Clay tile roofs
• Burnt clay tile roofs are only used for sloping roofs between about 20° and 50° inclination of rafter, and the tile shapes differ for each range of slope. It should be remembered that the rafter pitch is always steeper than the tile pitch (see illustration overleaf).
• Clay tile production is a traditional village craft in many regions, but uniform shapes and qualities are difficult to achieve. Mechanized plants produce good quality tiles, but at higher costs. An appropriate intermediate solution is provided by mobile presses with interchangeable moulds for different tile shapes (see ANNEX: Machines and Equipment).
• Depending on the clay type and production method, a major problem of clay tiles is the immense loss (in India about 35 %) due to cracking and breakage. A good remedy has been found in the use of ammonium chloride as an admixture varying between 0.1 and 1.0 %, depending on the type of soil (Bibl. 00.41).
• Clay tiles are heavy, requiring a strong substructure and closely spaced battens. Therefore, tile designs (eg Mangalore tiles), which require wider spacing of battens, are lighter and more economical. But generally, the weight of the roof and loose connection of tiles, make them susceptible to destruction in earthquakes.
• Good quality tiles with good overlaps are perfectly waterproof. The red colour, however, tends to absorb solar radiation, so theta suspended ceiling may be needed for indoor comfort.
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