In recent years, many older andhistoric buildings have beenaffected by the heavy rains and

flooding that occurred during hur-ricanes and tropical storms. Thepurpose of this booklet is to helpbuilding owners minimize struc-tural and cosmetic flood damage.It contains general advice writtento cover a wide variety of buildingswith varying degrees of flood dam-age. If you suspect that your build-ing may have some structuraldamage, contact a qualified struc-tural engineer or architect to thor-oughly assess the situation andsuggest remedies. Your state his-toric preservation office (SHPO)can provide you with a list ofarchitects who are experienced inthe treatment of historic buildings.

A description of the tax creditprograms for rehabilitation ofhistoric structures, free technicalpublications available throughyour state historic preservationoffice and the Federal EmergencyManagement Agency (FEMA),telephone numbers you can callfor more assistance, and addi-tional resources are provided atthe end of the booklet.

Once you are able to return toyour building, the first tasks willlikely be to remove mud anddebris and to inspect the buildingfor damage. Saving your build-ing, no matter how historic, isnot worth losing your life or risk-ing permanent injury. Pleaseobserve these safety precautions:

• Do not walk through flowingwater.

• Do not drive through a floodedarea.

• Stay away from power linesand electrical wires.

• Make sure that all of your elec-tricity is turned off. If any elec-trical wiring was submerged,have it inspected before turn-ing the power back on.

• Look before you step. Floodsdeposit mud which makes mostwalking surfaces very slippery.

• Be alert for gas leaks.

• Carbon monoxide exhaust kills.If you use electrical generatorsor charcoal grills, make surethat they are properly vented.

• Clean everything that got wet.Floodwaters carry sewage andchemicals. Hose down con-crete and masonry walls. Scruball surfaces with disinfectant.Discard any food and medi-cine that came in contact withfloodwater. Wear protectiveclothing and make sure thebuilding is properly ventilatedwhile working inside.

• Remember to follow localhealth guidelines concerningpreventive shots or vaccina-tions.

After the Water RecedesNo other “element” is as destruc-tive to buildings as water. Afteryour building has been saturatedand once the floodwaters recede, itis important that the dryingprocess begin immediately. Most ofthe damaging effects of water, suchas rot, rust, and spalling, can beminimized by reducing both inte-rior and exterior moisture levels.

The least damaging dryingprocess appears to be one thatbegins by using only ventilation.To speed evaporation, interior airmust be vented to the outside. Themost effective way to do this is toopen windows and doors and allowthe moisture to escape. Fans can beused to speed evaporation by mov-ing interior air and exhaustinghumid air to the outdoors.

Treatment of Flood-Damaged Older and Historic Buildings

1785 Massachusetts Avenue, N.W.Washington, DC 20036

202.588.6296

In 2005, floodwaters severely

damaged New Orleans and

other communities along the

Gulf Coast following

Hurricanes Katrina and Rita.

Using heat or dehumidifica-tion too soon can damage yourbuilding. As materials begin todry, small amounts of heat ordehumidification can be intro-duced. In particularly hot andhumid areas, however, such asthe Gulf Coast, experts recom-mend closing up the buildingand using dehumidifiers and airconditioners to complete thedrying once the ventilationceases to help. Use of mechani-cal means requires some caution:

• None of these devices shouldbe used when water makestheir operation dangerous.

• Ventilation remains the pri-mary means of removing inte-rior moisture. All of thesedevices must be used in con-junction with a ventilationplan designed to exhaust mois-ture-laden air.

• Beware of using industrial dry-ing equipment to remove mois-ture at a very fast rate. You arelikely to cause permanent dam-age to wood and plaster.

• If heaters are used without ven-tilation, the relative humidityin the interior may actuallyincrease and further spreadmoisture damage. If heaters arefuel powered, the lack of venti-lation can be very dangerous topersons inside the building.Enclosed portions of yourbuilding, such as wall cavities,may retain water for long peri-ods of time which can pose adanger particularly to woodenelements such as wall studs,floor joists, and columns. Itmay be necessary to open wallsand remove insulation. Latersections of this booklet containspecific recommendations.

Once the floodwaters recede,you will need to rinse remainingmud, dirt, and flood debris from allsurfaces with fresh water as soon aspossible. It is safer and easier toremove the mud while it is stillwet. Do not wait until the mater-ial is dry. Make sure that all elec-tricity is turned off before cleaningwith water. Avoid using high pres-sure water on historic materialsand exercise extreme care whenwashing decorative features anddamaged or loosened elements.

Silt and mud will accumulatenot only on the floor and fur-nishings, but in interior wall cav-ities as well. Be sure to openelectrical outlets and mechanicalchases and rinse these areas thor-

oughly. Check wiring and con-nections for damage and repair asrequired. Let areas dry beforeclosing them. Check heating andair conditioning ducts and cleanout any mud or dirt before turn-ing on the units. Large systemsmay need to be dismantled orcleaned by a professional.

To clean any remaining dirtand stains, use a standard non-sudsing household cleaningproduct as directed by the manu-facturer. Special care should beused when working on or aroundhistoric materials. After cleaning,use a disinfectant to kill thegerms, bacteria, and odor left by floodwaters.

Keep in mind that floodwatersand the remaining silt are conta-minated by sewage and chemi-cals. Protect your eyes, mouth,and hands, and wear a mask andrubber gloves when cleaning outdebris left by floodwaters. Usedisinfectants to wash your handsbefore eating.

Before you begin to clean upyour historic property, it isimportant to carefully documentany damage to the structure.This is essential not only forinsurance purposes, but also torecord important historic build-ing features. If building compo-nents are removed for cleaningor repair purposes, a photographwill help to ensure that they arereinstalled correctly.

