Influence of Design on the Service Life of Indirectly Fastened Natural Stone Cladding

Abstract

Indirect fastening is not yet a well-vetted method for attaching stone cladding from the point of view of designers and contractors, and a high incidence of failures has been observed in the field, suggesting inadequate design or inappropriate installation specifications. In fact, it has been shown that inadequate design is often responsible for significant defects that subsequently arise over the course of the facade life cycle. This study is intended to help determine the influence of cladding design parameters on the service life of natural stone cladding with an indirect fastening system. For that purpose, a survey of the state of degradation of 142 buildings in the Lisbon area was performed, based on visual inspections that allow describing the extent of the cladding area affected by the different anomalies evident on the cladding. A weighted numerical index of the extent of the cladding’s degradation (Ew) is established, thereby allowing identifying both the positive and negative impacts of each design characteristic on the service life of an indirectly fastened natural stone cladding system. This study analyzes the influence of parameters such as the type, size, color, density, and type of finishing of the stone plates; the location of the cladding in the facade; and the characteristics of the fastening system. The results obtained reveal that claddings with larger stone plates, with natural stones of lower density, located in taller areas of the buildings and with dowels located at less than 1/5 of the plate’s length from the corners present a higher incidence of defects, with higher deterioration rates. The information obtained in this study can be used by designers in order to mitigate the negative impact of some design characteristics, adopting adequate solutions that increase the durability and service life of indirectly fastened natural stone claddings.