PLANNING RULES FOR REAR EXTENSIONS

REAR EXTENSIONS AND PLANNING PERMISSION

If you want to add a rear extension to your house, you may need planning permission – requiring a planning application to your local authority. 

Planning applications cost money, take time, and require an assessment to be made by a local planning authority officer.  Your neighbours will be consulted and can object to your proposals. 

However, as with any extension to your house, you can undertake certain works without the need to apply for planning permission – subject to ‘permitted development’ rules being met in terms of extension size, type and location.    

The relevant rules are set out in the Town and Country Planning (General Permitted Development) (England) Order 2015, as amended.    

Rules for extensions to the rear of the house are some of the most generous in the GPDO as they are often out of sight and have a relatively low chance of impacting upon neighbours.  

REAR EXTENSIONS – PERMITTED DEVELOPMENT RULES

Rear extensions to a house will be classed as permitted development, so long as:

The total area of ground covered by the extension, as well as other buildings within the curtilage of the dwelling, does not exceed 50% of the total area of the curtilage (excluding the ground area of the original house*)

The height of the extension does not exceed the highest part of the roof of the existing house

The height of the eaves of the extension does not exceed the height of the eaves of the existing house

Where the extension is to be within 2 metres of any boundary of the property, the height of the eaves of the extension does not exceed 3 metres

If the extension is single storey, it does not exceed 4 metres in height and does not extend beyond the rear wall of the original house by:

more than 4 metres in the case of a detached house, or

more than 3 metres in the case of any other house

If the extension is to be of more than one storey, it must not extend beyond the rear wall of the original house by more than 3 metres and it must be 7 metres or more from any boundary of the curtilage opposite the rear wall of the house

The rear extension does not extend beyond the side elevation of the house if the house is on a corner plot and the side elevation fronts a highway

A planning application is needed if the enlarged part of the house would extend beyond a wall forming a side elevation of the dwelling, and would:

Exceed 4m in height,

Have more than a single storey, or

Have a width greater than half the width of the original dwelling

* the “original house” is as built or as it stood on 1 July 1948 (if it was built before that date)  

Specific permitted development rules apply to the creation of porches.

LARGER REAR EXTENSIONS – PRIOR APPROVAL

For larger rear extensions, in certain circumstances, a ‘prior approval’ application (neighbour consultation scheme) may be appropriate, rather than a full planning application. 

For a dwellinghouse not located in a Conservation Area, AONB, National Park, World Heritage Site, The Broads or in an area of special scientific interest, such a process would be appropriate, where, in addition to the above criteria:

only a single storey extension is proposed;

it will extend beyond the rear wall of the original house by no more than 8 metres in the case of a detached dwelling, or 6 metres in the case of any other house; and

will not exceed 4 metres in height

Householders looking to build a ‘larger extension’ have to notify their local council about the proposed extension who must give adjoining neighbours notice of the proposals and an opportunity to object.

Works cannot commence until the local planning authority notifies the householder that:

• no ‘prior approval’ is required, or
• gives ‘prior approval’, or
• 42 days pass without any decision by the local planning authority.

Conditions attached to all rear extensions

Development is permitted for rear extensions subject to the following conditions:

The materials used in any exterior work (other than those used for a conservatory) must be of a similar appearance to those used in the construction of the existing house

Any upper-floor window inserted in a wall or roof slope forming a side elevation of the house must be obscure glazed and be non-opening unless the opening parts are more than 1.7m above the floor of the room in which the window is installed

If the extension has more than one storey, the roof pitch of the enlarged part shall, so far as practicable, be the same as the roof pitch of the original house

SEPARATE RULES APPLY TO:

• Decking, balconies and raised platforms
• TV aerials or satellite dishes
• chimneys, flues or soil and vent pipes
• Any alteration to the roof of the existing house
• Changes of use

PERMITTED DEVELOPMENT – PROTECTED AREAS – REAR EXTENSIONS

If you live in any of the areas listed below, additional limitations on ‘permitted development’ will apply:

• Conservation Areas
• Areas of Outstanding Natural Beauty
• National Parks
• the Broads
• World Heritage Sites

In these areas, rear extensions are not permitted development if:

they are over single storey

they consist of or include cladding of any part of the exterior of the dwelinghouse with stone, artificial stone, pebble dash, render, timber, plastic or tiles;

they would extend beyond any side elevation of the house;

Contact your local authority or seek professional advice if you live in these areas. 

REMOVAL OF PERMITTED DEVELOPMENT RIGHTS

Permitted development rights can also be removed by your local planning authority, either through the addition of a Condition on a previous planning permission, or through imposition of an Article 4 Direction. 

CONTACT YOUR LOCAL PLANNING AUTHORITY BEFORE COMMENCING WORKS

For the purposes of planning, contact with the local planning authority is generally only necessary before carrying out permitted development where:

• ‘prior approval’ from the local planning authority is required under PD rules
• a ‘neighbour consultation scheme’ is in place
• the local planning authority has a Community Infrastructure Levy in place which requires developers to contact the local planning authority before carrying out permitted development. Failure to do this may result in the local planning authority imposing a surcharge on a developer
• the permitted development rights require the developer to notify the local planning authority of a change of use

Schedule 2 of the GPDO sets out when any advance notification is required.  If you are in any doubt, contact your local planning department or seek professional advice.

PERMITTED DEVELOPMENT RIGHTS FOR FLATS, SHOPS AND OTHER PREMISES

Permitted development rights under Part 1 of the GPDO only apply to houses – they do not apply to flats, maisonettes or other buildings. 

Check out our guides to non-householder PD rights (through the menu at the top of this page). 

PERMITTED DEVELOPMENT RIGHTS AND CIL

If a development is over 100 sq m in size, it may be liable for a charge under the Community Infrastructure Levy (CIL).

Check with your local planning authority whether they use CIL in your area and whether it applies to permitted development. 

AND FINALLY …  

PD rights are subject to change.  The guide above is for general information only and does not constitute advice.  Local and site-specific circumstances can differ and affect whether a planning application is needed.

Other consents (e.g. Listed Building Consent, Building Regulations or notifications under the Party Wall Act) may also be needed. 

To determine whether planning permission or other consents are required, seek professional advice or clarification from your local authority before starting works.