Adding a second storey to an extension can provide extra bedrooms, bathrooms or living space without taking up more of your garden. However, two-storey extensions can have a greater impact on neighbouring properties and the appearance of a house, making it important to understand the planning requirements before finalising your design.
Two storey extension planning permission depends on the location of the proposed work, its dimensions, the property’s planning history and the rules that apply to the site. Some two-storey rear extensions may qualify as permitted development in England, while others require a householder planning application.
This article explains how to determine which route applies, what the planning authority may consider and how to prepare for approval.
What Is Two Storey Extension Planning Permission?
Two-storey extension planning permission refers to approval from the local planning authority to enlarge a house with an extension that has two floors. For example, you might build a ground-floor kitchen extension with a bedroom and bathroom above it, or add two floors to the rear of your property.
Whether formal permission is required depends on the proposed development.
Under permitted development rights, certain two-storey rear extensions can be built without a full planning application if they meet all relevant conditions. However, a two-storey side extension generally requires planning permission, and additional restrictions apply to properties in designated areas.
It is also important to distinguish between extending a house outwards and adding storeys directly above the existing building. These are different types of development and may be subject to different planning rules.
Before proceeding, review the property’s planning history and check the relevant requirements. Planning Build’s guidance on planning permission rules provides a useful starting point.
When Do You Need Planning Permission for a Two-Storey Extension?
You will generally need a householder planning application if the proposed extension does not qualify as permitted development or the relevant rights have been restricted.
Common situations include the following.
Two-Storey Side Extensions
A two-storey extension that projects beyond the side elevation of the original house generally requires planning permission. The usual permitted development rules for side extensions allow only single-storey additions within the relevant limits.
If your proposal wraps around the side and rear of the property, the planning assessment may need to consider both the side and rear elements.
Extensions That Exceed Permitted Development Limits
A two-storey rear extension must meet specific requirements to qualify as permitted development. If it projects too far beyond the original rear wall, is too close to an opposite boundary or breaches another applicable condition, you will generally need planning permission.
Properties With Restrictions
Permitted development rights may have been removed or restricted by a planning condition or an Article 4 Direction. This means an extension that might otherwise qualify may require a formal application.
Listed buildings also need careful consideration. Depending on the proposed work, you may need listed building consent in addition to planning permission.
Extensions in Designated Areas
Under the general householder permitted development rules in England, extensions of more than one storey are not permitted development on designated land. This includes conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites.
If your property is in one of these locations, check the relevant requirements before assuming that a two-storey rear extension can proceed without planning permission.
What Are the Permitted Development Rules for Two-Storey Extensions?
In England, a qualifying two-storey rear extension may fall under permitted development if it satisfies all the applicable limitations and conditions.
Maximum Projection From the Original Rear Wall
The extension must not project more than three metres beyond the rear wall of the original house.
The original house generally means the property as first built or as it stood on 1 July 1948 if built before that date.
This distinction matters if the house has already been extended. Existing additions may affect the assessment of the total enlargement, so you cannot automatically assume that a new extension has a separate allowance.
For example, adding a first floor above an existing single-storey rear extension may require planning permission if the combined development exceeds the relevant limits.
Distance From the Opposite Boundary
A two-storey extension must not be within seven metres of a boundary opposite the rear wall of the house being extended.
This restriction helps control the relationship between the extension and neighbouring land. It is particularly important where gardens are short or the proposed building would occupy a substantial part of the available space.
Height and Roof Design
The extension must meet the relevant height restrictions. Under the general permitted development rules, it must not be higher than the highest part of the existing roof or have eaves higher than the existing eaves.
Where the extension is within two metres of a boundary, the eaves height must generally not exceed three metres.
The roof pitch should match the existing house as far as practicable. The appearance of the materials used for external work must also satisfy the relevant conditions.
Upper-Floor Side Windows
Upper-floor windows in a side elevation must generally be obscure-glazed and non-opening, unless any opening part is more than 1.7 metres above the floor of the room.
These requirements help protect neighbouring properties from overlooking and loss of privacy.
Meeting these dimensions alone does not guarantee permitted development status. All applicable conditions, including restrictions on the site and previous development, must be considered.
