Do you need planning permission to enlarge your home?
- Blue Lava Architecture
- Feb 19
- 4 min read
Updated: Feb 27
When you are extending your home, you will usually need planning permission from the local planning authority prior to starting your build. However, in some cases, this is not always necessary.
Depending on your proposed works, your extension may fall under permitted development (PD), a piece of planning legislation which allows certain enlargements and improvements such as internal alterations, changes to windows and doors, loft conversions & extensions, subject to meeting certain criteria.
In fact, PD rights offer a wide scope of opportunity to alter and extend your property;
In some cases it's even possible to achieve more under PD than through full planning.
Below is a list of what you may be able to achieve without planning, through Permitted Development...
Class A: Alternations to the House:
Rear extensions
Single storey PD - up to 3m for semi-detached and 4m for a detached house
PD "larger home extension - single storey ONLY up to 6m or semi-detached or 8m for a detached house"
Two storey PD - up to 3m, provided that:
it projects out from the rear wall of the original house only
it does not project out from a side wall
it is no deeper than 3m
it is within 7m from the rear boundary it extends towards
Side extensions
Extension width is limited to no more than half the width of the original house
it must not project forward of the "principle elevation" (typically the front of the house)
it can extend beyond the rear wall by up to 3 or 4m (semi or detached), subject to max. width
It can return around the rear corner of the house, as a side/rear extension provided that the overall width is no more then half of the original house.
Maximum height of extension
overall height is limited to no more then 4m and maximum eaves height is 3m (or 2.5m if built within 1m of a boundary).
Class B: Loft conversion
You are able to add a a loft conversion (which will often be the most cost effective way to increase your living accommodation). However, this conversion must:
Have a footprint of no more then 40m3 for terrace houses and 50m3 for a detached or semi-detached house. (Any previous enlargement to the original roof space in any part of the house must be included in this volume allowance)
Windows for a loft extension on a side elevation of a house must be obscure
Not extend above the original ridge height
Class C – other alterations to the roof
This involves any other minor alterations to the roof e.g the installation of roof lights/windows.
Class D - porches
You can build a porch so long as it is no higher than 3m, not within 2m of any boundary and has a ground area no bigger than 3m².
Class E: Outbuildings
Must not exceed more than 50% of the total un-built on your property.
Must only be one storey
It must be within height restrictions
Must not be used for accommodation/sleeping
The legislation also allows provision for hard surfacing, chimneys & flues and TV aerials and antennas.
Prior Approval
If you plan to construct a larger home extension, you must undergo the prior approval process. This involves submitting an online application along with detailed drawings of the proposed scheme to the local authority. The local authority will then notify all adjoining neighbours, allowing them the opportunity to provide feedback on your proposal. If the scheme complies with all PD criteria and no significant concerns are raised, the local authority will confirm whether prior approval is granted or deemed unnecessary.
The 'Original' house
This term is key. The limits for Permitted Development enlargements apply to the original house as it was built, or as it stood on 1st July 1948. Not necessarily the existing condition of the house which may have been extended previously.
For example; for a rear extension to a detached house, the 4m measurement for a PD extension will be taken from the original rear wall of the house. If the house has already had a 3m rear extension in the past, you would only be able to add an additional 1m under PD. If the PD allowance has been used up previously, you will be more limited in what is achievable, and this goes for all classes and types of alteration.
Limitations
So what can't be done under PD?
Firstly, PD rights are only applicable to houses. Certain types of property such as flats and maisonettes do not benefit from the same rights.
Listed buildings do not benefit from the rights as there are strict controls on any alterations that are made to a listed building to safeguard the historic character and fabric of the building.
Sites located within designated areas are restricted on what can be done under PD. Permitted Development is still possible in these locations, but certain rights do not apply. Such locations include:
Conservation areas
National parks
Areas of Outstanding Natural Beauty (AONB)
World Heritage Sites
The Norfolk or Suffolk Broads
Import information to note: Permitted development rights may have been removed from your property.
PD rights are often removed from a property as a condition of a planning approval, particularly on relatively recent developments where houses may be closer to one another. This is typically done to safeguard the area and retain openness where local authorities deem there may be a risk of over development if PD rights are allowed.
Permitted Development (PD) rights are often restricted as a condition of planning approval, particularly in estate developments where properties are in close proximity. This measure is typically implemented by local authorities as a planning condition.
How can we help?
PD can be a bit of a minefield with a number of quirks that mean complying with the legislation is not always as straight forward as it may seem.
Involving an experienced design professional as early as possible in the process will ensure that your project is correctly assessed against all the relevant criteria and designed appropriately.
At Blue Lava we have extensive experience with PD projects and have gathered the valuable knowledge required to navigate the legislation effectively and achieve our client's desired results time after time.
Disclaimer
The information in this blog post reflects the latest available planning fee details at the time of writing. While we aim for accuracy, final fees are subject to confirmation by the UK Government and may vary upon formal announcement. We recommend reaching out to us directly or checking the Planning Portal for the most up-to-date information before submitting your application.
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