Thatched PProperty Safety GGuide

Produced by your local Fire and Rescue Service

© 2006 Design produced in-house by Hertfordshire Fire and Rescue Service’s Graphics Department

Photographs courtesy of Hertfordshire Fire and Rescue Service and Norfolk Fire and Rescue Service.Illustration page 9 reproduced from MyGARD plc leaflet.

The Fire Service acknowledges the kind permission of John Albion Duffield & Pratt to use their publications

in the production of this guide.

Con

ten

tsIntroductionCauses

Precautions

Safety devices

Advice and Information

Checklist

Useful contact information

ChimneysFire pplanSmoke aalarmsKitchensElectricsDon’t ooverload ssockets!ContractorsBonfiresWater ssuppliesHeat ssensorsSprinkler ssystems

Summary oof aadvice

Spark aarrestorsHeat ddetectorsThe DDorset mmodelTar rremoversStovepipe mmonitors

Open ffires aand wwood bburnersChimney ffiresFaulty cchimneysSeasoned wwoodHeight oof cchimney

What iis HHeat TTransfer?

4

8

11

16

18

32

Introduction

2

Thatched

roofing is

enjoying a

revival in the

UK.

Roofing was traditionallymade from severalmaterials depending onlocation and availability.

Today, however, only threematerials are widely used,long straw, combed wheatreed and water reed, all ofwhich will burn rapidly in afire.

This booklet has beenproduced by your local Fireand Rescue Service as auseful guide for householders to help prevent afire occurring.

This booklet should be keptclose at hand and passedon to the new occupiershould you move.

Although fires in a thatchroof are not common, over90% start as a result of afaulty flue or chimney.

The thatch is designed torepel water and so for aFire and Rescue Servicethis makes it a difficult taskto extinguish such fires.

“prevention is essential,detection is nearly alwaystoo late!”

Recent research has

identified that a major

cause of chimney related

thatch fires is attributable

to heat transfer through the

brickwork of the flue into

the adjacent thatch. The

government-backed team

of scientists from the

National Society of Master

Thatchers (NSMT) have

conducted research into the

use of straw and reed as a

roofing material. In

particular their research

included an investigation

into the causes of

preventable thatch fires.

It was believed that themajor cause of thatch fireswas attributed to sparks orburning brands issuing fromthe chimney and igniting thethatch. In fact, controlledtests have shown that it isdifficult to ignite thatch withsuch a short-lived point ofignition as a spark. It is

particularly difficult to ignitewhen the thatch is cold andwet; as is invariably thecase when homeowners arelighting fires that sendsparks up the chimney.

Their experiments haveshown that the temperatureof the flue gases inside thechimney will heat thesurrounding brickwork. The‘hot bricks’ of the chimneywill heat the adjacent thatcharound the chimney. Thatchis an extremely goodinsulator and the heat willbe retained in the centre ofthe thatch around thechimney. The experimentsshowed that once a criticaltemperature of approx200°C was achieved at thethatch chimney interface,charring and pyrolysis ofthe thatch occurred andeventually developed into aroof fire. This processdevelops over long periodsof time.

Causes

3

What is Heat Transfer?

Many thatched homes were

built with single skin brick

chimneys that rise

centrally through a deep

thatch layer. They were

designed to cater for open

fireplaces, often smoking

inglenooks, where large

volumes of cooling air

drawn from draughty

rooms mingled with the

flue gases as they rose

through the flue. Diluted in

this way, the flue gases did

not reach sufficiently high

temperatures to pose a

threat to the thatch

adjacent to the chimney. As

the chimney traditionally

emerged through the

highest point of the thatch,

any partly combusted

particles were expelled

upwards and were

extinguished before they

drifted down towards the

thatch.

