A joint committee of the Karnataka state legislature has stirred controversy in the construction sector after claiming that the use of manufactured sand (M-sand) and stone dust in building projects is responsible for rising indoor temperatures.
The report, tabled in the recent session of the legislature, alleges that replacing natural river sand with M-sand—particularly in plastering—has made new homes warmer, especially during summer. “Although there is a government policy in place, many use stone dust instead of river sand to construct buildings. Further, M-sand is increasingly used for plastering walls in all under-construction buildings. This has severely impacted ambient room temperature,” the report stated.
The committee, led by Kollegal MLA AR Krishnamurthy, examined projects under the commerce and industries department across Karnataka. It concluded that widespread use of M-sand and stone dust by contractors has negatively affected indoor comfort levels and urged the government to ensure affordable supply of natural river sand for construction and repair work.
Experts question committee findings
The report immediately drew strong criticism from civil engineers and construction professionals, who dismissed the conclusions as “technically incorrect.”
“There is no scientific evidence to suggest that either stone dust or M-sand directly affects ambient room temperature,” said Shrikant S Channal, governing council member of the Association of Consulting Civil Engineers (ACCE). “The process of heat transfer depends on multiple materials and design factors, not just plastering material.”
Channal further noted that M-sand, when produced to standards, provides structural advantages. “It offers greater strength due to its uniform grading and cubical particle shape, which enhances binding. If the committee has data comparing M-sand and river sand structures, they should publish it. Otherwise, such recommendations create confusion,” he added.
Role of design and ventilation
Aswath MU, senior civil engineer and former president of ACCE (India), echoed these concerns, emphasising that a building’s internal temperature is influenced by several elements beyond plastering materials.
“Ventilation, design, roofing material and orientation play a major role in thermal comfort,” Aswath said. “It was validated by experts at the Indian Institute of Science (IISc) and IIT Madras, and the Bureau of Indian Standards (BIS) has issued specifications for the use of M-sand. Builders have been using it for more than a decade without any evidence linking it to indoor temperature changes.”
Quality control and environmental impact
While rejecting the committee’s conclusions, experts acknowledged the issue of quality. Aswath highlighted that many contractors use industrial slag or untreated stone dust marketed as M-sand.
“Genuine M-sand is manufactured through a controlled process to ensure particle size and quality. Stone dust, on the other hand, is simply a byproduct of crushing and does not meet the same standards. Citizens need to know the difference,” he explained.
Experts also cautioned that discouraging M-sand could have unintended environmental consequences. “If M-sand is banned, the demand for river sand will surge, leading to unsustainable mining and riverbed degradation,” Aswath said.
Conclusion
The legislature committee’s claims have triggered an intense debate between policymakers and engineers. While lawmakers call for a return to natural river sand, experts insist that M-sand, when produced and used according to standards, is both safe and environmentally preferable. With no scientific data published to support the committee’s findings, the controversy is likely to continue, placing pressure on the state government to clarify its stand on construction practices.