ISSUE 1/2001 VOLUME 19 NUMBER 1

Journal of architectural technology published by Hoffmann Architects, specialists in the rehabilitation of building exteriors. Façade Cleaning: For More Than Appearance’s Sake

Richard P. Kadlubowski, AIA and Coleman H. Bynum, AIA

hy should a building’s façade be Furthermore, if and when it is decided a Wcleaned? The issue of aesthetics first building’s façade will be cleaned, it may comes to mind. After all, a clean building be that only a portion—for instance, simply looks better than a dirty building. A that which is visible from the clean building presents a more hospitable sidewalk—will be cleaned. A front—and therefore a more attractive skyscraper in , for example, real estate prospect—to the public. Just as may be cleaned from the ground to we put our best foot forward with a neat, the sixth floors only, limiting the kempt appearance, a building looks its best cleaning effort to that portion of the when free of the grime, pollutants and building’s façade that is visible to staining that shadow its most visible—and bustling commuters. Cleaning the often most vulnerable—attribute, its ground floors only is a viable alternative façade. when it may be costly—not to mention foolhardy in a pollutant-ridden Of course, not all building façades warrant urban locale—to clean a building’s the same amount of care and attention. A façade completely. building’s location, function, and geographic and atmospheric conditions all play roles Finally, what it takes to clean a building in determining the level of cleaning effort situated in the country is typically far necessary to achieve the desired less an endeavor than if that same appearance. building were located in a metropolitan area. The rural building may warrant Consider function: Structures which only water soaking to remove mild house commercial activity, in business, contaminants (such as dirt), while the theatre or shopping districts, often warrant urban building would most likely a higher degree of cleanliness than do require a more in-depth cleaning buildings that house industrial—or less effort—to remove more hazardous public—activities. A bank building manager, pollutants—to achieve the same level for example, may choose to maintain an of cleanliness. > > > > > Workers pressure wash the concrete immaculate façade to greet clients and façade of a corporate office building. account holders, while a warehouse While aesthetics is the obvious—and owner may find it understandably primary—reason for cleaning a building unnecessary to achieve the same level of façade, the effort to expose the cleanliness for his structure. substrate for evaluation and repair runs

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Richard P. Kadlubowski, AIA and Coleman H. Bynum, AIA, Senior Architects with Hoffmann Architects, oversee a variety of façade cleaning projects for the firm. JOURNAL

