Providing you meet the criteria you can enlarge your loft by up to 40 cubic m in the case of a terraced house and 50 cubic m in the case of a semi-detached and detached house without the need for planning permission.

With roof alterations, the emphasis is very much on appearance and this is reflected in the above criteria. Materials used have to be similar to the existing, the alteration cannot exceed the height of the existing roof and you cannot introduce a veranda, balcony or raised platform into the scheme without it needing planning permission.

Planning Permission may not be required subject to the following limits and conditions:

A volume allowance of 40 cubic m for terraced houses or a volume allowance of 50 cubic m for detached and semi-detached houses.

  • If your property fronts a highway, you cannot extend beyond the roof plane which fronts the highway.
  • No extension to be higher than the highest part of the roof.
  • Materials to be similar in appearance to the existing house.
  • No verandas, balconies or raised platforms.
  • Side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor.
  • Roof extensions not to be permitted development in designated areas*.
  • Roof extensions, apart from hip to gable ones, to be set back, as far as practicable, at least 20cm from the eaves.
  • Designated areas include national parks and the Broads, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites.

Building Regulations approval is required to convert a loft or attic into a liveable space.

The guidance in this section is aimed at those properties which are no more than 2 storeys in height. Whilst the requirements are similar, they are more extensive for houses over 3 storeys and can extend to other parts of the building.

For any loft conversion, the regulations will be applied to ensure that:

  • the new floor is structurally sound
  • the stability of the structure (including the existing roof) is not endangered
  • allows safe escape from fire
  • safely designed stairs to the new floor
  • reasonable sound insulation exists between the loft conversion and the rooms below

Boarding Out for Storage

In most cases, the timber joist which form the floor of the loft (and the ceiling of the rooms below) have not been designed to support the significant weight associated with making the space habitable. An excessive additional load may mean that the existing joists are loaded beyond their design capacity. If you decide to lay flooring boards over the existing joists in the loft space, then you may require a Building Regulations Application…remember, a box of books can represent a substantial dead load.