The role of the Surveyor
in reducing
fires in thatched roofs
Presented by
Charles Chalcraft. MRPSA
www.thatchedhomeinspector.co.uk
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.
www.thatchedhomeinspector.co.uk
Fire in thatch
“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.
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
Arson
Copyright Graham Barratt
www.thatchedhomeinspector.co.uk
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
www.thatchedhomeinspector.co.uk
Heat Transfer through chimneys.
80% - 90% thatch fires are caused by solid fuel stoves.
• 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.
www.thatchedhomeinspector.co.uk
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
www.thatchedhomeinspector.co.uk
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.
www.thatchedhomeinspector.co.uk
BFCMA Guidance 10/12/12
British Flue &
Chimney
Manufacturers
Association
Dwellings with a Thatch and Combustive Roof
These 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.
www.thatchedhomeinspector.co.uk
Chimney stacks
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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?????
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Raised stack
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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
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Single skin flexible liner
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Spark arrestor & balanced flue
Copyright Stephen Boniface
www.thatchedhomeinspector.co.uk
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.
Request new B Regs to ban all metal liners.
Copyright Dorset Technical Committee
www.thatchedhomeinspector.co.uk
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.
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Physical Fire Barriers
• Calcium silicate board
• Mineral fibre thatchbatts.
• Glass fibre flexible membrane.
• Beware Snake oil products!!!
Copyright Promat
Copyright Graham Barratt
• Check permissions with Building
Control.
www.thatchedhomeinspector.co.uk
Electrics
Requirements 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.
www.thatchedhomeinspector.co.uk
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.
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Unprotected cabling in lofts
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Unprotected cables – impact damage
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Unprotected Cables - vermin
• Evidence of vermin
• Bait bags
• Unprotected cables.
• Major fire hazard.
• No linked smoke
detector in loft.
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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.
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More downlights
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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.
www.thatchedhomeinspector.co.uk
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.
www.thatchedhomeinspector.co.uk
Thatch & woodburners
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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.
www.thatchedhomeinspector.co.uk
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
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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.
www.thatchedhomeinspector.co.uk
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
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This course and all other photos are copyright Thatched Home Inspector.
www.thatchedhomeinspector.co.uk
Thatched Home Inspector
Surveys
Home Condition Surveys.
Custom Thatched Roof Surveys.
Consultancy
Thatch Consultant.
Thatch U Value calculations.
Courses
For RICS Training
Understanding Thatched Roofs.
CPD
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.
www.thatchedhomeinspector.co.uk
Contact details & services
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Charles Chalcraft
Holland Park Farm
Livaton Lane
South Tawton
Okehampton
Devon
EX20 2PP
Tel: 01647 231 706
www.thatchedhomeinspector.co.uk
info@thatchedhomeinspector.co.uk
www.thatchedhomeinspector.co.uk