Mothballing Historic Buildings

By The Old House Web
Sharon C. Park, AIA

Table of Contents

Parts of this story:
Documentation ~~ Stabilization~~ Mothballing ~~ Mothballing Checklist ~~ Maintenance Chart~~ Conclusion

When all means of finding a productive use for a historic building havebeen exhausted or when funds are not currently available to put a deterioratingstructure into a useable condition, it may be necessary to close up thebuilding temporarily to protect it from the weather as well as to secureit from vandalism.

This process, known as mothballing, can be a necessaryand effective means of protecting the building while planning the property'sfuture, or raising money for a preservation, rehabilitation or restorationproject. If a vacant property has been declared unsafe by building officials,stabilization and mothballing may be the only way to protect it from demolition.

This story focuses on the steps needed to "de-activate"a property for an extended period of time. The project team will usuallyconsist of an architect, historian, preservation specialist, sometimesa structural engineer, and a contractor. Mothballing should not be donewithout careful planning to ensure that needed physical repairs are madeprior to securing the building. The steps discussed in this Brief can protectbuildings for periods of up to ten years; long-term success will also dependon continued, although somewhat limited, monitoring and maintenance. Forall but the simplest projects, hiring a team of preservation specialistsis recommended to assess the specific needs of the structure and to developan effective mothballing program.

A vacant historic building cannot survive indefinitely in a boarded-upcondition, and so even marginal interim uses where there is regular activityand monitoring, such as a caretaker residence or non-flammable storage,are generally preferable to mothballing. In a few limited cases when thevacant building is in good condition and in a location where it can bewatched and checked regularly, closing and locking the door, setting heatlevels at just above freezing, and securing the windows may provide sufficientprotection for a period of a few years. But if long-term mothballing isthe only remaining option, it must be done properly.This will require stabilization of the exterior, properly designed securityprotection, generally some form of interior ventilation - either throughmechanical or natural air exchange systems - and continued maintenanceand surveillance monitoring.

Comprehensive mothballing programs are generally expensive and may cost10% or more of a modest rehabilitation budget. However, the money spenton well-planned protective measures will seem small when amortized overthe life of the resource. Regardless of the location and condition of theproperty or the funding available, the following 9 steps are involved inproperly mothballing a building:


  • 1. Document the architectural and historical significance of the building.
  • 2. Prepare a condition assessment of the building.
  • Stabilization

  • 3. Structurally stabilize the building, based on a professional conditionassessment.
  • 4. Exterminate or control pests, including termites and rodents.
  • 5. Protect the exterior from moisture penetration.
  • Mothballing

  • 6. Secure the building and its component features to reduce vandalismor break-ins.
  • 7. Provide adequate ventilation to the interior.
  • 8. Secure or modify utilities and mechanical systems.
  • 9. Develop and implement a maintenance and monitoring plan for protection.
  • These steps will be discussed in sequence below. Documentation and stabilizationare critical components of the process and should not be skipped over.Mothballing measures should not result in permanent damage, and so eachtreatment should be weighed in terms of its reversibility and its overallbenefit.

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    Documenting the historical significance and physical condition of theproperty will provide information necessary for setting priorities andallocating funds. The project team should be cautious when first enteringthe structure if it has been vacant or is deteriorated. It may be advisableto shore temporarily areas appearing to be structurally unsound until thecondition of the structure can be fully assessed. If pigeonor bat droppings, friable asbestos or other health hazards are present,precautions must be taken to wear the appropriate safety equipment whenfirst inspecting the building. Consideration should be given to hiringa firm specializing in hazardous waste removal if these highly toxic elementsare found in the building.

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    Documenting andrecording the building

    Documenting a building's history is important becauseevidence of its true age and architectural significance may not be readilyevident. The owner should check with the State Historic Preservation Officeor local preservation commission for assistance in researching the building.If the building has never been researched for listing in the National Registerof Historic Places or other historic registers, then, at a minimum,the following should be determined:

    The overall historical significance of the property and dates of construction;

    The chronology of alterations or additions and their approximate dates;and,

    Types of building materials, construction techniques, and any unusualdetailing or regional variations of craftsmanship.

    Old photographs can be helpful in identifying early or original featuresthat might be hidden under modern materials. On a walk-through, the architect,historian, or preservation specialist should identify the architecturallysignificant elements of the building, both inside and out.

