Post Satya Niketan tragedy, experts point to blind spots before construction even starts

Experts advocate for soil investigation, proper design, and quality materials to mitigate risks associated with unauthorized constructions.

With structural safety under scrutiny after Sunday’s deadly building collapse in Satya Niketan, experts said the issue goes beyond violations of building norms and unauthorised construction. They stressed that safety checks must begin before construction, with three critical factors – soil investigation, structural design and construction material – that must be assessed before a building comes up.

The Delhi government has repeatedly said in recent months that it will introduce a structural audit policy. Directions for such audits have also been issued by the Delhi high court. (NEERAJ CHOPRA/ANI)

The concerns are particularly relevant to Delhi, which falls in Seismic Zone 4, classified as having a “high risk” of earthquakes. Official estimates also suggest more than 60% of the city’s population lives in unauthorised or illegal areas, where buildings have often come up without adhering to construction or safety norms.

Experts said this makes construction-stage checks crucial rather than relying only on structural audits of existing buildings.

The Delhi government has repeatedly said in recent months that it will introduce a structural audit policy. Directions for such audits have also been issued by the Delhi high court, followed by a public notice mandating immediate audits of structures built before 2001 and of assembly and institutional buildings. Compliance, however, has remained limited.

On September 10, HT highlighted the manpower shortage faced by the Municipal Corporation of Delhi (MCD) – the civic body has only 249 empanelled structural engineers in a city with around 3.25 million residential buildings.

Sanjay Pant, former deputy director general of the Bureau of Indian Standards (BIS) and a member of the committee that revised the National Building Code (NBC), said soil investigation determines the foundation requirements of a building. “There are different kinds of foundations for different kinds of soil. A soil investigation is used to establish the load-bearing capacity of the site and determine the size and type of foundation required,” Pant said.

He said borewells are dug as part of such investigations to establish construction and design specifications, with requirements varying according to the size and topography of a project.

Divya Kush, former president of the Indian Institute of Architects, said proper soil investigation could make construction possible even in difficult terrain. “A multi-storey building is possible in a desert or even in the middle of the sea as long as proper soil investigation is done,” she said. Experts said this is particularly relevant to Delhi, where construction takes place across areas with varying ground conditions. Soil investigation, they said, should be completed before foundations are laid rather than becoming a document sought at a later stage.

The second concern is structural design. Experts said designs should be prepared by experienced structural engineers, but are sometimes undertaken by local contractors as a cost-cutting measure. A structural design determines how loads are distributed, how many floors a building can support and how it should be constructed, Kush said.

The third is construction material. NBC lays down requirements for mortar and other materials, but experts said contractors sometimes cut costs by reducing the quantity or quality of cement and steel or using unsuitable sand and aggregate.

“Cement and reinforced steel bars are particularly important to structural safety and require mandatory ISI marking. Inferior sand and oversized aggregate all contribute to weakening of the structure,” Pant said.

NBC specifies aggregate of no more than 20mm, while concrete should be of grade M25. Experts said some contractors, however, use concrete as weak as M15. For Delhi, experts said structural audits remain important for identifying weaknesses in existing buildings, but construction-stage compliance can prevent deficiencies from becoming embedded in structures. Soil conditions, foundation design, structural drawings, reinforcement and concrete quality should be checked while a building is being constructed.

“There are five important things that are needed for ensuring structural strength. Three of these are structural design, soil testing, and execution by using good quality material and workmanship. The other two are unforeseen load and repair and maintenance,” Pant said.