Identifying watertightness of low-slope roof membranes

by Dominique Lefebvre, P.Eng., and Bas A. Baskaran, PhD, P.Eng.

Photo courtesy GAF
Photo courtesy GAF

An accurate assessment of the watertightness of new and existing roofs can potentially save building owners hundreds of millions of dollars annually. The challenge for roofing specifiers is choosing the most effective exterior-to-interior watertightness evaluation techniques.

The fact is there is no single, straightforward method to accurately evaluate water ingress from the exterior roof membrane to the interior of the building. This has led to confusion among specifiers as to which method is most appropriate for a particular type of roof, and what information each test provides.

This dilemma has led the Roofing Industry Committee on Weather Issues (RICOWI) to review existing water-detection techniques to identify:

  • methods of operation;
  • capabilities of the tests;
  • test compatibility with various components; and
  • benefits and the shortcomings of each test procedure.

RICOWI’s Moisture Control and Green Committee led this investigation, as the group focuses on moisture-control issues and identifies specific roof performance metrics. Committee membership consists of manufacturers, property owners, and academics to ensure a diverse roofing community representation.

Addressing watertightness of roofs

While roof-evaluation techniques require access to the entire roof surface, they can narrow down potential problems, such as the HVAC penetrations on this roof. Photo © BigStockPhoto.com
While roof-evaluation techniques require access to the entire roof surface, they can narrow down potential problems, such as the HVAC penetrations on this roof.
Photo © BigStockPhoto.com

The main function of any roof is to prevent water entry into a building. This leads to the fundamental question of how to assess the watertightness of a roof assembly.

Watertightness detection is needed for both new and existing roof systems. For new construction, this watertightness evaluation provides confirmation to the property owner the roof was properly installed, and as such, can be used as a field commissioning tool.

For existing construction, a watertightness evaluation can be employed for the following two purposes:

  • to assess the current roof condition and determine if replacement is required after confirmation from test cuts and professional insight; and
  • to evaluate if the watertightness capacity of a roof was compromised after a major weather event.

From the perspective of the roofing specifier and property owner, effective nondestructive roofing and waterproofing testing can provide various practical benefits. For example:

  • pinpointing, documenting, and repairing wet roof areas to limit further damage to commercial low-slope roofs;
  • reducing the risk of structural damage and potential failure of new or existing roof systems;
  • identifying sound roof sections and replacing wet insulation to conserve time, materials, and energy use; and
  • targeting problem areas to accurately budget roof maintenance and improve specifications for competitive bidding procedures.
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