Monthly Archives: October 2010
‘Chajjas’ come in attractive types now but their placement is crucial for giving shade or letting in light and air
Differing tastes: RCC slab projection on buildings started during the colonial times but many buildings do without them
Well, if we walk around historic towns like Srirangam or Sringeri or Thrissur, chajjas are conspicuous not by their design, but by their total absence. Up north, even in the desert dwellings near Jodhpur, traditionally there were no major chajjas.
Sunshades, more commonly called as chajjas, are the little horizontal projections along the external wall, just above the windows to reduce sunshine and raindrops falling on the opening.
The clay-tiled sloping roofs of south India normally extend deep beyond all walls, windows and verandahs providing climatic protection, as such never had a typical chajja.
In north India, often there would be a small beading-like projection, sometimes a moulding to drip the water drop or a small stone slab above the opening. Only in important civic, religious or royal buildings, one could see a deep sloping projection supported by ornate brackets placed at an angle between the wall and the projection.
As such, the RCC slab projection called as chajja started during the colonial times, when buildings tended to be like a box, with flat roof, inviting vagaries of weather all around. In such cases, sunshades are necessary in our region for climatic protection, though we tend to see many multi-storeyed buildings without chajjas.
The flat chajjas are cheaper, but jet out of the walls like the rim of a cricket hat, and make the building look ordinary. They also tend to look discoloured after a few showers.
Builders have tried sloping ones, which demand deeper beams, tiles on top and painted finish at bottom — all leading to more RCC and cost. When chajjas happen between two houses within the narrow space there created by the bye-law setbacks, instead of protecting, the chajja can cut off the possible light and air into our own houses. There often are directions from where we get no major sun or rain, making the chajjas there totally futile.
Interestingly, if heavy rain lashes and the window is left open, water anyway gets in despite the chajja!
All the analysis above is not to negate chajjas, but to ensure a better understanding of how and where to use them. In the recent years in Bangalore, Mangalore tile chajjas have gained popularity. They are supported by fabricated mild steel frame and can be fixed into the wall only where we need, just before completing the building. Often, we have come across owners who wanted to check out which windows need them for a year and then fix them accordingly. With sloping clay tile top, leakage is not an issue and the pricing is also reasonable. Such tiled chajjas compliment the green aesthetics of the building.
Over the years, lintels, despite being less talked about, have dictated many aspects of structures and elevation
Minimising material consumption is among the basics of eco-friendly designs. Equally well, it may mean replacing one material by another which could be more effective and less energy consuming. On an overall basis, costs and volumes involved with lintels may not appear very high, hence most builders follow the standard practice. However, the alternative ideas here can not only save time, but create new kind of looks as well.
No plastered bands
Most designers would like to see their stone-walled building not to have RCC plastered bands created by the lintel and RCC slabs. To this end, a thinner version of RCC lintel is cast to be clad by stone on its elevation face, to get an all-stone look.
Where stone slabs are abundantly available, directly placing a stone slab on the opening and then continuing with regular stone masonry is equally popular and most often less costly. In such cases, the stone should be carefully chosen with hopefully no fault line or weak points. Both ideas ensure complete stone looks.
Niche, but not a loft
Creating a wall niche or a shallow shelf within the wall has been around for a long time, offering a practical solution to storage in an attractive way.
Lintel is needed here too, but only for half the internal wall. Often there would be a narrow 2′ wide opening, with very little weight to be borne from above. All such minimal cases can be managed even by two rods kept atop the niche or arched lintels in brick or stone.
The internal loft or storage slab below ceiling level is at the same height as the lintel, hence the two are merged with each other structurally. While casting concrete lofts has been a common practice, we have also realised that they can be dispensed with. When a wardrobe gets fixed to the wall side, the plywood plank at 7′ level, just above the shutter, acts like a loft slab. It may not be able to take all the weights a concrete slab can take, but then none of us can lift such weights even to keep them there! In a household case, most items that go into a loft can be managed by a wooden plank. In case we expect very heavy items, there could be just one concrete loft, or better still, a ground-level storage option.
Key points to note
In kitchens too, with the cooking platform below, lifting heavy items for storage above never happens. With modern options available for kitchen shelf designs, the RCC loft cast at a fixed height can more or less cause trouble fixing other modular units. As such, avoiding concrete lofts saves money and labour.
Over the years, lintels, despite being less talked about, have dictated many aspects of structures and elevation. We realise that the idea of 7′ level, which determines varied issues from human scale to cut-size wood, loft heights to chajja levels and feasibility of arches to air trap zones, is something we just cannot ignore!
Every era brings in a new wave of thinking and, with age, a new architecture is born. Concepts such as lintels and their design, for example.
How often do we observe the house where our parents lived? What kind of lintel do we see there? By any chance, do we live in a house built 30 or 40 years ago? When we return to such old houses, we notice, there often was no monolith lintel beam concept.
The window frame would be placed in position, then the bricks would be carefully placed above the frame with equal projection on both sides, to start the remaining part of the wall. Here the bricks tightly joined between the void, would act like horizontal means of load transfer, while a smaller part of the weight would be taken care of by the window frame. This concept can be further developed into what is called as flat arch lintels, which unfortunately is not very popular today. Instead of this bricks base layer, there could be a wood piece in some cases. During later years, the trend of casting a RCC lintel after the frame placement also started.
