Author Archives: rajeshkav

ROOFING WITH VOIDS

The mundane mud pot placed strategically by a skilled mason can cool your house.

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If people advise us to build only the way our forefathers built, to completely return to the vernacular ways and shun modernity, better not trust them fully. Returning to the past is, of course, a way of building eco-sensitively, but many not be either the sole way or the best way.

This is not to disapprove the benefits that we can learn from the past, but to forewarn ourselves about the possible traps in simply glorifying the past. Roofing practices provide good demonstrations for this theory. It’s well known how advanced were our seniors in providing long-lasting water-proof roofs with passive cooling and minimal annual maintenance. Comparatively, today we often complain about cracking and leaking concrete roofs which turn our houses into ovens in summer.

A thick layer of mud was among the simplest of solutions; it’s effective but not practical today in urban contexts, however much we may like to return to those age-old practices.

However, we may try to have a thick layer, but reduce the mass and weight by having voids inside. Roof heat transfers through conduction in solid materials and convection in empty space. Convective transfer of heat is very slow and much lesser than through solid mass. So, any hollowness embedded within the roof thickness reduces heat transfer, keeping the indoors slightly cooler.

Common practice

In many regions of northern India, it was a common practice to place small mud pots, either tea cups or 6 to 7 inch diameter clay trays, 3 to 4 inch deep on the terrace, with the bottom up. So, there is a cavity now above the roof top.

This layer of pots is filled to level using screed, either plain cement concrete 1:2:4 if water-proof terrace is needed or one may use stabilised soil-cement mix. Some lime may be added to provide water-proof qualities. The final top surface may be finished with white heat reflective cool roof coat, for additional thermal comfort inside.

In a recent project in Vikarabad near Hyderabad, this technique was revisited. Of course the availability of the clay pots led to using lesser number of pots than what’s ideal, but as an experiment to check its feasibility today, it was a success. In this case, this layer was laid over tandoor stone roofing, reviving another vernacular practice. It’s sad that though clay pots have multiple uses and benefits, their production has reduced due to the onslaught of produced products.

The void should be completely inside the slab to trap the heat there itself. Of course, once the air in the cavity gets heated up, some heat transfer would happen due to convection, but that would be much lesser than otherwise with no void at all.

The best is to have a ventilated cavity roof, which cannot be achieved by this simple using of clay pots. Only for very hot regions we may try such more advanced modes of passive cooling.

Pots inside thick mud phuska roof is not a new idea, but among those which are being forgotten. Before they are fully lost, we need to check the possibility of their modern applications.

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The great wall of India

Houses of the past had walls built with mud and exposed to sun and rain for many decades with no sign of damage or decay. 

20bgpKudaliIttigeManneVillagejpgWhat could be an effective solution towards eco, green and sustainable? If we select two – being local and being frugal – it may surprise most people. Haven’t we heard these words too often, which do not belong to our modern times anymore? It is too late to live local now in our hyper-urbanised contexts and frugal living is an unfortunate curse on the poor, to be eradicated at all costs.

Given such thoughts, can we relook at the local and frugal, not as a curse but as a studied choice? Something common that we see across India while travelling is housed with mud walls. How many of us observe them, without taking them for granted?

If we go searching for the local and frugal, every other region has much to offer, especially in natural materials like mud and stone. In an old house in the historic village of Manne near Bengaluru, one can still see the old walls built with a specific technique called “kudali ittige”. Typically owner-built houses, we can still meet the septuagenarian seniors who claim to have built the walls with their own hands.

Mud for construction was dug out from their own land, also to get irrigation ponds; so it’s a double benefit! After careful sieving to remove unwanted dry leaves, debris, hardened mud particles and such others, it is mixed with grass shreds and small stone pebbles. Depending upon the actual soil characteristic, they may add sand, silt or gravel, for mud with too much clay cannot be built with. After two to three days of preparing the mix with water and foot trampling, it is spread flat on the ground to about 3 to 4-inch thickness.