Take photographs and makewritten notes describing thedamage. A video recording isalso a very effective way to docu-ment flood damage. Take photosor videos of any discarded items.Because of the intensive cleanupthat takes place following aflood, materials might be cartedaway before an insuranceadjuster is able to assess the loss.

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Bonaparte, Iowa, has

rebounded from a 1993 flood

that deposited water and mud

throughout three blocks of the

town and damaged every

building in the town’s historic

riverfront district.

Create an inventory of founditems, dislodged architectural fea-tures, decorative fragments, andfurnishings. Do not throw awaymaterials at will. Furnishings andarchitectural elements can be car-ried a great distance by floodwaters,and items found on your propertymay be extremely valuable to anearby restoration project.

Hydrostatic Pressure

If your basement is flooded, it islikely that the level of water inyour basement is the same as thegroundwater level outside of yourhouse. When this happens, pump-ing the water from the basementwill do no good. New water willcontinue to seep in until thegroundwater level drops.

Foundation CollapseYou should be aware that pump-ing water from your basementcan be dangerous. This watermay be providing the necessarypressure to balance the hydrosta-tic pressure of the groundwater. Ifthe groundwater level is higherthan your basement floor and youpump the water from your base-ment, the foundation walls couldbe pushed inward and collapse.

If your basement is floodedwith several feet of water and youare reasonably certain that yourfloor drains are operational, youcan assume that the groundwatertable is high. It is advisable toleave the water in place until thegroundwater table sinks and thewater recedes by itself. If yourbasement contains only a fewinches of water, however, youmay be able to pump it out safely.Keep in mind that if the ground-water level is higher than thefloor, the water will return.

Even if you cannot pump thewater out of the basement, youshould still begin to ventilate the

rest of the building. The soonerthese materials dry, the lesschance of water-related problems.Consult with local health officialsto determine if there is any sanitiz-ing agent that can be used to treatstanding water in the basement.

Water can exert tremendouspressure on foundation walls andfloor slabs. If any portion of abuilding lies below the ground-water level, one of two thingswill happen: basement slab heav-ing or loss of mortar.

Basement Slab HeavingIf foundation walls are tightenough to hold back groundwater,it is likely to seep through thefloor slab, causing it to leak orheave. In some instances, veryhigh water pressure may beenough to raise the floor slab.Fortunately, this is not a commonoccurrence in historic buildings.

If your basement slab heaves,you cannot correct the problemimmediately. First wait until thesoil beneath the building driesthoroughly, as part of the prob-lem may be the presence of claysoils that expand when wet.Concrete slabs in newer buildingsare usually poured over a sandbed, which helps them to resistsoil pressures, while older con-crete floors were often pouredright over the existing dirt. If youpour a new slab or surface-coatthe existing slab before the claydries, the new slab or surfacecould crack when the clayshrinks to its normal dimensions.

If the slab is still heaved orcracks remain after the waterrecedes and the soil has dried,there is little you can do except torepair the cracks or, in the case ofsevere heaving, pour a new slab.

Loss of MortarThe basement may leak and fillwith water. This is usually the casewith older buildings and actuallyprotects the foundation walls fromcollapse if the groundwater level istoo high. Unfortunately, as waterpasses through stone and brickfoundation walls, it sometimescarries mortar with it.

The foundations of most olderand historic buildings are masonry.Stone foundation walls with softlime mortar are very durable,although the lime mortar does nothold up well to water erosion.Inspect the mortar of stonemasonry foundation walls toensure that it has not leechedfrom the joints and made the wallunstable. If a significant amount ofmortar has been lost, it can usuallybe replaced without dismantlingthe wall. In many cases, a “loose”mortar can be poured into thejoints to fill the voids.

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Figure 1 Hydrostatic Pressure

If water is pumped from basement when groundwater pressure ishigh, foundation walls may collapse.

Water in basement can help to offset high groundwater pressure.

Groundwater level

Interior water pressureHydrostaticpressure

Hydrostaticpressure

Groundwater level

Hydrostaticpressure

Hydrostaticpressure

Make sure that replacementmortar is not too hard for the sur-rounding stone. If the wall isconstructed of sandstone, thenew mortar should contain atleast two parts hydrated lime toeach part of white Portlandcement and nine parts sand(known as ASTM “Type O”mortar). If the foundation wall isconstructed of limestone or otherrelatively hard stone, a standardtuckpointing mortar may be used(ASTM “Type N” containingone part hydrated lime to onepart white Portland cement andsix parts sand).

If the foundation walls are con-structed of brick masonry or con-crete block, there will likely beless leeching of mortar than if thewalls were constructed of stone.Nevertheless, they should beinspected for missing mortar andrepaired in the same manner asaboveground walls, unless there isreason to suspect a more seriousstructural problem created by theflooding (see “FoundationErosion” below). Generally foun-dations constructed of concreteblock used a harder mortar con-taining gray Portland cement.

Erosion

Foundation ErosionWater currents and water travel-ing in underground “streams”can erode soil beneath founda-tion walls and footings. Althoughthis situation is not common,when it does occur the building’sfoundation will be destabilizedand repairs will be necessary. Thebest evidence of structural desta-bilization is the appearance ofcracks in the foundation wallsand in plaster or drywall abovethe foundations.

Keep in mind, however, thatnot all cracks that appear after aflood are indications of long-term instability. Some may resultfrom temporary expansion ofclay soil around the foundation.When the soil returns to its nat-ural water content, the cracksshould shrink or, at the veryleast, not expand. Other cracksmay result from moisture-relatedexpansion of wood beams andjoists tied to the foundationwalls. These cracks should shrinkas the wood dries.

Cracks from foundation ero-sion, however, can be expected toworsen over time as the buildingsettles slowly to its new soil sup-port. The best indicator of thistype of structural problem is cracksthat move. Movement, particu-larly widening of cracks, is a signof structural instability warrantingcareful examination by a qualifiedstructural engineer or architect.

