A High-Performance Mitigation Layer Cover Board

Why DensDeck^® Prime Roof Board?

DensDeck Prime Roof Board is engineered specifically for roofing applications, providing a durable cover board layer that helps strengthen and protect the entire roof assembly.

Its glass-mat-faced gypsum core delivers exceptional fire performance* along with compressive strength and resistance to challenging roof system conditions.

For nearly 40 years, DensDeck Prime Roof Board has been a proven solution trusted by specifiers, roofing system manufacturers, and contractors across the United States to enhance roof system resilience and long-term performance.

Benefits of Our Flat Roof Cover Boards

DensDeck Prime Roof Boards deliver multiple performance benefits that help strengthen and protect the entire roofing system.

Acting as a durable cover board and mitigation layer within the roof assembly, they enhance fire safety, improve resistance to wind uplift and impact, and protect critical insulation and membrane components.

Their compressive strength, acoustic control, and dimensional stability help roofing systems perform reliably under demanding conditions while supporting efficient installation and long-term system durability.

Understanding the Core Material

Gypsum is a mineral widely used in building materials because of its natural fire-resistant and stable properties. In DensDeck Prime Roof Board, the gypsum core is engineered specifically for exterior roofing applications to perform within demanding commercial roof assemblies.

A siliconized gypsum core provides structural stability and dimensional durability, while fiberglass mat facers on the front and back surfaces help protect the board and support resistance to impact and fire exposure.

With its enhanced gypsum core, coated face and back glass mats, DensDeck Prime Roof Board provides multiple benefits including increasing the force required to puncture the waterproofing layer vs. force required without a cover board.

DensDeck Prime Roof Board continues to provide a broad compatibility and high performance with many roofing adhesives, and in many cases no primer is needed when bonding directly to the coated face. Suitability for direct bonding or torching to DensDeck® Prime Roof Board should be assessed by the system designer.

Commercial Flat Roofing Systems

DensDeck Prime Roof Boards are ideal for commercial buildings and can be incorporated into a wide range of roof build-ups and applications, including assemblies designed to support rooftop solar (PV) installations.

DensDeck Prime Roof Board integrates easily into flat roof assemblies, adding strength, fire performance, and durability to the system. Acting as a protective cover board layer, it helps safeguard insulation and membrane components from rooftop traffic and equipment loads while supporting the additional performance demands often associated with PV-mounted roof systems and modern commercial roofing standards.

The Insurance Industry’s View of Fire and Solar PV

The insurance industry has raised significant concerns about the increased fire risks associated with solar photovoltaic (PV) panels installed on commercial flat roofs. Electrical failures within solar PV systems, such as arcing, and the flammability of materials used in the roof assembly can contribute to fires that are difficult to extinguish and may spread rapidly.

The geometry of solar PV panels often accelerates fire propagation, complicates firefighting efforts, and can hinder effective water application during fire suppression. Insurers are keenly aware of the financial and operational disruptions caused by such fires and now emphasize the importance of mitigating these risks through strategic choices in roof construction and maintenance.

To address these concerns, the insurance industry has made it clear that roofs with solar PV installations should prioritise non-combustible characteristics to limit fire spread and enhance resilience.

FM Approved roofing assemblies are highlighted as a best practice solution, ensuring robust fire performance and providing added protection against other risks such as wind uplift and water leakage.

By incorporating non-combustible ‘mitigation layers’ such as gypsum boards directly under the waterproofing and adhering to FM testing standards, businesses can not only safeguard their properties but also improve their risk profiles for insurers.

Wind Uplift in the UK and the European Union

Waterproofing systems and fasteners can be assessed to the relevant EAD and where required properties can be tested to the relevant EN standards.

Predominantly full-scale wind uplift testing is done in accordance with EN17686 and EN16002 (dynamic testing), results from full-scale tests are combined with results from the testing of fasteners and waterproofing to gather the required data that allows calculations to EN 1991-4 (with national annex data) to be carried out in order to assess the suitability of the system for its use.

Suitability is based on combined performance of components in relation to the geographical location, building height, etc. In mechanically fixed systems the number of fasteners required in the field area of the roof is determined along with additional requirements in high load areas, such as the perimeter and corner of the roof.

Find out more about DensDeck Prime Roof Board.

*as described and tested in accordance with ASTM E136

>> Read about more featured roofing solutions