(continued from page 1) a close second. It is nearly impossible Lastly, façade cleaning opens a building’s guidance of the design professional, must to gauge the condition of a masonry pores and allows the normal find a balance for the building’s façade at substrate, for example, when the transpiration of moisture. Moisture which point it is free of any contaminants façade is covered in dirt, grime and/or trapped within a masonry wall, for that may threaten the substrate while not a coating. In order to determine example, will remain there if a so scrubbed as to contradict the those areas which need to be waterproofing coating prevents its exit. In structure’s history. patched, repaired or resealed—or, in this case, as moisture is the leading cause some cases, to even properly identify of masonry decay, comprehensive façade To Clean Before or After Restoration/ the substrate—the façade should be cleaning to include removal of the Repairs? cleaned of any and all elements that waterproofing coating may be the key preclude its proper evaluation. component of the design professional’s Still another important factor to effort to restore the building. consider in preparing to clean a building Still another key motivation behind façade is when to do it: before or after façade cleaning is the effort to How Clean is Clean Enough? repairs and restoration work. As remove damaging pollutants such as previously mentioned, it can be difficult sulfur and nitrogen oxides, and other Once the decision has been made to to detect what may need to be repaired acid rain pollutants, from the façade. clean a building’s façade, the question of in a surface when it is heavily coated in These pollutants serve to accelerate ‘how clean is clean enough?’ may arise. dirt, stains, paint and/or other coatings. façade deterioration. Generally, the primary objective should And, as it is best to patch/repair a clean, be to remove any and all contaminants sound surface, it may be preferable to Case in point: moisture is the primary from the façade. Beyond this, the clean the façade before any repairs. cause of masonry decay. When question of ‘how clean is clean enough?’ moisture is coupled with soluble salts should be answered on a case-by-case However, there are exceptions to this from polluted rainwaters or with basis, with the full subjectivity of the somewhat loose rule. For example, atmospheric gases, the decay is building owner and/or manager. when a stone building has extensive leak accelerated. When the soluble salt problems, and the design professional dissolves in water, it travels deep into In the case of older buildings, however, must coordinate patching and sealant the masonry substrate through pores should they be so thoroughly cleaned as work, it may very well be a mistake to or cracks. Once the moisture to look new? Would the Pantheon in run the risk of even greater water evaporates, the salt recrystallizes, Rome suffer in our mind’s eye if its 1800- intrusion by adding water during exerting tremendous pressures which year history were somewhat forgotten in cleaning to already precarious areas. In break down the masonry from within. the gleam of pristinely scrubbed these instances, the design professional pozzolan 1 concrete? Indeed, many may choose to patch and seal areas of Additionally, atmospheric gases such individuals involved with the preservation water intrusion prior to the as carbon dioxide, sulfur dioxide and of historic structures argue that too commencement of cleaning. nitrogen oxides react with dirty, wet much cleaning strips these buildings of “a surfaces to form corrosive liquids such certain dignity earned with the passage Protection Against Damage as carbonic acid, sulfuric acid and nitric of time.” 2 They assert that the dirt patina acid. These liquids react with various represents a natural process of To ensure a successful façade cleaning elements in the masonry and may weathering which is of “important project, whether it be for stone and result in the formation of hardened historical significance and in character masonry, concrete, or aluminum, it is surface crusts and dissolution of acid- with older buildings viewed in a crucial to choose and implement the soluble cementing binders that hold contemporary setting.” 2 most appropriate method for the the masonry together. The formation surface. Protection against damage to of these dense surface crusts and the However, the fact remains that the personnel, to the building, to the site and washing away of acid-soluble binders, accumulation of surface staining goes far to the environment should be the if allowed to persist, are progressive beyond aesthetic deformation; heavy foremost consideration in choosing and deterioration processes. surface deposits contribute to the implementing the cleaning method. progressive decay of stone, masonry and concrete surfaces. The owner, with the

1 pozzolan: The Romans produced lime by burning limestone pieces. Mixed with volcanic ash (pozzolan) and water, it becomes a mortar. The Romans mixed this mortar with small stones, bricks and other materials to produce concrete.

