How to build a side-return extension

  • We earn a commission for products purchased through some links in this article.
  • Turn wasted outdoor space into a flexible living area with a side-return extension

    For many homeowners, the side-return area – the pathway that runs alongside the ground floor area of the house – is a redundant space. But by building on to it, you can make your home bigger and better.

    We’re here to answer those all-important questions.

    What structural work is involved?

    1) A new wall is built on either the boundary of you and your neighbour’s land, or solely on your side of the boundary.

    2) A roof is added (consider a fully glazed design or one with several skylights to flood the interior with light).

    3) The side wall to the existing rear room is either completely or partially knocked through. A steel frame may need to be inserted in the wall to support this new opening.

    4) A new floor is usually put in, level with the existing floor.

    Will I need an architect?

    Not necessarily. Some conservatory companies and specialist builders offer a complete ‘design and build’ package service, which saves paying extra fees to architects or structural engineers for drawing up plans.

    Do I need planning permission?

    Council rules changed in October 2008, so you no longer need planning permission for a ground floor side-extension as long as the extension is only single storey, no more than 4m high and no wider than half the width of the original house.

    You’ll still have to comply with Building Regulations and possibly with the Party Wall Act if you’re creating a new boundary wall between you and your neighbour, so speak to your local council’s planning office for details.

    How long will it take and how much will it cost?

    A simple side extension will cost from £20,000. Extra internal work, such as adding a new kitchen, and the style of the extension – for example adding glazed external doors – will affect the final figure.

    Plan for at least eight to ten weeks for the structural work, plus more for decorating the interior of the new space.

    Who do I contact?

    The Federation of Master Builders, 020 7242 7583,, has details of registered tradesmen.

    Local Authority Building Control, 020 7641 8737,, can advise on applying for Building Regulations Approval.

    The Institution of Structural Engineers, 020 7235 4535,, has details of engineers.

    Royal Institute of British Architects, 020 7580 5533,, has a list of architects in your area.

    All the latest from Ideal Home