NEGATIVE PRESSURE ROOF UPLIFT TESTING

David Amori, PE, RRC

NEGATIVE PRESSURE TESTING

NEGATIVE PRESSURE TEST

Description Using negative pressure to simulate and

test resistance to wind induced uplift on a membrane roof system.

NEGATIVE PRESSURE TEST

Test Summary Test pressures are obtained from the structural

engineer and/or governing agency. These usually include field, perimeter, and corner test pressures.

The apparatus is installed and pressure is gradually increased to the test pressure in 7.5 psf increments (held for one minute) while simultaneously recording the deflection of the membrane.

Failure is 0.25 to 0.94 of an inch deflection (FM) and one inch (ASTM).

NEGATIVE PRESSURE TESTING

NEGATIVE PRESSURE TESTING

NEGATIVE PRESSURE TEST

Test Summary Failure are typically cut open to make

observations regarding the failure mode Material Failure Delamination Fastener Pull Substrate Failure

NEGATIVE PRESSURE TEST

Application Insurability for specific carriers

Factory Mutual TWIA

Code Compliance New Construction Design Compliance

NEGATIVE PRESSURE TEST

Application Risk Assessment – as part of the evaluation

of a property this test is used to determine probable loss at incremental pressure (Hurricane Strengths).

NEGATIVE PRESSURE TEST

Relevant Standards ASTM E 907 – 96 (Reapproved 2004): Field

Testing Uplift Resistance of Adhered Membrane Roofing Systems

FM Global 1-52: Field Uplift Tests

WIND

WIND

25 psf

~ 25 psf

WIND

25 psf

25 psf

For roof slope < 7 degrees

45 psf70 psf

WIND

AFTER THE STORM

WIND DAMAGE DELAMINATION

WIND DAMAGE DELAMINATION

WIND DAMAGE DELAMINATION

WIND DAMAGE DELAMINATION

WIND DAMAGE FASTENER FAILURE

WIND DAMAGE FASTENER FAILURE

BEFORE THE STORM

NEGATIVE PRESSURE TESTING

NEGATIVE PRESSURE TESTING

FASNTERS RESISTING PRESSURE

FASNTERS RESISTING PRESSURE

FAILURE ANALYSIS - MATERIAL FAILURE

MATERIAL DELAMINATION

FAILURE ANALYSIS – CONSTRUCTION DEFECT

LACK OF TORCH

ROOF UPLIFT TESTING