On Sat, 06 Dec 2003 13:47:00 +0000, The Natural Philosopher
wrote:

..


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.


Pretty rigorous.


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.

That was one thing that I was thinking about, and should be avoidable
with proper sweeping of the chimney anyway.

I was thinking more in terms of log fires and during lighting with
paper etc. where small pieces of burning material can go up the flue,
or do you feel that they should have cooled sufficiently by the time
they have gone up the flue and potentially blown across and fallen
onto the roof? Presumably all this is OK or there would be many
more fires. I can appreciate that the greater danger is from
within.




..andy

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