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By David A. Deress
July 2012 -
Facilities Management Article Use Policy
Experienced forensic building envelope consultants know water infiltration is the most common problem for building envelopes on institutional and commercial buildings. While some cladding assemblies might be inherently more vulnerable to damage from water infiltration than others, the problem can affect any cladding system.
Water-infiltration problems commonly take place where cladding systems meet other envelope materials and systems. The challenge for maintenance and engineering managers is to develop maintenance and repair strategies — both proactive and reactive — that effectively target these areas.
Regardless of type, cladding systems are designed and expected to perform flawlessly within the field of the system. Maintenance for the field of the wall might be as simple as washing it occasionally, recoating the surface, or repointing mortar joints in masonry. Water infiltration concerns are consistently a question of the effectiveness of the cladding system where it interfaces with other systems or components.
Providing continuity of the water tightness of the wall across one system to the next is a common weak point that normally requires the most attention in maintenance. An interface is not just where two systems meet — for example, a curtain wall meets a masonry veneer wall. It also includes penetrations through the cladding system at building components, such as windows, outlets, light fixtures, louvers, and fenestrations.
Regardless of the components that make up the interface, sealant joints often are part of the assembly. If sealant joints were not part of the original design and construction, sealant installation is a common repair tactic to stop leaks because it is inexpensive and faster to install, compared to disassembling the interface detail and reworking it to improve its performance. It is easy to seal every joint within reach to solve a problem, but the risk is that tactic will not be effective or, worse, that it will cause more problems because it traps water that once could drain out.
Sealants are widely used on or in the interfaces of adjoining cladding systems to make them watertight, so it is essential that workers inspect and maintain sealants to provide the expected performance. Sealant joints might be the only line of defense against water infiltration in certain areas, such as at the perimeter joint between a window and the wall cladding.
Sealants are also critical elements in the assembly of cladding systems. For example, curtain walls and storefront-style fenestration systems have their own component-to-component interfaces that typically rely on sealant joints applied internally, as the systems are installed with gaskets at the frame-to-glass interface. These systems generally resist most water penetration at the exterior surface, with only incidental water expected to infiltrate the system, where it is collected and allowed to drain out.
When these systems do not function as designed, one common solution is to apply sealant to all joints exposed to the exterior to make system-assembly interfaces as watertight as possible. This tactic can work and be economical, but it also can trap water if a joint fails. The repair also requires expanded inspection and maintenance to keep sealed joints watertight.
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