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Protecting personnel without appropriate protection from touching, ingesting, inhaling or contacting Points of water infiltration that should be Of the three general categories of in any other way bird-related matter. repaired prior to façade cleaning: cleaning methods—chemical cleaning, Finally, the disposal of such substances water cleaning and abrasive cleaning— must comply with applicable federal, state chemical cleaning packs the highest risk and local laws and regulations. quotient to the individual. The design professional should require as part of Protecting the building the cleaning submittals a detailed description of the proposed materials In protecting against damage to the and methods of protection for building during façade cleaning, the preventing harm caused by the cleaning design professional should submit in work to all persons in the cleaning area. advance a detailed description, including > > > > > End of a copper joint cover is open in a Product data and Material Safety Data drawings and diagrams, of proposed joint in a projecting course. Sheets (MSDS) should be submitted for materials and methods of protection for all recommended materials and chemical preventing harm, damage or cleaning products. deterioration caused by the cleaning work to all building elements, materials The persons performing the cleaning and finishes. must adhere to the guidelines set forth in a chemical’s MSDS to protect against To protect surfaces of the building damage to themselves or the public. All intended to remain without cleaning, the precautionary measures should be read design professional instructs the carefully, and first-aid instructions—in contractor as to the specified protection case of contact or exposure—should be materials to protect all glass, metal, wood > > > reviewed. These instructions include and/or painted surfaces that should not > > Lead joint cover has been pushed out what to do in case of eye contact, skin be affected during masonry cleaning, for of the joint. Caulking in joint is brittle contact, inhalation and ingestion. Also example. These specified protection and not bonded to the stone. included in the MSDS are spill and leak materials may include masking products procedures as well as guidelines for that are sometimes part of a container handling, storage and shelf life. manufacturer’s chemical cleaning system. 100 square feet for each substrate and for each cleaning method Chemical cleaning products are not the Additionally, all windows and doors and specified. Full cleaning should not only potentially hazardous elements to other existing openings should be proceed until the test patch has been be aware of during façade cleaning. Bird temporarily sealed to prevent liquid and reviewed and accepted by the design droppings and other bird-related matter particulate entry. Again, materials used professional and the building owner. offer another source of some very to do this must be those specified by the unhealthy effects. And, as one can well design professional. Window and door Prior to test cleaning, it must be imagine, there is a distinct possibility that hardware should be checked for assured that the work of other trades one will encounter a considerable operability at the conclusion of the work. that might affect the cleaning work is amount of bird matter during façade fully complete. Cleaning should not cleaning. Test cleaning a patch of the façade is a commence until all other work has critical element of the façade cleaning ceased. When performing the test Bird droppings and other bird-related process. It is essential not only in patch, only the cleaning methods matter contain substances, including ensuring that the cleaning effort will have specified by the design professional agents of diseases such as Histoplasmosis the desired results but also in ensuring for each type of material and location and Cryptococcosis, that are harmful— that the chosen method will not damage should be used. Each cleaning and sometimes fatal—to humans. All the façade. Prior to initiating a full method indicated should be necessary precautions must be taken to masonry cleaning project, for example, performed in a manner which results prevent workers and other people test cleaning should be conducted for in uniform coverage of all surfaces,

(continued on page 4) 2 Boyer, David. W., Author, “Masonry Cleaning-The State of the Art,” Cleaning Stone and Masonry. 1986.

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(continued from page 3) including corners and moldings, and commencement of the façade cleaning Once the work of the cleaning operations which produces an even effect without project (i.e., A cleaning specification may has ceased, all temporary protection streaking or damage to the surface. require that masonry cleaning work not should be removed. be performed when temperatures may Finally, planning around Mother drop below 50 degrees-or soar above Furthermore, the design professional Nature is essential in protecting 90 degrees-Fahrenheit within 24 hours of should ensure minimum interference against damage to the building during the work.). with streets, walks and other adjacent façade cleaning. The weather can facilities. For example, the flow of water make or break a façade cleaning Protecting the site from soaking and cleaning operations project. If it is too cold, liquid cleaning should be continuously monitored to products and water will freeze to To protect the site during façade avoid damage to the building and sheets of ice. Conversely, if it is too cleaning, plans must be implemented to surrounding areas, and excessive warm, a chemical product’s drying confine dust, liquids, overspray and debris amounts of water should not be time may accelerate, so it may not to prevent detrimental effects to permitted to flow across walkways. Also, have time to work as it should and adjacent properties and to the public. plywood trafficways may be necessary may not wash off properly. Temporary protection such as barriers, for all surfaces such as roofs or terraces Furthermore, wind may cause enclosures, netting or other protection that will receive pedestrian traffic during additional problems with vapor and as needed should be provided and cleaning. The plywood should be free of overspray. The design professional erected to prevent harm to personnel splinters, fasteners and any other should specify stipulations on how to and adjacent portions of the building. irregularities that may damage the work around the weather prior to existing surface.

Water soaking is one of the least intrusive Protecting the environment façade cleaning methods:

The design professional should plan in

> > > >

> (Left) Water-soaking nozzles assembled advance any necessary precautions to to clean a limestone façade. prevent hazardous material from

entering the environment. All means

> >

> > > (Below) A worker scrubs and removes necessary should be utilized to prevent softened soil from the water-soaked contaminated water, chemicals, chemical limestone façade. fumes and abrasive particles from flowing into drains or entering air intakes and exhausts. Protection and waste collection systems should be in place before general cleaning begins.

