Track 4 / Presentation 1
Tufa Limestone Construction and Preservation Challenges: San Antonio Churches of Missions San José and Concepción
Anna Nau
Senior Associate, Powell & Carson Architects and Planners, Inc.
Quentin Collette, PhD
Director, New History
anau@fpcarch.com
collette@newhistory.com
The understanding of deterioration patterns, deformation and/or distress in historic stone constructions can be challenging to practitioners often lacking information on their original construction and material properties. In particular, the assessment of buildings constructed out of tufa – a type of limestone – requires specific knowledge and expertise given the soft and porous structure of this stone. Practitioners need in-depth information on the construction and properties of historic wall systems made of tufa to understand deterioration patterns and develop suitable restoration strategies allowing to restore both architectural and structural integrity. Therefore, we assessed the construction history, performed site investigations, and implemented pilot restoration treatments on tufa constructions to support restoration strategies. This paper discusses the construction techniques and properties of historic tufa wall systems and attempts to establish best-practice treatment approaches to help arrest water-induced deterioration patterns. The research used the Missions San José and Concepción churches located in San Antonio, Texas, as a case study.
The Missions San José and Concepción churches are constructed primarily out of tufa limestone, with some sandstone, and micritic limestone used at the carved façades. Tufa is generally characterized by its porosity, water permeability, and low compressive strength. Historic tufa wall systems at the churches historically featured stucco coatings acting as a protective, sacrificial wall covering, which provided some water impermeability to the wall systems. Today wall areas where stucco is eroded or missing allows for water infiltrations causing deterioration of the tufa, mortar joints, and interior wall finishes. Pilot restoration treatments for stucco and tufa were performed at the sacristy of Mission San José and the bell towers of Mission Concepción between 2011 and 2019. These pilot programs have established a sequence of treatments for mortar joint repointing and stucco restoration to reduce moisture levels within the wall systems. Pilot treatments evidenced the need to instate systematic repointing at exterior wall faces to reduce water infiltrations. In addition, it is suggested to restore stucco at wall areas that were historically finished with stucco. However, such stucco restoration poses philosophical questions about the exterior appearance of the churches. This research added to our understanding of historic tufa wall systems and the preservation of the San Antonio Mission Churches.
SOURCES:
Building and Monument Conservation and Ford, Powell & Carson Architects and Planners, Inc. December 2013. “Sacristy Window, Mission San José y San Miguel de Aguayo, Phase I Treatment Report.” Report.
Building and Monument Conservation and Ford, Powell & Carson Architects and Planners, Inc. January 2015. “Sacristy Window, Mission San José y San Miguel de Aguayo, Phase II Treatment Report.” Report.
Building and Monument Conservation. March 2019. “Treatment Report for the Upper North Tower, Mission Concepción, December 2018.” Report.
Conservation Associates. 2012. “Mission Concepción Exterior Finishes Survey 2011.” Report
Conservation Associates. 2013. “Mission Concepción Pilot Conservation Treatment and Emergency Stabilization Report, 2013.” Report.
Conservation Associates. 2019. “2019 Emergency Stabilization of the Historic Polychrome Stuccos and Conservation Treatment Planning for Mission Concepción, San Antonio, TX.” Report.
Fisher, L.F. 1996. Saving San Antonio: the Precarious Preservation of a Heritage. Lubbock: Texas Tech University Press.
Ford, Powell & Carson Architects and Planners, Inc. June 2016. "San Antonio Mission Churches. Conditions Assessment 10-Year Update." Vol. 1. Report FPC # 05890.
United States Department of the Interior. 2014. San Antonio Missions, Texas, United States of America: Nomination to the World Heritage List by the United States of America. UNESCO World Heritage Nomination Dossier.
Anna Nau is a Senior Associate at Ford, Powell & Carson Architects in San Antonio, where she has worked for over a decade on award-winning preservation and rehabilitation projects. She serves as project manager for the firm’s work at the San Antonio Mission churches and was part of the writing team for the San Antonio Missions’ successful nomination to the UNESCO World Heritage List in 2015. She holds a MA in architectural history from the University of Virginia, a MSc in architectural conservation from the University of Edinburgh, and a PhD in architecture and historic preservation from the University of Texas at Austin.
Quentin Collette, PhD is a Director at New History in Minneapolis, MN. He provides building documentation and assessment, design solutions, and project management services to New History’s projects and clients. He brings a unique background of business management, specialized experience in the assessment and design of historic structures, and construction history to the team. His education and project experience includes local, national, and international sites. Quentin is a frequent speaker at national and international conferences with publications in professional journals. He is an active member of North American and European preservation and construction history networks.
NAU - PUBLICATIONS:
Nau, A. 2019. “Ruskin, Morris and the Arts and Crafts Idea.” In The Rise of Everyday Design: The Arts and Crafts Movement in Britain and America. Penick, M. and Long, C. (eds.). p. 37-49. New Haven: Yale University Press.
Nau, A., and Q Collette. 2018. “Church of Mission San José, San Antonio: Using Construction History to Inform Preservation Approaches.” In Proceedings of the Sixth International Congress on Construction History (ICCH 2018), London: CRS Press (Taylor and Francis Group).
Nau, A. 2017. “Heritage and Identity in the Early Twentieth Century Preservation of the San Antonio Missions.” Arris: The Journal of the Southeast Chapter of the Society of Architectural Historians 28: 30-45.
COLLETTE - PUBLICATIONS:
Collette, Q. 2017. “Investigation of the Reinforced-concrete Construction of the Dotremont House in Brussels.” APT Bulletin 48 (1): 40–46.
Collette, Q, Wouters, I, D'Aniello, M & Landolfo, R. 2016. “Impact of the hot-driving process on the strength and ductility of steel rivets.” Proceedings of the 10th International Conference on Structural Analysis of Historical Constructions. Van Balen, K. & Verstrynge, E. (eds.). p. 1308-1315. Leiden: CRC Press/Balkema (Taylor and Francis Group).
Collette, Q, and I Wouters. 2015. “Unraveling the Design of End-of-the-19th-Century Riveted Connections in Belgium.” In Proceedings of the Fifth International Congress on Construction History (ICCH 2015), 1:481–90. Chicago: Construction History Society of America.
