Thatching a roof is an age-old tradition. It is hard, demanding work. Today it exists primarily as a restoration activity. Thatching is the craft of building a roof with dry vegetation such as straw, water reed, sedge, rushes and heather, layering the vegetation so as to shed water away from the inner roof.
There are more thatched roofs in the Ireland and United Kingdom than in any other European country. Quality thatching straw can last for more than 45–50 years when applied by a skilled Thatcher.
The only way to create a visually stunning structure is to use a genuine hand thatched roof. The creation of each genuine thatched roof is an art and as the thatching progresses the structure comes alive. Not only does the thatched roof look fantastic, it will also be completely water tight and offer year round protection from the elements.
Thatch, being a natural material, will mellow in colour from its original fresh straw to a dark sheen that tones in wonderfully with the South African outdoors. At the same time, the rustic roughness of textured thatch inside the building lends itself to co-ordination with other natural materials such as stone & wood etc. The high open ceilings in thatch roofed homes give the rooms a spacious, airy feeling that can be followed through with large window openings, and perhaps stone or slate floors to add to the rustic ambience.
Because thatching is a labour intensive process, the cost of a thatched roof is normally up to 60% higher than that of a conventional roof. This price difference can be limited, however, by using the roof space efficiently, with dormer windows and a mezzanine level for instance where the walling and plastering costs will be less. The insulating properties are very good, keeping the home warm in winter and cool in summer. Although thatch is one of the oldest building materials, modern, innovative laying techniques ensure that the interior finish is clean, with no loose pieces hanging down to harbour insects or encourage spider webs.
Design Of Thatched Roof
A thatched roof should have a minimum pitch of 45° and min 35° over dormer windows. Take advantage of the steep pitch to provide accommodation in the roof space to make the design more cost effective.
Try to keep a thatched roof as simple as possible, but the ability of thatch to adapt to free curved shapes to develop a less formal plan could be implemented.
Consider flashed areas; features that penetrate or interrupt the roof should be avoided as far as possible. Chimney shafts should be designed to penetrate the roof plane at the ridge, thus avoiding the necessity of back flashing.
Rain water must not be allowed to discharge from a high level roof onto a thatched roof at a lower level.
Thatch, 150 mm thick, has a mass of about 20-25 kg/m2. The roof framing normally consists of eucalyptus poles that have been chemically treated. The poles may be spaced up to 900 mm apart. But Building Societies in South Africa will usually insist on a maximum spacing of 700 mm and a minimum pole diameter of 100 mm.
The grass that is used to form the ridge capping is thinner, softer and more pliable than that used for the main roof. The lower edges of the ridge capping may be trimmed to a decorative profile with chevrons or scallops.
Alternatives to grass ridges are often used, the most common being preformed fibreglass, sheet metal and cement. The ridge is the most vulnerable part of a thatched roof and particular care must be taken to ensure that this feature is absolutely watertight.
A thatched roof will normally last for about 25 years if properly laid. Dekriet will typically last a little longer, up to 35 years. A thatch roof ridge require renewal every 4-6 years.
Thatch is still employed by builders in developing countries, usually with low-cost, local vegetation. By contrast in some developed countries it is now the choice of affluent people who desire a unique, rustic design for their home or who have purchased an originally thatched abode.