Different sizes

Just before it gets set and very dry, the mat-like spread is cut into blocks using an axe to the size required. Since no individual brick is made upfront, this method allows for making bricks with different sizes as may be required by the construction of external walls, pillars, niches, thin inner walls or so. Primarily it is a variation in doing sun-dried adobe bricks.

Using the same mud composition, slurry-like mud paste is made to be used as mortar.

The wall observed at the site has been partly exposed to sun and rain for many decades with no decaying. Mud consolidated has become like a stone!

The soil varies from place to place, some good for cultivation, construction, pottery or even for toys. Soil for tubers is not good for rice – amazing to see the worldwide local variation within the same global material, without which early human civilisations would not have evolved up to our generation.

If we are, to begin with soil and end with soil and if mud has sustained humans all these 200,000 years, it is not fair that we forget it.

When Nature warns building sector

Cyclone Fani devastated infrastructure because we ignored sustainable designing and healthy construction practices. 

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How many of us have consumed less food after seeing images of starving children? How many of us have used less water after seeing images of famine-stricken Karnataka villagers? Hardly any, or may be a minuscule few.

Given that, how many of us will live consuming less of Earth’s resources so there will be lesser greenhouse gas emissions, after reading about the cyclone in Odisha? Possibly a handful. The drought conditions in one State and cyclone with windy rain in another State – yesterday it was in Kerala, Coorg, Chennai or Odisha and tomorrow it could be in Bengaluru.

These are not freak accidental weather behaviours, but a manifestation of major climate changes emerging across the globe due to increased fossil fuel burning demanded by the millions of products that we are producing. Both the shop sales and e-commerce boast of lakhs of products to be brought, yet the human demand for more products is going unsatisfied. Are these connected to cyclone Fani? Yes. Bhubaneswar was ravaged in 1999, and remarkably recovered. But global warming has relentlessly increased, causing more cyclones worldwide, this time targeting the Odisha coast again. The fact that we lost very less lives is laudable, but how often can we keep preparing for cyclones? What about the livestock, green foliage, power lines, roadways and infrastructure lost forever?

Videos showing buses overturning, small structures coming apart, trees being uprooted prove that nature is more powerful than us. If we wish to claim control over her, please no way. The alarming matter is cyclones are becoming less predictable, as the recent issue of ‘Down to Earth’ reports about the catastrophe at length. It is a paradox that Bhubaneswar is hard hit, the city designed by Otto Koenigsberger who wrote the book ‘Manual of Tropical Housing for India’ – an early text book on climatology not only in India, but also in the world. Unfortunately, we cannot blame either of them.

What is the connection between sustainable designs and cyclones? Across the world, nature is unleashing revengeful punishments against humans in multiple forms and locations. Cyclone is not an event of today but an accumulated implication of our last few centuries of agriculture and urbanisation, hence a warning signal for the future.

Could we have designed and built such that our buildings will have less of manufactured materials, hence lower embodied energy, which means less carbon emissions with reduced greenhouse gases that do not lead to ozone layer depletion, hence cause less global warming?

Resilience to risks and adoption to climate change are the mantras today, instead of eliminating the risks and stopping the change. At this rate, it will be too late.

Can stakeholders of the construction industry – promoters, owners, builders, material manufacturers, designers, managers, marketers, offer such solutions that may minimise damage from possible future cyclones?

Build sensibly or perish

If we ignore valuable advice given by architects of yore and construct buildings against the laws of nature, we are doomed.

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Victor Olgyay is the name few hundreds would have heard of in India and few thousands in the whole world today. Nearly 60 years ago, he started working on his book ‘Design with Climate” which got published in 1963. If he could advise us how do design sensitively and comfortably so long ago, why do we continue to ignore his wisdom? Some of the research topics he wrote about were arrived at much before him too.

Many forewarning kinds of books appeared shortly thereafter. ‘Silent Spring’ by Rachel Carson published in 1969 was path-breaking research on how chemicals are negatively impacting nature, mainly focusing on those which were used in agriculture, pest control and related issues. The organic movement now spreading wide has made people aware of all these.

