Category Archives: concepts

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.

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.

Designing a chajja

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It can do as much harm as good, if not well designed.

The idea of seeking shade from sunlight is as ancient as the human civilisation itself and this statement may elevate the respect we should give to sunshades above our windows. However, we have reduced it to a ubiquitous flat RCC slab, often used everywhere without any reason.

The word commonly known today as ‘chajja’ is the projected element just above the window, which shades the opening, stops rain from entering the room and reduces sky glare while looking out of the room.

Ideally, each window needs to have specifically designed element based on the orientation, sun directions, rain patterns, monsoon wind, sun path and such others, besides the activities inside the room.

However, it is of common practice today simply to cast a flat RCC slab as an extension of the RCC lintel beam, which can do as much harm as good, if not well designed. Between buildings with a very narrow gap, sunshades will block the little light and air we can get, hence should not be provided. The buildings shade each other.

If the chajja is to mainly serve the looks and elevations, the ordinary flat projection will adversely affect. In a north facing windows which get minimal rain and harsh light, chajjas can be generally avoided, but for aesthetic reasons. So, fixing a flat slab is not a solution in every context.

Imagine the alternative, more attractive windows like arched windows, which is liked by many people for the character it gives to the building. In typical cases, it is avoided, because not all masons can build it and equally well because it cannot have a chajja!

In historic structures, a small cornice band would appear above the void, acting as a drip mould – directing the water flowing down the surface away from the window. Today, such decorative bands are out of practice. Negotiating the curve with a vaulted RCC is too costly due to centring and finishing it; Mangalore tiled chajja is ruled out in this profile and there can be no standardised chajja considering that curvature may vary between two windows. Unlike a normal window, arched ones definitely need protection from both top, called vertical shadow, and from sides, called the horizontal shadow.

One option is to place the chajja also in a curved profile, with the projection anchored to the wall itself. Inverted T sections can be grouted just above the arch following the same curvature which can take flat clay hourdi tiles, stone slabs or even lightweight in situ cast RCC slabs. Only the joints between the top materials need to be waterproofed.

Designing the right shade

Slabs come in many shades to protect your building from intense heat and rain.

02bgp-greensensGMG5BTPAL3Ask anyone if he or she prefers sunlight or shade – the answer is predictable with no failed guess! Shade is what all animals need, including humans.

Early architecture in the tropical zones of India had overarching criteria in creating shade and it was more critical than any other criteria. Incidentally, it continues to be an important consideration even today in eco-friendly designs.

Creating shade for the whole wall is among the early knowledge people picked up while designing for the climate. Initially achieved through simple ideas such as projected roofs, closely placed dense housing, deep verandahs, planting trees and such others, slowly led to windows set in thick walls, projected jharokhas and roof stone extensions. Traditionally, designs had deep roof eaves such that sunlight and rain would not penetrate deep into verandahs, porches, porticos, entrance mukha mantapas, balconies and walls facing south and west.

A formal study of buildings by experts led to a variety of options to shade specifically windows, leaving the wall open to sunlight. In normal buildings, it is common to see the horizontal chajjas or sunshades, done today mainly with RCC. Many windows also have vertical projections on both sides called fins, or it could be projections all around with a box chajja. RCC has emerged as the most prevalent material for all these, though it is not among the best options.

Among the less studied category are vertical drop slabs useful to stop both the sun and rain. They also protect our eyes from direct sunlight even when we are sitting outdoors in semi-open spaces such as balconies or entrances. Often, the upper floor common passages along the outer edges of commercial buildings would have them so the lower floors will not get direct rains. Most city homes have car porches with a room on the first floor so the clear height of the car porch may reach up to 13 feet. If the house faces south-west or direct west, evening sunlight would reach deep into the porch, heating up the car due to light and wetting it due to rains.

These vertical drops cannot be done with simple masonry, while complete concrete solutions could be costly. Traditional buildings could afford to have wooden planks in this area. Very often they are done with chicken mesh plastered on both sides, also called as Ferro-cement slabs, but they tend to crack under the strong sun over the years. Some designer buildings exhibit well placed horizontal louvres, which demand good detailing and execution.

Simple solution

A simple solution lies in using any stone slab, sheet metal, large clay tiles or matted material that can withstand direct sun and rain. They could be fixed with steel channel sections hung from roof slabs by inserting the slabs within the sides or grooves of the section.

If well designed and detailed to match the elevation of the building, the vertical drop slabs can be an element of attraction, rather being an ugly but unavoidable addition.