    By understanding the history of the resource, significant elements,even though deteriorated, may be spared the trash pile. For that reasonalone, any materials removed from the building or site as part of the stabilizationeffort should be carefully scrutinized and, if appearing historic, shouldbe photographed, tagged with a number, inventoried, and safely stored,preferably in the building, for later retrieval.

    A site plan and schematic building floor plans can be used to note importantinformation for use when the building is eventually preserved, restored,or rehabilitated. Each room should be given a number and notations addedto the plans regarding the removal of important features to storage orrecording physical treatments undertaken as part of the stabilization orrepair.

    Because a mothballing project may extend over a long period of time,with many different people involved, clear records should be kept and abuilding file established. Copies of all important data, plans, photographs,and lists of consultants or contractors who have worked on the propertyshould be added to the file as the job progresses. Recording actions takenon the building and identifying where elements that have been removed arestored will be helpful in the future.

    The project coordinator should keep the building file updated and giveduplicate copies to the owner. A list of emergency numbers, including thenumber of the key holder, should be kept at the entrance to the buildingor on a security gate, in a transparent vinyl sleeve.

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    Preparinga condition assessment of the building

    A condition assessment can providethe owner with an accurate overview of the current condition of the property.If the building is deteriorated or if there are significant interior architecturalelements that will need special protection during the mothballing years,undertaking a condition assessment is highly recommended, but it need notbe exhaustive.

    A modified condition assessment, prepared by an architect or preservationspecialist, and in some case a structural engineer, will help set prioritiesfor repairs necessary to stabilize the property for both the short andlong-term. It will evaluate the age and condition of the following majorelements: foundations; structural systems; exterior materials; roofs andgutters; exterior porches and steps; interior finishes; staircases; plumbing,electrical, mechanical systems; special features such as chimneys; andsite drainage.

    To record existing conditions of the building and site, it will be necessaryto clean debris from the building and to remove unwanted or overgrown vegetationto expose foundations. The interior should be emptied of its furnishing(unless provisions are made for mothballing these as well), all debrisremoved, and the interior swept with a broom. Building materials too deterioratedto repair, or which have come detached, such as moldings, balusters, anddecorative plaster, and which can be used to guide later preservation work,should be tagged, labeled and saved.

    Photographs or a videotape of the exterior and all interior spaces ofthe resource will provide an invaluable record of "as is" conditions.If a videotape is made, oral commentary can be provided on the significanceof each space and architectural feature. If 35mm photographic prints orslides are made, they should be numbered, dated, and appropriately identified.Photographs should be cross-referenced with the room numbers on the schematicplans. A systematic method for photographing should be developed; for example,photograph each wall in a room and then take a corner shot to get floorand ceiling portions in the picture. Photograph any unusual details aswell as examples of each window and door type.

    For historic buildings, the great advantage of a condition assessmentis that architectural features, both on the exterior as well as the interior,can be rated on a scale of their importance to the integrity and significanceof the building. Those features of the highest priority should receivepreference when repairs or protection measures are outlined as part ofthe mothballing process. Potential problems with protecting these featuresshould be identified so that appropriate interim solutions can be selected.For example, if a building has always been heated and if murals, decorativeplaster walls, or examples of patternedwall paper are identified as highly significant, then special care shouldbe taken to regulate the interior climate and to monitor it adequatelyduring the mothballing years. This might require retaining electrical serviceto provide minimal heat in winter, fan exhaust in summer, and humiditycontrols for the interior.

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    Stabilization as part of a mothballing project involves correcting deficienciesto slow down the deterioration of the building while it is vacant. Weakenedstructural members that might fail altogether in the forthcoming yearsmust be braced or reinforced; insects and other pests removed and discouragedfrom returning; and the building protected from moisture damage both byweatherizing the exterior envelope and by handling water run-off on thesite. Even if a modified use or caretaker services can eventually be foundfor the building, the following steps should be addressed.

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    Structurally stabilizingthe building

    While bracing may have been required to make the buildingtemporarily safe for inspection, the condition assessment may reveal areasof hidden structural damage. Roofs, foundations, walls, interior framing,porches and dormers all have structural components that may need addedreinforcement. Structural stabilization by a qualified contractor shouldbe done under the direction of a structural engineer or a preservationspecialist to ensure that the added weight of the reinforcement can besustained by the building and that the new members do not harm historicfinishes. Any major vertical post added during the stabilizationshould be properly supported and, if necessary, taken to the ground andunderpinned.

