Loft Conversion Regulations in the U.K.

Planning Permission

• Generally speaking, loft conversions are considered "permitted" development and do not require planning permission. However, caveats apply depending on the size, type and orientation of any extension to your loft space, so contact the planning department of your local council before you start building or renovating.

  If you live in a terraced house you can extend your roof space by up to 40 cubic metres (1,412 cubic feet) and if you live in a semi-detached or detached house by up to 50 cubic metres (1,765 cubic feet) without planning permission. However, if you want to build higher than the highest part of the existing roof or add a balcony you will need planning permission. Similarly, planning regulations stipulate that you must build any roof extension, unless it runs from the hip (the line where two adjacent sloping sides intersect) to the gable (the triangular section of wall at the front or back of a house), as far back on the roof as possible.

Fire Safety

• You will need Building Regulations approval to convert your loft into living space and some of the strictest regulations apply to fire safety. You must install a self-closing fire door capable of resisting fire for 30 minutes and one or more windows, measuring at least 450 mm (18 inches) square and accessible from the outside, through which occupants can escape in the event of fire.

Other Considerations

• Building Regulations also demand energy efficiency, so you need to consider the type and thickness of insulation that you will install in your loft space. You can choose any type of insulation---blanket, loose fill, foil foam---but it should be at least 150 mm (6 inches) thick; you will need to specify the type when you submit your Building Regulations application. In most cases, you will need to leave a gap of 50 mm (2 inches) between the insulation and the roof covering and ventilate the roof void to prevent condensation; rapid ventilation is also a requirement, but you can achieve this by installing a roof window that is equivalent to 5 percent or more of the floor area.