In green architecture, using local materials is an important criterion, but the idea of local has often been debated. If cement is locally available, does it become local? What if the local product is costlier than an out station product? Kota stone is a good case in point. This excellent flooring material travels all over India from Rajasthan, hence theoretically not so eco-friendly, but being natural lime stone and suited to a variety of conditions, it fares better than most local options.
Originating from the Kota region, hence getting the name, the stone has a pleasant greenish blue colour, going well with most interiors. Other colours like chocolate brown are also available, but with lesser popularity. For long, marble and granite dominated the scene, relegating Kota floors as the second choice, specially for passive areas, but now people are realising the advantages of Kota floors.
It is very durable, performs well under heavy use, takes mirror polish, reduces possibilities of slippage, and surface dust does not show off immediately. A gentle patch of shade appears on the surface, as such does not appear sophisticated, hence retains the rustic looks of natural materiality – an asset in earthy constructions.
Final finish
Among the major problems with Kota stone is the final finish, which is visible only after polishing. To that extent, the even consistency of colour shade and textural appearance is unpredictable. However, the subtle variation itself adds to the natural qualities! In case the quarried stone has weak surface densities, some surface flaking may happen during rough use. Generally Kota stone can be laid anywhere except the kitchen, singularly or in combination with marble, Jaisalmer yellow or such contrasting materials. It has also been used for wall cladding.
Floor height
Kota stones are up to 1.5 inch thick, hence need provision in floor height calculations. They come in 2x2 or 2x4 ft. size, with more joints than other stones, which of course can be disguised by using pigmented mortars. They are laid to level on a 1:4 mortar bed, and topped with cement slurry. Minor surface level variations get evened during polishing, normally done in seven rounds, including the final tin oxide round. Proper curing is a must, keeping the floor wet for about a week at least. Polishing with grinding stone should begin only after proper curing. With the surface generally rough cut, the first few rounds are necessary to get the surface level, with the later rounds adding the mirror-like polish.
Re-polished
Kota stone is much cheaper than marble and granite, hence makes economic sense. Depending upon the location, it can be laid polished side up anyway, but also can be laid the unpolished side up to get a textured floor finish. Though it is also a natural stone like granite, it can be re-polished over the decades if a fresh look is desired. Among the few eco-friendly materials, Kota stone floor can last as long as we want it.
(The writer is an architect working for eco-friendly designs and can be contacted at varanashi@gmail.com)
