Monthly Archives: February 2019

Designing a chajja


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.

Climate crisis, and the culprits

Degeneration of the atmosphere is mainly because of modern mechanical devices which have become part of our daily living. 

09bgp-greenPPGMD5D2QLK3jpgjpg.jpegAs schoolchildren, we started reading alphabets not as mere graphical forms, but as the starting letter of a larger word. So A for Apple, B for Ball, C for Cat, D for Dog and so on it goes. Imagine, if we were to start the same again to check what impacts ecology the most, it could be a bad start.

A can be for Atmosphere, but soon we may follow it with A for Agriculture, Accommodation and Administration, all of which in the ancient times effected ecology where human actions altered the landscape to cultivate; consumed resources to construct; and created systems to govern society with capital and operational expenditures.

In modern times, A can stand for Advanced Lifestyle, but equally well for Automobile, Air travel and Air conditioners. Incidentally, these three are strongly advocated by modernity to become the aspirations of every low and middle-income family, who constitute approximately 75 to 80% of the Indian population.

These three are also among the major human actions adversely affecting nature and leading to the climate crisis. For common people, they may not appear to do so directly, but are the indirect causes due to their production, operation, energy consumption and finally waste generation upon discarding. Even the climate subject experts do not go to the depths of varied components of lifestyle, their attributes and implications on atmosphere, but gloss over them broadly saying human actions are causing the climate crisis. Then, of course, there are many people who do not fully agree with this position too.

Take automobiles, for example. Though the first car was patented in 1886, the next 20 years would not have seen more than 200 cars on the road. There was increased production, but between the World Wars, more car companies were closed than founded. The handful few from Europe, U.S. and Japan survived into the 1940s when the real mass production of cars flourished.

As such, it is less than 75 years now that people are driving cars and less than 50 years with the worldwide spread. Most poor regions have very few cars, while more than 90% of Indians still own no vehicle at all. Yet, the havoc the automobile industry has caused to millions of years of fragile nature is frightening. Hundreds of pages of data pour in today, yet none of which has reduced either car production or car sales.

Immeasurable damage

In the U.S. alone, 75% of carbon monoxide and 25% of greenhouse gas emissions are caused by cars, besides many other toxic gases including ground-level ozone. Nearly three-fourths of all of U.S. gas consumption goes for cars. The resources consumed and waste generated in their production, sales, operation and finally scrapping or dumping is virtually immeasurable.

Given this, how do we analyse the impacts of our everyday living? How do we take ownership of our actions to realise we are digging our own graves? Do we need more advanced research on global issues or simple search into our personal matters?

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.