The pros and cons of a thatch roof

17 Dec 2010

For thousands of years, people have been using thatch to create durable roofs for their home, which would protect them from the elements.

Thatch, if properly installed, is one of the most beautiful and practical forms of roofing available today. Thatching is a craft that has never been taught in building school and is generally handed down from father to son, or in today’s world, a qualified thatcher will take about five years to train someone to become a master thatcher.  The thatching you find in modern homes comes from traditional African thatching techniques, as well as those stemming from Europe, mainly Germany, Holland and England. The settlers in the Cape even brought their own grasses for thatching from Europe before realising that local indigenous grasses were also ideal to use.

 

The kind of grass

Generally, finer grasses are the best for thatching, as long as the stem is less than four millimetres in diameter, as the thicker stemmed grasses are not suitable for thatching. The finer grass from KwaZulu-Natal is preferred over the slightly thicker stemmed grasses from the Highveld. The grass has to be dry and must have lost all its seed when it is harvested for thatching. The best time for collecting thatching grass is in winter when it is bone dry.

If you have opted for a thatch roof, it is important to ensure that you are not building near to or under any trees. If the thatch gets wet, it needs to dry out as soon as possible to prevent rot or fungal growth. If surrounding trees keep the roof in the shade for most of the day, the grass will have a much shorter lifespan than those in the full sun. The leaves from the surrounding trees will also drop onto the roof and keep it damp for even longer, which will also lead to rotting. Thatch that is well laid and found in very cold winter climates can last very much longer, because during the winter months the thatch actually freezes and all insect and fungal life found therein consequently dies. Believe it or not, thatch is also protected by sea spray as the salt sterilises the grass and its contents.

If the roof is properly laid and the right grass is used the average thatch roof can last for approximately 25 years, however, in the right climatic conditions, it would be able to last for up to 30 years.  

Pros and cons

Thatch is the best insulated roofing available to man. Most other roofs need to be insulated after they have been installed, while thatch roofs automatically offer excellent insulating properties, making it ideal for our hot local climate to keep the interiors of our homes cool in summer and warm in winter.

 

If thatch is well laid, it will be virtually maintenance free. Thatch is very vulnerable to being stripped by birds, especially weavers that can really destroy a roof within a year. If you need to protect your thatch, it is wise to cover it with a plastic mesh that will keep the birds away. Wire mesh can also be used, however, in time it will rust.

The weakest point of any thatch roof is the ridge. One can get it covered with a fibreglass hood or the old method of mortar will also do the trick. Ensure that the apex is always kept in good condition and that it remains completely watertight at all times. This is the most vulnerable part of a thatch roof and needs to be constantly maintained. If any work needs to be done on the thatch, always use an experienced thatcher, and do not allow any workmen to move around on the thatch, unless completely necessary.

Protecting your thatch

All houses with thatch roofs need to have lightning conductors installed to protect them from being struck by lightning and consequently burning down. These conductors need to be in accordance with the SABS Code of practice. If the house is very high or large, the mast would have to be very high to cover the whole area. This can be solved by putting in two masts or even a spike can be installed on the chimney to cover the area not covered by the spike.

If you have a chimney serving a fireplace in your home, ensure that the walls of the chimney are at least 220mm thick so that when the fire is burning, the outer skin of the chimney remains cool. Also make sure that all the joints between the bricks are well sealed so no smoke or flame can escape and cause problems. The chimney must be at least one meter higher than the roof and have a spark arrestor, made from stainless steel wire mesh, installed 700mm from the top of the chimney. Any sparks that fly out of the chimney should get caught in the mesh rather than land on the roof possibly causing a fire.

Not only is thatch beautiful to look at, but also very practical and if well installed and maintained, it can be one of the most durable and attractive roofs on the market. – Antonella Desi

Readers' Comments Have a comment about this article? Email us now.

Thank you for the informative article but I would like you to stress more on the dangers and I agree it looks very beautiful. I would just like to add that a thatch roof is very, very dangerous.  My daughter’s house with a thatch roof burnt down and I thank God that they were not inside.  They would have been trapped and you can imagine the consequences.  There was a felt fire that night and because it was winter they had also made fire in the fireplace.  It could have been sparks spread by the felt fire which was raging that night or the heat from round the chimney. The assessor said the over time the grass around the chimney because more and more dry, like charcoal and then just ignites on its own. The house was just seven years old and was furnished exquisitely but their lives are worth more than all that.   It has created some hardship for them which I am sure they will overcome. - Halima

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