Question to the Ministry of Housing, Communities and Local Government:

To ask His Majesty's Government, with reference to their Research and Analysis Building Safety Remediation: monthly data release - June 2025, updated on 2 October, what are the reasons for the difference between (1) their new estimate as of January 2025 for the total number of mid-rise residential buildings with dwellings in England of 39,000–59,000, and (2) the previous estimate published in 2021 of 71,000–79,000, in the context of the margin of uncertainty increasing from 8,000 to 20,000.

A description of the methodology for the revised estimate as of January 2025 can be found in the technical note that accompanies the monthly data release. It can be found here: Building Safety Technical Note June 2025

The revised estimates are based on the recently released Ordnance Survey National Geographic Database data which was not available when the original estimates were calculated. The key assumptions section of the Technical Note refers to the use of Ordnance Survey unique building identifiers in the higher building ranges and this was a key driver for the increase in the range of uncertainty.