    If the building is in a northern climate, then the roof framing mustbe able to hold substantial snow loads. Bracing the roof at the ridge andmid-points should be considered if sagging is apparent. Likewise, interiorframing around stair openings or under long ceiling spans should be investigated.Underpinning or bracing structural piers weakened by poor drainage patternsmay be a good precaution as well. Damage caused by insects, moisture, orfrom other causes should be repaired or reinforced and, if possible, thesource of the damage removed. If features such as porches and dormers areso severely deteriorated that they must be removed, they should be documented,photographed, and portions salvaged for storage prior to removal.

    If the building is in a southern or humid climate and termites or otherinsects are a particular problem, the foundation and floor framing shouldbe inspected to ensure that there are no major structural weaknesses. Thiscan usually be done by observation from the crawl space or basement. Forthose structures where this is not possible, it may be advisable to liftselective floor boards to expose the floor framing. If there is evidenceof pest damage, particularly termites, active colonies should be treatedand the structural members reinforced or replaced, if necessary.

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    Controlling pests

    Pests can benumerousand include squirrels, raccoons, bats, mice, rats, snakes, termites, moths,beetles, ants, bees and wasps, pigeons, and other birds. Termites, beetles,and carpenter ants destroy wood. Mice, too, gnaw wood as well as plaster,insulation, and electrical wires. Pigeon and bat droppings not only damagewood finishes but create a serious and sometimes deadly health hazard.

    If the property is infested with animals or insects, it is importantto get them out and to seal off their access to the building. If necessary,exterminate and remove any nests or hatching colonies. Chimney flues maybe closed off with exterior grade plywood caps, properly ventilated, orprotected with framed wire screens. Existing vents, grills, and louversin attics and crawl spaces should be screened with bug mesh or heavy dutywire, depending on the type of pest being controlled. It may be advantageousto have damp or infected wood treated with insecticides (as permitted byeach state) or preservatives, such as borate, to slow the rate of deteriorationduring the time that the building is not in use.

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    Securingthe exterior envelope from moisture penetration

    It is important to protectthe exterior envelope from moisture penetration before securing the building.Leaks from deteriorated or damaged roofing, from around windows and doors,or through deteriorated materials, as well as ground moisture from impropersite run-off or rising damp at foundations,can cause long-term damage to interior finishes and structural systems.Any serious deficiencies on the exterior, identified in the condition assessment,should be addressed.

    To the greatest extent possible, these weatherization efforts shouldnot harm historic materials. The project budget may not allow deterioratedfeatures to be fully repaired or replaced in-kind. Non-historic or modernmaterials may be used to cover historic surfaces temporarily, but thesetreatments should not destroy valuable evidence necessary for future preservationwork. Temporary modifications should be as visually compatible as possiblewith the historic building.

    Roofs are often the most vulnerable elements on the building exteriorand yet in some ways they are the easiest element to stabilize for thelong term, if done correctly. "Quick fix" solutions, such astar patches on slate roofs, should be avoided as they will generally failwithin a year or so and may accelerate damage by trapping moisture. Theyare difficult to undo later when more permanent repairs are undertaken.Use of a tarpaulin over a leaking roof should be thought of only as a verytemporary emergency repair because it is often blown off by the wind ina subsequent storm.

    If the existing historic roof needs moderate repairs to make it lastan additional ten years, then these repairs should be undertaken as a firstpriority. Replacing cracked or missing shingles and tiles, securing looseflashing, and reanchoring gutters and downspouts can often be done by alocal roofing contractor. If the roof is in poor condition, but the historicmaterials and configuration are important, a new temporary roof, such asa lightweight aluminum channel system over the existing, might be considered. If the roofing is so deteriorated that it must be replacedand a lightweight aluminum system is not affordable, various inexpensiveoptions might be considered. These include covering the existing deterioratedroof with galvanized corrugated metal roofing panels, or 90 lb. rolledroofing, or a rubberized membrane (refer back to cover photo). These alternativesshould leave as much of the historic sheathing and roofing in place asevidence for later preservation treatments.