To prevent cleaning chemicals or particles of dirt or mortar from flowing into drains, for example, the design professional may instruct that appropriate precautions be taken.

Cleaning Stone, Masonry and Architectural Concrete

Basically, all façade cleaning projects fall into one of four categories: chemical, non-chemical, abrasive and those that may require a combination of these methods. For example, though a

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masonry façade cleaning project may · Cleaning of the masonry façade must · Cleaning must be scheduled when there partially succeed with a non-chemical be scheduled for times when there is is no threat of freezing. water soaking procedure to loosen dirt no threat of freezing. and wash it away, it may be necessary to · Water may find its way through small supplement this method with an · Continuous cascading of water openings and cause premature decay. appropriate cleaning agent (chemical) to results in erosion. treat areas of heavy stains. · Water run-off must be controlled. · There exists the possibility that The building owner and/or manager interior surfaces, furnishings and · This method is not a replacement for should consult with the design equipment may be damaged. hand labor. professional to arrive at the façade cleaning method that is best suited to · Water run-off must be controlled. · This method should NOT be used to their building. apply chemical cleaners, as the chemicals Pressure Washing: Pressurized water, will be driven deep into the masonry. Water cleaning methods measured in pounds per square inch (psi), blasts contaminants away from Chemical cleaning methods Water Soaking: A slow, steady stream of the façade. This procedure is effective water 3 is used to loosen dirt and wash it on stone, masonry and concrete for Manufactured by companies to conquer away, a very effective method as the dirt the removal of light to moderate the “tough” façade stains, chemical becomes swollen and soft. A manifold of atmospheric and organic staining. This cleaning products work by dissolving the piping and nozzles is constructed for this method utilizing heated water (not to stains, allowing them to be rinsed away. purpose. Hand scrubbing with brushes exceed 160 degrees Fahrenheit) may Generally, chemical cleaners fall into one or rinsing with 400 psi (pounds per prove effective for removal of grease of four categories: acidic cleaners, alkaline square inch) water spray may follow the and oil stains. cleaners, organic solvents, and special non- water soaking. sudsing detergents. Sometimes referred to as power For each water soaking façade cleaning washing, pressure washing is specified The list of available commercial chemical project, the design professional by the design professional according to cleaners for different types of façade determines the appropriate: four parameters: surfaces is long and varied: Some are designed to remove efflorescence and salt a) duration of soaking (in hours); a) pressure rating (psi); staining. Others are used primarily to b) number of gallons of water per b) water flow rate; remove excess mortar, grout stains and minute per nozzle; and c) spray tip (type and size); and dirt. Still others are best suited for use on c) nozzle spacing. d) distance from the substrate. brick that may have high metallic content.

This method is very effective on stone, Limitations associated with this There are restoration cleaners designed especially limestone, and glazed brick. procedure are as follows: to combat extremely dirty and heavily However, there are possible limitations carboned masonry typically found in large related to this procedure—as there are · Pressure washing alone will not cities or high pollution areas. Commercial with any procedure—that must be taken remove severe staining. poultices, designed for areas in which the into consideration: contaminant has penetrated into the · High pressures are abrasive and may substrate, as opposed to being on the · Prolonged exposure results in oxidation partially remove mortar and etch surface, are available for different types of of natural components of masonry and stone. surfaces. Strippable masking materials are transports harmful salts deep into the available to protect glass, metal and masonry. · Oxidation of masonry may result. polished stone surfaces from the damaging effects of acidic brick cleaners. · Saturated masonry takes several weeks · Saturated masonry takes several to dry. weeks to dry. As is evidenced by the aforementioned examples, chemical products are

3 Water for façade cleaning should be from the municipal water supply and clean at the time of use. In some cases, the water used for cleaning (continued on page 7) building façades may need to be pre-treated with an ion-exchange water softening system in order to avoid staining, efflorescence and other problems.

