Do You Need Planning Permission to Extend in Maidstone?

What permitted development allows

Permitted development rights let you extend a house without a planning application, as long as the work stays within set limits. The limits are measured from the 'original house', meaning the house as it was first built or as it stood on 1 July 1948. If a previous owner has already added a conservatory or a rear extension, that counts against your allowance.

These are the main limits for a house. Flats and maisonettes have no permitted development rights for extensions.

• Single-storey rear extension: up to 4m deep on a detached house, 3m on a semi or terrace, and no more than 4m high.
• Anything within 2m of a boundary: eaves no higher than 3m.
• Side extension: single storey only, no more than 4m high and no wider than half the width of the original house.
• Two-storey rear extension: up to 3m deep and at least 7m from the rear boundary.
• Materials: similar in appearance to the existing house.
• Nothing forward of the principal elevation facing the road, and no more than half the garden covered by extensions and outbuildings.

The larger rear extension route

You can build a single-storey rear extension up to 8m deep on a detached house, or 6m on other houses, through the prior approval process. You notify Maidstone Borough Council, which writes to your neighbours. The council has 42 days to decide, and if a neighbour objects it will look at the effect on their light and privacy.

This route suits a lot of the 1930s semis and post-war estate houses around Allington, Barming and Shepway, where 3m is often not enough for a proper kitchen diner. It is not available in conservation areas or the Kent Downs.

Where Maidstone's local picture changes the answer

A large part of the borough is 'Article 2(3) land', where permitted development rights are reduced. That covers the Kent Downs National Landscape across the north of the borough, including Detling, Thurnham and Hollingbourne, and the conservation areas. There are conservation areas in parts of the town centre and in villages such as Bearsted, Loose, Boughton Monchelsea, Sutton Valence, Headcorn, Marden and Lenham.

On this land you cannot build a side extension or a two-storey rear extension under permitted development, and you cannot clad the outside of the house. A single-storey rear extension within the standard limits is usually still allowed.

• Listed buildings need listed building consent for most extensions, even small internal alterations. The borough has a lot of listed timber-framed and Kentish ragstone properties.
• Some estates have had permitted development rights removed by a planning condition or an Article 4 direction. Check your property's planning history on the council's online planning register.
• Some new-build developments around the edge of Maidstone come with conditions that restrict extensions.

Getting certainty before you build

If you think your extension is permitted development, it is worth applying for a Lawful Development Certificate from Maidstone Borough Council. The fee is half the cost of a householder planning application, and a decision usually takes around eight weeks. The certificate proves the work is lawful, which helps when you come to sell, because buyers' solicitors will ask for it.

If the extension goes beyond the limits, you need a householder planning application. The council aims to decide these within eight weeks, and it assesses designs against its local plan and residential extension guidance. Poorly handled applications are often refused over the effect on neighbours' light or the look of the street, so good drawings make a real difference.

What you need whatever the planning answer

Permitted development only deals with planning. Every extension still needs Building Regulations approval for foundations, structure, insulation, drainage and fire safety, either through the council's building control team or an approved inspector.

If you are building on or near a shared boundary, the Party Wall Act may require you to give your neighbours notice, usually at least two months before work starts. On the clay soils common around Maidstone, extensions near trees often need deeper foundations. It is better to know that at the design stage than to find out when the footings are dug.