    For masonry repairs, appropriate preservation approaches are essential.For example, if repointing deteriorated brick chimneys or walls is necessaryto prevent serious moisture penetration while the building is mothballed,the mortar should match the historic mortar in composition, color, andtooling. The use of hard portland cement mortars or vapor-impermeable waterproofcoatings are not appropriate solutions as they can cause extensive damageand are not reversible treatments.

    For wood siding that is deteriorated, repairs necessary to keep outmoisture should be made; repainting is generally warranted. Cracks aroundwindows and doors can be beneficial in providing ventilation to the interiorand so should only be caulked if needed to keep out bugs and moisture.For very deteriorated wall surfaces on wooden frame structures, it maybe necessary to sheathe in plywood panels, but care should be taken tominimize installation damage by planning the location of the nailing orscrew patterns or by installing panels over a frame of battens. Generally, however, it is better to repair deteriorated features thanto cover them over.

    Foundation damage may occur if water does not drain away from the building.Run-off from gutters and downspouts should be directed far away from thefoundation wall by using long flexible extender pipes equal in length totwice the depth of the basement or crawl space. If underground drains aresusceptible to clogging, it is recommended that the downspouts be disconnectedfrom the drain boot and attached to flexible piping. If gutters and downspoutsare in bad condition, replace them with inexpensive aluminum units.

    If there are no significant landscape or exposed archeological elementsaround the foundation, consideration should be given to regrading the siteif there is a documented drainage problem. If building upthe grade, use a fiber mesh membrane to separate the new soil from theold and slope the new soil 6 to 8 feet (200 cm-266 cm) away from the foundationmaking sure not to cover up the dampcourse layer or come into contact withskirting boards. To keep vegetation under control, put down a layer of6 mil black polyethylene sheeting or fiber mesh matting covered with a2"-4" (5-10 cm.) of washed gravel. If the building suffers aserious rising damp problem, it may be advisable to eliminate the plasticsheeting to avoid trapping ground moisture against foundations.

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    The actual mothballing effort involves controlling the long-term deteriorationof the building while it is unoccupied as well as finding methods to protectit from sudden loss by fire or vandalism. This requires securing the buildingfrom unwanted entry, providing adequate ventilation to the interior, andshutting down or modifying existing utilities. Once the building is de-activatedor secured, the long-term success will depend on periodic maintenance andsurveillance monitoring.

    Securing the building from vandals,break-ins, and natural disasters

    Securing the building from sudden lossis a critical aspect of mothballing. Because historic buildings are irreplaceable,it is vital that vulnerable entry points are sealed. If the building islocated where fire and security service is available then it is highlyrecommended that some form of monitoring or alarm devices be used.

    To protect decorative features, such as mantels, lighting fixtures,copper downspouts, iron roof cresting, or stained glass windows from theftor vandalism, it may be advisable to temporarily remove them to a moresecure location if they cannot be adequately protected within the structure.

    Mothballed buildings are usually boarded up, particularly on the firstfloor and basement, to protect fragile glass windows from breaking andto reinforce entry points. Infill materials for closing doorand window openings include plywood, corrugated panels, metal grates, chainfencing, metal grills, and cinder or cement blocks. The methodof installation should not result in the destruction of the opening andall associated sash, doors, and frames should be protected or stored forfuture reuse.

    Generally exterior doors are reinforced and provided with strong locks,but if weak historic doors would be damaged or disfigured by adding reinforcementor new locks, they may be removed temporarily and replaced with securemodern doors. Alternatively, security gates in an new metalframe can be installed within existing door openings, much like a stormdoor, leaving the historic door in place. If plywood panels are installedover door openings, they should be screwed in place, as opposed to nailed,to avoid crowbar damage each time the panel is removed. This also reducespounding vibrations from hammers and eliminates new nail holes each timethe panel is replaced.

    For windows, the most common security feature is the closure of theopenings; this may be achieved with wooden or pre-formed panels or, asneeded, with metal sheets or concrete blocks. Plywood panels, properlyinstalled to protect wooden frames and properly ventilated, are the preferredtreatment from a preservation standpoint.

