About the Grand Union Canal & Boston Manor Conservation Area
The Grand Union Canal & Boston Manor Conservation Area covers about 42 hectares and was designated by London Borough of Hounslow in 2001. Inside the boundary are 8 listed buildings (1 Grade I, 1 Grade II*, 6 Grade II). The most significant is Boston Manor House, Boston Manor Park, Grade I. Part of the area lies in flood zone 3, so an extension may need a flood risk assessment.
What changes inside the conservation area
Conservation areas are “Article 2(3) land”. You keep most permitted development rights, but these are removed or tightened.
- Rear extensionElsewhere: 3 m · 6 m with PANo 6 m / 8 m prior approval
- Two-storey extensionElsewhere: 3 mNeeds planning permission
- Side extensionElsewhere: Half the widthNeeds planning permission
- Loft conversionElsewhere: 50 m³Needs planning permission
- Garden roomElsewhere: 2.5 m high by boundariesNot beside the house
- PorchElsewhere: 3 m²Same limits
- Solar panelsElsewhere: 0.2 m projectionSame limits
- Air source heat pumpElsewhere: 1 unitNot facing the road
- Fences, walls and gatesElsewhere: 2 m · 1 m by a roadSame limits
- External claddingElsewhere: Matching materialsNeeds planning permission
- Tree workElsewhere: No notice6 weeks’ notice to the council
- Demolition (over 115 m³)Elsewhere: AllowedNeeds planning permission
Limits for a semi-detached house under the GPDO 2015. An Article 4 direction can remove more.
Article 4 directions here
These overlap the conservation area. Householder directions remove more of the rights above; change-of-use ones don’t affect extending a house.
- Dwellinghouses (C3) to small HMOs (C4) - borough-wide Article 4 DirectionChange of use
- Change of use or development that would result in new dwellings (Class MA/ZA)Change of use
Listed buildings in the conservation area
Any work affecting these needs listed building consent, inside or out. Each links to its entry on the National Heritage List.
- Boston Manor House, Boston Manor ParkGrade I
- Church of St LawrenceGrade II*
- 80, High StreetGrade II
- Gallows Bridge (over Brentford Canal), Grand Union CanalGrade II
- Garden Wall, 2 Sets of Iron Gates Gateposts to Boston Manor HouseGrade II
- Stables of Boston Manor HouseGrade II
- The Boatman's InstituteGrade II
- Toll House at Brentford LockGrade II
Streets in the conservation area
Streets with listed buildings inside the boundary. Boundaries often split a street — check your exact address.
The council’s appraisal
WEBGrand Union Canal & Boston Manor Conservation Area AppraisalLondon Borough of Hounslow’s description of the area’s character — what planners look at when you apply.Open on council site ↗Nearby conservation areas
Boundary and listed buildings from London Borough of Hounslow and Historic England via planning.data.gov.uk (OGL). Guidance only — not an official council check.