The humble zinc has emerged on top among materials that offer roofing solutions.

With the cost of construction shooting through the roof, a host of new roofing materials carry a promise against a hole in your pocket. The days RCC ruled the roost are clearly passé. A variety of metals and materials of polyvinyl genre are offering solutions that ensure a roof over every head. And to boot, they are cheaper, durable as well as recyclable.

The humble zinc has emerged on top among materials that offer roofing solutions. Zinc is a natural element that takes very little energy to manufacture compared to other metals used in equivalent applications. Rolled zinc is unique in that it reacts to the main components of the atmosphere by creating a self-protective coating. Thanks to the latter, zinc can easily last a hundred years. Rolled zinc is also 100 per cent recyclable and 95 per cent of it is effectively recovered and re-used in different areas of applications. It is also amenable to use as a cladding material for facades, interiors and partitions.

Long life

Nilesh Kumar from Umicore, a company that manufactures rolled zinc products sold under the brand ‘vmzinc’, says his company’s perforated zinc rolls could ensure a life of 80 to 100 years and are totally rain-proof. These could be used for all kinds of buildings such as schools, villas, bungalows, apartments, religious places and ordinary houses. However, zinc is not the sole metal that goes into ‘vmzinc’. The manufacturers use an alloy of zinc, titanium and copper. Thomas George, the company’s Bangalore-based regional sales manager, says that the cost ranges from Rs. 400 to Rs. 850 per sq. ft including the cost of installation of such roofs together with accessories. Curiously, Umicore has also come out with zinc-made sunshades, louvers as well as perforated partitions which while being see-through from inside obscure the inside view and allow rooms to be airy.

Installation

The zinc sheets could be installed vertically, horizontally, diagonally or as shingles, imparting traditional aesthetics. George says schools, public buildings and exhibitions centres install zinc roof in Europe not merely as a measure of cost-cutting but also for aesthetics. “You could dare to be creative with the material”, he claims.

Architect John Ronan used zinc-perforated sheets to clad the street-side exterior of the Poetry Centre in downtown Chicago (see picture) with a veil of perforated black zinc and erected a monument clothed in a visual filter. “This exceptional element lets passers-by know that they are walking by a cultural building. Ronan could have chosen the screen-printed text for the glass walls too (as we see in several Vayu Vajra buses in Bangalore). But he did not. This 1,900 sq. m building blends quietly into the surrounding urban fabric in a dual present-absent mode. The popularity of zinc with the newly trained architects in the West has in fact led to launch of a magazine on the topic, Archi Zinc Trophy, dedicated to zinc architecture. It is published in five European languages.

Tiles made of organic fibres together with high grade bitumen are also recyclable and amenable to versatile use in roofs. These tiles are light-weight, water-proof and carry the promise of retarding the pitter-patter (noise) of rain by 70 per cent. Onduline, a French company, has begun manufacturing Onduvilla tiles in Bangalore in both traditional format and sheet profiles. Puneet Patil, representative of Onduvilla, says these tiles are highly aesthetic in nature and are ideal for farmhouses, ashrams, schools, terrace coverings for standalone garages, villas, pavilion, and even for wall cladding. They can withstand the fall of coconuts or jumping monkeys. Though only meant for the final roof in multi-storey structures, they work out cheaper than RCC and are comparable with metal roofs. Interestingly, the company has recycled two lakh tonnes of material and earned carbon credits.

Patil dispels the fear that the tiles have an element of asbestos and says the tiles or sheets provide a lot of thermal and acoustic comfort. Sound-dampening effectiveness allows their use in schools and colleges where showers may interrupt classes.

In order to make the tiles totally seep-proof, specialised screws are provided to fasten them with the metal substructure. The screws, besides being layered with washers, come with a hat-like cap for covering the upturned end.

Roof gardens

For roof garden enthusiasts who harbour fears regarding inadequate drainage leading to seepage or dampness, Germany’s Doerken company has introduced Delta Terraxx, which is a dimpled sheet with welded geotextile installed as a protection-cum-drainage layer to the basement and its waterproofing system. These sheets are rot-proof, resist saline solution, inorganic acids, and alkalies, and can also be suitable for foundation-wall protection and drainage.

Sujay Shah, Managing Partner of Doerken GmbH, says civil structures in India are still not certified for drainage norms as no yardsticks are in place. Often dampness is misconstrued as inadequate drainage. He says these norms were initially standardised in Germany and were later recognised for worldwide application. For instance, for horizontal plain surfaces, the norm is .03 litre per metre per second while for vertical plain surfaces it is .3 litre per metre/second.

He says application of these norms will allow many building owners to go for roof gardens by laying membranes beneath the soil.

Laying such membranes has a side benefit too. In case of heavy downpours, these membranes will slow down the rain run-off and will help avoid water-logging or flooding on the street and basement.

Says Shah, a 150-page book on green roof and drainage solution has been published in Germany. Doerken was engaged for water-proofing the 57-km Gottherd tunnel in Switzerland.

Even the under-construction Marriott Hotel in Whitefield is using Delta Terraxx for green roof.

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