Monthly Archives: August 2012

Natural, strong and green

Building with local stones can be among the simplest of actions towards a sustainable future.

For those preparing for quiz competitions, there is curious information available. Stone is possibly the most omnipresent flooring material found in the world — from Roman roads to Hampi Bazaar streets. It is found everywhere, be it at Pompeii (city and commune in the province of Naples in Campania, southern Italy, famous for its ancient Roman ruins) or Poompuhar (a town in Nagapattinam district of Tamil Nadu). In all civilizations, stone was preferred for structures of cultural importance such as shrines, palaces, public halls and such others.

Being an everlasting material, stone is hard enough for outdoors and soft enough to be polished for indoors. The traditional polishing was not like the mirror polish by machines of today, but a fairly smooth and level surface achieved by hand tools used for stone dressing. Compared to the other known materials viz., wood, mud, sand and lime, nothing could come close to stone in strength and durability. No wonder, for thousands of years, stone has been the king of all construction materials.

Amongst the factors contributing to the popularity of stone, is its widespread availability. Found nearly in all parts of the world, people everywhere learnt how to cut it to size and use in construction.

By default it is a natural material, irrespective of the type or variety, as such is a green material of high order. Thanks to modern technology, stone can now be processed and industrially worked with for a wide range of direct and specialised applications.

Carbon footprint decrease

Durability is a marker for eco-friendly constructions. If the life span of a building can be stretched, its carbon footprint decreases, since the same embodied energy gives us greater returns.

Family houses lasting over centuries are spoken of with awe and the news is published in the media to state how they lasted for hundreds of years. The secret is no secret to people in the construction industry – it is the use of durable natural materials like stone.

Greedy exploitation

Archaeologists term a major part of human civilisation as the ‘Stone Age’, as if to recognise the way stone started to shape human destinies. We know how it continues to do so even today, in our computer era. Building with local stones can be among the simplest of actions towards a sustainable future. For the advocates arguing against stone, primarily because of reckless quarrying around urban areas, the answer lies in the comparison between the embodied energies going into local stone and the other manufactured materials apparently available cheap in the market.

The problem does not lie with stone as a material, but with the greedy modes of exploiting it. Mostly we are not sensitive to mother earth and do not carefully locate the quarries.

It is an apparent contradiction today to discuss stone in buildings for strength and longer life, when we are increasingly designing lightweight materials, and for shorter life! The worst is with interiors, where even the promoters sometimes expect to change it all in less than 10 years, even though there could be a polished granite floor below! It is time we re-validate our thinking process, and start building for bringing in longevity in our uses. With stone perhaps.

And we shall discuss a whole lot of them in the coming weeks.

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The over-familiar stone

Every bit of waste material at site can be used as hard aggregate, making granite ecologically meaningful.

Local materials play a crucial role in ensuring sustainability, but also face the danger of rejection. For many people, while the best of local material appear ordinary, the average material from elsewhere appears extraordinary! Granite is among the more commonly found hard stones in South India, which partly suffers from the above syndrome, despite being one of the most durable, cost-effective and natural materials around.

Granite is a versatile option, being applicable in a variety of modes – size stone wall, wall cladding, roof slabs, carved pillars and also durable floor. It takes fine polish and comes in a wide range of patterns and costs ranging from affordable to luxury. With a very hard surface, granite floor rarely gets scratches, hence lasts very long. Due to the hardness, it is always factory polished, saving equivalent time at site. Considering this fact, mixing granite with materials that require on site polishing can be risky.

Arguments against granite question increased quarrying that can deplete a resource, but compared to other manufactured materials, local granite has less embodied energy. Also, it can be used for kitchen counters, toilet wash basin tops, corner shelves and ledges for display.

Most such smaller pieces can be got from the larger slabs, by well-planned cutting. Every bit of waste material at site can be used as hard aggregate, making granite ecologically meaningful.