Modern enclosed solid fuelappliances are designed toburn efficiently and cleanly.This means that they burnat a much-increasedtemperature to promote a‘clean burn’. Solid fuelstoves can generate fluegas temperatures in excessof 300°C to 600°C. Whenthese appliances are fittedinto elderly chimneys andthere is only a 4-inch layerof brick between the flueand the thatch, then thethatch is especiallyvulnerable to the risk ofheat transfer. Modernchimney linings can preventflue leaks, but they do notsignificantly reduce thetemperature achieved byheat transfer within thethatch when the applianceis in constant or regularuse.

Precautions

4

Open fires and wood burners

It has been shown in teststhat the thatch adjacent tothe chimney can reach 85%of the flue gas temperatureafter only one day ofcontinuous use. The criticaltemperature of 200°C canbe achieved and sustainedwith relative ease.

Precautions

5

Chimney fires can occur inany home with a workingflue, including homes thathave conventional tile orslate roof. It should beremembered that soot isnot merely a by-product ofburning; it is a combustiblematerial in its own right. Asoot-lined chimney is achimney lined with fuel justwaiting to burn. Onceignited, the draught withinthe chimney can draw thefire into something akin toa jet engine exhaust. Thisextremely fiercecombustion is capable ofreaching such hightemperatures that thestructure or the chimney

can be significantlydamaged. In a thatchedhome the conventionalchimney fire carries theadditional risk of ignitingthe roofing material.

Old or poorly maintainedchimneys can deteriorateto the point where smokeand hot gases can escapefrom the chimney into theupper rooms, the roofspace or directly into thethatch. There are severaltell tale signs that indicateproblems with the chimney.

Chimney fires

Faulty chimneys

Precautions

6

Chimneys built before the1960’s, and this is true ofmost thatched homes, aremost likely of a single brickthickness and parged, notlined. The internalprotective parging orroughcast plasterwork willcrumble and disintegratewith age, leaving thebrickwork or stonework ofthe chimney exposed to theacidic condensate that isgenerated by modernappliances. The chemicalreactions that subsequentlyoccur accelerate the attackon the mortar and furtherdeterioration can be rapid.

Because of the great age of

many thatched homes, theconstruction of thechimneys can be highlyunconventional. Periodhomes, built before BuildingRegulations wereintroduced, often havetimber lintels over thefireplace and timber joistsbuilt into the chimneystacks. These can beexposed to scorching whenthe protective parging insidethe chimney disintegrates.

The combustion products

from burning sap in ‘green’

wood are the main cause of

tar deposits within a

chimney. When wood isproperly seasoned the sapcontent is substantiallyreduced and so is the tar.Apart from minimising thebuild up of tar, there is alsoa significant financialbenefit of burning properlyseasoned wood. With itslower sap content it givesoff more heat and offersbetter value for money.

Any staining of theplasterwork or wallpaperaround the chimneybreast,or black or brown localiseddeposits on the chimney inthe roof space should betaken seriously. Soot oncobwebs in the loft isanother vital sign thatsomething is wrong with thechimney.

Seasoned wood

Precautions

7

Irrespective of how dry theshed or garage is, storingwood inside will result in‘sweating’. Any sap, whichis drawn to the cut surfaceof the wood, will condenseon the surface as opposedto being taken away.Stacking it outside where itis exposed to the wind andsun properly seasons Wood.The wood should either bestored under a shelter orthe top layer should becovered to protect the stackagainst excessive rain.

A chimney with only a littlepart of the stack visible, islikely to be buried in deepthatch, raising the chimneystack does not reduce therisk of fire. Old propertiescan have thatch at theeaves up to 10ft deep,making this a property atrisk. One metre or more ofthatch round a chimney is apotential hazard, at the timeof re-thatching work withthe thatcher and the

conservation officer to haverecent layers of thatchremoved to reduce the risk.

Height of chimney

Safety ddevices

8

In the past, accepted

wisdom largely dictated

that a major cause of fires

in thatched homes was

attributed to sparks issuing

from the chimney and

igniting the thatch. As aconsequence, many ownersof thatched homes werepersuaded to install sparkarrestors on workingchimney pots. Although wedo NOT recommend sparkarrestors on chimneys, ifthey are installed they mustbe kept clean.