The best way to determinewhether a crack is moving is topurchase a device called a “tell-tale.” This small gauge is glued toa wall on either side of a crack. Itsmarkings indicate the crack’s hor-izontal and vertical movementover time. This device can beobtained from engineering or sci-entific supply firms or by contact-ing the manufacturer directly.(Avongard Crack Monitor, 1-800-244-7241, www.avongard.com).

Another way to determinewhether movement exists is toglue a glass microscope slideacross the crack. If the slidebreaks, movement is occurring.

Water may erode the soil adja-cent to your building. This canlead to two problems:

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Figure 2 Foundation Erosion

Flooding may have eroded soil adjacentto the foundation wall.

Water pathEroded soil at foundation wall leadsto continuing water damage.

If the footing is not below thefrost line, the foundation couldbe damaged by frost.

Soil should be replaced to prevent future waterand frost damage.

Water path

Fill with soil to provide positivedrainage away from building.

Wet insulation collapses under itsown weight inside the wall.

Wet insulation holds moisture keeping inside of thewall wet and creating conditions for rotting.

Wet insulation packed betweenjoists of sill plate keeps woodsaturated and rusts steel nails.

Cut holes in plaster or wallboard andremove wall insulation. Leave holes open toventilate wall cavities. If possible removebase trim, then reinstall after patching holes.

Remove insulation at sill andallow wood to dry.

The soil may be “dished” nextto the building which may resultin additional damage from futurerain. The soil adjacent to thebuilding should slope away fromit to ensure that future rains donot drain into the building. Afterthe floodwaters subside, checkthe soil drainage pattern and re-grade as necessary.

A less common soil problem isthe loss of enough dirt to protectyour foundation from frost-heav-ing during cold weather. If thefoundation is not sufficientlybelow the frost line, it mayheave upward when the groundbeneath it freezes. For this reason,it is best to replace any lost dirtadjacent to the foundation.

Heaving of Sidewalksand SlabsErosion can also affect paving.From a building conservationperspective, the worst problemoccurs when eroded slabs ofasphalt or concrete channelwater into, rather than awayfrom buildings. As with soil ero-sion, this can lead to water prob-lems from future rains.

If this condition exists, theslab should either be raised (bymudjacking for example) or itshould be removed and replacedwith one that drains properly.

Saturation of Insulation

With few exceptions, any insula-tion that has been immersed inwater should be removed for tworeasons:1)After being saturated, most

insulation is rendered perma-nently ineffective, particularlyloose-fill varieties, such as cel-lulose, vermiculite, rock wool,and blown fiberglass, whichtend to collapse under theirown weight.

2)Saturated insulation holdswater which, if left in place,can perpetuate high moistureconditions destructive to wood,masonry, and steel.

Some types of insulation maybe left in place after water con-tact, such as closed-cell styreneand urethane board insulationsthat do not absorb water. Theseshould be inspected to determine

whether they hold moistureagainst wood or masonry materi-als or steel fasteners. If so, theinsulation should be removeduntil all materials are dry. Anymud or silt that remains in thecavity should be removed regard-less of the insulation’s condition.

Other types of insulation, suchas fiberglass battens, must be eval-uated on a case-by-case basis. Glassfibers, in themselves, are not waterabsorbent, but if they impede theflow of air in a wall cavity, and thusthe drying-out process, it may benecessary to remove them.

Wood Rot

Wood rot occurs when naturalfungi—present in virtually allconstruction lumber—grow inwood. Like other living organ-isms, they need food (wood), air,proper temperatures (betweenabout 60-80 degrees F.), andwater in order to grow. In mostwood construction, the missingelement is water which is whyordinary wood lasts for centurieswhen protected from moisture.

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Figure 3 Treatment for SaturatedWood-framed Walls and Floors

Suggested treatment for ventilating saturated wood-framedwalls and floors.

Water saturation in wood-framed walls and floors

Fortunately for flooded build-ings, the fungi must exist over arelatively long period of time inorder for wood rot to be destruc-tive. Damage from a one-timeevent, such as a flood, is usuallynegligible if the wood is allowedto air dry. Problems occur whensaturated wood is encapsulated sothat the water cannot evaporate.

Two areas where wood is nor-mally encapsulated are wall cav-ities and sill plates, particularlywhen these areas are filled withinsulation. Figure 3 describestreatment of walls and sillplates. To properly ventilatewalls, it will probably be neces-sary to cut or drill holes—takingcare not to damage pipes andwires buried in the walls—andremove the insulation.

Masonry and ConcreteDeterioration

Soluble Salt DamageMasonry and concrete containimpurities, including water-solu-ble salts. When these materialsare saturated, the soluble saltsdissolve and are carried to thesurface during evaporation. Theresult is an unsightly whiteresidue called efflorescence onthe exterior or interior of thebuilding—wherever water evap-orates. These deposits are notusually harmful and frequentlythey dissolve and disappear natu-rally when it rains. Stubbornefflorescence maybe removedwith water, detergent and bristlebrushes, or with chemicals.

Soluble salts can cause signifi-cant damage when the building’sexterior surface has been treatedwith building sealer. If this is thecase, the salts will travel towardthe outside surface, but becometrapped behind the surface bythe sealer. The water vapor even-tually evaporates, but the salts

are left behind to crystallize andexpand, pushing off the surfaceof the brick or stone in a processcalled spalling.

The presence of paint onmasonry or concrete walls mayalso retard the passage of water.Because the paint does not pene-trate the masonry or concrete, itis usually removed by the waterpassing through the wall or by thesalt crystallization that takesplace just under the paint layer.While the paint may be removed,the surfaces of the brick, stone, orconcrete remain intact.

