Thatch Fire Membrane System

The Thatch Fire Membrane System is designed to meet the criteria as recommended by Building Control for both spread of flame and penetration, with the added benefit of providing the required thermal insulation values.

Please note that this system does not meet the criteria of ‘The Dorset Model’ for new build projects and extensions where the property is 12m or less from the boundary. If your project meets these criteria, please look at our Thatch Fire Board System.     

The system consists of:

• Thatchbatt® Wired Fixing System 
• Thatchbatt® Slabs
• Thatch Firewall Membrane

System overview:
This system will offer a fire barrier in accordance with BS476: Part 3: 2004 & CEN/TS 1187:2012, test 4.

The Thatch Firewall Membrane system offers a flexible, water resistant and breathable solution for those projects that are not able to accommodate the rigid Thatch Fireboard System. 

The Thatchbatts® are designed to be friction fitted between roof timbers that are set at 400mm centres. Thatchbatts® are non-combustible, semi-rigid, high quality resin bonded mineral rock slabs. These are therefore ideally suited for use within the construction of a thatched roof because they offer zero spread of flame and good thermal transfer properties.

The minimum requirement is for 50mm Thatchbatts®, however, consideration should be given to the following two points in relation to the thickness and possible full fill:

• If the Thatchbatts® are installed at the same depth as the roof timbers, then the fire resistance is increased in terms of reducing the charring to the roof timbers. Therefore, this will help protect the roof structure from either a fire on the outside or on the inside.
• An increase in Thatchbatts® thickness will also result in increased thermal values.

Although the Thatchbatts® have been designed to be semi-rigid, the wired fixing system is required to ensure that the top surface of the slabs are level with the top edge of the roof rafters.

Due to the flexibility of this system it is favoured for many existing properties.

1. Thatchbatts® are friction fitted between the rafters set at 400mm centres, they are then supported by the wired fixing system as detailed on the installation instruction document below.
   
   When using multiple layers of Thatchbatts® are being used, we recommend that the joints are staggered to give a more comprehensive solution.
   
   Thatchbatts® - Installation Instructions
   
   

2.   Thatch Firewall Membrane is then fitted directly on top of the roof rafters. The membrane is fitted horizontally with a minimum overlap of 75mm at each point the membrane joins.

The membrane can either be stapled or nailed to the roof rafters to hold it in place on a temporary basis until the battens are fitted.

25mm x 50mm battens are then fitted horizontally over the top of the Thatch Firewall Membrane at 300mm centres, with the first batten 125mm from the arris rail. Please note: if the Thatcher is going to use crooks, the size of the battens may need to be increased.

3.   If required, TAS Fire Silicone can be applied between the membranes at the point they join. For best results; apply a 5mm diameter bead of silicone using a wave effect pattern within the 75mm overlap point. Although the TAS Fire Silicone will have some instant grip, it will require 24 hours to fully cure. For best results, please ensure that the surface is clean and dry and not exposed to frost during the curing process.

The components within the Thatch Fire Membrane System contribute to a part of the overall roof construction. Therefore please consult with your Architect with regard to the performance of the complete roof structure, to include requirements for other components such as vapour barriers etc.

Additional information for both Thatch Firewall Membrane and Thatchbatts® is available from the main menu of our website.