Ensuring the right quality and price of granite is dicey, as it requires expertise. Mostly available in grey, black, pink, red and yellow, either in pure shades or mixed, granite is normally supplied in polished, brushed or flame finished textures. Sometimes it comes with softer surface, which gets rough over the years or small depressions called pitting may happen.

Patches

If disfigured at site, no re-polishing is possible. Some light-coloured granites develop patches of darker shade after laying, mostly due to absorptions from sub-floors, which has no major solutions.

While laying the slabs, matching the surface grains is commonly done, if the slabs are from a single quarry. Water-cut slabs with minimum grain patterns are easier for this match, with very thin paper joints.

Pigmented mortar mixes could be used to fill the joints to achieve best results in matched patterns. If not possible, laying in a mixed manner can also be attempted.

Granite tiles, coming in smaller sizes with random textures, cost half the prices of slabs, hence are worth considering.

Once laid, precision cutting is possible only with advanced drilling machines that demand high skill. Hence, it is better to plan the sizes, holes and such others in advance.

Granite, if quarried locally, comes at lower prices, which is to our advantage. Paying double or triple of this price, just for a non-local pattern, is simply not worth it.

If we are from the granite region and seek a green material with value for money, granite is among the best choices.

Kota, for a fresh look

Kota stone is much cheaper than marble and granite, hence makes economic sense. 

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 2×2 or 2×4 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.

Terracotta, totally natural

Terracotta tiles are among the best material for verandahs, terraces and sit-outs as they absorb water, let it evaporate and stay non-skid.

Ever wondered what could have been the choice for floor finish before machines came along? Even with machines around, not every time we had a distribution system, so their products had only a limited reach. This meant most parts of India had to find their own local solutions, which curiously depended upon mother earth. Consolidated mud floors topped with cow dung layer, appears to be among the local solutions, found nationally. It continues to be practised even now in villages and low-budget homes. However, the practicality of floor usages and frequency of maintenance reduces its popularity, giving way for improvised and compressed earthen tiles called terracotta tiles.

Initially produced as hand-made and sun-burnt clay tablets, soon people realised various modes of pressing mud into thin, strong, flat tiles. With the clay industry evolving a few centuries ago, floor tiles became a common product along with roof tiles. The costs incurred in the machine-made, kiln-burnt and well-finished tiles must have made them exclusive during the early decades, naturally finding their way into royal homes, houses of the rich, important public buildings and such others. Commonly found in historic structures, terracotta tiles are a surprise testimony to the durability of processed mud.

Though there are optional shapes, square tiles are better since they do not highlight the dimensional variations commonly found in kiln dried tiles. Some masons try placing them touching each other, but having a normal joint gap works better in the long term. Being factory produced, these tiles cannot be polished or repaired at site, hence careful laying is important. Though terracotta tiles are strong, they are prone to develop surface scratches, hence placing heavy furniture, pulling them around or doing heavy duties like workshop activities are not advisable. Tiles once brought to the site need to be stored away from sun and rain, due to their short shelf life in exposed conditions.

Terracotta tiles are among the best material for outdoors where water may come in – verandahs, terraces and sit-outs. They absorb water, later let it evaporate and stay non-skid. Accordingly, different grades for outside and inside are in the market. The occasional cracks in old buildings are more due to settlement of the structure, and not due to weak tiles. Slight fading may happen, yet the colour is integral throughout the depth of tile, hence lasts many decades. These tiles can be all over the house, but look good at informal family, study or sunken courts, but are not for kitchens and pooja rooms, where varied liquids may spill over. When it comes to heritage restoration and ethnic interiors, terracotta rules the market.

Top amongst green materials

In the list of green flooring materials, terracotta is among the top, with least embodied energy, life cycle cost and re-usability following demolitions as hard aggregates. They are totally natural, mostly local, generally economical and comparatively easy to lay with the best of earthy appearance — more than enough reasons for a studied reconsideration in these days of artificial materials.