The most obvious way to pre-vent salt damage is to never applysealer to a building. If your buildinghas been sealed, there is little thatcan be done to prevent spalling.

Freezing and Thawing DamageWhen water freezes, it expands.If the water is encapsulatedinside building materials, theexpansion can tear them apart.Thus, if significant amounts ofwater remain in masonry or con-crete by early winter, when theweather goes through rapid peri-ods of freezing and thawing, theresult is similar to the crystalliza-tion of salts: the faces of themasonry or concrete may spall.

Ordinarily, water will evapo-rate even from saturated masonryand concrete at a rapid enoughrate that freeze-thaw damage willnot occur. Some conditionsunder which evaporation may beimpeded and spalling may takeplace are described below.

• Masonry or concrete has beentreated with a building sealer.Although newer building sealersallow the passage of water vapor,they inhibit the flow of liquidwater and can slow the rate ofevaporation. Unfortunately, lit-

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Figure 4. Masonry and Concrete Deterioration

Sealer

32°F

Crystallized salts

Water trapped behind surface

Freeze SpallingFreeze spalling occurswhen liquid waterremains in the wallwhen the outside airtemperature reachesfreezing. Water turnsto ice crystals andexpands and spalls theface of brick or stone.

Soluble SaltsWater trapped inmasonry wallsdissolves soluble salts.As water migrates tothe surface, it carriesthe salts and depositsthem on the face ofthe brick or stone.These deposits, called“efflorescence,” areusually harmless andcan be easily removed.

The outside surface of the buildings are sometimes sealedto prevent water from soaking into the materials.Unfortunately, sealer also prevents liquid water frommigrating outward. Water is trapped behind the surfaceand, as it evaporates, allows soluable salts to re-crystallize.When this happens, the salt crystals expand and spall theface of brick or stone. Sealer also retards the migration ofliquid water and increases the chance that flood-soakedmasonry will be damaged by freeze spalling.

tle can be done to mitigate theeffects of building sealer. Somespalling may occur.

• Masonry or concrete has beenpainted. The vapor pressure ofthe water may cause some ofthe paint to fall off, helping tospeed evaporation. Otherwise,short of paint removal, littlecan be done and some spallingmay occur.

• Masonry or concrete has beencovered with another buildingwood siding or plasterboard. Ifthe covering was installed flushagainst the masonry or concrete,it should be removed temporar-ily to allow the wall to dry out. Ifthe material was installed oversleepers or spacers and an airspace exists, it may not be nec-essary to completely remove thecovering material, but it wouldbe helpful to provide air holes toventilate the wall.

Damage to Metals

Metal FastenersMost metal fasteners are made ofiron or steel which rust andexpand when exposed to water.Fasteners, such as nails, shouldnot be harmed by immersion infloodwaters, as long as they areallowed to dry soon after thewaters subside. Opening wallcavities and removing insulationmay be necessary. If nails are sub-jected to long-term moisture,rust may become severe and thenails may fail.

Rusted or weakened nailsprobably will not cause signifi-cant structural problems in thelower portion of a building—the portion most likely to beimmersed by floodwaters. Inmost cases, such as at the sillplate, the nails hold the wood inposition but are not solelyresponsible for its support.

The exception to this is oftenporch floor joists. Porches are fre-quently fastened to the houseonly with nails which, if they fail,may cause the porch to collapse.If your porch was submerged,make sure it is well ventilated byremoving solid porch skirts andallowing the air to flow freely.

Once the moisture is removed,iron nails pose cosmetic prob-lems by causing rust stains on fin-ished surfaces. This problem canbe corrected by driving the nailsfurther into the wood, caulkingthem, and applying a primerpaint with topcoat.

Damage to Exposed MetalsMost metals will not be perma-nently damaged by immersion inwater. Durable metals such as alu-minum, bronze, copper, and brassshould survive the flooding com-pletely intact. Commercial store-fronts with cast-iron columns andstoops may experience some rust-ing, but the surfaces can besanded clean and repainted.

Stamped iron-based metal,most commonly found in “tin”ceilings and stamped metal cor-nices on commercial storefronts,poses more of a problem. Stampedmetal consists of rust-prone iron,coated with lead and tin (called“terne”) or zinc (called “galva-nized”) to prevent rust. Thesecoatings are usually effective,unless water enters the insides ofthe stampings and is allowed tosit. The standing water penetratesthe protective coating and theiron rusts. Stamped metal cor-nices that have been immersedshould be inspected to make surethey haven’t filled with water. Ifso, find a way to drain the waterand ventilate the back side, eitherby carefully prying a portion awayfrom the building or by drillingsmall weep holes on the bottom.

The holes can later be filled withauto body filler and repainted.

There is no easy remedy forstamped ceilings that have beenimmersed except to dry thebuilding’s interior and to moni-tor the ceilings for possible rust-ing. Drilling holes to drain watermay be ineffective and removingsections of the ceiling wouldlikely result in damage to theceiling panels.

When repairs are necessary,stamped metal should be treatedlike auto body work. If surface rust-ing occurs on stamped metal, therust should be removed by care-fully scraping only the rusted areas,priming with a rust inhibitivepaint, and then painting. Do notsandblast or attempt to chemicallyclean stamped metal or the protec-tive coating will be removed andthe metal will rust quickly.

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Figure 5. Typical Coated Steel Used to Stamp Metal

Terne on zinc

Steel

Damage to Imbedded MetalsThe problems of exposed andimbedded iron are fundamentallydifferent. When exposed ironcorrodes, the problem is mostlycosmetic. When imbedded ironcorrodes, it can damage sur-rounding materials.

When iron rusts, it expandsand this expansion generatestremendous force. Of particularconcern in flooded buildings aremetal lintels—the flat pieces ofsteel used to support masonry orconcrete above door and windowopenings. Metal lintels are usu-ally used on brick buildings and,when they rust, they can liftwhole sections of a wall.

