What is a fire-resistant cover board?


Fire resistant cover boards are high performance building components used to increase the fire rating of a roof assembly and potentially offer improved protection and safety. Glass fibre faced gypsum core cover boards have been specifically developed with fire resistance in mind as both the main components are classified as non-combustible. DensDeck® Roof Board is classified as A1 in accordance with with EN 13501-1 and non-combustible as described and tested in accordance with ASTM E136.

The glass fibre facers on both sides of a cover board form the first line of defence from fire. Gypsum consists of 21% chemically combined crystalised water and 79% calcium sulphate. If a fire breaks out, the energy from the heat gradually vapourises the chemically combined water, calcining the gypsum. To illustrate this, if 15.6mm fibre glass gypsum was specified for a 2,000m2 commercial roof, the amount of crystal water within the build-up would equate to approximately 5,682 litres.

Where is a fire resistant cover board installed?

High density gypsum core cover boards are installed over insulation layers and below the waterproofing membrane. Because of the chemical make-up of gypsum, the board in this position can help prevent external fire sources from penetrating the building.

Fire resistant roof boards have the same chemical profile, but they are installed over the roof deck and below the insulation layer. The roof board slows flame spread and can help protect the layers of a roof build-up from internal fire and heat spread.

Fibreglass facer gypsum cover boards and roof boards are versatile high performance building components. Aside from fire performance enhancement, they offer further benefits, and it is not uncommon for a roof system to include both types of board.

How versatile are fire resistant cover boards?

High density cover boards are relatively lightweight and easy to transport and install. They do not require specialist tools, and installers can cut them to size in situ. The boards have a high compressive strength that helps increase the structural stability of the roof system. Further benefits of cover boards are:

• Compatible substrate for the waterproofing layer
• Waterproofing membrane puncture protection
• Protection of the insulation layer from compression
• Increased acoustic performance

How is the DensDeck® Roof Board different from other fire-resistant cover boards?

The DensDeck® Roof Board is a high-density gypsum board that further improves a fibre glass facing with a non-asphaltic coating. Compared to cementitious cover board, this results in a more uniform spread of adhesive and increased material compatibility without a need for a primer. The more robust bond with single ply membranes and cold mastic or torch applied modified bitumen helps achieve high wind uplift values.

The DensDeck® Prime Roof Board is also enhanced with patent protected EONIC® Technology that doubles the water resistance of the board when compared to a standard gypsum core board. Even after a 2-hour soak test, the board offers greater flexural strength than other gypsum fibre, alternative coated glass mat and HD ISO High-Density Polyiso board.

To find out more about DensDeck® Roof Boards and to see how their specification can enhance the performance of your commercial roof systems, contact us.


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