Another early text, ‘Man Climate and Architecture’ by Baruch Givoni, got published in 1969, making the 1960s a decade of awareness building. However, after 50 years, the use of construction chemicals both in numbers and quantity is growing at an alarming upward curve.

India should be proud of the fact that it is among the first in the world to have had its own book on designing eco-friendly architecture, albeit written by a German. ‘Manual of Tropical Housing’ by Koenigsberger and others was published in 1973, and for more than 45 years we have an early manual for reference.

We have our own manual on climatology, but how much of it do we follow except as a textbook in colleges? How many students who study it for examinations forget it soon after and design architecture against climate? Why and who influences our construction industry decisions?

‘Design with Climate’ by Victor refers not only to all the basics of climate in general but applies that knowledge to design and construction. It contains topics such as an adaptation of shelter to climate; effects of climate on man; solar controls; bioclimatic charts; regional characters; microclimatic effects; basic forms of houses; morphology of town structures; thermal effects of materials; designs for different climatic zones and such others. Even though the book focuses on the U.S., the theory is applicable universally.

As such, more commonly needed data on wind, airflow patterns, heat, solar glare, sky factors, Sun path diagrams, shading devices, light intensities, passive cooling methods, lessons from traditional architecture, implications of massing and such others are all there. It is amazing to see how Victor attempted to cover a wide variety of topics with actual calculations using the early instrumentation available, which is so close to the more realistic ones available today with all software.

In many ways, its subtitle, ‘Bioclimatic approach to regionalism’ was the original contribution of Olgyay. This thought process, directly or indirectly, later led to many terminologies such as Bio-mimicry, Biomorphism, Biophilia, critical regionalism, eco-friendly ideas, local architecture, sustainable designs, green buildings and so on, and we can read shades of bioclimatic approaches in many other related theories like New Urbanism or even in Zero Carbon Cities.

It is easy to say Victor was ahead of his times to thank him, but it is a pity that we pay no attention to his research and advice even now, continuing to design against climate. It is time to realise climate change has already gone beyond our control and merely trying to design with climate will not stop the juggernaut. We have hurt, angered and irritated climate so much that now she is retaliating by warming up and speeding up in the form of cyclones, hurricanes and tsunamis.

Listening to Victor Olgyay and many others could have saved the east coast of India, mainly Bhubaneshwar and Puri, from being devastated by cyclone ‘Fani’. Are we able to see the connection between designing with climate and cyclones like ‘Fani’? If we are not, we as the human race are doomed.

For a ‘mudcrete foundation’

The composition may vary between places, though the basic considerations may include cement as the binding material.

11bgp-MudcreteFoundation1jpgThe first material early humans discovered for their construction purposes must have been mud under their feet and strangely it continues to be valid even today.

To deepen this exciting thought, just imagine a case where we dig out mud and put it back as the foundation! Yes, it was proven as a simple and fast system in many villages of Karnataka for small houses.

Excavated mud is added with broken tiles, stones or pottery with jaggery, lime and water. The mix is well trampled for two days while keeping wet, so it gains the required strength to be placed back.

Despite being a time-tested method, mainstream-size stone approach replaced it, and now sadly, the concrete column foundation is side-lining even the stone one, though RCC is mostly unwanted, costing more and damaging nature even more.

Concrete is like hard rock, but is a human product with cement, sand and coarse aggregate. If cement content can be reduced, the mix can last longer, but the prescribed mix strength cannot be compromised with. This is where mudcrete can step in.

Safe area

One safe area to replace concrete by mudcrete is in the foundation where the soil is hard with good bearing capacity. With both wall sides, the trench will never give way.

A normal 1:4:8 concrete mix at the trench bottom may act as a levelling and anti-termite course. Subsequently, mudcrete may be placed in layers of 9 inch each, compacted to about 6 inch thickness. At maximum two courses a day, a 3-ft.-deep foundation can be raised in 3 days, very safely.

The composition

The composition of mudcrete may vary between places, though the basic considerations may include cement as the binding material; sand to reduce shrinking and cracking; lime to resist termite attacks; mud as the base inert material; and brick bats, aggregates from rubble, broken stone pebbles or construction waste as the coarse material.