If your building has metal lin-tels and they were immersed inwater, some rusting is likely tooccur, although the rust expan-sion caused by the flooding alonewill not cause a great deal ofimmediate damage. Of greaterconcern is damage to the sur-

rounding materials which mayallow water to enter on anongoing basis and cause moresevere rusting in the future.

After the water recedes andthe building materials dry, checkthe mortar joints near the lintelsto see that the mortar has notcracked or fallen out. If it has,repoint the area immediately tomake sure that water cannotenter to create further rusting.Before repointing, scrape themetal to remove any loose rustscale. It is uncertain whether rustinhibitive primers are effective inretarding rust in these situations.

If other iron-based metals areimbedded in masonry or con-crete, inspect them periodicallyand repair cracks in the sur-rounding materials if they occur.

Damage to Interior Finishes

DrywallDrywall that was submerged willprobably have to be replaced.Drywall consists of a relativelysoft gypsum material held inplace by a paper “sandwich.” Thepaper does not hold up well towater saturation and, in mostcases, wet drywall will simply dis-solve. If it was not wet severely,drywall may be salvageable afterit dries. Even so, FEMA recom-mends replacement as contami-nants may make it a permanenthealth hazard. As with otheraspects of flood cleanup, use yourjudgment about whether toretain or discard affected drywall.

Plaster, on the other hand, is unpredictable when wet.Sometimes it survives with nodamage, other times it must bereplaced. Its durability dependson the plaster mix, the skill usedin application, the degree of satu-ration, whether it is applied towalls or ceilings, and the type of

lath used. Plaster over metal lathis more likely to require replace-ment than plaster over wood lath.

Check for obvious areas whereplaster must be removed, such asceilings with large sags. If yourceiling sags in an area more thanabout three feet in diameter, itmay be difficult to repair thedamage. That portion of the ceil-ing may need to be removed withcare. Falling plaster, especiallywet falling plaster, can be danger-ous. If the water level was abovethe ceiling and you suspect that itmay contain standing water, youmay want to poke drain holes—with a nail attached to the end ofa long stick—in the plaster beforeattempting to remove it. Do notstand directly under the areabeing prodded in case the plasterloosens and falls.

Except for areas of obviousdamage, the best way to determinewhether plaster must be replacedis to let it dry and then inspect it.Here are some suggestions abouthow to determine whether plastershould be replaced:

• The surface condition of plas-ter may not tell you whether itis sound. If the plaster keys(sections of plaster that serveto anchor the plaster to thelath) have fallen off or if thelath has come loose from thebuilding structure, the plastermay need to be replaced.

• You can sometimes tell if plas-ter is sound by tapping lightlyon the wall with a piece ofwood. Unsound plaster willsound hollow.

• If you ventilate wall cavities byopening holes, look for brokenplaster keys. There will alwaysbe a few broken keys, but if thenumber is excessive, the plas-ter is likely in poor condition.

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Figure 6. The Effect ofFloodwater on Metal Lintelsin a Brick Masonry Wall

If lintels rust, makesure that mortar injoints is inspectedand repaired regularly.Otherwise, rustingand joint separationwill worsen.

As lintels rust, they pushmortar joints apart.

Steel lintels

• Plaster damage can be repairedby re-anchoring the plaster tothe wall studs and ceiling joistswith screws and plaster washers.Sound plaster, especially decora-tive plaster, should be retainedin place if it is salvageable.

Damage to Wood Floors and TrimIt is difficult to determinewhether wood trim that has beensubmerged needs to be replaced.Most wood will expand anddeform when wet and then returnmore or less to its original form asit dries. The behavior of an indi-vidual piece of wood depends onits species, grain pattern, methodof anchoring, and whether itsgrain structure was damagedwhen the wood expanded againstother materials.

Tongue and groove hardwoodfloors are unlikely to return totheir original condition. Whenthey expand, their grain struc-tures are usually damaged. If youhave a saturated hardwood floor,let it dry thoroughly. Then, if itremains cupped, you can decidewhether to sand the floor flat orreplace it. When possible, retainoriginal hardwood floors.

Non-interlocking board floors,such as plain pine boards, stand agood chance of returning to theiroriginal shapes when dried. Alight, surface sanding and somere-nailing may be necessary.

Wood trim around baseboards,ceilings, doors, and windows islikely to survive a flood becauseit can usually expand withoutcrushing its fibers. After drying,it should return to its originalform and should be retained.

Wooden doors in older and his-toric buildings are likely to be paneldoors that add to the character ofthe building. Replacement withstandard, hollow-core, flush doorsmay not be appropriate and theoriginal doors should be retained

when possible. Fortunately, paneldoors usually survive flooding sur-prisingly well. If you have paneldoors, let them dry in place. It mayhelp to open them to allow betterair circulation. As they dry, warp-ing should disappear, and their fitand the condition of their gluejoints should be inspected beforedetermining whether they needfurther repair. Be sure that thedoors are completely dry beforeattempting to repair or planethem. Also, if the original glue wasnot waterproof, the joints mayhave to be re-glued.

If you need to replace anydoors, consider replicating origi-nal panel doors. Hollow coredoors will likely need to bereplaced because their internalspacers are usually made of card-board which dissolves in water.

Damage to Interior PaintAfter the flood, most painted inte-rior surfaces that were under waterwill have to be repainted due towater damage or contamination.Do not paint interior surfacesuntil they are completely dry andthe interior humidity has returnedto nearly normal levels. Theexception is that wall surfaces canbe painted with flat latex painteven if some dampness exists.

The paint on some surfaces,such as window trim, may havebeen damaged and will be softenough to scrape off. If so, newpaint will not adhere until theexisting paint is removed and thewood is dry. Because the woodtrim may contain lead-basedpaint, especially in older buildings,observe caution when removing itand dispose of it properly.

