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Following the recent refusal of the controversial HMO conversion at 149 Herlwyn Avenue (Ref: 19188/APP/2025/3239) on 20th March, a new planning application has already been submitted for the site. While the previous application for a six-person House in Multiple Occupation was rejected due to over-intensification and poor living standards, this new submission (Ref: 19188/APP/2026/820) represents a notable change in strategy.
How the Proposals Compare
The most striking difference between the two applications is that the new “Householder” proposal actually seeks to create a larger building footprint than the refused HMO plan. Despite moving away from a high-occupancy use, the physical scale of the development has increased.
Why the Increase in Size?
The increase of 2.2 square metres in the new application is primarily due to the inclusion of a loft conversion and rear dormer, which was not part of the original HMO floor area calculations. While the HMO plan focused on squeezing maximum occupancy into the existing and extended ground floor, the new plan utilizes the roof space for a single-family setup.
Ongoing “Retrospective” Issues
Residents should note that the “part-retrospective” nature of this development continues. The new filing explicitly states that building works commenced on 1st January, without prior consent. The applicant now expects the current phase of construction to be completed by June 2026.
Biodiversity Perspective
Because this is now a Householder Application, the applicant has claimed an exemption from Biodiversity Net Gain (BNG) rules.
The RRA remains vigilant. While a householder extension is generally less intensive than an HMO, we are concerned that the increased physical scale (now over 50 square metres of new space) must still respect the character of the road. We will be monitoring to ensure this is not a “backdoor” attempt to facilitate the previously refused over-intensification under a different name.
Next Steps
We encourage residents to view the new plans on the Hillingdon Planning Portal under reference 19188/APP/2026/820. We will continue to watch the application as the consultation period for this new application begins.
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