Proportions also change based on specific characteristics of mud and size of brick bats.

If the mud has more than half as gravel, about one-fourth silt and minimal clay, around 10% , it suits the purpose. Likewise, brick bats could be 20 to 40 mm in size, more of it in the lower sizes.

Given this, cement, sand, mud and the coarse material can be around 1:2:7:10 for a stronger foundation, and can increase mud to 10 and brick bats up to 20, based on site studies. Of course, all this needs expert supervision and engineering calculations.

A major step towards reviving it happened recently near Bengaluru for the house of Timmaiah along with students of architecture from KSSA, hoping to train the next generation. Mudcrete concept is diluted today for varied reasons, mainly lack of applied knowledge among the younger generation, hence failures. The ideal soil composition and availability of coarse aggregates could also be the causes.

However, there is no real reason why this should not be revived, at least for small and safe applications. May be it’s a matter of mind and time.

Mudcrete, not concrete

Natural materials last for long, while produced ones have to perish someday.

04bgp-GreensensG205QF96I3jpgjpgThis is a fact – longevity of construction hinges around one simple phenomenon: Natural materials last for long, while produced products have to perish someday. Even cement and concrete which are ruling the building industry today are not as strong or durable as the construction industry is making us believe so.

Incidentally, the idea of mixing fine particles, coarse aggregates and binding materials together was originally discovered during the days of Roman Empire, nearly 2200 years ago. They used broken bricks or stones with volcanic ash or pozzolona mortar, adding slaked lime too.

The Pantheon dome spanning 142 feet and rising to the same height has no reinforcement; it’s just the Roman Concrete, still standing tall after 2000 years. Innumerable markets, large gateways with wide vaults and many structures all over their ruled area stand testimony for this wonderful material. The parts of Roman ports submerged in the sea are still there, undisturbed.

After the fall of the Roman Empire, the making and building with concrete got lost. What we call as concrete today could be theoretically same as the older version, but the materials we mix and their proportions are not the same. However, we use the same name, despite the paradox that our concrete may not even live up to 100 years and in no way it can last 2000 years!

With minimal research and testing in this possibly new material that has been termed as mudcrete or earthcrete, not many people have confidence in this combination. However, in areas where load transfer has to happen only by compression, i.e. foundation, walls and such others, mudcrete is an economical and simple option.

Cheaper alternative

In civil engineering applications, stabilised mud mix has been successfully tried as a cheaper alternative for rock fill under roads and also in land reclamation. There have been a few structures built at Auroville. Many rural areas continue to mix mud with local brick waste and pebbles for varied applications. Yet, very little information is available from co-professionals and even on the Internet.

The quality and composition of mud varies between places; as such it is important to check the gravel, silt and clay contents of the mud to ensure the prescribed proportion is maintained. Brick bats, stone pieces and many other such materials are better suited as the larger aggregates.

Principles followed in rammed earth walls are also partly used here, though heavy ramming may be disastrous. If we were to revive mudcrete, many more ideas about how to use it will emerge.

For a masonry pier foundation

Though laying the foundation is the first task at site, it should be the last decision to be taken.

27bgp-greensense1erodefoundationjpgThe most invisible, but critically important part of any building is the foundation. Incidentally, though it is the first task at site, it should be the last decision to be taken, after all the ideas about the superstructure of walls, voids, roofs and such others are finalised.

Traditionally, foundation meant only one option – dig into the ground, run a thicker and widening wall down under all along the wall. Even if the building were to have intermittent wooden pillars, arches or any other design feature, full-length wall foundation was mandatory. Possibly, the failure of earlier structures would have made people wiser, to evolve the load-bearing wall system.

The idea of isolated column foundations connected by beams at ground level was introduced when the RCC frame construction became popular, where we could save time and money by not digging into the earth all along the wall.

Locations with loose soil composition, water-logged sites, constructing along sloping grounds and such other contexts hugely benefited by the RCC column footings. The discovery of this frame construction system with plinth beam is gaining popularity even in rural areas today.