WallpaperIn many cases, older and historicwallpaper may be saved after aflood, but the decision to retainor remove it is a difficult one. Onthe one hand, FEMA cautions

that wallpaper paste may be abreeding ground for molds andcontamination and that wall-paper significantly wet by flood-waters may have to be removedand replaced, even if it appearsto be in good condition. On theother hand, if the wallpaper is ofhistorical importance or originalto your house, you may decide toretain it. The decision will bebased on the degree of waterdamage, the cost of replacementor reproduction, and climatecontrols that may limit futuregrowth of mold and bacteria.

If your house is historic and theextent of damage determines thatthe wallpaper must be removed,carefully remove several squarefeet, all the way down to the plas-ter. If possible, take samples fromseveral different locations includ-ing the ceiling. Label which roomthe paper came from and storetemporarily in a dry part of thehouse until the paper can be per-manently preserved.

Floor CoveringsMost older and historic homesretain few of their original floorcoverings and most floor coveringscan be discarded with no effect ona building’s historic character.

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Figure 7. Possible Effect of Saturation on Plaster Walls

Moisture causes woodlath to expand anddeform, causing plasterkeys to break off.

Wood lathFinished plaster surface

Plasterkeys

One exception to this rule istile floors which may be original.Even though tile is a durablematerial, the materials beneathit, such as wooden sub-floors andgrout beds, may have been dam-aged. The only way to determinewhether a tile floor is sound is toinspect it when all of the build-ing materials are dry. This mighttake a long time as the tileimpedes the evaporation process.

If a preliminary inspectionshows that the underlying struc-ture may be damaged, the tilefloor can be removed and re-laidwhen the materials have dried.Or the decision whether toremove or reinstall can be post-poned until the materials havethoroughly dried with the tilefloor in place. The latter methodtakes longer, but minimizes dam-age to the tiles.

The most common residentialfloor covering is wall-to-wall car-peting. Because of the risk of con-tamination, carpeting touched bythe flood waters should be dis-carded, unless it is small enoughto be laundered, such as an arearug, or valuable enough to be pro-fessionally cleaned, such as anOriental rug.

Floor tiles, such as vinyl floor-ing, and sheet flooring are proba-bly not historic and should beremoved to aid the evaporationprocess if the underlying woodenfloor was submerged. On rareoccasions, some sheet flooring,such as linoleum, may be histori-cally significant. If this is the caseand you wish to retain it, let thefloor dry as best it can. Once dry,if the floor is level and the floor-ing adheres, you may leave it inplace. If the bond between thefloor and the covering fails, youmay be able to remove and re-laythe flooring. There is no guaran-tee that either of these techniqueswill succeed. If it is impossible tore-lay the floor, make sure to savesamples of the historic flooring.

Exterior Paint Problems

Paint failure is likely to occur onany painted surface wet directlyby floodwater or on surfacesthrough which excessive amountsof water will evaporate. Paintfailure resulting from the passageof water or water vapor will showup as large sections of paint peel-ing all the way down to theunderlying building material. If

this happens, allow the under-lying materials to dry thoroughlybefore attempting to repaint. Ifyou paint before all the buildingmaterials have dried thoroughly,the water vapor pressure will“bubble” the new paint and ittoo will peel.

If the building materials arevery wet, it may be necessary topostpone painting for a longtime. You may wish to use awater-repellent wood preserva-tive to help to protect the woodfrom water-related damage andthe effects of sunlight until youcan safely paint it.

Summary

Churches, schoolhouses, stores,banks, homes, courthouses, andbarns in river and coastal com-munities often bear watermarkson the walls where owners pencilin the dates and levels of signifi-cant floods—the 1937 Flood,the 1973 Flood, the JohnstownFlood. Yet many of these build-ings have stood the test of timeand survived devastating floods.While floodwaters can cause sig-nificant damage to historicbuildings, they do not spell the

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Many older buildings have

withstood the test of time and

have survived devastating

floods. With proper cleaning

and drying out, they can be

restored for future use.

– Photo by Mary Ruffin Hanbury

end. With proper cleaning anddrying out procedures, the onlyreminder of floodwaters in his-toric structures should be awatermark and date on the wall.

Resources

The Preservation Briefs series,published by the National ParkService, provide useful technicalinformation in dealing with theeffects of floodwater damage toyour old or historic building.Many of these are availableonline. For a listing of topics go towww.cr.nps.gov/hps/tps/tpscat.htm.You can also order copies fromthe Government Printing Officeby calling 1-866-512-1800 or by sending an e-mail toContactCenter@gpo.gov.

The National Park ServiceMuseum Management Programoffers a useful primer on disasterpreparedness, management andresponse. For more informationgo to www.cr.nps.gov/museum/publications/index.htm

The Federal EmergencyManagement Agency (FEMA)also produces several publica-tions that may be helpful to you.These are:• Repairing Your Flooded

Home – FEMA 234

• Flood Emergency andResidential Repair Handbook– FIA 13

• Floodproofing ResidentialStructures – FEMA 102

• Design Manual forRetrofitting Flood-ProneResidential Structures –FEMA 114

Copies of these publicationsmay be available through yourstate or local office of emergencyservices. Or go to www.fema.gov/library/prepandprev.shtm#floods.Printed copies of many of theresources listed in the FEMA

Library are available in theFEMA Publication DistributionCenter. Call 800-480-2520 forordering information.

