Planning a house extension in Bromley? Before committing to drawings or construction, it helps to understand the local planning context, permitted development rules, likely costs and the constraints that could affect your project.
This guide brings together practical information for homeowners considering rear extensions, side extensions and other house extension projects in the London Borough of Bromley, with links to official planning information and tools to help you research your next steps.
Quick answer
Some house extensions in Bromley can be carried out under permitted development rights, while others require a planning application. What applies depends on the property, the proposed extension and any restrictions affecting the site. Some parts of the London Borough of Bromley are subject to Article 4 Directions that remove particular permitted development rights, so the property should be checked before relying on permitted development.
If planning permission is required, Bromley has specific validation requirements for householder applications. Depending on the project and site, these can include site photographs, location and block plans, existing and proposed floor plans and elevations, with additional information required in some circumstances.
What should you check before extending a house in Bromley?
1. Permitted development rights
Some extensions may fall within permitted development rights, subject to national limits and conditions. However, permitted development rights can be restricted by the type of property, previous alterations, planning conditions or an Article 4 Direction. Check the individual property before assuming that planning permission is not required.
2. Conservation areas and local restrictions
Bromley contains a number of conservation areas where additional planning considerations may apply. If your property is within a conservation area, the design, scale, materials and impact of an extension may require particular attention.
3. The site and neighbouring properties
Consider how the proposed extension relates to neighbouring homes, boundaries, access, existing trees, drainage and the character of the surrounding area. These factors can influence both the design of the project and the information needed for a planning application.
4. Building Regulations
Planning permission and Building Regulations are separate. Even where an extension does not require planning permission, Building Regulations approval may still be required for matters such as structure, insulation, fire safety, ventilation and drainage.
Common house extension projects in Bromley
Homeowners in Bromley consider a wide range of extension projects, depending on the type of property, available space and the way they want to use their home. Rear and side extensions are particularly relevant to many traditional houses, while larger properties may offer opportunities for more substantial alterations.
Rear extensions
A rear extension can create additional kitchen, dining or living space and improve the connection between the house and garden. The appropriate depth, height and design will depend on the property and the planning route available.
Side extensions
Properties with usable space alongside the house may have potential for a side extension. Design considerations can include the relationship with the boundary, neighbouring properties, access, drainage and the effect on the original character of the house.
Wraparound extensions
A wraparound extension combines rear and side development to create a larger area of additional floorspace. These projects can provide significant layout flexibility, but their scale and relationship with neighbouring properties mean the planning and design considerations should be examined carefully.
How much does a house extension cost in Bromley?
Extension costs in Bromley can vary significantly depending on the size and complexity of the project, specification, access, structural work and contractor pricing. As Bromley forms part of Greater London, homeowners should also allow for the generally higher construction costs associated with London and the South East.
Published 2026 cost guides indicate broad extension construction costs of around £1,800–£3,300 per m², depending on specification and project type. These figures should only be treated as early-stage benchmarks. VAT, professional fees, planning and Building Regulations fees, structural engineering, kitchens, specialist glazing and unexpected site conditions can materially affect the final budget.
Estimate your extension cost
Use the BetterPlanHomes Extension & Loft Cost Calculator to explore an indicative early-stage project range based on your project type, approximate floor area, specification and location.
Planning permission and permitted development in Bromley
Whether an extension needs planning permission depends on the property, the proposed works and any restrictions affecting the site. Some extensions can be carried out under permitted development rights, provided they meet the relevant national limits and conditions.
Article 4 Directions in Bromley
Some areas of Bromley are affected by Article 4 Directions. These can remove particular permitted development rights, meaning work that might normally be possible without a planning application could require permission. Always check whether an Article 4 Direction affects the individual property before relying on permitted development rights.
Conservation areas
Bromley has numerous conservation areas intended to protect areas of special architectural or historic interest. If a property is within a conservation area, additional restrictions and design considerations may apply. The location, scale, materials and appearance of an extension can therefore be particularly important.
How can I confirm whether my extension is permitted or development?
Bromley Council states that it does not provide an informal determination of whether proposed works constitute permitted development. If you want a formal decision confirming whether a proposal is lawful, you can apply for a Lawful Development Certificate.
How does a planning application work in Bromley?
If your extension requires planning permission, an application can be submitted to the London Borough of Bromley, usually through the Planning Portal. Before submitting, it is important to check Bromley’s current validation requirements because an incomplete application may be treated as invalid.
What documents might you need?
