Sharon C. Park, AIA is the Senior Historical Architect, Technical Preservation Services, Heritage Preservation Services Program, National Park Service, Washington, D.C. The author wishes to thank the following individuals and organizations for providing technical review and other assistance in developing this publication: The attendees, speakers, and sponsors of the Diagnosing Moisture in Historic Buildings Symposium held in Washington, DC in 1996 and funded by a grant from the National Center for Preservation Technology and Training, National Park Service ; Hugh C. Miller, FAIA; Michael Henry, AIA, PE, PP; Baird M. Smith, AIA; Ernest A. Conrad, P.E.; William B. Rose; Rebecca Stevens. AIA; Wendy Claire Jessup; Elizabeth Sasser, AIA; Bryan Blundell; George Siekkinen, AIA; Larry D. Dermody; Kimberly A. Konrad; Barbara J. Mangum and the Isabella Stewart Gardner Museum, Boston; Gunston Hall Plantation; Friends of Meridian Hill; Friends of Great Falls Tavern; The National Trust for Historic Preservation; Thomas McGrath, Douglas C. Hicks and The Williamsport Preservation Training Center, NPS; the staff at Heritage Preservation Services, NPS, Charles E. Fisher, Brooks Prueher, Anne E. Grimmer, Antoinette Lee, and especially Kay D. Weeks.This publication has been prepared pursuant to the National Historic Preservation Act, as amended, which directs the Secretary of the Interior to develop and make available information concerning historic properties. Comments about this publication should be directed to de Teel Patterson Tiller, Acting Manager, Heritage Preservation Services Program, National Park Service, P.O. Box 37127, Washington, DC 20013-7127. This publication is not copyrighted and can be reproduced without penalty. Copyright photographs included in this publication may not be used to illustrate publications other than as a reference to this Preservation Brief, without permission of the owners. Normal procedures for credit to the authors and the National Park Service are appreciated.

Washington, DC October, 1996

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