    There are a number of ways to set insert plywood panels into windowsopenings to avoid damage to frame and sash. One common methodis to bring the upper and lower sash of a double hung unit to the mid-pointof the opening and then to install pre-cut plywood panels using long carriagebolts anchored into horizontal wooden bracing, or strong backs, on theinside face of the window. Another means is to build new wooden blockingframes set into deeply recessed openings, for example in an industrialmill or warehouse, and then to affix the plywood panel to the blockingframe. If sash must be removed prior to installing panels, they shouldbe labeled and stored safely within the building.

    Plywood panels are usually 1/2"-3/4" (1.25-1.875 cm.)thick and made of exterior grade stock, such as CDX, or marine grade plywood.They should be painted to protect them from delamination and to providea neater appearance. These panels may be painted to resemble operable windowsor treated decoratively. With extra attention to detail,the plywood panels can be trimmed out with muntin strips to give a shadowline simulating multi-lite windows. This level of detail is a good indicationthat the building is protected and valued by the community.

    If the building has shutters simply close the shutters and secure themfrom the interior. If the building had shutters historically,but they are missing, it may be appropriate to install new shutters, evenin a modern material, and secure them in the closed position. Louveredshutters will help with interior ventilation if the sash are propped openbehind the shutters.

    There is some benefit from keeping windows unboarded if security isnot a problem. The building will appear to be occupied, and the naturalair leakage around the windows will assist in ventilating the interior.The presence of natural light will also help when periodic inspectionsare made. Rigid polycarbonate clear storm glazing panels may be placedon the window exterior to protect against glass breakage. Because the sun'sultraviolet rays can cause fading of floor finishes and wall surfaces,filtering pull shades or inexpensive curtains may be options for reducingthis type of deterioration for significant interiors. Some acrylic sheetingcomes with built-in ultraviolet filters.

    Securing the building from catastrophic destruction from fire, lightning,or arson will require additional security devices. Lightning rods properlygrounded should be a first consideration if the building is in an areasusceptible to lightning storms. A high security fence should also be installedif the property cannot be monitored closely. These interventions do notrequire a power source for operation. Since many buildings will not maintainelectrical power, there are some devices available using battery packs,such as intrusion alarms, security lighting, and smoke detectors whichthrough audible horn alarms can alert nearby neighbors. These battery packsmust be replaced every 3 months to 2 years, depending on type and use.In combination with a cellular phone, they can also provide some levelof direct communication with police and fire departments.

    If at all possible, new temporary electric service should be providedto the building. Generally a telephone line is needed aswell. A hard wired security system for intrusion and a combination rate-of-riseand smoke detector can send an immediate signal for help directly to thefire department and security service. Depending on whether or not heatwill be maintained in the building, the security system should be designedaccordingly. Some systems cannot work below 32F (0C). Exteriorlighting set on a timer, photo electric sensor, or a motion/infra-red detectiondevice provides additional security.

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    Providing adequate ventilationto the interior

    Once the exterior has been made weathertight and secure,it is essential to provide adequate air exchange throughout the building.Without adequate air exchange, humidity may rise to unsafe levels, andmold, rot, and insect infestation are likely to thrive. Theneeds of each historic resource must be individually evaluated becausethere are so many variables that affect the performance of each interiorspace once the building has been secured. Amechanical engineer or a specialist in interior climates should be consulted,particularly for buildings with intact and significant interiors. In somecircumstances, providing heat during the winter, even at a minimal 45F (7C), and utilizing forced-fan ventilation in summer will be recommendedand will require retaining electrical service. For masonry buildings itis often helpful to keep the interior temperature above the spring dewpoint to avoid damaging condensation. In most buildings it is the needfor summer ventilation that outweighs the winter requirements.

    Many old buildings are inherently leaky due to loose-fitting windowsand floorboards and the lack of insulation. The level of air exchange neededfor each building, however, will vary according to geographic location,the building's construction, and its general size and configuration.

    There are four critical climate zones when looking at the type and amountof interior ventilation needed for a closed up building: hot and dry (southwesternstates); cold and damp (Pacific northwest and northeastern states); temperateand humid (Mid-Atlantic states, coastal areas); and hot and humid (southernstates and the tropics).

