Gregory Phillips’ radical extension won the 2008 Daily Telegraph Homebuilding and Renovating Award for Best Extension/ Remodel

Adding an extension is not simply a case of tacking a new room (or rooms) on to your home. You will need to think carefully about how old and new work together (both externally and internally) as well as all the cost, planning permission and project management implications.

These top tips will help you get your project off to the best start.


  • Define your objectives and prepare a realistic project schedule.
  • Plan ahead and set up a contingency fund.
  • Approach the planners first and find out what is likely to be acceptable.
  • Look carefully at finance. How much value will your extension add? What are the best deals on loans?
  • Put structural works before cosmetic and aesthetic improvements and work from the outside of the house inwards.
  • Make sure you know the difference between a quotation – a firm price and what you can expect to pay for the specified works – and an estimate, which is much less specific.
  • Always try to go for a fixed price contract.
  • Make sure the designer of your extension knows all about and allows for movement joints. With the generally dryer climate we have been experiencing in recent years buildings have been tending to move more.
  • Pay attention to the style of the windows.
  • Aim to get the shell weathertight as early as possible.
  • Check that the builder has relevant past experience and a good trading history; that he has an office address and his own headed notepaper; that he is able to offer references; and that he has third party insurance.


  • Change your mind if all all possible. It may result in a hefty budget overspend.
  • Ignore site and home insurance. Is your contractor’s cover sufficient or do you need to take out extra provision?
  • Forget the contract. It is essential to cover yourself. An exchange of letters is not sufficient.
  • Pay for any work in advance.
  • Necessarily go for the lowest quote. Busy builders may not be as competitive. References are far more important.
  • Add too many bedrooms and not enough bathrooms. A good rule of thumb is one bathroom for every two bedrooms, with an en-suite for every guest bedroom. Otherwise, end valuemay be affected.
  • Run into money problems. Make sure your extension is properly planned, designed and costed. If your builder has financial problems, be sure your contract is one that contains an adjudication clause.

Don’t Forget to Think Ahead

With sufficient forethought you will have planned your extension so that it will both be a great source of satisfaction to everyone living in the house, and also add at least as much to the value of the property as has been spent on it hopefully considerably more.

Finally, remember that although this might be your first extension, it may not be your last. Perhaps you have enjoyed the project so much that you cant wait to undertake another!

With this in mind it will pay to put a great deal of thought into the internal design of your extension and try to avoid poky corridors, corners and awkward links that are essentially wasted space. All these will appear a great deal worse if at a later stage you choose to add a second extension. Seamless flow and clarity are the watchwords in the design of any good extension.

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