In a recent survey by theteam of scientists fromNSMT, it was found that ofall the thatched propertiesinvestigated, which hadsuffered chimney relatedfires, many had some typeof restrictor on the roof.This was often a cloggedspark arrestor.

If a spark arrestor is fittedor is going to be fitted itmust be kept clean to allow

it and the chimney to workefficiently. The NationalAssociation of ChimneySweeps recommend that ifa spark ‘arrestor’ is fittedto a chimney in regular use,the chimney should beswept every 3 months andthe spark arrestor takendown and thoroughlycleaned.

There are systems

available, which use heat

detectors inserted into the

thatch around the chimney

connected to a control

panel. The system isdesigned to give an audiblewarning when thebrickwork and thatcharound the chimneyapproaches a criticaltemperature. Installationcosts and an annualmaintenance program needto be considered, togetherwith a risk managementstrategy to be adoptedwhen an alarm is given.

Spark arrestors

Heat detectors

9

The system is designed togive an early warning of a potential overheating of thethatch so measures can betaken to reduce thetemperature of the chimneyi.e. extinguish the fire in thegrate and inspect thechimney.

Working in closeassociation with the fireservice, thatcher’s, builderselectricians, insurers,scientists and buildingcontrol divisions throughoutthe county of Dorset havegrappled in recent yearswith the local planningdemands for new thatchedproperties to be built. As aresult a design guide hasbeen drawn up called the

‘Dorset model’, whichmeets the criteria of all thespecialist advisersappointed to the technicalcommittee. By following thisdesign guide it is possible tobuild a new house with athatched roof.Some of the principles inthe Dorset model could beconsidered if any majorrenovation work of re-roofing is planned.Consideration could begiven to:

burning wood, when hot fluegases condense in thecooler parts of the chimney.As the coolest region is theuppermost section of theflue, ignition of the tar at thispoint represents a seriousthreat to the thatch.

There are chemical productsavailable that can be appliedto the embers of the hearth

fire or firebox in a stove todry out the tar deposits inthe flue and cause them to

Constructing aa ffireproofbarrier bbetween tthe rroof timbers aand tthe tthatchlayer. TThe tthatch wwould then bbe vviewed aas‘sacrificial’ iin tthe eevent ooffire aand tthe ffireproofbarrier wwould hhelp sstop the rroof ffire ffrom ggettinginto tthe sstructure oof tthehouse. TThis wwouldtherefore ddrasticallyreduce tthe eeffect oof aathatch rroof ffire.

Insulating tthe fflue oof tthechimney tto rreduce ttherisk oof hheat ttransfer.

Safety ddevices

The Dorset model

Safety ddevices

10

The build up of tar deposits

within the flue can

increase the risk of a

chimney fire. Tar depositsare encouraged to form,particularly when burningwood, when hot flue gasescondense in the coolerparts of the chimney. Asthe coolest region is theuppermost section of theflue, ignition of the tar atthis point represents aserious threat to the thatch.

There are chemicalproducts available that canbe applied to the embers ofthe hearth fire or firebox ina stove to dry out the tardeposits in the flue andcause them to disintegrate.This treatment should berepeated at therecommended intervals toprevent new deposits fromforming. Routine sweepingand scraping of the flue willstill be required, especiallywhere heavy tar depositspersist. A qualified chimney

sweep will be able to giveyou further adviceregarding the best productsto suit your particularrequirements.

Careful management of

any solid fuel or wood-

burning appliance is an

effective way of reducing

the risk of heat transfer

from the chimney to the

thatch. Using stovepipethermometers to monitorthe temperature of the fluegases leaving the appliancegives a good indication ofhow high the temperaturesin the upper part of thechimney will be. The fireboxcan be suitably managed toensure that the flue gastemperature is notexcessive (approx 200c) atthe level of the thatch.

Stovepipe monitors

Tar removers

Advice aand iinformation

11

Chimneys should bechecked or surveyed toensure that they arestructurally sound, wellmaintained and able to copewith the demands made ofthem by modern heatingappliances.

