Planning Permission for Sheds and Greenhouses

Extract from Planning Portal
(note OBL Ltd is not responsible for the contents of this text):

You will need to apply for planning permission if any of the following cases apply on the land around your house.

You want to put up a building or structure which would be nearer to any highway than the nearest part of the "original house", unless there would be at least 20 metres between the new building and any highway. The term "highway" includes public roads, footpaths, bridleways and byways.
More than half the area of land around the "original house" would be covered by additions or other buildings.
The building or structure is not to be used for domestic purposes and is to be used instead, for example, for parking a commercial vehicle, running a business or for storing goods in connection with a business.
You want to put up a building or structure which is more than 3 metres high, or more than 4 metres high if it has a ridged roof. (Measure from the highest ground next to it.)
If your house is a listed building, and you want to put up a building or structure with a volume of more than 10 cubic metres.
If you live in a Conservation Area, a National Park, an Area of Outstanding Natural Beauty, or the Broads, and you want to put up a building or structure with a volume of more than 10 cubic metres (though it might be allowable as an extension)

The words "original house" have a particular meaning.

Note: in all cases, if your new building would have a volume over 10 cubic metres, and come within 5 metres of the house, it would be treated as an extension. Also, if your new extension would bring some existing garden building within 5 metres of the (extended) house, that existing building's volume could be deducted from your overall volume entitlement for the house, as if it were another extension.

Ask your council if in doubt.

Calculating the volume of a building or extension is not easy. It is important to get it right if you are deciding whether planning permission will be needed. To help you we have provided a handy calculator (see link below). The answer to the calculation is always given in metric because the relevant legislation uses metric measurements.

Launch the volume calculator (opens in a new window which you may need to resize).

Requires Flash. Download the free plug-in from Macromedia.