Fire Retardants for Thatched Roofs

Fire - Causes

Investigations have shown that many thatch fires relate to the use of wood burning stoves and have occurred within 30 minutes of the stove being lit. The use of unsuitable materials to ignite the wood burner is also a factor.

Whilst sparks and embers generally have little energy (the exceptions being those generated through chimney fires) there are other causes which may increase the risk of the effects from ejected sparks and embers:

Spark Arrestors – If not thoroughly cleaned at least once a year, tar and soot deposits can potentially build up and ignite causing a chimney fire in their own right, which in turn could cause a thatch fire. Whilst spark arrestors were once deemed an effective measure, a suitable bird guard is preferred as long as the chimney continues to function efficiently.

Chimney Height – The risk of a thatch fire is further increased when the chimney height has been reduced following many years of re-coating works. This is more common with thatching materials such as combed wheat reed and long straw. Where possible increasing the height of the chimney and/or chimney pot or reducing the depth of thatch will result in fewer sparks reaching that thatch which in turn reduces the chances of a fire starting.

Over the years, we have seen a pattern of thatch fires emerging around Easter. This can be partially attributed to the cold Eastern and Northerly winds which usually coincide with a lengthy dry spell resulting in many homeowners using their wood burners and open fires further into the year. In addition, birds start nesting around this time and many can nest in chimney stacks without owners knowing. If not already the case, it would be prudent to ask your chimney sweep to check for any build up either from nests or a result of usage over the winter months.  A suitable bird guard or cowl can prevent this.

Fire Retardant Sprays

The main purpose of a fire retardant is to starve the ignition area of oxygen and therefore delay the spread of flame and the full development of a thatch fire. The idea is to buy more time so that the fire and rescue service have a greater chance of extinguishing the fire before it fully develops.

Thatchsayf Spray System is a water based solution containing fire retardant and intumescent ingredients for the protection of thatched roofing.

This environmentally friendly solution is applied externally to the thatch surface and penetrates the stems of the thatch by up to 75mm, forming a thin protective film on the surface of the thatch stems.

A treated roof will offer protection from a number of fire risks, including sparks, ejected embers, bonfires, Chinese lanterns, fireworks and barbecues.

On exposure to these risks, Thatchsayf Spray System will ‘foam up’ (intumesce) and form a carbonised char, which binds the thatch stems together, cutting off the supply of oxygen to the fire, delaying the spread of flame and lowering the radiated heat output.

The application of Thatchsayf Spray System is undertaken by our fully trained employees using specialist spraying equipment and is normally carried out between March and the end of October. This is due to the high levels of moisture in the air during the winter months.

Once a roof is treated, the homeowner is issued with a Certificate of Completion, which is valid for five years after which re-application is required.

A new build/newly thatched roof offers a good opportunity to treat a roof. However, an existing thatched roof can also be treated as long as it is in good condition. Thatchsayf Spray System can be applied as a standalone product or in addition to having a physical fire barrier system installed.

We suggest you contact your insurance company to check if any discounts are available for taking a proactive approach by treating the roof with a fire retardant spray and fire barriers.


Thatchsayf Spray System has been tested to vigorous testing by the British Research Establishment (BRE). Further details of testing is available upon request. Thatchsayf Spray System is tested to BS476 Part 3 and achieved the designation of EXT.S.BA

The benefits of Thatchsayf Spray System

  • Fire penetration may be delayed for over 30 minutes with no spread of flame
  • Can be applied to new or existing thatched roofs
  • Contains preservatives
  • Retards bacterial and fungal growth including moss
  • Application is fully certified for 5 years
  • Environmentally friendly

May reduce insurance premiums

Posted on September 28th 2023

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