The first measure is toensure that the chimneysare regularly swept by anexperienced and preferablyqualified chimney sweep,who should be able toidentify potential problemsat an early stage.

If a chimney lining has beeninstalled, this should beinternally inspected atintervals, especially whenthe main fuel burnt is wood,as tar deposits are highlycombustible and corrosive.The majority of chimneylinings were not designedwith thatched homes inmind. Metal liners arevulnerable to corrosion anddo not have a long life

expectancy in associationwith wood burningappliances. CCTV can beused to inspect the internalcondition of the flue.Potential hazards can beidentified, diagnosed andremedies prescribed by aqualified chimney engineer.

One way of addressing therisk of heat transfer fromthe flue to the thatch is touse an insulated flue liner.There are a number ofinsulated flue linersavailable on the market.Metal liners are availablewith insulation or an infillcan be used around theliner. This infill is aninsulating material such as‘vermiculite’ or ‘pumice’.Clay liners can be used orthere are pre-formedcement modulesincorporating kiln burnt andpumice aggregate. Thesehave very good thermalqualities.

Whichever type of lining isconsidered, the chimney

Chimneys

should be scrupulouslycleaned prior to installation to remove combustibledeposits that mightotherwise ignite betweenthe lining and the flue. Acompetent chimneyengineer who understandsthe special risks associatedwith thatched propertiesshould install any linings.

Make sure all your familyknow what to do in theevent of a fire and how to escape safely. Your fireplan should include:

Your Fire Service stronglyrecommends smokealarms are installed in yourproperty.

Advice aand iinformation

12

Planning your escaperoutes and keepingexits clear.

Keeping door andwindow keys handy.

Considering how a firein your house will bedetected. Have you got a sufficient amount ofsmoke alarms and arethey in the correct position?

Smoke alarms

Fire plan

13

Advice aand iinformation

Two-thirds of fires that

start inside the house

relate to the kitchen.

Consideration should be

given to:

Check for signs of loose

wiring and faulty plugs or

sockets, such as scorch

marks or flickering lights.

Replace any worn or taped-up cables and leads.

Installing a fire blanket.

Keeping items that cancatch fire easily, such astea towels and oven

gloves, away fromcookers and toasters.

Never fill chip pans morethan one-third full of oil.

Consider a thermostatically controlled deep fat fryer.

As a CFS (Community Fire Safety) Department,we do NOT recommend fire extinguishers to beused in the kitchen. Afire blanket is safer and much more effective touse.

Electrics

Kitchens

Fit a smoke alarm on every floor of your home,ideally in the hallway orlanding ceilings.

Put a smoke alarm inthe loft space and linkthis to others inside thehouse.

Don’t put a smoke alarmin the kitchen where itcan be set offaccidentally.

Test the batteries once aweek. Alarms areavailable with 10-year batteries.

Advice aand iinformation

14

Consider having yourelectrical system checkedby a qualified electrician inaccordance with theInstitution of ElectricalEngineers (lEE) guidance. If your incoming powersupply is overhead, check tosee if it is the insulatedtype. If you are in doubt yourpower supplier can give youfurther advice.

If you are having any workdone on your house thatwill involve ‘hot works’ suchas plumbing or paintstripping, make sure thecontractors are fully awareof the potential risk of athatch fire.

It is always good practice tolimit the number andlocation of any bonfires toreduce the risk of fire toyour property. It is also agood idea to discuss thiswith any neighbours whohave a bonfire near yourproperty.

Assess the water suppliesto your property. Considerhaving an outside tap withenough hose pipe to reacharound your house includingthe roof. This will help youcontrol any small fires youdiscover. Only tackle a fire ifit is safe to do so.

Bonfires

Water supplies

Contractors

Don’t overload sockets!

Advice aand iinformation

15

There are systemsavailable, which use heatdetectors inserted into thethatch around the chimneyconnected to a controlpanel. They are designed togive an early warning if thethatch is overheating. Thefire in the grate can then beextinguished to allow thechimney and the thatch tocool down.

