Green Roofs - Living Architecture Monitor - Summer 2018 - 32

IRMA VS CONVENTIONAL INSULATED ASSEMBLIES

FIGURE 1: When the membrane is applied
directly to a structural concrete deck, the
concrete provides excellent grounding for the
test currents.

FIGURE 2: Whether conducting High or Low
Voltage testing, breaches will not be detected
when there are electrically insulating
materials between the membrane and the
conductive deck.

FIGURE 3: Insulated assemblies can be
accurately tested when there is an alternative
ground installed directly below the membrane
to accept the test currents.
LIVING ARCHITECTURE MONITOR / SUMMER 2018 / 32

ELD testing is straightforward and extremely reliable when the membrane is applied
directly to a highly conductive substrate such as a structural concrete deck (see Figure
#1). The test currents travel through any breaches and easily connect to a readily available ground. However, ELD is also becoming the go-to integrity test on conventional
roofing systems, with insulation installed between the membrane and the conductive
deck. The same properties that make insulations and coverboards thermal insulators
also create electrical resistance to the current utilized with ELD (see Figure #2). The
presence of these poorly conductive and nonconductive materials prevents the test
currents from reaching the conductive deck. These assemblies cannot be reliably
tested unless an alternative grounding material is placed directly under the membrane
to receive the test currents (see Figure #3). When the alternative ground is needed
but not specified there can be significant confusion for all parties, since roofing and
waterproofing contractors will need to purchase and install an alternative grounding
product that is not in the specification.

SPECIFYING ALTERNATIVE GROUNDS

In 2014 ASTM released Standard D7877, providing guidelines for ELD testing on
these conventional insulated systems:
"In roof assemblies where the membrane is installed over electric insulating material such as insulating foam or a protection board, or both, the electric path to any
conductive deck is interrupted. The situation can be remedied by placing a conductive
material directly under the membrane. The conductive material provides the return
path for the test currents."
To ensure compliance with the ASTM Standard, the design community can specify
similar language in the design documents, for example:
"In assemblies where the deck is not electrically conductive or there are nonconductive materials installed between the waterproofing membrane and the conductive
deck, e.g. insulation, coverboards, vapor retarders, etc., an alternative grounding
medium must be installed directly under the membrane to accept the Electronic Leak
Detection test currents."
By requiring an alternative ground in the assembly, specifiers can ensure that a thorough and accurate Electronic Leak Detection survey can be performed.

BETTER SPECS MAKE BETTER TESTING

ELD specifications also often fail to adequately define the requirements for a highquality survey, regardless of the type of assembly being tested. As with any other aspect
of construction, ELD specifications should be robust, and include requirements for
provider experience, equipment employed, testing procedures followed and deliverables.
In many instances, several of these important aspects are incomplete or absent, and in
some cases documents may only contain one line referencing this critical integrity test
(e.g. "Perform an electric integrity test of the membrane.").
If in doubt about the how to specify Electronic Leak Detection for a certain assembly, architects, engineers and designers can request the assistance of experienced
ELD service providers. Independent third-party firms can help specifiers navigate
alternative ground options and the different types of leak detection testing available.
With this valuable assistance, specifications can be written to ensure that experienced
personnel employ appropriate technologies, correct leak detection procedures are
followed, and a high-quality report will be delivered. Properly specified and applied,
ELD testing will help us all deliver higher quality, more trouble-free assemblies.
1. ASTM D7877-14, Standard Guide for Electronic Methods for Detecting and Locating
Leaks in Waterproof Membranes. ASTM International
Peter Brooks has been performing nondestructive testing for over 36 years and is a former
Director of Roofing Consultants Institute Region I. peterb@iranalyzers.com.
LIVINGARCHITECTUREMONITOR.COM

http://www.LIVINGARCHITECTUREMONITOR.COM

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Summer 2018