See the following, Chambers, J. Henry 1976 Cyclical Maintenance for Historic Buildings. Office of Archeology and Historic Preservation, National Park Service, U.S. Department of the Interior. Washington: Government Printing Office. I bought my copy directly from GPO for $2.75 in 1978, so don't know whether it is still available for sale. Mike -- Mike Jacobs * Arizona State Museum * University of Arizona * Tucson, AZ 85721 Tel: (602) 621-6312 * Fax: (602) 621-2976 * Email: [log in to unmask]