Andy Hall wrote:

On Sat, 06 Dec 2003 10:43:35 +0000, The Natural Philosopher
wrote:



To ensue the chimney 'starts' well, you need s good blaze from the word
go. That means newspaper and dry kindling, or better a firelighter, or
even as I sometimes do, ten minutes with a plumbers blowlamp to get the
fuel going. Once the cghimney is going, you need to mae sure the room
has adequate ventilation - I have underfloor ducts for the fire to avoid
draughts, they work very well. ANY negative pressure in the room will
stop the fire drawing, sister-in-law had a dreadful fire that wouldn't
draw unless the doors were open. Eventually it was left unattended and
burnt the house down. Literally and seriously.


On that subject, what precautions do you need to take to avoid small
burning particles that are going up the chimney from landing on the
roof and burning it? Just curious..


Fisrt of all, most thatch house that burn, don't burn from outside. The
classic cases are electrical shorts or hot flue gasses escaping via a
cracked flue with rotting mortar, and setting teh dry thatch underneath
aliht.

To this end, modern thatched rooves are subject to the followng regulations

- final exit height of stack and pot MUST be 2.2 meters above thatch
ridge etc. this is reckined to be enough to carry sparks away.
- thatched roof must be a minium distance from boundary of property, or
(in my case) there is no adjacent buildings, nor planning consent or
indeed possibility of such to put up a property closer than, IIRC 5 meters.
- fireproof breathable board (supalux/masterboard/multiboard is used
UNDER the thatch to reduce chances of an attic fire setting thatch alight.
- smoke alarms everywhere. This is pretty standard anyway no matter what
the roof.
- no timber stricures are allowed closer than I think 20mm to teh
stacks. In my case we used supalux board spacers and metal hangers to
carry the ridge to stack loads.
- all flues must be lined with ceramic flue liners or steel insulated
liners.
- some fairly srong regs on use of e.g. ceiling mounted spots under
thatched rooves. Mine are actually under fully boarded attic floors.


That takes care of most of the normal mechanisms. The one remaining
poetntial problem is a chimney fire, which can indeed eject huge
quantities of burning material. In normal use the flue gases cool down
fast as they rise up teh chimney, and no burning material is carried up.

Chimney fires are all about dirt flues and burning too hot. If you get
one, you puit teh fire out below immediately with buckest of water, and
block teh flue to starve the oxygen. It goes out n a few seconds. Its
very unlikely that it would hurt damp wet thatch, but I have a hose
always connected outside anyway.

The fire that hapopened was to a timber farmed house but tiled roof. The
fire was piled high, surrounded by firewood and newspapers, had no
guard, a very small hearth and a history of rolling logs off the front.
Which is probably what it did, onto the carpet. In short, it was
criminally negligent to leave it burning while we all went down the pub.

Open fires need to be treated with respect. But so does a motor car. We
are less used to fires, than cars, these days...


.andy

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