The role of the Surveyor in reducing fires in thatched roofs Presented by Charles Chalcraft. MRPSA.

The role of the Surveyor in reducing

fires in thatched roofs

www.thatchedhomeinspector.co.uk

Presented by

Charles Chalcraft. MRPSA

Surveying Thatch

• Surveying Thatch is a specialist operation• Requires specialist training• Understanding Thatched Roofs Courses in Devon, 8th May &

14th August• RICS Understanding Thatched Roofs Courses in Hampshire

& Suffolk. 14th May – Bury St. Edmunds Suffolk• Today’s course is an extract from the Understanding

Thatched Roofs course.• There are some flyers about the course with the model of the

thatched roof – otherwise known as Ethel.


Fire in thatch

Main Causes.

Heat transfer through chimneys.

Fires in chimneys.

Vermin eating through electric cables

Downlights & outside lights

Fires originating in the house.

Workmen/plumbers

Bonfires

Arsonwww.thatchedhomeinspector.co.uk

“Data collected over the last 18 years, is the equivalent to the loss of 1 thatched building per week due to fire, currently 994 properties”.

For chimney related fires alone, costs exceed £25,000,000 per year.

Copyright Graham Barratt

Multi coated roof


• Typical for roofs in the Westcountry.

• Both Long straw and Combed Wheat Reed roofs Can be up to 3m thick.

• Middle area of thatch is often dust.

• Excellent insulation and dry.

• Water reed roofs in the Eastern Counties are often single coat.

Copyright Charles Chalcraft

Heat Transfer through chimneys.

• Central chimneys surrounded by thatch.

• Old 4 inch brick chimneys, lime mortar.• 1-3m depth of combustible, dry,

insulating thatch.• Badly fitted, inappropriate liners.• Too large a stove for size of room.

• Flue gases of modern solid fuel stoves can reach 450°C to 600°C

• Thatch will char when temperature through bricks exceeds 180° to 200°C.

• Thatch burns at well over 1000° C.


80% - 90% thatch fires are caused by solid fuel stoves.

Copyright Charles Chalcraft

Condition of Chimney stacks


• Part of brick stack that is normally covered with thatch.

• Major fire hazard for multi coated thatched roofs with a central chimney and a solid fuel stove.

• Building Notice requirement for installing solid fuel stoves, wood burners, multi fuel stoves & liners.

• AD - J Building Regulations.

Copyright Paul Norman

Chimney Liners• Does the liner fit the purpose?• There needs to be adequate thermal separation of exhaust gases to

the existing flue.

• Suggested liners:-• Pumice, clay, ceramic & concrete liners + backfilled with suitable

insulation.• New Twin wall stainless steel with Rockwool insulation + backfilled

with suitable insulation. (Beware old twin wall – insulation decays)

• Refer to HETAS notes – Chimneys in Thatched Properties• Methods to cool the flue – vented flues.


BFCMA Guidance 10/12/12


British Flue & Chimney Manufacturers Association

Dwellings with a Thatch and Combustive RoofThese require special attention and should only be worked on by experienced installers. Attention is drawn to the HETAS guide on thatched properties. The home owner’s insurance company must be advised of proposed works.

Chimney stacks

• Building Regulations AD – B terminate 1.8m above the ridge!• Many multicoated roofs have too much thatch on them.• Stacks are therefore too short.• Recommendation for pots to be no more than 600mm.• Lack of maintenance on stacks within the thatch.• Is the stack stable enough to support additional courses of brick to

raise the height?• Listed Building Consent required to raise height of chimney.• Spark arrestors not recommended by many Fire Brigades.• Bird guards recommended.• Condition of chimney within thatch & in loft?????


Raised stack


Stove too big


11Kw multi fuel stove in a room 4m x 4.5m

Size of stove for this room should be 4.2Kw

Stovesonline kilowatt calculator http://www.stovesonline.co.uk/calculator.asp

Single skin flexible liner


Spark arrestor & balanced flue


Copyright Stephen Boniface

The Dorset Model 2009


Guidelines for Fire Barriers in New Roofs

Rafters overdrawn minimum of 30 minute fire barrier (integrity & insulation), barrier to be water resistant. 50 x 25 battens recommended on micro-porous board to allow thatch to breathe.Use of flexible material or cavity foam as a fire resisting barrier is not acceptable for Dorset Model.

Chimney pot should terminate 1.8m above ridge. To minimise condensation chimney pot max height 600mm.

Interlinked mains & battery powered smoke alarms, with one or more in roof void.

Building Regulations AD – B.Copyright Dorset Technical Committee

Request new B Regs to ban all metal liners.


Fire Barriers

• Physical Barriers - are visible in the loft

• Chemical Barriers - Fire Retardant sprays

• New builds, Fire Barriers, Dorset model

• Currently NO relevant Fire Barrier Test. Tests are on vertical frames for fire curtains.

