Type of property

For a start, there are different rules for different types of properties.  Permitted development (PD) rights don’t apply to flats or maisonettes or converted homes, such as barn conversions. Similarly, listed properties have their own rules. If your property is listed, any changes will need listed building consent.

PD rights are restricted or removed completely for homes in protected locations, such as conservation areas, national parks, areas of outstanding natural beauty, the Norfolk or Suffolk Broads and World Heritage sites. In these areas, PD rights are non-existent and you will require planning permission.

For all extensions

The size of a proposed extension and its location as well as the building materials and type of windows will all play a part in whether it comes under permitted development or not. The rules include:

• Extensions cannot be higher than the highest part of the existing roof or higher at the eaves than the existing eaves
• When the extension comes within two metres of the boundary, the height of the eaves cannot exceed three metres.
• Only half the area of land around the original house can be covered by extensions or other buildings
• The materials used on the exterior of the extension must be similar to the existing house.
• The project cannot include balconies (except for Juliet balconies), verandas or raised platforms, chimney, flue, or soil and vent pipe.

If your heart is set on something different, for example, a bold, contrasting extension to a period property or a new master bedroom with a walk-on balcony, you will need planning permission.

Side extensions

A popular project for Victorian terraces and semis is to extend the living space into the side return area – the passageway that runs alongside the house. Owners of detached houses may also be able to extend beyond the side elevation of their property. To qualify for PD rights, the side extension:

• Can only be single storey.
• Can only be up to half the width of the original house
• Cannot exceed four metres in height.

Single-storey rear extension

While all front extensions require planning permission, rear extensions can qualify as permitted development within certain parameters:

• Cannot exceed four metres in height
• Cannot extend beyond the rear wall of a detached house by more than four metres or three metres if semi or terraced.
• Subject to ‘prior approval’ the limit for single-storey extensions has recently been increased to a depth of eight metres for a detached property or six metres for any other house. But you need to inform your local planning authority of the proposed project by submitting a prior approval application. Council planning officers will then decide if it’s permissible under PD rights or requires a planning application.

Two-storey rear extension

The rules are stricter, for obvious reasons, for double-storey rear extensions.

• Can extend by no more than three metres from the rear wall of the original house
• Cannot come within seven metres of the property’s rear boundary
• The pitch of the roof must match the existing house as closely as possible
• Upper, side-facing windows to be obscure glazed, any opening to be 1.7m above ground

Loft extension

Under permitted development, you can extend into your loft space without having to get full planning consent if the project meets certain criteria:

• The additional volume created does not exceed 40 cubic metres of living space for terraced houses, or
• 50 cubic metres for detached properties and semis.
• Roof extensions, apart from hip to gable ones, to be set back as far as practicable or at least 20cm from the original eaves.
• An extension beyond the plane of the existing roof slope of the principal elevation is not permitted development. All dormer windows will require planning permission.

Additional storeys

Recent tweaks to permitted development rules mean homeowners can, in theory, add entire storeys to their homes rather than undertaking a traditional loft conversion, which often has the disadvantage of sloping roofs.

• Subject to ‘prior approval’, homeowners can build two additional storeys on top of the principal part of a detached house (not the garage) consisting of at least two floors. If the roof space is to contain living space it would count as one of the two storeys.
• Subject to prior approval, build one additional storey on top of a bungalow
• Only owners of properties built between 1948 and 2008 qualify for this new permitted right.
• Neighbours will be consulted and any impact on them taken into consideration. Decisions will be made on a case-by case basis.

While larger rear extensions and additional storeys come under permitted development and can be built without full planning permission, it still involves a prior notification to the relevant local authority. Councils must give a decision within eight weeks. When considering a prior notification, they will look at the external appearance of the project, adequacy of daylight within the proposed dwelling, impacts on neighbours, transport and highways implications. While PD rights makes building large rear extensions and additional storeys easier, it’s not dissimilar to a normal planning application.

Front porches & outbuildings

Adding a porch to any external door of your home is another home improvement you can make under permitted development, provided:

• Keep a footprint of three metres square maximum
• No part is more than three metres above ground level
• Porch cannot be within two metres of the boundary or the highway.

PD also allows for outbuildings, so long as they are sited behind the front elevation, don’t take up more than half the garden and aren’t more than three metres in height (2.5m where within two metres of a boundary or four metres for a dual-pitched roof).

Not all houses have PD rights and they are subject to various restrictions and conditions, so always take professional advice. A local architect or qualified surveyor can advise if PD could work for your project or if it might be better to apply for planning permission which can open up a world of design possibilities.

If you are looking to make some home improvements, you may find some of these services useful