A story in stone: The Chapadi system of construction

By  Staff Writer

The construction of a building is no doubt a highly cost-intensive affair. From buying a decent piece of land to the final finishing materials, there are numerous factors involved that an average middle-class family in an urban locale can only hold on to their dream of having a home by a thread. Every month sees a certain amount set aside, and every other spare penny meticulously saved, towards realizing this dream. To this end, cost-effective construction techniques engineered by Architects that effectively bring down the cost have begun gaining momentum. One such technique that was widely known in the Bangalore city area during the 90s, is the stone chapadi construction system pioneered by two Architects who defied prevailing high-cost-of-living conditions and endeavoured for innovation in the building industry.

During the late 80s, a typical house in Bangalore would cost around ₹3 lakh.When architects Shankar and Navnath Kanade of Shilpa Sindoor Architects, Bangalore built a home for less than a third of that cost, the substantial savings from such a project in a city as expensive as Bangalore were sensational. What followed was covered by popular newspapers instigating further awareness and interest in this particular system.

Stone Chapadi system of construction is very simple and straightforward in concept. Shankar and Navnath Kanade noticed that almost all pavements in Bangalore, and empty sites, were demarcated with vertically placed granite stone slabs, a predominant stone found in Karnataka. “It made us think; why are these stone slabs used everywhere? Then we realized that these were the cheapest materials available at the time!” This led to an in-depth analysis of the typical expenditure in building a structure, and they found that more than 60% of the total cost is spent for constructing the walls! To cut down this cost of this portion with the highest percentage of expense, the Kanades came up with an innovative, simple system of vertically stacking stone slabs or stone chapadi as it was called locally.

Cost comparison between conventional and chapadi systems. Image source: Shilpa Sindoor Architects

 

To hold the stone slabs in place, precast lime-cement blocks were designed, which when stacked one above the other will form the columns. Initially, these blocks were designed with a groove on each of the four sides to hold a 4″ thick stone slab in between. In the process of lifting and inserting the stone slab into the grooves of adjacent columns, it was discovered that the precast blocks would get displaced because the stone slab was heavy. “The blocks were held only by mortar and thus were very weak. We then created a hole in the center of the precast lime-cement blocks, into which waste reinforcement rods can be inserted and poured in with cement concrete. This gives rigidity to these columns to withstand the force of inserting stone slabs.”

Subsequently, this entire cumbrous process of inserting the slabs in between two rigid columns was avoided by constructing one column first, sliding the stone slabs into position in the grooves and then constructing the adjacent column at the end of the positioned stone slabs.

The focus was on minimizing the use of cement and concrete as much as possible. Each stone slab measures approximately 6’6″ long, 1″ wide and 4″ thick, and is equivalent to 1 foot of brick masonry work. “For every 1′ of the chapadi wall, there is only one horizontal joint, whereas in normal brick-masonry there will be several more vertical and horizontal joints. The amount of cement mortar used is again reduced immensely.” The thickness of the stone slab being only 4″, this would not suffice to prevent heat from the exterior to seep to the inside. To inhibit this, a 2″ layer of mud is plastered on the inside followed by laying half-bricks (again saving cost) made specifically for this purpose by the manufacturer.  Thus, the overall wall thickness becomes 8″ and heat is prevented entry. The bricks are mortared with mud and pointed with cement on the exposed surface.

(Top) Section through a Chapadi wall. (Bottom) Exterior and Interior of Keremane house.

 

The foundation trench measures about 3’x3′ and 3′ deep, depending on soil condition. The footing consists of two stone slabs of 2’x2’x8″ thick and another two stone slabs 1 1/2′ x 1 1/2′ and 8″ thick over which the precast lime-cement blocks will be stacked (Refer image below). The adjacent column’s foundation will be 2m across, making it unnecessary to have a foundation below the space in between two columns; this brings down the cost tremendously.

Foundation for pre-cast lime-cement blocks. Image source: Shilpa Sindoor Architects

“…the building will age naturally and gracefully, accepting the inevitable weathering and beauty in imperfections.”