    Once closed up, a building interior will still be affected by the temperatureand humidity of the exterior. Without proper ventilation, moisture fromcondensation may occur and cause damage by wetting plaster, peeling paint,staining woodwork, warping floors, and in some cases even causing freezethaw damage to plaster. If moist conditions persist in a property, structuraldamage can result from rot or returning insects attracted to moist conditions.Poorly mothballed masonry buildings, particularly in damp and humid zoneshave been so damaged on the interior with just one year of unventilatedclosure that none of the interior finishes were salvageable when the buildingswere rehabilitated.

    The absolute minimum air exchange for most mothballed buildings consistsof one to four air exchanges every hour; one or two air exchanges per hourin winter and twice that amount in summer. Even this minimal exchange mayfoster mold and mildew in damp climates, and so monitoring the propertyduring the stabilization period and after the building has been securedwill provide useful information on the effectiveness of the ventilationsolution.

    There is no exact science for how much ventilation should be providedfor each building. There are, however, some general rules of thumb. Buildings,such as adobe structures, located in hot and arid climates may need noadditional ventilation if they have been well weatherized and no moistureis penetrating the interior. Also frame buildings with natural cracks andfissures for air infiltration may have a natural air exchange rate of 3or 4 per hour, and so in arid as well as temperate climates may need noadditional ventilation once secured. The most difficult buildings to adequatelyventilate without resorting to extensive louvering and/or mechanical exhaustfan systems are masonry buildings in humid climates. Even with basementand attic vent grills, a masonry building many not have more than one airexchange an hour. This is generally unacceptable for summer conditions.For these buildings, almost every window opening will need to be fittedout with some type of passive, louvered ventilation.

    Depending on the size, plan configuration, and ceiling heights of abuilding, it is often necessary to have louvered opening equivalent to5%-10% of the square footage of each floor. For example, in a hot humidclimate, a typical 20'x30' (6.1m x 9.1m) brick residence with 600 sq. ft.(55.5sq.m) of floor space and a typical number of windows, may need 30-60 sq. ft.(2.75sq.m-5.5 sq.m) of louvered openings per floor. With eachwindow measuring 3'x5'(.9m x 1.5 m) or 15 sq. ft. (1.3 sq.m), the equivalentof 2 to 4 windows per floor will need full window louvers.

    Small pre-formed louvers set into a plywood panel or small slit-typeregisters at the base of inset panels generally cannot provide enough ventilationin most moist climates to offset condensation, but this approach is certainlybetter than no louvers at all. Louvers should be located to give crossventilation, interior doors should be fixed ajar at least 4" (10cm)to allow air to circulate, and hatches to the attic should be left open.

    Monitoring devices which can record internal temperature and humiditylevels can be invaluable in determining if the internal climate is remainingstable. These units can be powered by portable battery packs or can bewired into electric service with data downloaded into laptop computersperiodically . This can also give long-term information throughoutthe mothballing years. If it is determined that there are inadequate airexchanges to keep interior moisture levels under control, additional passiveventilation can be increased, or, if there is electric service, mechanicalexhaust fans can be installed. One fan in a small to medium sized buildingcan reduce the amount of louvering by over 50%.

    If electric fans are used, study the environmental conditions of eachproperty and determine if the fans should be controlled by thermostatsor automatic timers. Humidistats, designed for enclosed climate controlsystems, generally are difficult to adapt for open mothballing conditions.How the system will draw in or exhaust air is also important. It may bedetermined that it is best to bring dry air in from the attic or upperlevels and force it out through lower basement windows. Ifthe basement is damp, it may be best to zone it from the rest ofthe building and exhaust its air separately. Additionally, less humid dayair is preferred over damper night air, and this can be controlled witha timer switch mounted to the fan.

    The type of ventilation should not undermine the security of the building.The most secure installations use custom-made grills well anchored to thewindow frame, often set in plywood security panels. Some vents are formedusing heavy millwork louvers set into existing window openings. For buildings where security is not a primary issue, wherethe interior is modest, and where there has been no heat for a long time,it may be possible to use lightweight galvanized metal grills in the windowopenings. A cost effective grill can be made fromthe expanded metal mesh lath used by plasterers and installed so that themesh fins shed rainwater to the exterior.

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    nical systems and utilities">Securing mechanicalsystems and utilities

    At the outset, it is important to determine whichutilities and services, such as electrical or telephone lines, are keptand which are cut off. As long as these services will not constitute afire hazard, it is advisable to retain those which will help protect theproperty. Since the electrical needs will be limited in a vacant building,it is best to install a new temporary electric line and panel (100 amp)so that all the wiring is new and exposed. This will be much safer forthe building, and allows easy access for reading the meter.