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Façade Cleaning

Hoffmann Architects has developed and implemented façade cleaning programs for a number of its clients. The following narratives briefly discuss the diverse plans prepared for some of these clients.

Rockefeller Center , New York ( Management Corporation)

As part of an overall rehabilitation plan, the design professionals of Hoffmann Architects implemented water soaking followed by scrubbing with brushes to clean the Indiana Limestone façades of the landmark Rockefeller Center > > > complex. The water soaking, which did > > Our Lady of Angels Motherhouse and Chapel Enfield, . Hoffmann Architects cleaned the facades of existing water repellents to enable the brickwork to breathe. not threaten to etch the stone, was initiated after repairs so as not to allow water to enter open joints. Absolutely that lies between ’s 5th Southern New England Telephone no chemicals were used during the and 6th Avenues and 48th and 51st (SNET) cleaning process. Streets—and so that water runoff did Hartford, Connecticut not pose any problems. Most of the Hoffmann Architects scheduled the cleaning work was therefore completed Hoffmann Architects initiated a repair cleaning work so as not to impede the during the night when relatively few and cleaning effort to rehabilitate the pedestrian traffic along the busy block people were in the area. limestone façades at SNET’s Hartford facility.

A combination of chemical and non- chemical methods was used to achieve the desired cleaning results for the structure. The cleaning effort began with long periods of water soaking (12- to 24-hour soaks) followed by scrubbing with clean, natural bristle brushes to remove > > > > > at Rockefeller Center New York, New York (Rockefeller Center Management Corporation)

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(continued from page 5) stains. Lastly, a chemical cleaning Vassar College numerous and designed to solve a variety product was used to remove heavy Vassar Observatory of cleaning issues. It is essential to follow stains. Poughkeepsie, New York the design professional’s guidelines set forth in the submittals and the The Prudential Insurance Company Congregation Rodeph Sholom manufacturer’s guidelines outlined in the of America Bridgeport, Connecticut Material Safety Data Sheets when Eastern Operations Office implementing a chemical façade cleaning Dresher, Pennsylvania New York Stock Exchange method. Handling and storage, clean-up New York, New York and disposal, and safety and first-aid As part of a comprehensive restora- information should be reviewed in tion effort, Hoffmann Architects Verizon Communications advance. implemented a plan to clean the New York, New York concrete façades of Prudential’s Handling of cleaning wastewater Eastern Operations Office. No Xerox Corporation The runoff from chemical cleaning and chemicals were used during the Corporate Headquarters rinsing operations falls into three cleaning process. To ensure successful Stamford, Connecticut results during pressure washing of the categories: non-hazardous wastewater, acidic/alkaline wastewater that can be facade, consistent parameters—for Xerox Document University neutralized on site, and wastewater type and size of tip, pressure rating Leesburg, Virginia (psi), water flow rate and distance from classified as special or hazardous waste. the substrate—were maintained from United States Capitol Non-hazardous wastewater may be the beginning to the end of the project. Washington, District of Columbia released to sanitary sewers, storm (The Architect of the Capitol) Chase Manhattan Centre sewers, or by soaking into the ground. 1201 Market Street Fred French Building Acidic/alkaline wastewater must be Wilmington, DE 551 contained and neutralized prior to New York, New York release to sanitary sewers—it should Hoffmann Architects utilized a (Metropolitan Life Insurance Company) combination of methods to clean the never be released to storm sewers per Environmental Protection Agency (EPA) polished granite and concrete facades Our Lady of Angels Motherhouse and regulations; the design professional of Chase Manhattan’s one-block-square Chapel should verify in advance the “industrial office complex. Enfield, Connecticut wastewater pretreatment program” of (Felician Sisters of the Order of St. the municipality. Both the polished granite water table Francis) and the concrete façades were water soaked for 12- to 24-hour periods. Hazardous wastewater that contains The water table was further low- compounds such as methylene chloride New York, New York pressure washed at two to four (a paint stripper) must be contained, hundred psi. Areas of heavy stains— pumped into storage tanks and taken to 250 such as the concrete above the loading a licensed Transport, Storage and New York, New York dock that carried the exhaust from Disposal (TSD) facility. countless trucks—were treated with a MetLife Building chemical cleaning agent. Abrasive cleaning methods New York, New York (Metropolitan Life Insurance Company) Of the various methods to clean stone, masonry and concrete, abrasive cleaning Mattatuck Museum is unique in that it is designed to Other Façade Cleaning Projects: Other Façade Cleaning Projects: (Bank of Boston Building) completely remove the outer portion of Waterbury, Connecticut the substrate on which the stain sits, The Hartford Insurance Company The Hartford Insurance Company rather than merely dissolving and Corporate Headquarters Corporate Headquarters washing away the stain. For this reason, Hartford, Connecticut

