How to plan an extension

An extension is one of the biggest and most complicated home improvement projects you can undertake. Whether you’re undertaking a single or double storey extension there are a number of things that you’ll need to take into account.

Here’s a list of things to consider when adding an extra room to your house:

  • Deeds
  • Layout
  • Size, setting and neighbours
  • Planning permission

Check your deeds

Before you start any building work it’s important that you check the deeds to your house. You should pay special attention to the deed as it contains information on the work you can and cannot do to the property.

If you’re unsure we recommend you consult a solicitor for extra help and advice in interpreting the deeds. Note that if you’re allowed to build an extension, you’ll have to notify your mortgage lender if you are still paying a mortgage on your home.


Plan the amount of space you’d like to add and how much space you can actually create from your existing house by reconfiguring the current layout.

You can create extra space by building an extension upwards and/ or outwards. Building an extension upwards means creating a two-storey extension. Building an extension outward means building an extra room on the side of the house.

It’s best to consult an architect so that you get the best extension to suit your home and maximum benefit from the space available. You also need to blend the exterior of the extension to the original house or plan as much as possible to align yourself with local planning rules and regulations. Do this by using a similar architectural style and similar materials.

When drawing a blueprint for the extension, take into consideration the layout of your pipe runs and all electricity circuit layouts for an effective plumbing and wiring plan. Establishing these in advance of building work starting will prevent any costly mistakes further down the line.

Size, setting and neighbours

You’ll need to determine the size of the new extension and its location. Many people choose to build on garden space to extend towards the back of their homes. Be cautious with your planning; a side-extension may block access to the back of your house and building over too much of your garden may reduce the value of your home overall.

There are also regulations around what percentage of your land you can build on and how big your extension can be in relation to the original structure – you’ll need to make sure you have all of the correct permissions before work commences. If your neighbours have an extension, it’s worth finding out their experience with their project as rules and permissions vary from place to place.

Prior to starting the extension project, you should consult your neighbours about your plans. Get permission in writing and make sure they are aware that an extension can take months to complete.

Two-storey extensions

As you need to add in an extra room at first floor level, planning and building a two-storey extension is complex. The extra space required for the first-floor room is taken from existing rooms and corridors so that your home’s structure isn’t compromised. For two-storey extensions, you also need to consider how the new extension will affect ventilation and natural lighting to the existing rooms.

Simply adding a second storey on top of a single-storey extension is relatively easy to accomplish. The foundations are crucial when planning to build an extension to your house. It’s highly recommended that you seek advice and help from an expert when planning and building an extension.

Planning permission

Generally, an extension is considered a permitted development which means you won’t necessarily need planning permission; although a listed property or a property in a conservation area will require planning permission. Permissions vary from area to area so it is always worth consulting with your local planning office in advance of any work.

The information contained within this article is strictly for guidance only. Rated People recommends that you always check current sources of information in case regulations have changed. Rated People cannot accept any liability for miscommunication of the law in the case of a change in regulation or any action done to a property based on the information held in this article. Rated People © 2013.
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