On the flip side, this system meant the total building be built with concrete columns and beams resulting in budget escalation, higher embodied energy consumption and the need for a technically better supervised project. On most occasions, for simple G+1 houses, RCC frame is simply unwanted, but adopted to hike project costs to financially benefit all in the team. RCC is also short lived, unsustainable and difficult to dispose upon demolition some day in the future.

Imagine a case where the conventional load-bearing wall foundation would have worked out costlier due to soil condition, which gets realised only after the earthwork excavation. Is there a way out to economise without compromising on the load bearing capacity of the foundation?

Curious solution

Structural engineer Ravindranath Bontadka came up with a curious solution for a house in Erode by merging the plinth beam concept with load-bearing wall.

Load points were located, masonry piers as if the house would have masonry columns was introduced and the top of these piers connected by plinth beam. Now, the house plinth is ready for its nominal one or two floor construction without any RCC columns, but has equivalent to column footings underneath built with conventional size stones.

Surplus mud dug out from foundation trench was used for making interlocking stabilised mud blocks, leading to a win-win situation. Of course, we need to seek expert advice before venturing into such hybrid concepts.

Eco-friendly and cost-effective architecture is not a one-stop solution to be applied all over the country, like the RCC frame and slab system. Everywhere we see the one and only type of building with columns and slabs cast, later covered with walls, be it on a hill slope or the seaside. It’s time to localise our actions.

CATENARY – AN ARCH LIKE NO OTHER

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Versatility, affordability and ease of shaping bricks to the required size are its main features.

Every visitor to London knows of St. Paul’s Cathedral, but might not have thought how the dome is standing. Barcelona is synonymous with the Church of the Sagrada Familia by architect Antoni Gaudi but very few know what ensures it stands tall. They both use the principles of catenary arch, a rarely used but phenomenally unique concept in construction. Simply stated, if we were to hang a chain, it would hang loose in some curve to stay stable. If we draw up this curvature and reverse it to make an arch along the same profile, that arch will be stable with no other support. That’s precisely what masons of builder Arunkumar got done at Adivaram in Salem.

Once understood how to build, catenary arches are very simple, as has been proved at Auroville. Though the hanging chain has been a popular imagery, it is better to make a large scale template at site to get the arch profile as precisely as possible. Though mathematical explorations for this curve started from the 1600s, marking it physically at site is still the best with our local construction teams.

No single key stone appears at top, with the small curved profile there. With certain parts appearing as if straight, catenary does not have the same radius of curvature all along, but it varies. The first brick resting on ground is laid normal, slowly curving in later, so the load transfer finally happens at right angle to ground.

Contrast

Even for heavy loads, the top can be thin with thicker base, as such, it takes lesser materials to take the same load compared to segmental or semi-circular arch. To that end, catenary arch has its height or rise more than the span or the width. In contrast, most other arches have their span more than the rise. Centring support can come from a pile of dry masonry, wooden template or a moving framework.

Catenary can start right from the ground, making it easier for the mason to build it up, also enabling better head room heights especially in doorways. Of course, fixing door frames needs extra precaution. While it is very strong along the curve transferring the load, it may crack if any lateral load or side thrust is applied on it as it may happen while drilling for fixing and grouting door frame.

In principle, catenary arches become very handy and contextual where many other arches fail to fit. Being a rare sight, Europe often employed this typology as entrances for public buildings, making them appear grand.

While the visual reasons are still valid, what makes it more appropriate today are its versatility, affordability and ease of shaping the bricks to the required size. In an extended form, catenary vaults create rare interior spaces, while offering a real sight to the eyes. It’s time they start re-appearing in Indian buildings.

Arching, or upturning the curve

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The early arches were long poles bent with two ends fixed deep into the ground, series of which gave a perfect shelter.

The day early humans observed thin blades of grass curving down, may be with dew drops still wet and shining in the morning sun-rays, the discovery of arches must have begun. Cobwebs so commonly found then would have been hanging down in a curve, making people think of upturning the curve. There, the arch would have been discovered.

The early arches were long poles bent with two ends fixed deep into the ground, series of which gave a perfect shelter with what we call today as a vaulted roof. Incidentally, even now rural and poor people create make shift shelters in this manner! Arch starts right from the ground up.

