A Guide to Loft Conversion

A Guide to Loft Conversion

Loft conversion is a common practice in creating additional living space. Apart from the advantage of having extra space, loft conversions can also add value to homes. But before starting any loft conversion work, there are certain regulations that you need to check. In this guide for loft conversion, you’ll determine whether you need planning permission and which building regulations you need to comply.

Planning Permission on Loft Conversion

Most loft conversion do not require planning permission because it falls under permitted development rights. However, you need to adhere to several parameters. If you exceed the limits or your home is in a conservation area, you need to apply for planning permission. Before starting work, always check with your local planning office.

You don’t need planning permission if you follow the following parameters:

  • Volume of additional space must not exceed 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached houses.
  • No extension should exceed the plane of existing roof slope at the principal elevation or front of the house.
  • Extension should not be higher than the highest part of the roof.
  • Roof extensions, apart from hip to gable ones, to be set back, as far as practicable, at least 20cm from the original eaves.
  • Materials should be similar in appearance of the existing house
  • No verandas, balconies or raised platforms.
  • If the windows face the side, it needs to be obscure glazed. It should also be 1.7 metres above the floor.
  • The roof enlargement cannot overhang the outer face of the wall of the original house.

If you own a flat or maisonette, please know that there is a separate regulation for this housing type. Also, Restricted zone and other designated areas such as national parks or heritage site do not allow roof extensions.

Loft Conversion Building Regulations

Having no planning permission requirements does not mean you don’t need to follow building regulations. You may refer topParts L, K, B and P of the Building Regulations. You need to follow specific building regulations:

Building Regulations Pack

Floors and Junctions

Building a loft will require new floors, beams and junctions. Your existing and new structural elements must be able to carry the load of your new loft. Consult a professional if you are unsure about this.


Building new walls to support any existing or new roofs where existing supports have been removed. You also need to ensure that there is enough sound insulation between rooms.


Any loft requiring new windows/dormers will need to follow certain regulations.


Roof enlargements due to loft conversion required to follow roof building regulations. Including compliant roof insulation.

You may also refer to our Ultimate Building Regulations Pack for complete building regs specifications and drawings. For areas protected under the law (Conservation, Heritage, Protected Species) contact you local planning office.

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