Can thatch be applied
onto an existing structure? Most other roofs are constructed
at a pitch smaller than the recommended minimum pitch of 45 degrees . Should
the existing structure be adapted for a thatch roof, it would need to be designed
by an engineer and modified to attain the minimum angle required. Most thatch
roofs in South Africa are constructed from poles and not sawn timber, the roof being
exposed from the inside, unlike conventional roofs, which are fitted with ceilings.
How long does it take to thatch a roof?
A team of three men under normal working conditions will thatch between seven and ten
square meters of surface area per day. A normal domestic house roof of 350 m2 roof
area would take 6 teams about seven days to thatch.
How much does it cost?
The cost of
a thatch roof is dependant primarily on the maximum span of the roof. The greater the span,
the higher the cost per square meter. The cost of the roof should be determined from
engineered structural drawings.
Does thatch keep out water? Yes. Thatched
roofs do keep out water. This is possible because of the minimum pitch of 45 degrees, and
because the thatching grass is a waxy organic material that is packed to a density of
approximately 35 kg/m2 throughout the roof. These elements work to- gether to provide a roof
that is not only beautiful, but watertight.
Isn't thatch a fire risk?
Yes it is, as any other com- bustible material. However people living in thatch roof homes are
more aware of the fire risk and take more pre- cautions and as a conse- quence fewer thatch
homes burn down pro rata in relation to other forms of roofing.
Does thatch hold up in coastal storms?
If the roof and especially ridges and gables are constructed and thatched correctly thatch
roofs can withstand severe wind and storm conditions. |
Is there a "real" roof underneath?
No. There is no need for a sub-roof. The thatch is applied directly to the
rafters. Some owners choose to install a normal interior ceiling, while others choose to
leave the thatch exposed. The trend in SA is to leave the thatch exposed.
How long does a thatched roof last?
The life of a thatch roof is dependant on a number of factors. The quality of the grass used,
the angle at which the roof is constructed and climatic conditions. Thatch will last far
longer in a climate that is either hot and dry or cool and damp. Should the climate be hot (30
degrees plus) and high humidity, the conditions for fungal growth is good and leads to deterioration
of the roof in a far shorter time. An average life span for the thatch layer under normal climatic
conditions in SA is approximately 20 years.
What about pests?
Thatch roofs occasionally do harbour insects. Very often as a result of insects laying eggs on
the grass prior to thatching and occasionally while the building is inhabited. Use of a good insecticide
is recommended on these occasions. The exterior of the roof is subject to damage by baboons and
monkeys. This damage is alleviated by covering the entire thatch surface with galvanised wire netting.
How often should a thatch roof be brushed or combed?
Thatch roofs should only be combed when necessary. Combing is necessary when
the grass is seen to be sagging or sliding on the roof . The roof is combed to maintain the correct
compaction and then it is essential that all twine stitching be pulled up tight to prevent further slide.
Do all thatch roofs go black?
Yes, all thatch roofs do go black. The discolour- ation is due to fungal growth. Good thatch surface
texture blackens more rapidly than poor surface texture due to less exposure of the grass stem.
The climate also determines the rate of fungal growth.
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