Fire resistant roof board

Fire resistant roof boards are gypsum core cover boards that help protect the roof system and the building itself from the spread of fire and heat. Depending on their classification, cover boards can be used over both combustible and non-combustible decks in low slope and flat roof systems of residential and commercial buildings. This allows for specification with metal, bituminous and single ply systems for roof terrance, green and solar PV roof applications. The fire resistance benefits both new build and roof refurbishment build ups.

Gypsum core cover boards are deemed fire resistant because the gypsum material is classified non-combustible1Gypsum contains crystalised water incorporated into its structure. In a fire, the energy from the heat vaporises the crystalised water calcining the gypsum and creating a natural fire-resistance.

Fibreglass mat facers act as the first line of defence and help maintain the structural integrity of the board in the case of fire. Two boards are usually installed. Cover boards are fitted over the insulation layer to help shield the roof build up from external fire sources. Roof boards are installed below the insulation layer to help resist internal fire and heat from spreading into the roof space.

What is the application of fire resistant DensDeck® Roof Boards

DensDeck® Roof Boards can be specified to improve the fire rating of roofing systems in commercial and industrial developments. Our cover boards help address specific challenges of large span commercial structures, solar roof installations and commercial roofs with technology or equipment installed on them that may be a potential fire hazard. They help protect both the equipment of buildings in critical sectors such as datacentres and biotechnology centres and public in-service buildings such as airports, museum, libraries.

DensDeck® Roof Boards are designed from two non-combustible materials, gypsum core and fibreglass mat facings. The chemical composition of gypsum makes it an effective fire retardant material. It consists of 21% chemically combined water to 79% inert calcium sulphate. In a case of a fire, the heat would release the chemically combined water as water vapour. This helps resist surrounding materials from combusting and slows flame spread.

DensDeck® Roof boards can be installed as cover boards or roof boards. When used as cover boards, they are positioned above the insulation layer and below the waterproofing layer. This way the roof assembly is more protected from external fire sources such as a failed solar panel or a burning ember from a nearby building. Roof boards are installed below the insulation layer, on top of a structural deck. They help protect the roof space from internal fire spread.

1DensDeck® Roof Boards have an A1 fire classification in accordance with BS EN 13501-1 and are classified as non-combustible as described and tested in accordance with ASTM E136 or CAN/ULC S114

Fire resistance

What are the benefits of fire resistant roof boards?

• Resistance from the fire spread
• Resistance from external fire sources
• Resistance from the internal fire spread
• Resistance from heat transfer


DensDeck® Prime Roof Board
Thickness (mm)6.4 (¼ inch)12.7 (½ inch)15.9 (⅝ inch)
Length (mm)243824382438
Width (mm)1219

Roof protection boards

The DensDeck® Roof Board helps protect all types of flat roof build ups from natural forces such as hail and wind. They provide dimensional stability to the roof system and shield the waterproofing membrane from dead loads of heavy plant and sudden impact, such as dropped tools or flying debris, whilst adding additional fire resistance.

Sound Reduction

DensDeck® Roof Boards help block the sound penetrating through a roof assembly into a building. Our cover boards help increase occupant acoustic comfort even in high noise commercial settings such as airports.

Acoustic performance >

Fire Resistant

DensDeck® Roof Boards help protect the roof assembly from external fire sources, such as malfunctioning solar panels or embers from a nearby building. They also help to protect the roof space from internal fire spread.

Fire resistance >

Weather Resistance

DensDeck® Roof Boards enhance fastener pull through, increase membrane bond strength as well as dimensional strength. This means greater resistance to wind uplift and repeated hail strikes.

Weather resistance >

Roof Access

DensDeck® Roof Boards spread loads and helps protect the insulation layer installed underneath roof build ups. Our cover boards have high compressive strength and add structural strength to the roof assembly, absorbing foot traffic and helping protect from sudden, damaging impacts.

Roof access >


Datacentre construction has a unique set of demands on the building envelope performance. The roof system must be robust and waterproof. Any moisture penetrating through the building envelope could cause service disruption with considerable commercial impact or even damage the expensive equipment. Specification of fibreglass mat face gypsum cover boards is ideal for both new datacentre projects and roof renovations that seek fast project delivery times and exceptional building performance.

Heritage buildings

Conservation and refurbishment of roofs for heritage buildings demands attention to detail. They often use roof coverings made from traditional materials, making installation more time and labour intensive.

Heritage roofs may have areas that are difficult to access, posing a challenge when it comes to the installation and the performance of the roof system. Cover boards are specified to make roof refurbishment easier. They also help increase the building performance of traditional, heritage buildings.

Museums & libraries

Roofing systems for museums and libraries have the important function of protecting valuable collections and creating a safe, comfortable space for the public visiting the facilities. Museums and libraries often combine traditional heritage buildings and striking modern extensions.

This allows architects and designers to blend high performing heritage roof refurbishments with modern green, metal, solar panel roofs, roof terraces with parapet systems or a fusion of the various roof types. Cover boards are a crucial part of these roof build ups capable of enhancing their performance and extending their design life.


Airports, hangar and maintenance buildings, car parks and other buildings in the aviation sector present their own set of challenges. These projects have intensive schedules and once finished, the highest level of building performance is expected to keep passengers comfortable and safe.

The performance enhancing capabilities of fibreglass mat face gypsum cover boards are ideal for specification in the aviation sector.


The construction of biotech centres must overcome a very specific set of challenges. These buildings fall within the critical sector and the expectation is that their roofing systems must be very robust.

Specification of fibreglass mat facer gypsum core cover boards enhances the performance and longevity of roof systems for biotech centres. It can also target improvement in specific areas of building performance, as required by each project.

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