Precast will be the next best thing in construction industry
Brief our readers about the project you are handling. At what stage of construction it is?
The project we are currently pursuing is a mass housing project under PMAY spread across 400 acres in Vasai, which is considered to be gateway to Mumbai. The project will be known as Suraksha Smart City and is poised to deliver 1,00,000 apartments, which will be combination of economically weaker section (EWS) 30 sq m, low income group 45 and 60 sq m under PMAY guidelines. Project has just completed its planning stage and we broke the ground in February 2020 and started with piling work.
What are time lines of the project?
Project is scheduled to be delivered in the next five years as we have time commitment towards PMAY. MHADA being governing body in Maharashtra, they will be monitoring the timeline and other aspects of project.
How is the construction planned and is there any new construction technology being considered?
The volume we are looking at is huge. We are aiming at 25 lakh cubic meters of concrete and 2,50,000 tonnes of reinforcement to be consumed over the next five years. It becomes extremely difficult to deliver such a high volume with conventional construction methods. Even if we consider system like Mivan, the labour requirements will be no less than 10,000 per shift. Other technologies like tunnel form have its limitations of design flexibility.
So the only feasible option we could see was "precast" construction. But the biggest negative of precast construction in India was water seepage through joints. Thanks to some really compromised precast construction by big construction houses in major cities of India like Delhi and Mumbai. Considering the project is aimed at first time home buyers, we wanted to give them pleasant experience at least by mitigating the leakage and dampness issue.
We put our brains in understanding, studying, analysing the reasons contributing to weaker joints and thus seepage and leakage. After a comprehensive study, we concluded that it cannot be conventional precast which will help us. To achieve watertight joints, speed, quality and waterproofing in wet areas, we decided to go with 3D construction.
In India, a few construction houses had tried 3D precast, but that was limited to only non load bearing, light weigh toilet areas.What we planned was extremely unique and path breaking. We are doing 3D precast, which is load bearing in fact the only load bearing element consisting of all wet areas in building including kitchen, toilet and bath which is 140 sqft and weighing around 25 tonnes.
So our project is combination of 3D, 2D , some special elements for lift, beam and staircase and hollow core slabs. The design is so optimised that compared to conventional design we optimised steel and reinforcement coefficient by almost 15 percent.
What are the basic grounds on which one should prefer precast technology for the houses being constructed under PMAY?
Every construction project has its own requirement. In India, majority residential projects don't demand speed. Most of them progress as per velocity of sales. Now RERA coming as governing authority, the speed is committed but still speed is not the only criteria. So majority suitably use conventional systems of construction.
A few construction projects have voluntarily adopted to precast but failed as the capex was high and the progress achieved by precast was not supported by inflow of sales/funds. The ideal situation is to opt for precast, where sales are committed for residential projects or the early completion is going to pay premium for commercial projects like hotels, office spaces, Malls etc are advised in precast as its early completions shall give early revenues.
Further residential projects, which are under PMAY, where allocation of units is done and one has to deliver in stipulated time. It is not possible to complete the project with conventional methods but use modern technology instead.
The primary requirement in deciding precast as construction technologies are: speed of construction, volume of construction and positive cash flows. A project with 5,000 apartments to be delivered in two years is ideal size for precast project provided there are no cash flow issues.
In terms of cost and speed if one uses conventional method of construction over precast what will be the shortcomings?
In terms of speed, conventional construction system can never match the speed given by precast.About the cost there are few dimensions to it.
If the volume is less than 2 million sq ft
Precast manufacturing facility is not on site and away more than 100 km
Project tenure is more than three years
Skilled precast manpower not available
Concrete quality - specially SCC and early strength concrete is not achieved In above situations,precast becomes expensive than conventional construction system.
Does the defect liability period for prefab/ precast house differ from that of conventionally constructed house?
Ideally the quality of construction achieved in precast is far superior to conventional construction methods. The only challenge in precast in joinery. Defect liability period in precast is governed by one monsoon cycle unlike in conventional which ranges from six months to 24 months.
How has been the buyer's preference for prefab/precast houses?
At few high-end apartments including row houses, bungalows the acceptance for precast is good. But at EWS and allied category as the customer belong to bottom of pyramid being ignorant of modern construction practices like precast was showing some resistance to precast. But with technology spread through social media is so fast that acceptance for precast at least in metro cities for all customer base is moderate.
In olden days many have attempted to popularise the precast housing in India but failed miserably; what can be the reasons?
Precast is a system; a concept needs to be adapted according to your local conditions. Meaning when you think of precast it comes with mechanised way of production, advanced logistic management, erection or installations and most importantly skilled manpower to execute from production to erection.In India, we lacked appropriate capex in technology. People have invested in localised precast machinery and equipment. The quality of precast elements produced was compromised.
The skilled and trained manpower was never available. Over a period, enterprises did not make efforts on skill development and retention of trained manpower. So the product at the end was compromised.
The material science of precast is very crucial especially with concrete. Precast demands a robust concrete mix design with SCC (self-compacted concrete) properties, early strength for lifting. Failing this the Element quality is compromised and production cycle is compromised if early strength concrete is not designed. To summarise, the machinery, manpower, material and money all were not invested seriously and hence failed miserably.
It is learnt that for using precast technology of construction, one needs trained and highly skilled man power. What is the situation in our country with specific reference to your project?
Skilled manpower is must. And considering that we are planning 3D construction, the requirement becomes much more significant and unavoidable.India is practising precast for quite a long time now. The skilled manpower is available in India but is scattered. We already identified the required skill set. We have already employed management and supervision level trained manpower. We are also in touch with specialised skilled manpower in Gulf, Asian counties like Singapore, Thailand and European countries.
For us, being 3D precast producer, our manpower requirement which is worked out on per cum basis is significantly low. Compared to other 2D precast the manpower requirement is reduced by 25 to 30 percent per cum.
It is said that architecture of the dwelling units should gel with the environment. Prefab/precast technology is coming from outside, how it is adapted to the local conditions?
What is critically important in precast is planning. Precast does not allow much alterations in design once precast facility is set.I would say its myth that precast technology is not Architecture design friendly. What is important is an optimised architectural design which needs to be designed keeping precast as technology in mind.Elevations projections, other artistic details everything is possible in precast.
Please comment on the applicability of 3D printing technology to mass housing. Is it used in any part of the world?
Three-dimensional (3D) printing is great technology in construction. But it comes with its own limitations. It's good for small houses or low-rise buildings. It's not suitable for high-rise buildings. Further its most expensive technology so far may be because the volume is much low.
What do you think is the future of prefab/precast construction in India? Can one expect luxury houses also being constructed with Prefab technology?
India is going to be biggest precast market of Asia. This decade is "precast decade". You will see many projects executed through precast technology. The investment in "precast technology" is huge. The sales of precast machine manufactures in last year have been highest in decade. International players are entering India to execute precast jobs gives same indication that India in next big thing for precast.
Luxury villas with precast is something which is possible and done inafew parts of India like Delhi, Hyderabad and Baroda. The concrete surface is so clean and engineered that there no need of secondary treatment like paint. Some good textures give great character to outer facade and to structure.It can be clearly said that precast is next best thing to look forward in construction industry.