Performance standards for historic building exteriors

NYC 9/11 Public Portal Document

Cleaning Methods and Materials: The identification of type of soiling, dust, dirt, or debris and specific building materials (e.g. stone, cast stone, concrete, brick, 'terra cotta) is necessary in order to determine appropriate building cleaning programs.

Stone- Gentle w"p" at7~1eping, and gentle water cleaning with a detergent, is appropriate. Mild acidic and alkaline chemical cleaning can be carefully considered for use based on material appropriateness if detergents are not effective. Air abrasive cleaning can be appropriate if abrasive grit types are carefully considered and tested.

Cast Stone- Gel e~w,ater leaning and gentle water cleaning with a detergent is appropriate.

Brick- Gent-l'er'ateel`tar-ungrand gentle water cleaning with a detergent, is appropriate. Acidic and alkaline chemical cleaning can be considered for cleaning unglazed brick when detergents are not effective. Acidic and strong alkaline chemical cleaning solutions should not be used on glazed brick. Abrasive cleaning can potentially damage brick surfaces.

Terra Cotta- Terra cotta should not be abrasively cleaned, or cleaned with acidic or strong alkaline cleaning solutions as these methods can damage glazes. Waterrcleaning•, or water cleaning in combination with a detergent, is. appropriate.

Health, Safety, and Environmental Issues:

♦t'responsibi~lity'"' f tt a Ar pl,'icant=tTbtariTlilllocall%federalleand~statel ,11?i'sythe permits_prior~to.the,.. comp encenlenttofawork~andfa h,~e'r eitTalil~localtstate>Ean'difederalflaws~w,it - respect the application:and~disposa~l~of;potentia~llh'aza_rdous waste' l ateiialls

Sources: • AIC Ethics and Standards Committee. "AIC Code of Ethics and Guidelines for Practice." Revised August, 1994.

Grimmer, Anne E. "Dangers of Abrasive Cleaning to Historic Buildings." Preservation Brief Number 6. Washington, DC: National Park'Service, 1979.

New York Landmarks Conservancy. Historic Building Facades: The Manualfor Maintenance and Rehabilitation. New York: John Wiley & Sons, Inc., 1997.

Weaver, Martin E. "Removing Graffiti from Historic Masonry." Preservation Brief Number. 38. Washington, DC: National Park Service, 1995.

Note: National Park Service Preservation Briefs, including those references in these performance. standards, are available on the Internet; Keyword Preservation Briefs.

19

NYC-WTC 000093730