Fire Barriers & Retardants

New Build Thatch & Extensions

As stated in Building Regulation Approved Document B Volume 1, 2019 Edition; If the performance of thatch or wood shingles cannot be established, they should be regarded as having an EROOF (t4) (European class) classification in Table 12.1. See Thatch Building Regulations for more information.

It is recommended that the guidelines set out in Approved Document B are followed in terms of distance to the boundary.

In summary, both our Thatch Firewall Membrane System and Thatch Fireboard Systems meet the requirements as a suitable fire barrier, with the only exception being the distance to the boundary. If a boundary issue is present then the recommendations of the Dorset Model are suggested. On this basis, only fireboard can be used and we, therefore, recommend our Thatch Fireboard System.

Find out more on U-Values and Condensation Risk Analysis.

Thatch Fireboard System

This system is more commonly used on new roofs due to the timbers being straight and strong enough to accept them and when the recommendations set out in Approved Document B and the Dorset Model needs to be achieved. Find out more about Thatch Fireboard System.

Thatch Firewall Membrane System

Thatch Firewall Membrane System is a flexible alternative that can be used providing the Dorset Model requirements have not been requested.

This system has also been tested in accordance with BS476: Part3: 2004 & CEN/TS1187: 2012, test 4. Find out more about Thatch Firewall Membrane System.

Thatchsayf – Fire Retardant Spray

In addition to one of the fire barrier systems the thatch can also be treated with Thatchsayf a fire retardant spray. When exposed to heat, Thatchsayf will foam (intumesce) and form a carbonised char, which binds the thatch stems together, cutting off the supply of oxygen to the fire and slowing down the spread of flame in the event of sparks or embers landing on the thatch.

Find out more about Thatchsayf.

Thatch Alert System

Thatch Alert Chimney Monitor System has been specifically designed to monitor the temperature of the chimney brickwork at the point where it meets the thatch. The system acts as an early warning device to inform the home owner of potential high temperatures and needs to been installed prior to the thatch being fitted. Find out more about Thatch Alert System.


  • Certificate of Supply documents are available on request, additional information about the project may be required to enable these to be completed.
  • When selecting suitable products for your project, please review the detailed information available in the system documents, including taking into consideration other components that make up the complete thatch roof system such as breathable membranes and vapour checks.
  • In addition to the required fire tests, each system has the relevant COSHH & MSDS statements and where required CE marking
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