The Impact of Hail on Membrane Roofs

May 20, 2015

When hail (even pea-sized) hits the roof of your commercial/industrial building, damage is inevitable. A quick visual walk-over can reveal obvious punctures to the membrane even to the untrained observer, but what is just as concerning is the destruction you don’t see.

Common Types of Hail Damage

These damages accelerate degradation of the roof system, causing loss of durability, efficiency, and reduced service life. Unlike damage caused by windborne debris or foot traffic which is isolated, hail damage is often widespread. A recent assessment by D. C. Taylor Co. of a hail-damaged shopping center roof revealed more than 200 punctures in a 100-square-foot area, with compressed dents in the polyiso insulation board of up to 0.75-inch depth.

What to Expect When You Inspect

Whenever you feel that your roof has sustained damage from a storm, regardless of whether it produced hail stones, it’s best to hire a professional to conduct a thorough roof inspection.

While ASTM Intl. does not produce any standards or guides that define a method for the assessment or evaluation of hail damage to membrane roofing systems, generally recognized methods can be employed to determine the level of property loss.

Visual inspection

A trained professional will be able to walk the roof in a traverse pattern and, often using magnification instrumentation, identify physical irregularities such as micro-cracking, abrasion, evidence of compression, tension, flexure, and over-bending.

Destructive Testing

Areas identified with a large number of irregularities may require further physical examination. Because much of the damage sustained during a hail storm lies beneath the surface, you should expect that some destructive testing will occur.

A knowledgeable roofing contractor will clean the area; remove debris, water, and dust; and scrub the surface of the membrane. The top surface will be examined, and indentations will be marked and counted. A large square area of the membrane will be cut on three sides and folded back to expose the bottom surface. Again, indentations will be counted and marked.

The insulation will also be carefully examined and indentations marked. Photographs should be taken as a part of the inspection records. Hail impacts will be carefully examined to document conditions and determine changes to the materials and components and type and extent of the damage.

Samples may be taken for further examination. The insulation and membrane will be replaced and where appropriate, fasteners installed. The membrane will be cleaned and primed before self-adhesive joint covers are applied and rolled to secure adhesion. Voids will be checked to insure a watertight seal.


The area may also be examined using an infrared camera and/or moisture meter. This instrumentation will provide another visual examination and help reveal additional hail impacts and the moisture level of the roof membrane and insulation substrate.

Rather than wait until small, often unforeseen damage escalates into wet insulation and roof leaks, call in the pros. “If you have hail, you need to have a professional come and inspect,” advises Roy Rambo, Project Manager, D. C. Taylor Co., Cedar Rapids, IA.

Contact D. C. Taylor Co. today to schedule a roof inspection!

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