After the Flood: Emergency
Stabilization and Conservation Measures
Preservation Assistance Division,
U.S. National Park Service
After the flood waters begin to recede, the focus of relief
efforts becomes returning things to normal. During this phase, many
historic structures and properties are needlessly lost and damaged
through hasty clean-up procedures. The best way to help a historic
district, property, or structure prevent additional damage and
maintain its integrity and character during these times of duress is
with the use of proper caution and concern.
While the water is receding, plan the future steps to
rehabilitation and restoration carefully. Each decision made today
affects future decisions which will need to be made tomorrow. The
following areas of concern should be addressed during planning.
Personal Safety: The First Priority
- Return to the area only after it has been declared safe by local
emergency management officials. Follow all emergency rules, laws
- Identify potential hazards and solicit expert advice and
assistance to minimize the dangers. Report and stay clear from
loose power lines or damaged utilities.
- Turn off all utilities associated with the historic property to
prevent further damage and minimize future hazards.
Documentation: Developing a Condition Assessment Report
- Prepare a visual record showing the scope of the disaster and
the damage to the historic fabric. This is best done through
annotated photographs, and narrated videotape taken before the
cleanup actually begins.
- Create an inventory of found items, dislodged architectural
features, decorative fragments, furnishings, collections, etc. DO
NOT THROW AWAY MATERIALS AT WILL. Many items may prove their value
as the surrounding restoration or rehabilitation projects proceed.
- Use the gathered information to have a team of preservation
professionals develop a prioritized plan of stabilization, repair,
Structural Stabilization: Temporary Measures
- Identify potential deficiencies and provide temporary shoring to
protect life, property, and belongings while the water levels are
receding. Successful shoring can be accomplished without increasing
the damage to the historic features or materials. All shoring
measures should be planned with the assistance of qualified
structural engineers or contractors.
- Support unstable or leaning structures or features with
temporary bracing and reinforcement.
- Strengthen exposed foundations or brace areas of undermining by
following engineers recommendations.
- Brace and strengthen decayed or damaged floor and ceiling
structure. Check bearing locations for movement or settlement.
- Clean and repair the structure's roof and roof drainage system
in order to protect the building from future storm damage.
- Provide temporary protective roof coverings where the existing
roof has been damaged.
- Clean, repair and reconnect gutters and downspouts.
- Drain contained water slowly and carefully from the interior of
the structure to prevent undue stress which may cause structural
failure. Make sure the decreasing water level remains equal to the
exterior and adjacent conditions.
Drying Out: Natural Ventilation and Time
- Carefully remove trapped mud and collected water/storm debris as
water recedes. Do not unnecessarily damage covered historic
finishes or materials.
- Remove standing water and water-logged furnishings and debris
that maintain a source of moisture within the structure.
- Drain the water from the basements and crawl spaces. Standing
water will migrate and perpetuate the moisture problems on the upper
- Furnishing should be moved to allow air movement and ventilation
- Remove and dry water soaked rugs, boxes, and materials.
Paperwork and books may require special care and considerations.
- Remove water soaked insulation from the attic and if easily
accessible without damaging historic fabric and materials, remove
insulation from cavity wall construction.
- Check and drain trapped water from mechanical chases, equipment,
and HVAC ductwork.
- Remove residual moisture in a gradual and controlled process
through natural ventilation. Do not use mechanical dehumidification
which may cause additional damage.
- Open windows and doors. Provide protection and security
measures as required through the use of screens and vents.
- Provide moderate ventilation through the use of fans. Heating
may be provided when conditions warrant, but do not hurry the
process. Natural drying is preferred.
- Allow plaster to dry gradually, avoiding cracking and separation
Forced drying through the use of dehumidifiers and heaters may
draw excessive moisture through the plaster leading to excessive
expansion, cracking, and powdering of the finished surface.
Carefully remove all flood soaked Gypsum Wall Board. It is a
porous material which degrades under extreme moisture trapping
fungus and bacteria that pose health hazards.
- Remove trapped water from cavity wall construction and interior
partitions by carefully removing the baseboard and drilling a drain
hole through the plaster and lath near the bottom of each wall
cavity. Do not damage architecturally significant or character
- Remove non-historic artificial wall covering and panelling which
may trap moisture within the wall. Consult a preservation
specialist on the treatment of historic wall finishes.
- Allow wood to air dry gradually. Promote even drying through
proper ventilation. In most cases, swelling and warping of the
solid wood, flooring and framing, will be minimal and decrease as
the wood drys. Laminate wood surfaces may experience separation and
warping caused by the uneven drying of the layers.