For a typical householder extension application, Bromley’s current checklist requires an application form, site photographs, a site location plan and existing and proposed floor plans. A block or site plan is also required where the proposal increases the building footprint, while existing and proposed elevations are required where the proposed work is visible. Depending on the property and proposal, additional plans or supporting documents may also be required.
What happens after submission?
Bromley’s validation team first checks whether the application contains the required information. Once an application is valid and registered, adjoining or immediate neighbours are notified and relevant consultees may be contacted. The application is placed on the public register before being passed to a planning officer for assessment and a recommendation.
Can you track applications in Bromley?
Yes. Bromley’s online planning register allows homeowners to search applications, view plans and other application documents, follow progress and review previous planning decisions. Looking at relevant applications near your property can also provide useful context, although previous decisions do not guarantee that a new proposal will receive the same outcome.
How to research recent extension applications in Bromley?
Looking at recent and historic planning applications can help you understand the types of extension proposals being considered in your area. Bromley Council’s Public Register allows you to search applications by location, date, application type and description, as well as view application documents and decisions where available.
What should you look for?
- Extensions to properties similar to your own
- Rear, side and wraparound extension proposals
- The scale and relationship of extensions to neighbouring properties
- Planning officer reports for decided applications
- Reasons attached to approvals or refusals
- Design changes between different applications at the same property
Previous applications can provide useful context, but they should not be treated as a guarantee that a similar proposal will be approved. Planning applications are assessed on their individual circumstances and against the development plan and other material planning considerations. Bromley states that its current development plan includes the Bromley Local Plan and the London Plan.
Local planning considerations for extensions in Bromley
Design and local character
Bromley’s planning policies place importance on the design of residential extensions and their relationship with the existing house and surrounding area. The council’s Local Plan states that extensions should respect or complement the style and materials of the main building. This means the scale, roof form, materials and position of an extension can all be important considerations when developing a proposal.
Trees and Tree Preservation Orders
Trees can be an important consideration when planning an extension in Bromley. The borough has more than 2,000 Tree Preservation Orders, and special provisions also apply to trees within conservation areas. If an extension could affect a protected tree or its roots, this should be investigated early in the design process.
Trees in conservation areas
Trees within conservation areas can also have additional protection. Bromley Council states that anyone intending to cut down or carry out work to a tree in a conservation area generally needs to give the council six weeks’ notice. This can be relevant to extension projects where foundations, access or construction work may affect existing trees.
Neighbouring propoerties and extension design
The relationship between an extension and neighbouring properties should be considered from the beginning. The position, height and scale of the proposed development, together with boundaries and the existing character of the site, can influence the appropriate design. Reviewing nearby planning applications can provide useful context, but each proposal is assessed on its own circumstances and against the relevant planning policies.
Bromley extension checklist: what to check before you commit
- Check whether the property is within a conservation area or affected by an Article 4 Direction.
- Establish whether the proposed extension may fall within permitted development rights or require planning permission.
- Check whether protected trees or trees within a conservation area could be affected.
- Review relevant nearby planning applications for useful local context.
- Consider boundaries, neighbouring properties, drainage, access and site constraints.
- Develop an initial layout and understand how the extension will improve the existing home.
- Prepare an early-stage budget and allow an appropriate contingency.
- Identify the drawings, photographs and supporting information that may be required for an application.
- Check whether Building Regulations approval and other consents may also be required.
- Consider obtaining a Lawful Development Certificate where formal confirmation of permitted development status is important.
Useful Bromley planning resources
Before progressing with an extension, use the London Borough of Bromley’s official planning resources to check the latest requirements affecting your property.
- Check permitted development and Article 4 Directions — link to Bromley permitted development guidance. Bromley confirms that Article 4 Directions remove particular permitted-development rights in some parts of the borough
- Check householder application requirements — link to Bromley’s householder validation checklist. This is especially useful because Bromley currently requires items such as site photographs, location plans and floor plans for householder applications, with further information depending on the proposal.
- Submit a planning application — link to Bromley’s householder application guidance. Bromley directs online applications through the Planning Portal.
- Check current validation requirements and charges — link to Bromley planning validation requirements. This is worth linking rather than copying charges into our article because the figures can change.
Planning a rear extension in Bromley?
BetterPlanHomes’ Rear Extension Pack brings together practical guidance on planning, indicative costs, design and layout considerations, common technical risks and the steps to consider before progressing with your project.
Use it alongside local planning research to build a clearer picture of your project before committing significant money to design or construction.
Last reviewed: September 2026. Planning rules, local requirements and fees can change. Always check current information with the London Borough of Bromley and other relevant authorities before making project decisions.