Physical Fire Barriers


• Calcium silicate board

• Mineral fibre thatchbatts.

• Glass fibre flexible membrane.

• Beware Snake oil products!!!

• Check permissions with Building Control.

Copyright Promat

Copyright Graham Barratt

ElectricsRequirements of BS 7671. Wiring

systems in spaces adjacent to thatch should be suitable selected and installed to minimise:

1. Temperature rise;2. Ingress of foreign bodies, such as

fragments of thatch & other debris;3. Deterioration due to corrosion;4. Mechanical damage by fauna or

impact;5. The spread of fire, given the

increased risk due to the presence of combustible materials.


Electrics in loft


PVC conduit only protects against mice, not rats or squirrels.

Conduit should run along the middle of the loft. Conduit running along the purlin is in danger of mechanical damage by the thatcher from outside.

If conduit has to run along purlin should be on INSIDE face.

Unprotected cabling in lofts


Unprotected cables – impact damage


Unprotected Cables - vermin


• Evidence of vermin• Bait bags• Unprotected cables.• Major fire hazard.• No linked smoke

detector in loft.

Beware of Downlights


• No downlights in upstairs ceilings.

• No intumecsent hood.

• Experimental use of PVC conduit.

• Bad positioning of cables. Should run down middle of loft.

• LED lights give off nearly as much heat as halogen.

More downlights


Outside lights & Cables

Halogen outside light – within 1 m of thatch. Hazard.

Condition 3 ~ Electrics & Risks

Copyright Wesley Marriot

Wire netting

• All Long straw roofs netted against bird strike.• Ridge netting is often cemented into the chimney fillets, and is held

by long wire staples.• All over coat netting has to be fitted correctly so that in the event of

a fire it can be pulled off. Must NOT be nailed or stapled at eaves = Condition 3.

• Wire netting should be at least 300mm away from any electrical source, closer = Condition 3.


Thatch & electrics• When you are doing a survey. Look for the following:-• New type consumer unit with RCD’s

• In the loft• Rat & mouse droppings• Evidence of rodent damage to cables or foam pipe lagging• Positioning of cables• Protected cables• Unenclosed lights• Unprotected downlights• Linked smoke alarms

• Outside• Outside lights within 1m of thatch especially halogen lights.• Wire netting within 300mm of any electrical source.• Wire netting nailed/stapled to wall plate.


Thatch & woodburners• Height of chimney – 1.8m above thatch?• Should have no spark arrestor• If present spark arrestor needs cleaning x 2 p/year• Bird Guard• Blocked chimney – jackdaws nesting• HETAS sticker on register plate.• Woodburner too big for room.• Documented information about the installation• Chimneys swept x 2 p/year.• Dry logs.• Condition of chimney stack within thatch.• Annual inspection of stove by a HETAS engineer.


Survey recommendations to purchasers

• CCTV survey of chimney to establish:

1. Type, suitability, age & condition of liner.

2. Stability & condition of chimney stack.

• Electrical cable survey in loft. NICEIC

• No woodburners.• No spark arresters.• Chimneys swept minimum of twice per year.• No downlights.• Major reductions in insurance by removing woodburners &

installing LPG look alikes.


Resources• Please follow this link for information about:-

• HETAS; ESC; The Dorset Model; & more.• http://www.thatchedhomeinspector.co.uk/relatedlinks.htm

• Understanding Thatched Roofs courses:-• http://www.thatchedhomeinspector.co.uk/index.htm

• Downloadable: Thatch & Woodburners information sheet.

• National Society of Master Thatchers www.nsmtltd.co.uk

• This course and all other photos are copyright Thatched Home Inspector.


http://www.thatchedhomeinspector.co.uk/relatedlinks.htm

http://www.thatchedhomeinspector.co.uk/index.htm

http://www.nsmt.co.uk/

Thatched Home Inspector


SurveysHome Condition Surveys.Custom Thatched Roof Surveys.

ConsultancyThatch Consultant.Thatch U Value calculations.

Courses CPDFor RICS Training Understanding Thatched Roofs. 6 hours

For Thatched Home Inspector Understanding Thatched Roofs Courses in Devon. 6 hours The Role of the Surveyor in reducing Fires in Thatched Buildings. 1 hour“Hands on” Weekend Thatching Courses.In House training.

Contact details & services

• Charles Chalcraft • Holland Park Farm• Livaton Lane• South Tawton• Okehampton• Devon• EX20 2PP• Tel: 01647 231 706• www.thatchedhomeinspector.co.uk• [email protected]


http://www.thatchedhomeinspector.co.uk/

mailto:[email protected]

The role of the Surveyor in reducing fires in thatched roofs Presented by Charles Chalcraft. MRPSA.

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Transcript of The role of the Surveyor in reducing fires in thatched roofs Presented by Charles Chalcraft. MRPSA.