Track 5 - TALL / Presentation 2
Evolution of Design Standards for Mid-Century Thin Marble Building Skins, 1940 - 1980
Lurita McIntosh Blank, NCARB, RBEC, APT RP
Principal; Raths, Raths & Johnson, Inc.
lmblank@rrj.com
Thin stone wall systems use two-inch and thinner stone panels as the primary weather barrier and aesthetic finish for a building’s façade. These systems evolved with the modern curtain wall and rose in popularity as a mid-century façade technology and continue in regular use today. Despite the growing appreciation for modern heritage, many of the important early examples of these façade systems are in the “shoulder season” of architectural fashion – old but not yet vintage. Unfortunately, thin stone wall systems often age ungracefully due to a poor understanding of long-term stone behavior, poor waterproofing performance, and an inability to manage condensation. Additionally, the lack of mass in a thin panel of stone means that these systems are susceptible to large thermal movements which can stress panel anchors. Insufficient panel support and lack of anchorage redundancy can cause seemingly spontaneous failures. Infamous failures of thin stone panels are well-known in the industry, but for every Finlandia Hall, there exist dozens of facades of lesser recognition with equally critical performance concerns.
The evolution of thin stone wall systems followed fascinating changes in architectural taste, industry standard development, building code, façade engineering, and construction technology. In early examples, these systems were mounted more like traditional dimension stone cladding, but by the latter half of the twentieth century, it was not uncommon for thin stone walls to eliminate the backup entirely, anchoring the stone panels directly to the structural frame, in truss configurations, or as panels captured within a curtain wall system. As more mid- and late-century commercial buildings cross the age threshold into “historic,” engineers and architects engaged in restoration of more traditionally historic buildings will increasingly encounter thin stone wall systems. Understanding the historical development of these systems is foundational to understanding their distress pathologies and failure modes, as well as for conveying the historical significance of the façade technology itself.
This presentation will review the birth and development of thin stone walls through comprehensive and original research conducted on the technical publications, design guides, and industry standards published from the 1940s into the 1980s. Attendees to this presentation will gain not only an understanding of the history of design of thin stone wall systems but how the historical design guides can inform the preservation of these systems for the future. Practical application of evaluation methodologies, stabilization strategies, and preservation approaches will be reviewed through case studies, with an in-depth review of one of the earliest known thin stone veneer buildings in the United States – the Dental Branch Building.
Designed in 1951, the Dental Branch Building was clad in extremely thin panels of Georgia Etowah (Pink) Marble, quarried in Tate County, Georgia. Thin stone applications on building exteriors were unknown in Houston at the time, requiring the design architects to successfully petition for a change in the local building code. Mounted as stacked panels with wire tie anchors, the façade used 5/8-inch and 7/8-inch-thick large dimension marble panels. Over time, distress and deterioration of the cladding led to performance issues and localized failures. This case study and other thin stone wall systems will be used to demonstrate the evolution of the façade system, stone material behavior in thin panels under varying installation conditions, and condition assessment and investigation methodologies for thin stone wall systems. Stabilization and repair challenges will be discussed with focus on understanding the impact to a better approach for preservation of this important architectural technology.
Lurita McIntosh Blank, NCARB, RBEC, APT RP, is a Principal with Raths, Raths, & Johnson, where she leads the historic preservation and federal services. She specializes in materials conservation, façade restoration, and stone consulting. Lurita is a Registered Architect, a Registered Building Envelope Consultant through IIBEC, and a Recognized Professional through APT.
