Rear Extensions in Merton

The single-story rear extension is the foundational architectural move for expanding family homes across the London Borough of Merton. Whether pushing out from a Victorian terrace in Colliers Wood or expanding a detached 1930s home in West Wimbledon, the rear extension unlocks critical open-plan kitchen and dining space.

While often viable under Permitted Development (PD), pushing for maximum depth or ambitious glazing requires navigating Merton’s strict Full Planning parameters.

Depth, Height, and Boundary Proximity

If applying for Full Planning, Merton planners actively assess the physical volume against the original home:

• The Depth Matrix: Merton generally accepts single-story rear depths of 3 to 3.5 meters on semi-detached and terraced properties, and up to 4 meters on detached homes. Proposing a 5-meter deep extension outside of the formal 'Prior Approval' PD framework will almost certainly be refused for excessive massing and daylight loss to the immediate neighbors.
• Boundary Height Limits: The intersection of the extension with the party wall is heavily controlled. The eaves height directly adjacent to the boundary should not exceed 3 meters. If you are proposing an asymmetrical pitched roof, the highest point must slope away from the neighbor to pass the 45-degree amenity test.
• Garden Retention: A core Merton policy mandates the preservation of usable outdoor space. If your expansive rear extension, combined with pre-existing outbuildings, consumes more than 50% of your original rear garden, planners will veto the application, arguing it constitutes 'overdevelopment' of a family plot.

Official Merton Council Resources

Before committing to any major architectural project, we strongly advise cross-referencing your ambition directly with the local authority. The following links provide direct access to Merton Council's live planning portals and heritage registries:

• Merton Planning & Building Control Portal
• Search Live Merton Planning Applications
• Merton Heritage, Conservation Areas & Article 4 Directions

How We Can Help

If you are considering a major refurbishment, extension or basement in Merton, our in-house architectural and construction teams are highly experienced with the specific constraints and policies of this council. Do not leave your planning application to chance—our Planning & Permissions and Architecture services are explicitly designed to handle strict London authorities from initial conceptual design through to final, legal consent.

Once permission is secured, our Refurbishment & Interiors division carefully manages the execution, guaranteeing the design integrity is maintained throughout the build phase.

*Published in the Hampstead Renovations Planning Guide Collection — delivering expert design and build strategies for London's most heavily guarded conservation boroughs.*