    Most heating systems are shut down in long term mothballing. For furnacesfueled by oil, there are two choices for dealing with the tank. Eitherit must be filled to the top with oil to eliminate condensation or it shouldbe drained. If it remains empty for more than a year, it will likely rustand not be reusable. Most tanks are drained if a newer type of system isenvisioned when the building is put back into service. Gas systems withopen flames should be turned off unless there is regular maintenance andfrequent surveillance of the property. Gas lines are shut off by the utilitycompany.

    If a hot water radiator system is retained for low levels of heat, itgenerally must be modified to be a self-contained system and the watersupply is capped at the meter. Thisrecirculating system protects the property from extensive damage from burstpipes. Water is replaced with a water/glycol mix and the reserve tank mustalso be filled with this mixture. This keeps the modified system from freezing,if there is a power failure. If water service is cut off, pipes shouldbe drained. Sewerage systems will require special care as sewer gas isexplosive. Either the traps must be filled with glycol or the sewer lineshould be capped off at the building line.

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    and monitoring plan">

    Developinga maintenance and monitoring plan

    While every effort may have been madeto stabilize the property and to slow the deterioration of materials, naturaldisasters, storms, undetected leaks, and unwanted intrusion can still occur.A regular schedule for surveillance, maintenance, and monitoring shouldbe established. The fire and police departments should be notified thatthe property will be vacant. A walk-through visit to familiarize theseofficials with the building's location, construction materials, and overallplan may be invaluable if they are called on in the future.

    The optimum schedule for surveillance visits to the property will dependon the location of the property and the number of people who can assistwith these activities. The more frequent the visits to check the property,the sooner that water leaks or break-ins will be noticed. Also, the morefrequently the building is entered, the better the air exchange. By keepingthe site clear and the building in good repair, the community will knowthat the building has not been abandoned. The involvementof neighbors and community groups in caring for the property can ensureits protection from a variety of catastrophic circumstances.

    The owner may utilize volunteers and service companies to undertakethe work outlined in the maintenance chart. Service companieson a maintenance contract can provide yard, maintenance, and inspectionservices, and their reports or itemized bills reflecting work undertakenshould be added to update the building file.


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    Mothballing Checklist

    In reviewing mothballing plans, the following checklist may help toensure that work items are not inadvertently omitted.

    • Is the roof watertight?
    • Do the gutters retain their proper pitch and are they clean?
    • Are downspout joints intact?
    • Are drains unobstructed?
    • Are windows and doors and their frames in good condition?
    • Are masonry walls in good condition to seal out moisture?
    • Is wood siding in good condition?
    • Is site properly graded for water run-off?
    • Is vegetation cleared from around the building foundation to avoidtrapping moisture?
    • Have nests/pests been removed from the building's interior and eaves?
    • Are adequate screens in place to guard against pests?
    • Has the building been inspected and treated for termites, carpenterants, rodents, etc.?
    • If toxic droppings from bats and pigeons are present, has a specialcompany been brought in for its disposal?
    • Have the following been removed from the interior: trash, hazardousmaterials such as inflammable liquids, poisons, and paints and canned goodsthat could freeze and burst?
    • Is the interior broom-clean?
    • Have furnishings been removed to a safe location?
    • If furnishings are remaining in the building, are they properly protectedfrom dust, pests, ultraviolet light, and other potentially harmful problems?
    • Have significant architectural elements that have become detached fromthe building been labeled and stored in a safe place?
    • Is there a building file?
    • Have fire and police departments been notified that the building willbe mothballed?
    • Are smoke and fire detectors in working order?
    • Are the exterior doors and windows securely fastened?
    • Are plans in place to monitor the building on a regular basis?
    • Are the keys to the building in a secure but accessible location?
    • Are the grounds being kept from becoming overgrown?
    • Have utility companies disconnected/shut off or fully inspected water,gas, and electric lines?
    • If the building will not remain heated, have water pipes been drainedand glycol added?
    • If the electricity is to be left on, is the wiring in safe condition?
    • Have steps been taken to ensure proper ventilation of the building?
    • Have interior doors been left open for ventilation purposes?
    • Has the secured building been checked within the last 3 months forinterior dampness or excessive humidity?