In recent years there havebeen many advances indomestic sprinklersystems. The life safetyadvantages and the extraproperty protection can beconsiderable.

Sprinkler systems

Heat sensors

16

Checklist

Recent research has

shown the major cause

of fires in thatched

properties is heat

transfer from the

chimney into the thatch.

The thatch then reaches

its ignition temperature

and a roof fire can

develop. It is important toinsulate the chimney flueto prevent the heat fromtransferring into thethatch layer. This isespecially important when a solid fuel or woodburner is installed as they burn at highertemperatures thanconventional open fires.

Have the chimney swept

regularly by a qualified

chimney sweep. Achimney in regular useshould be swept twice ayear.

Only burn seasoned

wood.

Have the chimney

inspected by a qualified

chimney engineer.

If you have a spark

arrestor fitted clean it

regularly. This should be

done every 3 months on

chimneys in regular use

and the arrestor should

be taken down to clean.

Develop a fire plan for

your home.

Smoke alarms should be

installed throughout your

home. If you have a loftspace then an interlinkedsmoke alarm should beinstalled which is linkedto at least one otherwithin your home.

Summary of advice

Checklist

17

Install a fire blanket inthe kitchen.

Check the electricalsystem throughout yourhome.

Be careful when usingblowtorches or heat guns(when plumbing orpainting etc).

Restrict the use ofbonfires near to yourproperty.

Consider a system ofheat sensors within thethatch around thechimney. This will giveyou an early warning ofany overheating of thethatch.

Install an outside tapwith enough hose toreach around the houseincluding the roof. Thiscan be used to extinguishany fires at an earlystage.

Residential sprinklersystems will greatlyimprove the fireprecautions within yourhome. The advantageswill be much better lifesafety and propertyprotection.

If you are undertakingrenovation work or re-roofing, consider forminga fireproof barrierbetween the roof timbersand the thatch layer. Anythatch fire will then bemainly restricted to thethatch and will not getinto the structure of thehouse so greatly limitingthe damage from fire.

Useful ccontacts...

18

The contacts listed will give

you specialist information

regarding their products.

See back cover for local

Fire and Rescue Service

contact details.

National Association of

Chimney Sweeps

www.chimneyworks.co.uk

Local area Fire

Prevention Officers

www.firekills.gov.uk

National Fireplace Association

www.nfa.org.uk

English Heritage - Listed

buildings/graded properties

www.customers@english-

heritage.org.uk

The National Society of

Master Thatchers (NSMT)

www.nsmtltd.co.uk

The East Anglian Master

Thatchers Association

www.eamta.co.uk

The information contained in this document is alsoavailable upon request in large print and in communitylanguages. Please contact your Local Fire and RescueService stating the format you require.

This ‘Thatched Property Safety Guide’ has been produced by your local Fire andRescue Service. It offers a variety of useful information and practical advice for bothyou and your home. We hope you find it informative and helpful.

For further information and advice see the ‘useful contacts’ section at the back ofthis booklet.

FREE HOME FIRESAFETY CHECKS...Contact your local Fire and Rescue Service to arrange yourappointment using the numbers below.

We will sit and work through a questionnaire with you answeringany questions you may have. We will then do a ‘walk around’inspection of your home with you, giving advice on potential firehazards that exist and where necessary we will also supply and fitsmoke alarms free of charge.

Visits will take place by mutual agreement and Fire and Rescuepersonnel will always show an official ID card.

It won’t cost you a penny and it could save your life.

SMOKE ALARMSThey’re not an EARLY warning. They’re your ONLY warning.

BEDFORDSHIRE AND LUTON 01234 351 081

CAMBRIDGESHIRE 01480 444 666

ESSEX 0845 601 2495

HERTFORDSHIRE 0800 587 3347 (Freephone)

NORFOLK 0800 917 8137 (Freephone)

SUFFOLK 01473 260 588

Contact Your local Fire and Rescue Service...