Cement plastering the walls is completely avoided, except for kitchens and bathrooms where a plastered brick wall is necessary for waterproofing. “Normally, in construction, the maximum amount of cement is consumed in plastering – even much more than the slabs. In Stone chapadi system, there is no plastering; it is entirely exposed natural material construction. It is thus cost effective and the building will age naturally and gracefully, accepting the inevitable weathering and beauty in imperfections.”

 

Keremane row houses, showing exposed stone and brick construction.  Image source: Shilpa Sindoor Architects

 

The maximum possible distance between two columns was based on the weight of a slab that a labourer could lift; the slabs are lifted and placed in position and the Kanades did not want this to be done by a machine as that would defeat the whole purpose of cost-efficiency. “At the time we began, there was abundant unemployment and unskilled labour available in Bangalore. We felt this chapadi system could generate employment as there would be a need for 4 labourers for every 1 mason, as opposed to the 2:1 ratio that is prevalent in common systems.” The labour component is 50% in stone chapadi buildings, double that of normal construction.

In terms of planning, the expenditure was brought down further by minimizing the number of windows without cutting out light, by using a system prevalent since ancient times – the courtyard. “If you compare a window and a courtyard with the same dimensions, the latter gives 10 times more light than the former, simply because it receives direct light throughout the day. And besides, using windows in an urban context doesn’t make sense. You’ll only see the neighbours wall or window! So your house might as well open to the sky, stars and clouds.” says Shankar Kanade.

 

Skylight covered courtyard in Keremane row house.

 

Though Shankar and Navnath Kanade pioneered the stone chapadi system of construction as early as 1987, the first building using this technique was constructed only two years later, when they were approached by a desperate bank employee who was shunned by other architects when he requested for a home built within 1 Lakh. “We told him we can build his home within his budget, but he should not interfere with the construction of the building. And he agreed! We didn’t take any fee – it was kind of like our own laboratory where we were testing and experimenting with our system. In fact, we finished the project within Rs.90,000, saving some money for him!” laughs Shankar. So over the next two or so years, on a 30’ x 40’ site in Vidhyaranyapura, the Kanades evolved and perfected their innovative technology, building a single-bedroom house with a central courtyard.

 

Plan and photos of the first house in Vidhyaranyapura.  Image source: Shilpa Sindoor Architects

 

Over the years, Shankar and Navnath have built around 50 to 60 buildings, both single and multi-storeyed, with this system. The relatively larger buildings include Asha Niketan, a home for the differently-abled, Keremane row houses, and an institutional building, the Spoorthidama building.  With rapid urban development in metropolitan cities of India, Bangalore too was not spared. The stone quarries were taken over by developers and the price of stone was increased significantly, rendering the prime purpose of the stone chapadi system obsolete. Presently,it’s easier and comparatively less expensive to get natural materials like laterite stone, even if it’s from 300 km away.

The stone chapadi construction system was a well-working and practical solution for cost-efficient construction. It reduced the use of industrial materials that cause pollution, and at the same time increased the employment of more unskilled labour; less cement, less steel, no paint, only pure quintessential Architecture. “Cement and steel are bought from men who are already the Tatas and Birlas of the nation. Stone chapadi system fundamentally takes the money that goes to the already-rich men, and gives it to those who need to feed their families for the day.” In addition to the system being cost-effective in totality, it was also expense-appropriate.

 

Shilpa Sindoor Architects was established in 1975 by Ar. Shankar Kanade and Ar. Navnath Kanade, both graduates of Sir J. J. College of Architecture. Based in Bangalore, they have always strived to innovate new and better ways to create Architecture, not just buildings. Their Architecture is of the purest form, using natural materials to create spaces and buildings that live and age naturally. They are known to have pioneered the ingenious system of the stone chapadi system and have won several awards including the Commendation prize – Design Ideas Competition 1999 on Disaster Resistant Housing jointly sponsored by HUDCO and Hari Om Ashram Trust. They can be found at their charming fifth floor office at 511, Commerce House, 9/1, Cunningham Rd, Kaverappa Layout, Vasanth Nagar, Bengaluru, Karnataka 560052.

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