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(continued from page 7) abrasive cleaning is generally not absorption and other decay processes. JOURNAL is a publication of Hoffmann recommended for restorative facade Architects, specialists in the cleaning projects. Grit blasting, · Grit blasting may increase the need for rehabilitation of building exteriors. grinding wheels, sanding disks, sanding repointing. The firm’s work includes investigative and belts and wet sandblasting (grit rehabilitative architecture/engineering blasting combined with high pressure Cleaning Aluminum services for the analysis washing) all fall into the category of and resolution of problems within abrasive cleaning. New methods, Cleaning architectural aluminum is a roofs, facades, glazing, and structural using very small (20- to 100- micron) relatively simple process. As the strength systems of existing buildings, plazas/ grit and containment of the cleaning and durability of aluminum is not terraces, and parking garages. area, are available which are far less materially affected by dirt or oxidation, Please send news, technical information, intrusive to the substrate. While cleaning is generally necessary only as an address changes, or requests for free abrasive cleaning methods are aesthetic measure. Therefore, the subscriptions to Editor, Hoffmann effective in removing a variety of frequency of cleaning is primarily Architects JOURNAL, 432 Washington surface stains, the limitations associ- determined by the desired appearance Avenue, North Haven, Connecticut 06473. For answers to specific questions ated with the various techniques are of the structure. Other maintenance or for information on the services numerous: with which aluminum cleaning may be conveniently combined and local Hoffmann Architects offers, please contact Sandra Matheny at atmospheric conditions also play roles in · Removal of masonry surface (203) 239-6660. exposes a softer substrate to more determining the frequency of aluminum rapid deterioration. façade cleaning. 432 Washington Avenue North Haven CT 06473-1309 203 239-6660 · Abrasive cleaning techniques are Mild cleaners, solvent and emulsion ineffective in removal of subsurface cleaners, abrasive and etching cleaners, 500 Fifth Avenue, Suite 830 New York NY 10110-0899 staining. steam cleaners and power-driven brushes are among the methods used to 212 789-9915 · The significant amount of dust clean aluminum façades. The building 1001 Connecticut Avenue NW owner and/or manager should consult Washington DC 20036-5525 created by abrasive techniques makes 202 530-1100 the monitoring of progress difficult. with the design professional to arrive at the aluminum façade cleaning method For more information on the · Airborne silica dust present safety that is best suited to their building. topics discussed in this article, hazards; sandblasting is banned in Cleaner concentration and application visit us on the web at many municipalities. time instructions, as well as the www.hoffmannarchitects.com, manufacturer’s safety precautions, should or contact us at · Abrasive cleaning opens the surface be followed carefully to ensure a safe and [email protected]. area of the treated substrate to effective façade cleaning project. Editor: Maryellen Apelquist atmospheric corrosion, water Graphic Services: Maryellen Apelquist

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