Fire Board

A fire proof boarding has proven to be one of the most effective products to limit the damage to property during a thatch roof fire.  The fireboards are fitted to the rafters creating a barrier between the thatch and roof timbers.

Fire boards can only be installed during a complete re-thatch where all thatch layers are removed and the roof structure is made suitable or on a new build project, where the Dorset Model is the standard building regulation.  On historic buildings consent must be obtained

NSMT has been become aware of an increase in the number of thatched roofs with dampness issues which are not related to the thatch.

These roofs have had MgO – Magnesium Oxide – boarding fitted as a fire barrier.

NSMT has had samples of MgO board tested and found some contain hygroscopic contaminants. This means they can attract moisture. They can attract moisture to saturation point which can cause serious damage to the interior structure through corrosion to both the fixings of the timber work, the fixings of the boarding and the fixings of the thatch. It has been noted that moisture can drip from the boarding and cause damage to electrical installations and interior decoration.

There is another type of board made from Calcium Silicate which can satisfy the requirements of the Dorset Model which hasn’t received any recorded issues

  • Installations should be carried out by competent installers recommended by the main contractor and this should include the fitting of fire board and battens to manufacturers instruction.
  • Alert the main contractor in writing if you have to thatch over MgO board of the potential risks.
  • If you come across an issue with MgO board and moisture, refer the owner or main contractor back to the supplier of the board and advise them to contact their insurer.