A new resource from theHeritage Emergency NationalTask Force identifies federalfunding to help plan for emer-gencies, buy disaster supplies, ortrain staff for next year’s hurri-cane season. Before and AfterDisasters:Federal Funding forCultural Institutions providesinformation on 15 federal grantand loan programs to help cul-tural institutions and historicsites prepare for and recover fromdisasters. The 32-page booklet isonline. In addition, up to 50 freecopies can be ordered fromFEMA by calling (800) 480-2520and asking for FEMA publication#533. www.heritagepreservation.org/PDFS/Disaster.pdf

FEMA has ten regional offices.Each region serves several states,and regional staff work directlywith the states to help plan fordisasters, develop mitigation pro-grams, and meet needs whenmajor disasters occur.

The location of FEMARegional Offices and the statesserved are listed below.

FEMA Region I99 High Street, 6th FloorBoston, MA 02110(617) 956-7506(CT, MA, ME, NH, RI, VT)

FEMA Region II26 Federal PlazaNew York, NY 10278(212) 680-3609(NJ, NY, PR, VI)

FEMA Region III615 Chestnut StreetPhiladelphia, PA 19106(215) 931-5608(DC, DE, MD, PA, VA, WV)

FEMA Region IV3003 Chamblee-Tucker Rd.Atlanta, GA 30341(770) 220-5200(AL, FL, GA, KY, MS, NC, SC, TN)

FEMA Region V536 South Clark St.Chicago, IL 60605(312) 408-5500(IL, IN, MI, MN, OH, WI)

FEMA Region VIFederal Regional Center800 N. Loop 288Denton, TX 76209(940) 898-5399(AR, LA, NM, OK, TX)

FEMA Region VII9221 Ward Parkway, Suite 300Kansas City, MO 64114(816) 283-7061(IA, KS, MO, NE)

FEMA Region VIIIBuilding 710, Box 25267Denver, CO 80225-0267(303) 235-4800(CO, MT, ND, SD, UT, WY)

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Figure 8. Moisture-relatedPaint Failure

Illustrated here are theeffects of saturatedinsulation in a wood-framed wall. Liquid waterand water vapor passingoutward through the woodpush the paint off thebuilding, all the way downto the bare siding. A similartype of paint failure willoccur if flood soaked wallsare painted before theyhave dried completely.

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Aflood-damaged home needs special care to remove moldsafely and effectively. Mold begins to grow on materials that

stay wet longer than two or three days. The longer it grows, thegreater the health hazard and the harder it is to control. So, assoon as it is safe to return, don’t delay cleanup and dry out.

Take photographs for insurance purposes before cleaning up.Do not wait for the claims adjuster to see the site before remov-ing wet and moldy materials. Most homeowners’ insurance poli-cies do not cover mold damages or clean up costs, but floodinsurance may cover it.

Mold and HealthSome people are much more sensitive to mold than others, butlong-term or heavy exposure is unhealthy for anyone. Mold cantrigger allergic reactions and asthma attacks, may lower resistanceto illness, or have other effects. Young children, the elderly, andpeople in poor health are most vulnerable. Some molds can maketoxins that exist in live or dead spores and fragments. “Blackmold” is a misleading term; many molds are black.

Mold testing is not usually needed and is rarely useful to answerhealth concerns. Some insurance companies and legal servicesmay require sampling for evidence. Professional mold remedia-tion contractors may test before and after cleanup to check thecleanup’s effectiveness.

If you hire a contractor, seek a licensed mold remediation con-tractor with special training and equipment. Get in writing thecost, methods, and steps to be used. Compare their procedureswith the following guidelines.

Do-it-yourself Mold Clean Up StepsTo clean up safely and effectively, follow these steps and refer toEPA’s A Brief Guide To Mold, Moisture, and Your Home or MoldRemediation In Schools and Commercial Buildings available onlineat www.epa.gov/mold or the CDC’s Mold Prevention Strategies andPossible Health Effects in the Aftermath of Hurricanes Katrina andRita available online at www.bt.cdc.gov/disasters/mold/report/.

1. Wear Protective Gear During Cleanup People are mainly exposed to mold by breathing spores and skincontact. Wear gloves, goggles, and a respirator rated N-95 orhigher. Some respirators have valves to make it easier to breathe.

2. Isolate Work Area and Ventilate to OutdoorsDisturbing mold colonies during cleanup can cause a huge releaseof spores into the air, so seal off the moldy areas from the rest ofthe house. Open windows, and don’t run the central air system

during cleanup. Tape plastic over air grilles, and drape plastic inthe stairwell if the second story is dry and clean. If power is on,put a fan in a window to blow out and exhaust mold-filled air tothe outdoors.

3. Remove Moldy Porous Materials Porous moldy or sewage-contaminated materials should beremoved, put in plastic bags if possible, and thrown away. Toreduce the release and spread of mold spores, it is helpful to covermoldy material with plastic sheeting before removing it.

• Remove all flooded carpeting, upholstery, fabrics, and mat-tresses right away. It’s best to discard them, but if you hope tosalvage a valuable item, have it cleaned, disinfected, and driedquickly outside the home. Never reuse flooded padding.

• Remove all wet fibrous insulation—even if wallboard appearsto be dry. Wet insulation will stay wet far too long, leading tothe growth of hidden unhealthy mold and decay fungi insidethe walls. Cut wall covering above the level that was wet;water can wick up above the flood level.

• It’s best to remove all moldly porous materials, especially if thereis heavy or long-term mold growth—including gypsum wall-board, processed wood products, ceiling tiles, and paper products.

• Plaster, wood paneling, and non-paper faced gypsum boardwalls that are dry, in good condition, and have no insulation inthe wall can be cleaned and sanitized to salvage them. There isa risk of mold on the back side, however, which can releasespores into the home through air leaks in the walls.

• Remove vinyl wallpaper, flooring, and other coverings of wetmaterials.

4. Clean and Disinfect Surface mold can be effectively cleaned from non-porous materi-als such as hard plastic, concrete, glass, and metal. Solid woodcan also be cleaned. Cleaning should remove, not just kill, themold, because dead spores can still cause health problems.

