1. The "V-Shaped" Historic Roof
Many 19th-century properties in the London Borough of Hammersmith & Fulham (LBHF) (particularly in areas like Brackenbury Village) were originally constructed with "Butterfly" (or London V) roofs. From the street, the roof is hidden behind a parapet. From the rear or above, the roof dips downward into a central valley gutter, resembling butterfly wings.
2. The Presumption Against Loss
If your property possesses an intact, original butterfly roof, the LBHF Local Plan deploys a fierce "presumption against loss." The Conservation Officer views these distinctive "V" shapes as a critical, vanishing element of Victorian London's skyline topology.
3. Mansard Conversions on Butterfly Roofs
Normally, adding a mansard roof during a Full Refurbishment requires entirely destroying the V-shape and building a flat, box-like roof structure spanning across the old valley. In a Conservation Area, if your butterfly roof is visible from any public vantage point (including distant side streets or railway lines), the council will categorically refuse the mansard application.
4. The Streetscape Audit
To defeat this policy, our Planning Directorate must execute a forensic "Streetscape Roof Audit." We do not attempt to argue that the butterfly roof is not historic. Instead, we use drone photography to prove to the council that 80% of the other houses on that specific terrace have already destroyed their butterfly roofs via planning permissions granted decades ago.
We argue that forcing our single client to retain an isolated butterfly roof in a sea of mansards creates an "architecturally disjointed" streetscape, and that ironically, completing the terrace with a final mansard provides better visual unity.
5. The Compromise: The Folded Mansard
If the street is completely intact and a full mansard is impossible, our Architecture team occasionally engineers a highly complex compromise: The "Internal Folded Mansard." This retains the distinct V-shape of the party walls at the rear boundary while squeezing heavily compromised, geometry-limited living space into the original valley void.
How We Can Help
If you are considering a major refurbishment, extension or basement in Hammersmith & Fulham, our in-house architectural and construction teams are highly experienced with the specific constraints and policies of LBHF. 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.*