Mangalore tile roofs are eco-friendly and amply prove their durability and ease of installation. A look by our eco-friendly architect
Mangalore tile roofs have often suffered for no mistakes of their own. Of course they are fragile, demanding careful handling; the bottom surface attracts salt deposit and there could be more cobwebs! However, the decreasing popularity is also a result of our generation forgetting how to build with tiles. Innumerable mistakes have been committed by us in design and construction, especially in areas such as roof angles, support members, corner junctions or managing rainwater. It's but natural that people have lost faith in the system itself. Additionally, alternative roofing ideas with ample flexibility, security and availability have marginalised the tiled shelters.
Being labour intensive and based on local resources, the fact that tiled roofs are eco-friendly goes without debate. Millions of such roofs all over India amply prove their durability and ease of doing. The frequent statements about “how cool traditional homes used to be” is a testimony to their contribution to comfort.
Traditionally, all tiled roofs rested on timber sections called joists, rafters and purlins, when it was easy to lift the tiles to get in. Nowadays, mild steel sections have replaced them in most areas, due to shortage of carpenters and cost considerations. Welding an additional bar under the tile converts the support into a typical grill, just like at windows, ensuring safety and security. The common complaint is that the bottom surface collects salt deposits and develops white patches. Painting this face with tile colours reduces the visibility of salt patches. If additional budget is possible, clay ceiling tiles can be installed under the main tile, providing aesthetic appeal and increased thermal comfort.
The right slope
Unknowingly, many designers provide a low angle for the roof, which decreases the overlap between tiles and rainwater slips into the building. A minimum of 25 degrees slope is necessary for any tiled roof, though in the past, much steeper 33 or 45 degree slopes were provided. The junction of roof with wall surface needs to be well done with part of the roof going into the wall and finished with curved water-proof beading. A sloping roof with tiles demands basic geometry in the plan form, to ensure proper matching of the slope angles, high points called ridges, low points called valleys, edges called eaves, ends called hips or gables and such others. As such, even before we start the construction, calculations and drawings become necessary to ascertain that the roof sits properly! Carpenters who routinely do such roofs have it all in their mind.
If tile has to top a RCC roof (such double roof lacks design logic), placing the tiles on mortar strips is a better detailing than pasting all tiles over a thick layer of mortar. Once pasted, locating water seepage and replacing the cracked tile is very difficult. Both tile and mortar being good conductors of heat, such roofs do not provide passive cooling.
Mangalore tiles might have been criticised, but building with sloping roofs has not reduced much, suggesting a continuing validity for the idea.
(The author is an architect working for eco-friendly designs and can be contacted at firstname.lastname@example.org)