After cleaning, you may use a disinfectant to kill any moldmissed by the cleaning. If there was sewage contamination, disin-fection is a must. If you disinfect, follow label directions and warn-ings, handle carefully, and never mix bleach with ammonia oracids. Many disinfectants kill molds, but do not prevent regrowth.

Mold Removal Guidelines for your Flooded Home

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• Remove any sediment. Hose out opened wall cavities.

• Wash dirty or moldy materials with non-phosphate all-purposecleaners. Rough surfaces may need to be scrubbed. Rinse surfaces,but avoid pressure spray which can force water into materials.

• Disinfect wall cavities and other materials after cleaning. Soilcan make some disinfectants less effective. On colorfast, non-metal surfaces, you can disinfect with a solution of 1/2 to 1 cuphousehold chlorine bleach per gallon of water. Do not use inthe air conditioning system. Milder, less corrosive disinfectantsinclude alcohols, phenolics, and hydrogen peroxide.

5. Consider Borate TreatmentHaving a professional pest control applicator apply a borate treat-ment to wood framing can provide resistance to termites, decay,and mold. Other fungicides may also help inhibit mold regrowthduring drying. Do not apply sealants to wood.

6. Flush the Air After cleaning and disinfecting, air out the building. Use fans inwindows to pull mold spores to the outdoors.

7. Speed DryDry all wet materials as quickly as possible. Close windows andturn on air conditioner or heat, run fans, and use a dehumidifier,if possible. If there is no power, keep windows open.

8. Remain on Mold AlertContinue looking for signs of moisture or new mold growth. Newmold can form in as little as two to three days if materials staywet. Wood and other materials that may look dry can still be wetenough to support regrowth. If mold returns, repeat cleaning and,if possible, use speed drying equipment and moisture meters.Regrowth may signal that the material was not dry enough orshould be removed.

9. Do Not Restore until all Materials Have Dried CompletelyWood moisture content should be less than 20 percent. Do notuse vinyl wallpaper, oil-based paint, or other interior finishes thatblock drying to the inside.

Mold can spread quickly in buildings that have experienced flooding.

It is important to begin the drying out process as soon as possible to

prevent further damage.– Photo by Mary Ruffin Hanbury

FEMA Region IX1111 Broadway, Suite 1200Oakland, CA 94607(510) 627-7100(AZ, CA, GUAM, HI, NV,CNMI, RMI, FSM, AmericanSamoa)

FEMA Region X130 228th Street, SWBothell, WA 98021(425) 487-4600(AK, ID, OR, WA)

Assistance of various types isavailable from your state historicpreservation office. Assistanceincludes survey and assessment ofdamage of historic resources. Inaddition the SHPO administersthe historic rehabilitation taxcredit program for owners ofincome producing properties cer-tified by the SHPO as historicrehabilitation projects. These taxcredits may help to offset the costsof carrying out flood damagerepair. Other specific flood-relatedassistance may be available in yourstates. To find the SHPO in yourstate call (202) 624-5465 or go towww.ncshpo.org

The National Endowment forthe Arts’ Museum Program isconcerned primarily with works ofart and with institutions that carefor and exhibit works of art. Fundsfrom several categories within theMuseum Program can be appliedtoward disaster planning. Formore information call (202) 682-5400 or go to www.arts.gov.

The American Institute forthe Conservation of Historicand Artistic Works (AIC) hasestablished a website for sharingand disseminating informationon the recovery of cultural mate-rials. AIC’s Disaster RecoveryPage has key links to resourcesuseful for the recovery of collec-tions affected by the hurricane.For more information go toaic.stanford.edu.

The Small Business Adminis-tration (SBA) can provide bothdirect and bank participationdisaster loans to qualified home-owners and businesses to repairor replace damaged or destroyedprivate property when the SBAadministrator declares a “disasterloan area” under SBA’s statutoryauthority. For more informationgo to www.sba.gov/disaster_recov/index.html or call (800) 659-2955.

The National Center forPreservation Technology andTraining (NCPTT) uses tech-nology to serve the future ofAmerica’s heritage throughapplied research and professionaltraining. The Center’s websitelists useful publications andassessment tools for disasterrecovery efforts. For more infor-mation go to www.ncptt.nps.gov.

About the Authors

This publication is adapted fromthe State Historical Society ofWisconsin’s Treatment of Flood-Damaged Older and HistoricProperties, prepared by Jim Sewell,senior preservation architect.Richard Wagner of David H.Gleason Associates drafted theillustrations based on Mr. Sewell'soriginal drawings. The section onmold removal was developed byClaudette Hanks Reichel, Ed.D.,professor and extension housingspecialist at LSU AGCenter,Louisiana State University.

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As the Floodwaters Recede—A Checklist of Things To Do

The following checklist will help you respond to flood damagein historic and older buildings. Read the steps through care-

fully and take time to plan. While it is tempting to wade right inwith a shovel and mop, it is very important to develop a plan forcleanup and rehabilitation. Unfortunately, overly zealous cleanupefforts can result in historic materials being carted away, exces-sively rough cleaning methods, and the unnecessary loss of his-toric fabric. The best way to prevent additional damage to historicstructures and materials during a time of duress is to use cautionand plan ahead.

l Follow all emergency rules, laws, and regulations

l Turn off all utilities

l Document building damage

l Wear protective clothing

l Stabilize any unstable structures with temporary bracing

l Use caution when pumping basement water

l Keep building properly ventilated

l Clean everything that got wet with a disinfectant

l Allow saturated materials to dry using natural ventilation

l Check for foundation damage

l Replace soil around foundation

l Save historic materials if possible

l Use caution when removing lead-based paint or any productscontaining asbestos

l Clean and repair roof and roof drainage systems to protectbuilding from future damage