When is a loft conversion permitted development?

A loft conversion is a great way to add extra space to your home and can add significant value as well. Loft conversions are normally permitted development, which means you won't need to apply for planning permission - great news as it is costly to go through the process plus extra hassle and time added. So is your loft conversion permitted development? Here are some guidelines to help:


When is a loft conversion permitted development?

If you want your loft conversion to be within permitted development, here are the main conditions:


1. Your loft conversion is less than 40 cubic metres

Size has a large impact on applying for planning permission. If your conversion is less than 40 cubic metres in a terraced property, or less than 50 cubic metres in a detached property, then you will fall within permitted development. 50 cubic metres is in fact quite large, roughly 18ft by 12ft in size which would accommodate a bedroom and en-suite. Do bear in mind that this includes any previous extension to the loft space.


2. The loft conversion is no higher than the highest part of your roof

Loft conversions are normally in line with the highest part of your roof, as increasing the roof height would be very costly. However, some circumstances such as not having enough height in your loft space may mean that you would raise the roof of your loft conversion, which would mean your loft conversion would likely require planning permission.


3. The look of your loft conversion is in-keeping with your existing home

You must keep the style of your loft conversion the same as your existing home, such as using the same colour and style of tiles, bricks and windows. Homeowners tend to be more creative with the look of a kitchen extension whereas most loft conversions are consistent with the original home, so this is unlikely to be an issue.


4. You are not including a veranda, balcony or raised platforms

If you want your loft conversion to fall within permitted development then you can't add any of features mentioned above. Again most loft conversions won't include these and if you do fancy a balcony, carefully consider if you will actually use it - it will add more to the cost and will mean extra paperwork.


5. The roof of your loft conversion does not extend beyond the plane of the principle elevation facing the highway

Put very simply, this means that if you are facing a road, the windows must be Velux and any dormer windows must be to the rear of the house.


6. Side facing windows must be obscured and the opening must be 1.7 metres above the floor

For a Velux or Dormer conversion, this shouldn't present an issue as the windows are normally facing the rear of the home. But if you are planning a hip to gable loft extension, and are therefore likely to have a side facing window, plan your new en-suite or bathroom to the side so the obscured window works for you.


7. Roof extensions, apart from hip to gable, must be set back at least 20 cm from the eaves

This is fairly standard and shouldn't cause an issue. Also be aware that the new roof enlargement cannot fall outside the wall of the original house if it's within permitted development.


Are there any exceptions to look out for?

If your property is within an area of natural beauty, is listed, within a conservation area, a National Park and the Broads, or a World Heritage Site then you will have to apply for planning permission. Also, many of the permitted development rights do not apply to flats or maisonettes, so do check the planning permission rules in this instance.


Are there any other regulations that I should comply with?

Even though you may not require planning permission you always need to ensure the extension is compliant with building regulations. If you live in a semi-detached or terraced property, you will need to serve notice to your neighbours under the Party Wall etc Act 1996, so make sure you keep them informed early in the process to help everything run smoothly.


Remember and always check with your local planning authority before going ahead with any renovation work.

If you are about to start planning a loft conversion, read Your Guide - Loft Conversions, for more information. Or if you want an idea of your loft conversion cost, check out our cost estimate tool.

Published: May 8, 2019

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