However, there never were anything like lintel member running all along the house, yet these buildings have been with us for centuries. Having said this, let us also agree there are many advantages of continuous RCC lintels. The only plea here is to think if such lintels are judiciously required or not.
Lintels are needed for sure above any and every opening, be it a door, window or wall niche. When we provide them only above such openings, it is called as cut lintel system. They are short in length with adequate bearing on the wall at their ends, and can be managed with minimum reinforcement. To save time, often they are cast on ground, to be lifted up once the walls are ready. Such pre-cast RCC units also save on centering and concreting labour. Cut lintels may not offer any quake resistance, and as such need to be evaluated against all other criteria.
Another popular approach is to merge the lintel with the wall material. Exposed brick walls may look nice with the plastered RCC band, yet they can also be built without the lintel being visible. The outer edge would have a brick, with the thin lintel behind. If it is a hollow clay block, the concrete can be filled within the hollow of the block, creating beam-like support. There have been experiments where hollow blocks have been cast into a monolith beam by inserting reinforcement bars into them. Such walls, with the chajja or the sunshade above the window, tend to look very neat with the aesthetics of single material.
Continuous RCC lintels have gained popularity, nearly wiping out other solutions
Native wisdom: In a wall with exposed materials, designing the lintel aesthetically is important
Construction practices have been handed over to us from millions of years with millions of methods. This maze offers no help to us in picking the best practices for today. As such, we build today in a bewildering variety and how we build continues the past ideas rather randomly. Imagine a rich kid with thousands of toys, all of which are good for playing. What the child chooses to play with, discard, safeguard or reject is beyond any logic of theory – it is determined only by the child at that moment.
Such a vast constructed precedence enables justifying whatever we do. Lintels are an apt example of this state of confusion, where we blindly follow some past procedure. Most builders give it no thought; hence they are more like a neglected cousin among all wall practices. Only a logical structural engineer and a contextual architect can together question the idea of lintel or design the right kind of lintel beam.
Lintel is a short beam in wood or steel or concrete placed above an opening in the wall, to support the triangular part of wall above it.
It may appear not related to the discourse of green architecture, but it does contribute by being cost effective, following a judicious design. In a wall proposed to be plastered, lintels become invisible after the finishing, but if it is all exposed materials, designing the lintel aesthetically becomes very important.
The recent practice in Bangalore has been to cast the so-called continuous RCC lintel all over the wall at 7′ height, irrespective of the location of openings. In the name of strength, it made beams too frequent; if plinth and roof beams are also around, shooting the construction cost upwards. In the name of tying all the columns, it contributed to frame construction, often unnecessarily. Such intermediate beams also covered up possible weak masonry or low construction quality. To cap it all, it made the life of consultants easy, simply to repeat it in all buildings, without any specific designing and drawing, at the cost of owners. Thus, the continuous RCC lintels gained popularity, nearly wiping out other local and creative solutions.
Can we avoid lintels all together? Yes, if all doors and windows are taken up to roof bottom. We will discuss these tall openings during the forthcoming essays. If the windows are placed first, then casting a formal RCC lintel can be replaced by other on-site solutions.
Can the lintels be discontinuous? Can we conceal them within stone or brick walls? Are there options outside concrete? Let us brood over such queries to get right answers.
This essay emerges from an interesting comment about how architects, and many others too, live luxuriously and drive posh cars, but advice mud and clay to their clients!
Practice first: Show eco-friendly ideas in your house and office
It could be partly true, though such a generalisation will be unfair to many architects who live a modest life. Living green never meant suffering, being deprived or denying comforts, either for the self or for others. Limiting our needs and being judicious about consumption is the key to green living. Individually, there could be subjective variations to these needs – there are eco-friendly architects who refuse to own cars or own offices, but many others have good cars and offices. As specialists in green architecture, there are architects who jump on prestigious outstation projects, but there also are consultants who prefer to stay local believing that travelling has high carbon footprint.
Having said this, let us accept the universal truth and Gandhian philosophy in saying better practice first, than preach. A prospective house owner need not preach, instead may directly start with an alternative idea of one’s choice for the house to be lived in. However, it is the consultants and contractors who are in a fix, especially so if they are themselves living in a conventional house. Also, they may preach dozens of eco-building ideas, but cannot have a single house full of all such ideas. While it may be ideal to showcase eco-friendly ideas in one’s own house and office, or also in living, criticising such ideas only because the consultant does not live in them would be a loss for the construction industry at large.
Belief in the alternative has to evolve not from a fancy standpoint, but from a heartfelt belief to change. It can not only be a desire, but also has be an action. Trust me for saying this – most of us who have been designing with a difference, have struggled in the beginning where questioning client, lack of prior projects, apprehensive contractor, ignorance of ecology and every such issue was a major obstacle.
Prior to our own first few projects, we showed what other consultants had already built to convince the clients. Often there were cases of first-time idea itself, with no exact precedent to show, which was a challenge. However, with a willing client, cooperating contractor and seemingly foolproof idea, the construction took off! With more than a dozen architects in Bangalore working out of the mainstream, today, there are hundreds of alternatives, already proven.
Themes and justifications apart, we need to realise that green or eco-friendly ideas have their own aesthetics. Building with mud is an apt example. Despite having been the most common construction material in the world, today it is the last choice simply because the urban world looks down upon this option. The alternative has to become an attraction not only for eco or cost or cultural reasons, but also for its new aesthetics.