How Big Can A House Extension Be?

The size of a house extension depends on what part (or parts) of the house you want to extend. For example, you do not need planning permission to create new windows or doors or to use the loft in the house as one of your bedrooms. However, for an outhouse or garage, or any other building that is attached to the house, it is mandatory to take planning permission.

However, if you want to make a single-storey extension, you can extend it upto 15 per cent of the area of the house or 70 cubic metres (whichever is less). In case of a two-storey extension, you can extend it upto four metres or 15 per cent of the area of the house (whichever is less). Roof extensions can be done upto approximately fifty cubic metres.

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