For the official rules, consult the Planning Portal’s extension guidance.
What Will the Council Consider When Assessing Your Application?
When a two-storey extension requires planning permission, the local planning authority assesses the proposal against the development plan and other relevant planning considerations.
The main issues may include:
Design and appearance: The extension should be considered in relation to the existing house and the surrounding area. Its scale, roof design, materials and proportions can influence the assessment.
Impact on neighbouring properties: The authority may assess whether the extension would cause unacceptable loss of daylight, overlooking, loss of privacy or an overbearing effect on adjoining homes.
Height and massing: A two-storey extension can appear dominant if it is too large or positioned close to a neighbouring boundary. The relationship with nearby buildings and gardens is therefore important.
Local character: The council may consider whether the design is appropriate for the street, the existing property and any relevant heritage setting.
Site layout: The position of the extension, the available outdoor space and the relationship with boundaries may also be relevant.
Approval is not guaranteed simply because the extension meets the needs of the household. The design must be assessed in its specific planning context.
How to Apply for Two Storey Extension Planning Permission
If your proposal requires approval, preparing the right information can help the local planning authority understand the design and assess its impact.
1. Assess the Property and Proposed Design
Start by establishing the purpose, location, dimensions and appearance of the extension. Check whether the house has already been extended and whether any restrictions affect the site.
This early assessment can help identify potential planning issues before you invest in detailed drawings.
2. Prepare Architectural Drawings
A planning application will generally require drawings showing the existing house and the proposed extension. Depending on the project, these may include:
- A location plan identifying the property.
- A site or block plan showing boundaries and the extension’s position.
- Existing and proposed floor plans.
- Existing and proposed elevations.
- Sections showing heights and the relationship with the existing building, where needed.
The drawings should accurately represent the design and show how the extension relates to neighbouring properties.
Planning Build can help with planning permission drawings as part of the preparation process.
3. Prepare Supporting Documents
Depending on the property and the local authority’s requirements, you may need additional supporting information. This could include a planning statement explaining the proposal and addressing relevant planning considerations.
Other documents may be needed where the site has heritage constraints or other specific issues.
Check the local planning authority’s validation requirements before submitting your application.
4. Submit the Application
In England, a householder planning application can generally be submitted through the Planning Portal or the relevant local authority’s application arrangements.
You will need to provide the application forms, drawings and required supporting documents, together with the applicable fee.
The authority will check whether the application is valid before progressing to consultation and assessment.
5. Respond to Queries and Await a Decision
The planning authority may consult neighbours, assess the proposal against local policies and request additional information.
The usual statutory determination period for a householder application is eight weeks from validation, although some applications take longer. The timescale may be affected by the complexity of the proposal or an agreed extension of time.
Do not begin work that requires planning permission until the necessary approval has been granted. You should also check any conditions attached to the decision before construction starts.
For more information, see Planning Build’s guide to the planning application process.
What If You Want to Add a Storey Above Your Existing House?
Adding one or more storeys directly above an existing house is different from building a two-storey extension at the rear or side.
In England, specific permitted development rights may allow qualifying houses to be extended upwards, subject to prior approval and strict conditions. These rights do not apply to every property and have separate eligibility requirements, height limits and design restrictions.
If your project involves raising the roof or adding an entire floor to the main house, assess it separately rather than applying the rules for a conventional rear extension.
You can check the Planning Portal’s guidance on additional storeys and extending upwards to understand the different route.
Do You Need Building Regulations Approval?
Planning permission and building regulations are separate requirements.
Planning permission addresses whether the extension is acceptable in planning terms. Building regulations cover technical standards such as structural safety, fire safety, insulation, ventilation and drainage.
A two-storey extension will generally need careful consideration of building regulations, even if it qualifies as permitted development for planning purposes.
You should also check whether party wall procedures, listed building consent or other approvals apply before construction.
How Planning Build Can Help
Understanding the planning requirements early can help you assess whether your two-storey extension is feasible, identify potential restrictions and prepare the right application.
Planning Build can help you review your proposal, understand the relevant planning route and prepare drawings and supporting information for submission.
Explore our planning permission services or contact Planning Build to discuss your project.
