Prefab Housing

Sumit Maity & Shalini Maity give an architect’s perspective on Prefab Technology based on the large prefab housing projects undertaken by them.

Prefab Housing

Civil Construction in India has not been as much industrialized as it has been in the West. Presently, it shares barely 1-2% of the real estate market, though as per a recent study, it is expected to grow @8.5% in the decade of 2016-2026. Several reasons are attributed to the ‘late blooming’ of technology-driven constructions in under-developed and developing nations, which mainly include high initial cost, low labour wages, scarcity of knowledge and skill, unreliability of continuity of work, and also a prejudice against precast technology.

In 2012, the national housing shortage was estimated by the Technical Group as 18.78 M, out of which more than 95% was for the lower income category. It is important to keep this data in mind, as the visual exposure of ‘precast construction’ in the low- income housing is much higher than those in the commercial and other large projects. Where the other large projects can have fancy façades veiled around the precast building skeleton, the low income housing have to be technology-smart with boundary level optimized components without any cosmetic wraps.

Intervention by Architects
Architects’ duty would be to look at prefab technology not merely as a technological tool for faster construction, quality assurance, early delivery and its related economic gains etc. Their creative abilities can turn the otherwise ‘perceived repetitiveness’ of pre-fab into ’rhythmic aesthetic’, a rudimentary mechanized product into ‘simplistic elegance’.

However, as the technical initiator of a project, on a broader perspective, few issues remain from an architect’s point of view:
  • Appropriate stage for deciding about technology.
  • Importance of basic knowledge about pre-casting and component joinery.
  • Understanding of potentials and limitations of a technology.
  • Understanding the resources and capacity of the agency.
  • Architects Intervention- structural modulation and component modulation.
Housing projects of DDA using Prefab Technology
In 2008-09, the Delhi Development Authority initiated large housing projects to be constructed with precast technology. However, as per their recent practice, housing jobs are tendered on design-build model, which include works from initial concept preparation to completion. Till date, about 60,000 houses have been built with prefab technology and about 13500 houses are under construction. All these projects are executed by B.G. Shirke Construction Technology - the pioneers of prefab technology in India.

EWS Housing Project of DDA (2010 – 2013)
Delhi Development Authority came out with a tender in the design-build model specifying RCC Prefab Technology as mode of construction.

Prefab Housing

A total of 20,000 dwelling units each of carpet area 25 sqm were constructed on 9 housing pockets, with a total site area of 46 HA. The total plinth area of approx. 6,50,000 sqm was built in ‘G+4 floors’ configuration. As a precast construction, structural elements like columns, beams, slabs, and stairs were all precast with AAC block masonry infill walls.

Prefab Housing

Fulfilling rigid tender conditions of unit area of 25 sqm and G+4 configuration, a prototype building with 3 stairs and 12 units at each level was developed. In the absence any other variation in built form, the urban scape relied heavily on the green spine networks - pedestrian connectivity

LIG & EWS Housing Project of DDA (2013- 2018)
Prefab Housing
This tender also came out in the design-build model, specifying RCC Prefab Technology as mode of construction.

A total over 34,000 dwelling units (LIG type) with carpet area of 35 sqm each and EWS type of carpet area 25 sqm each were constructed on 10 housing pockets, with a total site area of 67 HA. In total, about 27,850 LIG units with total plinth area of approx. 14,24,000 sqm were built in G+12 floor configuration, along with about 6,200 EWS units with a total plinth area of approx 2,10,000 sqm built in G+4 floors’ configuration.

The precast construction method for the EWS remained the same as in the earlier ones, wheresas in the LIG buildings, a combination of RCC wall panels and columns, beams, slabs, stairs, and parapets were all precast with partial AAC block masonry infill walls.

Tender stipulations for the unit carpet areas were very rigid, though without any capping on the building height. Since the available FAR needed to be consumed in each site, here, the architectural modulation strategy was different. Ten identical units with a lift lobby and stairs were used to make a block – L10, and similarly with eight units and stair block, L8 and L8a were developed. None of these blocks could make a full-fledged building, but combining them at tandem, with 3, 4, 5 or 6 blocks, building-clusters with varying semi enclosed open spaces were achieved.

Prefab Housing

Cat-II (MIG) and EWS Housing of DDA (2015-2019)
Unlike the earlier ones, this tender was technology neutral, BGS won the tender and could continue in prefab considering their previous experience.

A total over 4,900 dwelling units –Cat-II type with carpet area of 77 sqm each and EWS type of carpet area 29 sqm each were constructed on 2 housing pockets, with a total site area of 8.75 HA. In total, about 665 cat-II units with total plinth area of approx. 82,000 sqm were built in 2B+S+13 floor configuration, along with about 4200 EWS units with total plinth area of approx 2,20,000 sqm built as G+15 floors. The construction method used in both the building typologies are a combination of RCC wall panels and the columns, beams, slabs, stairs, parapets were all precast with partial AAC block masonry infill walls.

Prefab Housing

Ongoing 3BHK, 2BHK, & EWS Housing of DDA
This tender was also technology neutral and was won by BGS. A total of 13,450 dwelling units - 3 BHK type with carpet area of 100 sqm each, 2 BHK with 77 sqm, and EWS type of carpet area 29 sqm each are being constructed on 9 housing pockets, with a total site area of 51 HA. In total, about 3000 units of 3 BHK, 6,200 units of 2BHK, and over 4200 EWS units with total plinth area of over 23,00,000 sqm were built in 2B+S+12-18 floor configuration. The construction method in both the building typologies are a combination of RCC wall panels and the columns, beams, slabs, stairs, parapets were all precast with partial AAC block masonry infill walls.

Architectural expression attempts to breaks the otherwise perceived monotonous prefab façade using diverse components in a rhythmic manner. A simple panel with a circular void is used as a signature component, which continues to smaller blocks like a gate house.

Prefab Housing

The ongoing DDA project does exhibit the potential of prefab technology going beyond low-income housing in the Indian context. Somewhere it also says the relevance of issues raised earlier to bring out the best result with prefab technology.

About the authors:
Sumit Maity, B.Arch (Cal-gold medalist), M.Sc –Urban & Regional PLG (UK) and Shalini Maity, B.Arch (SSAA) are from Sumit Maity Architects. Practicing in Delhi since 1999 they have won several national and international architectural competitions.
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