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    Maintenance Chart

    1-3 months; periodic

    • regular drive by surveillance
    • check attic during storms if possible
    • monthly walk arounds
    • check entrances
    • check window panes for breakage
    • mowing as required
    • check for graffiti or vandalism
    • enter every 3 months to air out
    • check for musty air
    • check for moisture damage
    • check battery packs and monitoring equipment
    • check light bulbs
    • check for evidence of pest intrusion

    every 6 months; spring and fall

    • site clean-up; pruning and trimming
    • gutter and downspout check
    • check crawlspace for pests
    • clean out storm drains

    every 12 months

    • maintenance contract inspections for equipment/utilities
    • check roof for loose or missing shingles
    • termite and pest inspection/treatment
    • exterior materials spot repair and touch up painting
    • remove bird droppings or other stains from exterior
    • check and update building file


    Providing temporary protection and stabilization for vacant historicbuildings can arrest deterioration and buy the owner valuable time to raisemoney for preservation or to find a compatible use for the property. Thethree highest priorities for a mothballed building are 1) to protect thebuilding from sudden loss, 2) to weatherize and maintain the property tostop moisture penetration, and 3) to control the humidity levels insideonce the building has been secured.

    While issues regarding mothballing may seem simple, the variables andintricacies of possible solutions make the decision-making process veryimportant. Each building must be individually evaluated prior to mothballing.In addition, a variety of professional services as well as volunteer assistanceis needed for careful planning and repair, sensitively designed protectionmeasures, follow-up security surveillance, and cyclical maintenance.

    In planning for the future of the building, complete and systematicrecords must be kept and generous funds allocated for mothballing. Thiswill ensure that the historic property will be in stable condition forits eventual preservation, rehabilitation, or restoration.

    Further Reading

    Cotton, J. Randall. "Mothballing Buildings." The Old-HouseJournal. July/August, 1993.

    Fisher, Charles E. and Thomas A. Vitanza. "Temporary Window Ventsin Unoccupied Historic Buildings." Preservation Tech Note (Windows,No. 10). Washington, DC: National Park Service, 1985.

    Frazier Associates. "Mothballing Historic Buildings." PreservingPrince William, 2. County of Prince William, VA, 1990.

    Michell, Eleanor. Emergency Repairs for Historic Buildings. London:Butterworth Architecture, 1988.

    "Mothballing Vacant Buildings," An Anti-Arson Kitfor Preservation and Neighborhood Action. Washington, DC: Federal EmergencyManagement Agency, 1982.

    Solon, Thomas E. "Security Panels for the Foster-Armstrong House."Association for Preservation Technology Bulletin. Vol XVI no. 3& 4, 1984. (note the design of the panels, but be aware that additionallouvering may be needed on other projects).


    The author, Sharon C. Park, Senior Historical Architect, Heritage PreservationServices Division, National Park Service, would like to acknowledge theassistance of the following individuals in the preparation and review ofthis publication. H. Ward Jandl served as the technical editor and assistedwith producing this Preservation Brief. In addition the following personshave provided invaluable information and illustrations: Ernest A. Conrad,PE; Doug Hicks, NPS Williamsport Preservation Training Center; Thomas C.Taylor, ColonialWilliamsburg; Karen Gordon, Seattle Urban ConservationOffice; Kevin B. Stoops, Seattle Department of Parks and Recreation; MichaelMills, AIA; Christine Henry, architect, Mary Beth Hirsch, Ohio HistoricalSociety. Thanks also to Heritage Preservation Services Division staff membersMichael J. Auer, Anne E. Grimmer, Kay D. Weeks, Tim Buehner, and Jean Travers,and to the numerous staff members of the NPS Regional offices who submittedcomments. All photographs and drawings are by the author unless otherwisenoted. Washington, D.C. September, 1993

    This publication has been prepared pursuant to the NationalHistoric Preservation Act of 1966, as amended, which directs the Secretaryof the Interior to develop and make available information concerning historicproperties. Technical Preservation Services (TPS), Heritage PreservationServices Division, National Park Service prepares standards, guidelines,and other educational materials on responsible historic preservation treatmentsto a broad public.

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