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How To Plan An Excellent Extension

Extensions can be an effective way to increase the value of your property and create some extra space in your home without having to move house.

This article highlights some of the key factors you should take into consideration when planning your extension, so that your project can run smoothly.

There are many different types of extension. Before you start your project, decide which type you want to build and which will suit you needs the best. You could plan one of the following:

  • Basement extension or conversion
  • Loft extension or conversion
  • Conservatory
  • Front porch
  • Extend upwards one or two storey
  • Extend outwards one or two storey


You should also decide what function you wish your extension to serve. Extensions can become bedrooms (with ensuite), offices, gyms, libraries or even cinema rooms – what you choose to do with the new space is up to you.

You will also need to consider access to the extension, space it will take up in the garden or driveway, soil type it will be built on to ensure secure foundations, and height and width of the extension.

Extensions require careful planning, and you need to determine whether you will require planning permission. You will need planning permission if:

  • The extension covers an area bigger than half the area of land around the house or covers more than half the garden.
  • The extension extends higher than the roof.
  • The extension extends beyond the rear wall of the original house by more than 3m if semi or terrace and 4m if detached.
  • The extension is higher than 4m for a single-storey.
  • Materials are not similar to the original house.
  • The extension will have a veranda, balcony or raised platform.
  • A two-storey extension is closer than 7m to the rear boundary.
  • The extension goes forward of the building line of the original house.
  • A side extensions is not single storey, more than 4m in height and more than half the building in width.
  • The extension extends a detached house by more than 8m in the rear, if single storey, or 3m, if double.
  • Is a listed building.


If you do need planning permission or are not sure whether you need planning permission, it is best to get professional advice from a surveyor. You will also need to apply for building regulations in order to undertake the work.

Your extension may also fall under The Party Wall etc. Act 1996. You can find further details here.

A typical extension will cost between £1,000 – £2,160 per metre². Don’t forget to take into consideration flooring, windows, electricity, heating, and any other fittings. Also consider the building and design costs if you hire someone to do this for you.

There are many options when it comes to designing, planning and managing your extension. You can use structural engineers for the design and calculations of load-bearing parts of the structure. You may also wish to hire an architect, use a design and build company or self-build your extension yourself.

If you are planning an extension, make sure you take into account these points before you begin. Decide which type of extension you wish to build, what that space will become, determine whether you need planning permission, how much the extension will cost, and how you will design, plan and manage the work. This will ensure that you plan your extension carefully so that your project can run smoothly and your extension can be a success.