Many kinds

However, majority of the later arches were erected upon certain height of the wall, called springing point which could be above the average human height, to avoid someone at the edge of arch from hitting the head into the arch. With such side supports and no more limits to height, there evolved semi-circular, elliptical, segment, pointed, multi foliated and even flat arch.

Among these, a special type is called centenary arch, which is among the very few arch types which start right from the floor like pointed arch, horse shoe arch and such others. With not much of side wall support or springing point needed, it can be erected in a smaller space, still enabling undisturbed movement of people.

European Gothic churches had evolved a system called pointed gothic arches, which is behaviorally different from the catenary curve. Incidentally, many churches of those days employed both the types, in the process popularizing the latter. The gently curving profile of catenary gets generated because of the very method of generating the curve.

When a chain is hung holding on to two ends, it hangs on a curved fashion to stay with equilibrium. Reversing the curve also maintains the equilibrium, giving us a profile that is stable and is called the catenary curve. The geometry of the curve is traced and repeated in building the arch.

Load transfer

Structurally, the load gets transferred in a catenary arch along the curvature and reaches the ground. No lateral buttress, side support and wall below is mandatory. As such, the upper parts can be thinner and lower parts thicker to take greater load or can be uniformly thin all along in case of nominal loads. However, if there is substantial weight to be supported, the wall parts edging the arch at bottom need to be wide enough to take the load.

Catenary arches tend to appear like an inverted English V with no sharp turn. Being a self- supporting profile, that too from the ground up, it creates a unique aesthetic statement. Considering their possible fit into narrow spans, they make excellent option for entrance doors without compromising on movement areas.

That’s precisely what made Sanjay choose this type of arch for his school building at Salem!

Advantage Arches

The indoor spaces and outdoor styles created by arches are unparalleled both in history and contemporary designs.

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The most fascinating chapter in the history of architecture could be to find how humans managed to keep the roof up there. The idea of the shelter must have started then.

It is believed that the earliest method of forming space could be by watching two branches kept inclined to each other supporting each other. So multiple such tree branches inclined together could form a secured space between them, creating a cone-shaped hut. Next four branches kept vertical with horizontal members on top could have created a flat-roofed structure, but this would still be a small space considering the kind of branches one could get – not always straight, often bending in the centre, roof collapsing from the edge and such other mishaps happening.

All this would have changed with brick making, among the earliest technologies discovered by humans, shaping it with sun drying. Soon wall making complete with varied openings like doors, windows and perforations would have followed. One of the challenges was to support the wall part above the openings. That’s when, possibly, arches were discovered.

Arches transfer the wall load by compression, i.e. loads move from one member to another by pushing them vertically or diagonally, and not by tension where they move horizontally too like in a beam. How humans learnt about the strength of curves could be an exciting research topic, for there were very few naturally curved objects to learn from. It’s possible, a playful curving of a twig could have led to trying out a wall opening with a curved profile, creating the first arches in history.

In comparison to horizontal opening topped with flat lintel, the arched top offers a multitude of benefits. Its profile changes with every variation in width and height, with a new look every time. There can be dozens of arch types, while flat lintel is flat forever. Aesthetic theories associated with arches far outweigh those with horizontal ones. The indoor spaces and outdoor styles created by arches are unparalleled both in history and contemporary designs. Of course, along with advantages, also come challenges. If built upon a support system, its strength is unknown until the supports are removed. To construct the arch without such support takes some skill. A basic knowledge of geometry applied to construction is necessary to plan them out, depending upon the span, rise, springing point and keystone on top. The joint between the arch edge and wall needs to be well thought out. Based on the width of opening and load from above, arches may be in one or multiple courses. They also pose problems in fixing frames and shutters, including for windows or doors.

Despite challenges faced, arches continued to rule the world of architecture. When masonry construction declined, being replaced by frame systems, arches were in reduced demand. Now we are realising that framed buildings, especially those in RCC, have higher embodied energy, hence less sustainable. It’s time to revisit arches