Georgia-Pacific Building Produts

DensDeck® Roof Boards / Superior Hail Resistance in a Cover Board

DensDeck® Roof Board, with its high-compressive strength, provides the ideal cover board in commercial roofing assemblies where membrane, insulation and other components are vulnerable to damage caused by different types of impact - notably large-sized, fast-moving hail.

When a "large hail event" occurs, as defined by the National Weather Service1, the damage to a commercial roofing system can be catastrophic and costly. Even a single occurrence can cause cracks and punctures that can allow moisture to penetrate into the membrane and below - causing problems that are expensive to correct. This is especially true for large single-ply membrane roof systems with extensive surface area.

DensDeck® Roof Boards Prevail in Third-Party Hail Testing1

Extensive hail testing at the laboratories of Jim Koontz & Associates2, showed that DensDeck® Prime Roof Boards consistently display superior puncture and impact resistance, protecting thermoplastic roofing membranes better than high-density polyisocyanurate (HD ISO) cover boards.

Third-party testing during 20141 revealed that:


DensDeck® Roof Boards are more resilient during simulated hail events, and less likely to allow membrane damage;

compared to identically-tested roofing assemblies featuring high density polyisocyanurate (HD ISO) boards.


See the difference when a "freezer ice ball" simulating tennis ball-size hail (2.5-inch diameter) is fired at an assembly -

• first with an HD ISO coverboard;

• then with DensDeck® Prime Roof Board. Play the Movie.


The 2.5-inch ice ball fired into 1/2" HD ISO cover board shows
53% deeper indentations (0.132")


…compared to results using a 1/4" DensDeck® Prime Roof Cover Board (0.086").


In FM 4473 testing, using 1.5" to 2.5" ice balls, assemblies with


HD ISO or no cover board showed 25-30% greater indentation with a 2.5-inch ice ball


…compared to results using a 1/4" DensDeck® Prime Roof Cover Board (0.086").

1 National Oceanic and Atmospheric Administration, noaa.gov/features/03_protecting/hail.html

2 Hail testing (or impact resistance testing of rigid roofing materials by impacting with freezer ice balls) conducted by Jim Koontz & Associates July 21 - August 1, 2014, in its Hobbs, N.M. laboratory, according to FM 4473 (using NBS 23 standards). Based on average results using 1-1/2" to 2-1/2" freezer ice balls. Assemblies included a base layer of 2", 20-psi polyisocyanurate insulation; and configurations were covered with 45 mil thermoplastic polyolefin (TPO) or 48 mil polyvinyl chloride (PVC) membranes.

DensDeck® Prime Roof Board Stands Up to Hail

The 2014 test series at Jim Koontz & Associates simulated the impact of hail in a variety of roofing scenarios, producing consistent results throughout testing.

FM 4473 (using NBS -- National Bureau of Standards -- 23 standards) hail test results² indicate that DensDeck® Prime boards offer key benefits against hail damage versus HD ISO products:

  • Less likelihood of membrane damage - assemblies with DensDeck Prime panels exhibited less indentation that stressed the membrane and that can potentially result in membrane failure.
  • More resilience during hail events - assemblies with DensDeck Prime panels withstood larger hail sizes that may cause cover board fractures.

Protection When Warranties Fall Short

Hail damage is typically not covered under traditional roofing warranties. Today's building owners and facility managers are all too aware that roof damage from a single hail storm can run into the hundreds of thousands of dollars. As part of a hail-resistant roofing solution, DensDeck roof cover boards add impact resistance to the roof surface - in turn helping minimize inventory loss, building down time and repair costs when hail storms occur.

How May We Assist You?

For more information or to find a DensDeck® specialist in your area call 1-800-226-6119 or click to send your request.



For recommendations and limitations of use for DensDeck Roof Boards, click here to download the technical brochure. Georgia-Pacific Gypsum does not warrant or provide specifications for any specific roofing assembly or any component other than DensDeck Roof Boards. Consult with the appropriate system manufacturer or design authority for system specifications and instructions.

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