data Base of Historic Buildings

Equally important to both pre-event and post-event mitigation is having a 
reliable inventory of all historical properties as well as other resources of 
the area, including maps of historic buildings sites. It is also important to 
have names and contact information of contact persons responsible for making 
decisions relative to historic buildings. A reliable inventory can help in quick 
response as well as collaboration between regional and state agencies concerned 
with historical preservation, helping to mitigate the damage to flooded 
historic buildings.

Many programs are written to outline mitigation procedures. However, it is 
imperative that these programs offer solutions to help communities decide what 
to do and how to implement the solutions so as not to further damage historic 
properties.