Within the Government’s Permitted Development regulation, the vast majority of homeowners won’t have to acquire planning permission from the local authority to be able to modify or expand their loft space. Obviously there are specific requirements that must be met in order for your loft conversion to fall within Authorized Development.

These include:

  • A volume allowance of 40 cubic metres for terraced houses
  • A volume allowance of 50 cubic metres for detached and semi-detached houses
  • No extension past the plane of the current roof slope of the principal elevation that 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
  • Dormers are not allowed on a principal elevation that fronts a highway
  • Roof extensions are not permitted in designated areas (including national parks, Areas of Outstanding Natural Beauty, conservation areas and World Heritage Sites)
  • Roof extensions, apart from hip to gable extensions, to be set back as far as practicable at least 20cm from the eaves.

There are numerous advantages to working within the Permitted Development regulations.

In contrast to planning permission, it’s not subjective and doesn’t depend on numerous external factors for example neighbours, style and impact. Rather, it’s either within regulation or it isn’t - there aren't any grey areas.

During the preliminary appointment we’ll be in a position to let you know whether or not your property and intended loft conversion is catagorized within the permitted development regulations or not. And then for your own reassurance, before we lay a brick we’ll apply at the Local Authority on your behalf for a Certificate of Lawfulness to cover the planned works.



If for some reason your property doesn’t fall within the allowed development regulations, it doesn’t automatically mean that you won’t be in a position to change or extend the property.

Planning permission is required if:

  • You're looking for a small, medium or large dormer in front of the house
  • You want to use materials that happen to be different to those used on the current property
  • Your house is within a designated area for instance a national park, Areas of Outstanding Natural Beauty, conservation area or World Heritage Site
  • You wish to build past the plane of the current roof slope that fronts the highway
  • You want to build to a higher level than the current roof
  • You want to build a veranda, balcony or elevated platform

If your project matches any of the listed criteria on the left, you will have to apply to your Local Authority for full planning permission

If that is the situation it is nothing to be concerned about. As a part of our service we’ll liaise with the Local Authority as your representative. We’ve worked alongside planning departments throughout the Sussex area and consequently are very experienced with the protocols and guidelines.

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From Brighton's leading loft conversion and extension specialists