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Construction : Technology | September 2017 | Source : CW-India

How can builders play a key role in making affordable housing a win-win situation with the right technologies?

In 2014, Mahindra Lifespace Developers ventured into the affordable housing space with the establishment of its vertical 'Happinest'. 'Back then, when we took into account the housing deficit and divided it into various segments, 95 per cent of the deficit was in the EWS and LIG category,' says Sriram S Mahadevan, Business Head, Happinest.

A company largely into the mid-premium range of residential projects, Mahindra Lifespace Developers realised there was an opportunity to address the unmet needs of the emerging Indian middle class, while broadening the company's portfolio. With this, the company took off into the affordable space with its two pilot projects in Chennai and Boisar. Over the years, the company has used several technologies to great success in its projects. Considering an average timeline of 20 months (compared to 26 months the conventional way) to complete an affordable housing project, Sriram S Mahadevan and Amit Pal, Vice President-Projects, Mahindra Lifespace Developers, share the key technologies that have made this segment a happy bet for the company.

Tech talk for success
We started with looking into 32 construction technologies that were being adopted world over for low-cost housing, or what is popularly known as affordable housing in India. We conducted a detailed study on these and shortlisted three technologies that would suit Indian conditions. We did our own feasibility study considering a model - our pilot project Happinest, Avadi - to determine the construction period with this technique and how would we adopt or deploy it in India. Based on our own feasibility study, we made our own hybrid technology: A combination of shortlisted techniques. Hybrid is basically a concept of sheer wall (RCC wall) with the building envelope as a block work. We call these lightweight blocks. Also, conventional foundations are either isolated or raft; but based on the soil investigation report and geotechnical studies, we tied up with IIT-Madras and designed and developed trench foundation technology. With this technology, we started erecting sheer walls above foundations. Then these are covered with a building envelope, which is done with lightweight blocks. In the market, building blocks consist of several materials such as concrete, red clay bricks, fly-ash, aerated autoclave, etc. But what we adopted in Happinest, Chennai, is cellular lightweight concrete (CLC) blocks, produced in our in-house plant at site. Here, the building envelope was made with CLC, which we have designed and filed a patent for. This helped us achieve our first pilot with a construction area of 4 lakh sq ft with 604 units in Chennai - in a flat 20 months.

What is affordable?
A major chunk of Phase-1 of Happinest, Avadi, was sold in the range of Rs 10-20 lakh; Rs 10 lakh for one-BHK and Rs 20 lakh for two-BHK (approximately). Our Happinest Boisar project would typically be in the same range. So, affordable housing does not mean 'low-cost' housing; it means quality housing at an affordable price. And staying true to our principle of green development, even our affordable housing projects are pre-certified by the Indian Green Building Council (IGBC) as 'Green Homes'.

Application and advantages
Speaking of the foundation, the soil condition is basically expansive outside city limits. This makes construction difficult during the rains. Hence, coming above the ground at a faster pace becomes crucial because managing the superstructure is easy after this. The trench foundation helps in faster construction because you make the trench and pour mass concrete as foundation. And with the mass concrete, you place the steel reinforcement wherever required as per design. So where a typical building foundation takes about 30 days, we achieve it in 15 days with this type of foundation. Our slab cycle time with shear walls is around eight days. The second benefit is reduced dependency on skilled labour. In the case of a conventional structure, skill dependency is high. But in the case of a trench foundation, you have to see the alignment of the trench and need not depend on highly skilled manpower or more manpower.

This is more in a mechanised form, where there is a transit mixture and a pump and you just pour concrete. Third, these types of foundations use soil friction, making the building more structurally stable. It also helps build earthquake resistance parameters. Hence, these foundations are suitable for building with ground plus four or seven storeys, especially in expansive soil.

The hybrid technology also benefits the building envelope. Conventional concrete blocks are heavy. Red-clay bricks, which are lighter, are not available in the best quality nowadays and we do not use the same due to depletion of fertile top soil. So, the options are concrete blocks, AAC blocks, fly-ash bricks and a concrete wall. You certainly do not want to make a building envelope with a concrete wall because you need better thermal efficiency. In this scenario, CLC is a lightweight solution with a density between 600-700 kg per cu m, which actually floats in water. This also results in improved productivity as it becomes easier for labourers to lay the blocks and offers better thermal insulation properties.

We have also started a 'living building assessment', which means ascertaining how the building is actually behaving. To begin with, we monitor temperatures at different floors in different flats. So, the records have it that there is a clear difference of a minimum of 2oC owing to CLC's thermal insulation properties. Also, we manufacture CLC blocks at our own plants on site and quality parameters are maintained by us. So, the water absorption in the blocks developed by us is less than 12 per cent; this helps prevent any kind of leakage and external water from coming inside. The CLC blocks consist of 80 per cent fly-ash and 6 per cent cement; the rest is water and foam.

Concept of modularity
We have also used the concept of modularity - ready-to-fix components รป in both projects. Moving away from the conventional way of marble and granite used in kitchens, we have made a frame with mild steel structures; like hollow box sections. This frame is then brought to the kitchen and erected, we fix marble at the top of the frame and the kitchen platform is ready. This activity does not take more than three to four hours.

The way forward
We are not limiting ourselves to hybrid technology. We are continually researching and evaluating cost-effective, design-friendly, soil condition-friendly and time-effective technologies, starting from the foundation level. We have also studied some techniques that are not conventional for foundations, and innovative approaches to reduce the turnaround time for finishing activities like plastering, tiling and painting. Our aim is to start putting newer technologies to use that would help us achieve our projects affordably and efficiently.


- SHRIYAL SETHUMADHAVAN

 
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