Historic preservation guidelines are becoming an increasingly larger factor in the commercial construction industry, thanks to the Economic Recovery Tax Act of 1981 and an emerging social attitude that older buildings have intrinsic value. In other words, historic preservation is going “mainstream,” and is no longer restricted to museums and other nonprofit applications.
The Secretary of the Interior's Standards for Historic Preservation state that “surface cleaning of structures shall be undertaken with the gentlest means possible. Sandblasting and other cleaning methods that will damage the historic building materials shall not be undertaken.” The guidelines for application of the standards make reference to the more detailed preservation briefs for additional guidance.
Preservation Brief No. 1, “The Cleaning and Waterproof Coating of Masonry Buildings,” discusses various cleaning methods, but without definitive conclusion. While the brief provides the reader with valuable information, there is still a need for further information in determining what constitutes “the gentlest means possible.”
It is the purpose of this paper to equip the reader with adequate information and a procedure for selecting the most appropriate cleaning method for a given project in terms of adherence to historic preservation standards. This will include an amplification on the role and merits of “water-safe” cleaning technology.
The principles described are exemplified in terms of specific projects undertaken by Clean-America, Inc., and are illustrated by means of photographs and data relating to specific details.