Barnet Local Plan: Key Planning Policies for Homeowners

Introduction

The London Borough of Barnet is one of the largest London boroughs, covering a substantial area of outer north London including Hampstead Garden Suburb, Finchley, Barnet, Hendon, Edgware, Whetstone and East Barnet. Barnet's Local Plan sets out the planning policies that the council applies when determining planning applications. For homeowners considering extensions, loft conversions or other works to their properties, understanding the key Barnet policies is important preparation.

Barnet's Local Plan Overview

The London Borough of Barnet's adopted Local Plan (2012, with ongoing review) includes the Core Strategy and the Development Management Policies document. These are supplemented by Supplementary Planning Documents (SPDs), including the Residential Extensions and Alterations SPD which is directly relevant to most householder planning applications.

Barnet's planning policies are applied alongside the Mayor of London's London Plan, which takes precedence on certain policy matters.

Residential Extensions SPD: Key Requirements

Barnet's Residential Extensions and Alterations SPD sets out detailed guidance for householder planning applications. Key policies include:

Scale and Proportion

• Extensions must be clearly subordinate to the original dwelling — typically meaning they should not be larger in floor area than the existing house
• The height of extensions should not exceed that of the principal dwelling (a two-storey extension cannot be taller than the existing two-storey house)
• Rear extensions should not project beyond a depth that would be harmful to neighbouring amenity or overdominance of the garden

Materials

• External materials should match or complement the host dwelling — typically matching brick colour, type and bonding, with window proportions sympathetic to the original
• uPVC is generally not supported in conservation areas or where brick is the dominant external material

Impact on Neighbouring Properties

• Barnet applies the 45-degree rule as an informal guide to daylight impact — extensions should not project beyond a line drawn at 45 degrees from the nearest habitable window of a neighbouring property
• Rear dormers should not overlook neighbouring gardens, and Juliet balconies or roof terraces at upper levels require particular care in relation to privacy

Rear Garden Size

• Barnet expects a minimum garden depth of approximately 10–15 metres to be retained behind any extension. Extensions should not create an overdominance of the plot by built form relative to garden space.

Conservation Areas in Barnet

Barnet has a significant number of conservation areas, including:

• Hampstead Garden Suburb (administered jointly by Barnet and the HGS Trust)
• Hadley Green
• East Finchley Central
• Whetstone High Road
• North Finchley Town Centre

In conservation areas, Barnet applies its Conservation Area Character Appraisals and Management Plans alongside the general residential extensions guidance. Article 4 Directions in conservation areas remove permitted development rights, requiring planning permission for a wider range of works including satellite dishes, cladding, window replacements and some extensions. Applications in conservation areas must be supported by a heritage statement and a Design and Access Statement.

Hampstead Garden Suburb Special Controls

Hampstead Garden Suburb is a unique case in Barnet's planning framework. In addition to Barnet's standard conservation area policies, the Hampstead Garden Suburb Trust (a local charity) has control over the estate through a separate legal framework (the Hampstead Garden Suburb Act 1906 and its successors). Homeowners within the Suburb must obtain Trust consent as well as Barnet planning permission for most external works. Trust design guidance is detailed and demanding; the Trust is not a planning authority but has significant influence over how Barnet determines applications within its boundary.

Trees in Barnet

Barnet's tree policy is one of the more active in outer London. Key requirements include:

• Trees on public highway verges are the responsibility of Barnet's tree officers and cannot be pruned or removed without consent
• Trees within conservation areas have automatic protection — Barnet must be notified six weeks before any work is carried out on trees of any size within a conservation area
• Individual trees with a trunk greater than 75mm diameter at 1.5m height that are covered by a Tree Preservation Order require consent before pruning or removal

Pre-application discussions with Barnet's tree officer are strongly recommended before any extension project where trees might be affected.

Green Belt in Barnet

Parts of north Barnet — including areas around Hadley Wood, Barnet Gate and the Hertfordshire/Essex border — fall within the London Green Belt. Within the Green Belt, extensions to existing dwellings must not be disproportionate in scale, typically meaning cumulative additions of not more than approximately 40% over the original floor area. Barnet applies the national NPPF Green Belt policy to these cases.

Permitted Development in Barnet

In areas without Article 4 Directions, Barnet properties generally benefit from standard permitted development rights for single-storey rear extensions, loft conversions and outbuildings. An architect should confirm the permitted development position for any specific property before committing to a design approach.

Pre-Application Advice

Barnet Council offers a paid pre-application advice service for householder and other planning applications. Pre-application discussions are recommended for:

• Applications in conservation areas or involving listed buildings
• Applications involving trees with TPOs
• Larger extensions where neighbour impact is a concern
• Any application where the permitted development position is uncertain

Conclusion

Barnet's planning framework is broadly supportive of well-designed residential improvements, with clear guidance on scale, materials and neighbour impact. Conservation areas — particularly Hampstead Garden Suburb — require more specialist knowledge and planning preparation. Working with an architect experienced in Barnet planning applications will maximise your chances of a successful outcome and avoid costly resubmissions or amendments.