Thatch roofing - Innovations in fire protection
If one look at the quote above one can deduct that there has not been a lot of innovations in the thatching industry, there has however been huge advances in the fire protection of the thatching material. Modern laying techniques also eliminate the exaggerated fire risk that many people fear regarding thatch. Nowadays various fire blankets are placed in between the thatch and with the correct compaction the fire risk is virtually eliminated and with the use of lightning conductors, thatch is no longer the hazardous material of the past.
Lightning conductors should always be installed to protect the thatched buildings. For single masts the angle of protection is 45° from the highest point downwards and one should make sure that the whole roof is covered by at least one meter above the roof of the building. For a high risk zone of lightning for example on sloping ground or on a hill, the angle of protection is only 30° from the highest point downwards along the pole and naturally the lightning conductor will have to be a lot taller or multiple conductors can be installed. When more than one lightning conductor is installed, the angle of protection between them is 60° from their highest points downwards along the poles.
For lightning protection purposes, it is strongly recommended that galvanized steel wire should not be used for binding the thatch, and rather a suitable natural material should be used. Poplar and wattle sticks are commonly used and some use cane or thatch strands. Tar treated string should not be used for binding as this can create a fuse-like effect in the event of fire.
Chimney stacks should be constructed in such away that the outer faces in contact with the thatch do not become hot. A full brick thickness (220 mm) is normally sufficient to satisfy this requirement. All mortar joints in the stack must be properly filled. The top of the stack must extend to at least 1m above the highest point of roof and a spark arrestor, (stainless steel wire mesh), fitted close to the top, covering the full width of the flue, must be built into the flue around the edges to prevent sparks flying out and possibly ignite the roof.
Cabling & Services
Electrical power supply and telephone cables should enter the building by means of underground ducts, and all electrical wiring in the roof space should be run in screwed metal conduit, with all junction boxes properly sealed.
Combustible material should not be allowed to accumulate near the house. A number of thatched roofs have, in the past, been set on fire as a result of the burning of garden refuse in the vicinity.
Sufficient space must be allowed between buildings to prevent fire spreading to the thatched building from adjacent buildings and vice versa. Some countries’ regulations calls for at least a 15m distance between the building and its plot boundary line.
REDUCTION OF COMBUSTIBILITY
Fire retardant chemicals
Many fire retardant chemicals are available these days that can be applied to thatch by immersion or spraying, but as these chemicals are generally water soluble they are, in time, largely washed out by rain as they do not penetrate the material but only form a surface coating.
A lot of exposure to the sun will also gradually evaporate the chemicals and might leave the top layer unprotected.
Fire resistant blankets
A protective, noncombustible membrane can be laid under the thatching grass to act as a blanket preventing the spread of fire between the thatch layers. Materials that are generally used for such a purpose is aluminium, building paper or glass fibre. The disadvantage of such a measure in warm, humid or high rainfall areas is that because of the impervious membrane or blanket, air flow between the thatch is restricted and will enhance the growth of destructive fungi. To allow air flow through the thatch to avoid fungi growth the chosen membrane should be sufficiently perforated.
FIRE FIGHTING FACILITIES
Soaking with water
Perforated horizontal pipes can be provided on each side of and running parallel to the ridge, controlled by stop taps at ground level. The pipes can be of galvanized steel or copper, perforated with holes at sufficient intervals along the length of the pipe to discharge water over the roof surface in the event of fire. Alternatively a horizontal pipe may be run inside the roof at the ridge, with 'spreaders' protruding through the thatch at sufficient intervals. Such installations can be used to soak the thatch in the event of a fire risk. A high rate of water discharge is needed for this to be effective and will not be able to run of a domestic water supply. Special arrangement will need to be made with the local council for such an installation.
There are two schools of thought about the value of swimming pools as a source of water supply for fire fighting. Some local authorities consider that a pool can be useful if located near enough to the house and with unrestricted access for the fire brigade.
However, some specialist organizations believe that thatch burns so rapidly that the fire brigade can rarely reach the scene before the fire has got a hold and that initial use of water from the brigade's unit tanks would be quicker than using a swimming pool supply.
A long-handled metal rake should be provided in an easily accessible place, for pulling down smoldering thatch from the roof. The handle may be fitted with a suitable clip to which the nozzle of the hose pipe may be attached, thus improving the reach of the jet.
Even when all these precautions have been taken, the occupant of a thatched house must always exercise care when handling open fires in or near the house e.g. when preparing for a bbq or burning garden refuse or if fireworks are being discharged in the vicinity.