Curtain-wall Cautions: How to Avoid Installation Problems

April 29, 2007
Publication: Glass Magazine
Author(s): Derek McCowan Brown, Mark A. Michael Louis

Abstract: Exterior wall construction has evolved during the past century and a half. We have moved from massive masonry walls that support the floors of a building to slender walls that hang off the slabs. The heavy load-bearing masonry walls of the past absorbed rainwater and dried to the inside and outside. Contemporary glass and metal curtain walls rely on sealants and gaskets to prevent leakage to the interior. A small defect in these joint seals can lead to leakage into the wall system that likely includes gypsum wallboard and other materials that deteriorate quickly.|Modern glass-and-metal curtain walls have become popular because of their sleek appearance, light weight and, most importantly, the speed at which they can be used to close in a building. "Stick-built" or field-assembled systems are typically erected mullion by mullion, similar to a child's erector set, and infill panels of glass, metal or stone are glazed into the openings during erection or shortly thereafter. "Modular," or "unitized," curtain-wall systems include large multipanel sections or modules that are assembled and glazed in the factory and placed on the building using a crane or hoist. Modules include gasketed mullions at the perimeter that interlock with the perimeter mullions of the adjacent modules. Both stick-built and modular systems generally require significantly less time to install than more traditional backup walls and cladding, an important factor during these times of high labor costs and aggressive construction schedules.|Glass-and-metal curtain walls can provide an attractive, durable and cost-effective cladding solution, but in many buildings, these wall systems are plagued with problems ranging from air and water leakage to falling trim covers.|This article discusses some of the most common curtain-wall design problems that afflict owners, architects and developers. A second article will discuss design issues, and the final article will cover fabrication and construction related issues and items relating to laboratory and field testing.