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Do I Need Planning Permission for a Loft Conversion?

If you are wondering which loft conversion regulations apply to you, then you are not alone. There are so many rules and regulations that it can be hard to decide whether you should extend with or without planning permission.

Most of the time, you can convert your loft subject to specific limitations and conditions without applying for planning permission. You only need to make a certificate of lawfulness application to prove your development falls under permitted development rights for which your designer need to prepare your loft conversion planning drawings and floor plans, and your application form.


What are Permitted Development Rights for Loft Extensions?

Permitted development rights give you permission to make certain changes to a building without the requirement for planning consent.

But be careful: Permitted development rights only cover building projects located outside of conservation areas and there are strict limits to what is allowed under PD. What’s more, in some circumstances local planning authorities can suspend permitted development rights in their boroughs by issuing what are known as Article 4 directions.

But even if you are in a conservation area or the council has an Article 4 direction about loft conversions, that doesn’t mean that you can’t build one. It simply means that you have to apply for planning permission.




What Changes are Permitted?

Your loft extension is subject to limits. For instance, you can only add 40 cubic metres to terraced and semi-detached houses, and 50 cubic metres to detached houses.

Any visible changes must be in keeping with the original building. Things you can’t do under PD rights include adding a balcony with a balustrade projecting from the building, or using colours that contrast with the original house.

Alterations to the roof space with additional room fall under Class B of Permitted Development Rights. The drawings your designer will be submitting for your Certificate of Lawfulness application should indicate that your loft conversion design meets the limits and conditions of permitted development rights. Failure to do so means that your application will not be accepted.

Your loft conversion is permitted by Class B subject to the following conditions:

  • the materials used in any exterior work must be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse;

  • the enlargement must be constructed so that other than in the case of a hip-to-gable enlargement or an enlargement which joins the original roof to the roof of a rear or side extension the eaves of the original roof are maintained or reinstated; and the edge of the enlargement closest to the eaves of the original roof is, so far as practicable, not less than 0.2 metres from the eaves, measured along the roof slope from the outside edge of the eaves; and other than in the case of an enlargement which joins the original roof to the roof of a rear or side extension, no part of the enlargement extends beyond the outside face of any external wall of the original dwellinghouse;

  • any window inserted on a wall or roof slope forming a side elevation of the dwellinghouse must be obscure-glazed, and non-opening unless the parts of the window which can be opened are more than 1.7 metres above the floor of the room in which the window is installed.

You will require planning permission for loft conversions if:

  • any part of the dwellinghouse would, as a result of the works, exceed the height of the highest part of the existing roof;

  • any part of the dwellinghouse would, as a result of the works, extend beyond the plane of any existing roof slope which forms the principal elevation of the dwellinghouse and fronts a highway;

  • the cubic content of the resulting roof space would exceed the cubic content of the original roof space by more than 40 cubic metres in the case of a terrace house or 50 cubic metres in any other case;

  • it would consist of or include the construction or provision of a verandah, balcony or raised platform, or the installation, alteration or replacement of a chimney, flue or soil and vent pipe.




What is a Certificate of Lawfulness?

When you don’t need planning permission, but want proof that your conversion or extension was covered by permitted development rights, you can apply to your council for a certificate of lawfulness (sometimes known as a lawful development certificate). This can be important when you decide to sell the property.



Do I Need a Party Wall Agreement for Loft Extension?


Unless you have a detached house, you might need a Party Wall Agreement with your neighbours. Whether you do or don’t depends on whether your works will affect the walls that you share with the neighbours.

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