Test, repair, test again (repeat as necessary)

Water leakage during initial diagnostic testing identified deficiencies in the flashing above the head of the window assembly. Photos courtesy WJE

When evaluating an existing building enclosure (or component thereof) for sources of reported water leakage, it is important to follow an appropriate systematic testing program that targets specific components and/or interface conditions to identify those that are contributing to the leakage. Through this process, a clear understanding of mechanisms necessary to create water transport through the system should also be developed (i.e. air pressure differentials, effectiveness of drainage provisions, water accumulation within the system, etc.), to ensure an effective repair approach is developed. It is also important diagnostic testing be appropriate to recreate conditions that result in the reported leakage and not so severe as to create other ‘leak sources’ which mask the actual problem(s). There are several guides available to assist in identifying sources of water leakage in building enclosures, such as ASTM E2128, Standard Guide for Evaluating Water Leakage of Building Walls, and AAMA 511, Voluntary Guideline for Forensic Water Penetration Testing of Fenestration Products; however, the appropriateness of such guides (or parts thereof) should be determined by a knowledgeable investigator, as testing procedures outlined may not necessarily apply to the particular building under study. It is also important to understand there is a difference between diagnostic and performance verification testing and experience has shown enclosures reporting in-service water leakage often leak during diagnostic testing without a static air pressure difference being induced across the plane of the enclosure.

Water leakage resulting from discontinuities in sealant at splices in subsill component, identified during verification testing following repair of the head flashing. 

Once sources of water leakage have been identified, and repairs to address conditions of concern developed, repairs should be implemented on a trial basis and tested for effectiveness and to determine if additional sources of leakage exist. (The identification of additional sources of water leakage during this process does not indicate the initial diagnostic process was ineffective but highlights the complexity of enclosure systems and the comprehensive approach often required to fully diagnose leakage sources.)

As an example of this iterative testing process, a recently installed sophisticated operable window system was reportedly experiencing widespread water leakage along its head extrusion during prolonged wind-driven rain events, resulting in wetting of much of the interior of the window assembly and water ponding on the floor slab. Conditions replicated during initial diagnostic testing revealed localized abandoned fastener penetrations in the through wall flashing above the head of the window as a significant contributing source of water leakage. The flashing system was repaired to correct this condition and the assembly was retested to verify the effectiveness of the repair. During verification testing, while water leakage was eliminated at the head of the system, water leakage (originally masked by the extent of water leakage during initial testing) occurred at the sill of the system. Subsequent diagnostic testing revealed deficiencies at the subsill splices were also contributing sources of water leakage associated with the window assembly. Retesting of the system following subsequent repairs to the subsill resulted in verification that all sources of water leakage had been identified and properly remediated. (Had verification testing not been performed following the initial repair, a source of water leakage would have remained, leaving the assembly still vulnerable to leakage in the future.)

Jeffrey Sutterlin, PE, is an architectural engineer and associate principal with the Princeton, New Jersey office of WJE, specializing in investigation and repair of the building envelope. He can be reached at jsutterlin@wje.com.

David S. Patterson, AIA, is an architect and senior principal with WJE’s office in Princeton, New Jersey. He specializes in investigation and repair of the building envelope. He can be reached at dpatterson@wje.com.

The opinions expressed in Failures are based on the authors’ experiences and do not necessarily reflect that of The Construction Specifier
or CSI.

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