Forced drying through the use of dehumidifiers and heaters will
cause uneven drying, resulting in the cupping, warping, and checking
of the wood.
Monitor the wood. If wood elements remain damp after the other
moisture problems have subsided, fungus and/or rot and decay may
- Remove sheet vinyl, linoleum, or VCT tile to allow for maximum
evaporation. Protect and store historic floor finishes that have
- Protect the wood floors from undue traffic and abuse, until they
are dry. Wood becomes soft and easily damaged when it is wet.
Housekeeping Maintenance: Initial Cleaning and Repair
- Rinse remaining mud, dirt and flood debris from all surfaces
with freshwater. Do not use high pressure water on historic
materials. Use extreme care and caution around decorative features
and damaged elements.
- TURN OFF ALL ELECTRICITY BEFORE CLEANING WITH WATER.
- Open electrical outlets, mechanical chases, etc. and rinse these
areas thoroughly. Check wiring and connections for damage and repair
as required. Let areas dry before closing them.
- Check for loose plaster; and either resecure it in place or
carefully record and remove it by hand. Decorative elements which
are loose may be carefully recorded, removed, labeled and saved for
- Supporting loose plaster: Plaster may be temporarily supported
through the use of plywood and wooden T braces. Use padding and
care to protect all decorative elements from additional damage when
using this method.
- Securing loose plaster: Secure loose plaster and lath to the
original framing by using screws and plaster washers. Protect
decorative elements from damage by carefully selecting the
- Decorative wood elements may become loose or detached during
flooding. Check for loose, damaged or deteriorating wood. Either
resecure loose elements in place or carefully record and remove it
by hand, labeling and saving the element for reinstallation.
- Securing loose wood: secure loose wooden elements to the orginal
framing by using or reinstalling original fastenings. Protect
decorative elements from additional damage by carefully reusing the
- Use standard non-sudsing household cleaning products as
directed by manufacturers instructions to remove remaining dirt, and
stains. Special care and caution should be used when working on or
around historic materials. After cleaning, use a disinfectant to
kill the germs, bacteria and smell left by flood waters.
- Do not use cleaning solutions that will trap or impede moisture
movement within the historic materials.
After the Flood; Water Damage and Your Historic
Building (Video). Historical Preservation Information
Services, University of South Dakota, 1994. Produced by Video
Reflections of Souix Falls, SD.
Bucher, Ward. "Drying-In and Drying-Out: Flood-damage lessons
from Hurricane Hugo," Old House Journal, March/April
1991, p. 40-43.
Federal Emergency Management Agency. Flood Emergency and
Residential Repair Handbook. Flood Insurance
Administration 13, March 1986.
Federal Emergency Management and the American Red Cross.
Repairing Your Flooded Home. Washington, DC. 1992. FEMA
document #234. This publication is being distributed through FEMA
and American Red Cross emergency efforts. Single copies may be
obtained by calling FEMA Publications Department, Wash. DC. (202)
646-3484. FEMA Region 9 - CA region, phone: (415) 923-7100 or (415)
923-7120; FEMA Bldg. 105, Presidio of San Francisco, San Francisco,
Flood Recovery Booklet. Iowa Cooperative
Preservation Consortium. Iowa City: State Historical Society of
Iowa, 1993. This booklet reprints a variety of preservation
guidance fact sheets including excerpts from Repairing Your Flooded
Home by the American Red Cross and technical tips on protecting
paper documents and art work from the National Instititure for the
Conservation of Cultural Property (NIC) and the American Institute
for Conservation of Artistic Works (AIC). Tel. for Iowa Historical
Society, (319) 335-3916.
James, Sarah. Safeguarding Your Historic Site: Basic
Preparedness and Recovery Measures for Natural Disasters.
Federal Emergency Management Agency, Region 1. 1993. Developed with
the assistance of the National Trust, NPS North Atlantic Region, and
SHPOs from Maine, Vermont, and New Hampshire, this publication is
currently being printed in a limited first edition, due to a
shortage of funds. Additional copies may be purchased, printed and
distributed. For further information contact Sarah James (617)
Treatment of Flood-Damaged Older and Historic
Buildings. Information Booklet No. 82, 1993. Washington, DC:
National Trust for Historic Preservation, 1993. Excellent 16 page
bulletin discusses damage and treatment with a practical checklist
and lists of organizations that can help.
Nelson, Carl L. Protecting the Past from Natural
Disasters. Washington, DC.: National Trust for Historic
This information was produced and compiled by the
Preservation Assistance Division, National Park Service, Washington,
DC. (202) 343-9578
rev. January 17, 1995