A rammed wall with coloured earth

Faster construction, perks of low maintenance and aesthetics are the positives.

19bgp-greenppgnIs building with mud an outdated technology? Is it no more practical to do so, considering that a large number of manufactured and marketed materials have flooded our times, claiming better performance and perfection, besides variety?

This is a myth of sorts, which can be felt if we study the properties of mud, its durability and the range of aesthetic expression mud architecture achieves between different regions. With cob, adobe, soil cement block, interlocking mud blocks, rammed earth walls, pigmented walls and such others, the soil of the same place too can have multiple appearances.

Strangely, there are people who believe that natural materials like mud will have a supply problem, while factory produces like cement can be supplied forever. All manufactured materials require raw materials from some sources, mostly taken from nature itself, so they too have their limitations.

Architects, engineers and builders have built a wide range of elements using mud. To list a few, rammed earth foundation, stabilised soil cement block walls, different kinds of arches, corbelled projections, walls with inter locking mud blocks, vaults without shuttering, flat arch lintels, patterned and differently moulded blocks for parapets or compound walls, perforated walls in jaali, masonry domes without shuttering, mud block filler slab roofs, load-bearing pillars, rammed earth floor finishes, solid cob benches and fixed furniture, facia finishes, surface washes and such others have already proven themselves as doable and durable.

Should we believe that continuous innovation and constant change are the only paths towards a better future? Not really, with the carbon footprint of construction industry ever increasing. Fortunately many people today talk about the need to revive the past wisdom and blend it with modern times. But how many are willing to change the course towards natural materials is the million dollar question, especially if there are business risks associated with real estate and construction investments.

One mode of achieving it can be by value addition to the traditional mud construction. Patterned rammed earth walls have proven to be a pointer here, with increasing popularity. The mud composition needs to be the same as for other mud walls with around 15% of clay and silt each, the rest being sandy soil, but mud of different colours needs to be procured to achieve the layering of the earth. Such ideas not only let the skill-sets of the mason continue but also make them feel proud of their accomplishments.

The challenge is facing each one of us. The ecological advantages of minimising on cement, the financial advantages of faster construction, the life cycle advantages of low maintenance and the visual advantages of aesthetics of earthy construction need to be reached out to the masses.

In promoting mud architecture, each one associated with the construction sector, from the mason to the media, can play a role.

For passive cooling of your home

The design behind the ventilated cavity filler roof.

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Global warming is happening much earlier than ever predicted, at which rate we may leave nothing for our future generations. While it is mandatory on all of us to reduce our consumptions, wastages, trash generation and such other measures, it is equally important to devise ways of comfortable living without depending upon energy and electricity.

Cavity roofs have been a partial solution towards passive cooling, with embedding clay pots, hollow filler tiles and such others. However, during extreme summers even the hollow clay tiles are becoming less effective.

Heat gets transferred through conduction and convection, the former through solid materials and the latter through voids and spaces. When the building terrace receives direct sun rays, it gets heated up and starts to pass the heat downwards into the room below. Even the voids inside the hollow clay filler roof would let the heat go through it, for this trapped air also gets heated with the surface heat being very high. In other words, the present day hollow clay filler roofs will let heat transfer through both the processes of conduction and convection, the void being a sealed one.

In case the trapped air inside the void which gets heated up is not sealed but move across to let cool air in, then the heat transfer would somewhat reduce. This can be achieved by inserting a small length of electrical conduit pipe between the voids of the hollow clay filler blocks, which are embedded within the RCC roof.

Once all the blocks are in place, a small length of pipes are inserted such that their ends are within the void of the filler block. It is not a continuous end-to-end pipe, which serves no purpose at all, but short connections between the voids. As the air inside the void gets heated up, it moves along the pipes to equalise the heat all over the filler block. At the edge block, this hotter air moves out of the block itself, while cooler air enters the voids from the other end.

Between the two outside edges of the slab, one would have breeze called windward direction and the other end will not have much air movement, called leeward direction. Air moves from windward to leeward directions, in the process pushing out the hot air accumulated inside all the voids of the filler roof. This would reduce the heat gain inside the room.

The ends are finished with a slight bend to block rainwater. Pipe pieces should not move so much that their end is within the tile gap which gets filled by concrete, in which case the continuous air movement will get blocked. All that the builder contractor has to oblige is let a few helpers insert the pipes, which is fairly fast. It’s a one-time investment of time and effort, to achieve passive cooling of a slightly higher order.