Depending on your home’s layout, and as long as the new layout complies with building regulations, a ground-floor extension can be turned into pretty much anything, typically a kitchen-diner-family room, but also a den/playroom, home office, or bedroom and bathroom. If you can run to a two-storey extension, you’ll increase both your living and sleeping space, perhaps adding a dressing room or extra bathroom upstairs.
2. The problem with two-storey extensions is that they often require planning permission; whereas ground-floor extensions can often be done under your home’s permitted development (PD) rights, providing it has them. Flats and maisonettes don’t have PD rights, while, for example, houses on ‘designated land’, such as conservation areas, have fewer PD rights than those not on designated land, or no PD rights at all - ask your local council if in doubt. If your home doesn’t have PD rights or you want to build an extension that can’t be done under PD, you’ll have to apply for planning permission, which can be a long process.
3. The Government has changed the PD rules for a limited period - currently until 30 May 2019. As a result, many terraced and semi-detached houses can extend to the rear by 6m (on the ground floor) without planning, or a whopping 8m for detached houses. This is double the usual size and so faced opposition from some MPs when it was debated in Parliament. The agreed compromise was that the local council will have to be notified of a planned extension (certain details must be provided) and then adjoining neighbours will be given the chance to object. If they object and the council upholds their objection, you can’t proceed.
4. To be done under PD, an extension must conform to the rules regarding width, height and materials, etc. For example, the maximum height of a single-storey rear extension must be 4m, two-storey extensions must be no closer than 7m to the rear boundary, and verandas, balconies and raised platforms aren’t allowed. Go to www.planningportal.gov.uk to find out more.
5. While you can get flat-pack extensions, just as you can get flat-pack homes, most extensions are built in a more conventional way, with an architect designing it and a builder constructing it out of bricks or blocks. If the architect also manages the project and contractors (usually charging a percentage of the build cost), you should have less to do and worry about. You may prefer to manage the build yourself, or get the builder to organise everything. As well as time to build the shell of the extension, you’ll need to factor in fitting-out time - kitchens and bathrooms often take longer than other rooms and will also, of course, be more expensive. Like any big home-improvement project, an extension can easily go over budget, so keep a careful eye on the numbers and schedule and always have a contingency fund for unexpected problems.