Do I Need Planning Permission for an Extension?
- 3 hours ago
- 5 min read
Extending your home can be a great way to create more space without moving, but one of the first questions most homeowners ask is whether they need planning permission.
The answer is: not always.
Some extensions can be built under Permitted Development rights, while others will require a full planning application. Whether your project falls into one category or the other depends on the size, position and design of the extension, as well as the type and location of your property.
What is Permitted Development?
Permitted Development allows certain types of work to be carried out without making a full planning application.
For house extensions, this can include some:
single-storey rear extensions
side extensions
loft conversions
alterations to roofs
porches
outbuildings
However, there are limits and conditions attached to Permitted Development rights.
An extension that exceeds those limits, or a property where those rights have been restricted, may still require planning permission.
When might an extension need planning permission?
Planning permission may be required if your proposed extension:
is larger than the limits allowed under Permitted Development
extends too far from the original rear wall of the property
is too high
sits too close to a highway in certain circumstances
uses materials or a design that does not meet Permitted Development requirements
includes a two-storey extension that exceeds the relevant limits
affects a property where Permitted Development rights have been removed
is being built to a flat, maisonette or another type of property that does not benefit from normal householder Permitted Development rights
Location can also make a significant difference.
Does where I live affect the rules?
Yes.
Properties in certain designated areas can be subject to additional restrictions.
These may include:
Conservation Areas
National Parks
Areas of Outstanding Natural Beauty
World Heritage Sites
other protected or designated areas
Listed buildings are also subject to separate controls, and Listed Building Consent may be required even where planning permission is not.
It is therefore important to look at the individual property rather than assuming that the rules applying to a neighbouring house will necessarily apply to yours.
What about Article 4 Directions?
A local planning authority can use an Article 4 Direction to remove particular Permitted Development rights from a defined area or group of properties.
This means work that would normally be permitted without planning permission may require an application.
Article 4 Directions are often used where a council wants additional control over changes to the appearance or character of an area.
Do newer houses always have Permitted Development rights?
Not necessarily.
When planning permission is granted for a new housing development, the council can impose conditions removing some or all Permitted Development rights from individual properties.
This is particularly important on newer housing estates.
Before relying on Permitted Development, it is worth checking the original planning permission for the development to see whether any restrictive conditions were imposed.
How large can a rear extension be without planning permission?
There is no single answer that applies to every property.
The permitted size depends on factors including:
whether the house is detached or attached
whether the extension is single or two storey
its height
its proximity to boundaries
how much of the surrounding land would be covered by buildings
whether the property is within a designated area
There is also a larger home extension process that can allow some larger single-storey rear extensions through a prior approval procedure rather than a full planning application.
Because several rules apply simultaneously, it is worth checking the complete proposal rather than relying only on one measurement.
Can I build a side extension under Permitted Development?
In some circumstances, yes.
A single-storey side extension may fall within Permitted Development if it satisfies the relevant restrictions on:
width
height
position
materials
However, different restrictions can apply in designated areas, and side extensions may be more sensitive from a planning perspective than rear extensions.
What about a two-storey extension?
Some two-storey rear extensions can fall within Permitted Development rights, but the rules are more restrictive than they are for many single-storey extensions.
Issues such as:
distance from boundaries
roof design
window positioning
overall height
impact on neighbouring properties
can all become important.
For many larger two-storey proposals, a householder planning application is the more appropriate route.
Do I need planning permission if my neighbours have similar extensions?
Not necessarily.
A neighbouring extension can be useful evidence of what has previously been accepted in the area, but it does not automatically mean your proposal is permitted.
The neighbouring property may:
have obtained planning permission
have different Permitted Development rights
have a different plot arrangement
have been extended before the current owner purchased it
have been built under different planning rules
Each property needs to be considered individually.
Should I apply for a Lawful Development Certificate?
Even where an extension appears to fall within Permitted Development rights, it can be sensible to apply for a Lawful Development Certificate.
This gives you formal confirmation from the local planning authority that the proposed work is lawful.
That can be particularly useful when:
selling the property
remortgaging
dealing with solicitors
demonstrating to a future buyer that the extension did not require planning permission
It also provides greater certainty before construction begins.
What happens if I build an extension without the correct permission?
If planning permission was required and the work is carried out without it, the extension may be considered unauthorised development.
The local planning authority may investigate and could require:
a retrospective planning application
alterations to the work
or, in more serious circumstances, removal of the unauthorised development
It is usually much easier to establish the correct planning route before work starts.
Planning permission is separate from Building Regulations
Even if your extension does not require planning permission, it will usually still need to comply with the Building Regulations.
These cover matters such as:
structural safety
insulation and energy efficiency
fire safety
ventilation
drainage
electrical safety
glazing
accessibility
Planning permission and Building Regulations are separate systems, so receiving approval under one does not automatically satisfy the other.
How can I find out whether my extension needs planning permission?
The best starting point is to review:
the proposed size and position of the extension
the original property
previous extensions
the planning history
any restrictions on Permitted Development rights
the property's location
relevant local planning policies
For straightforward projects, this may establish a clear answer.
For more complicated proposals, it may be worth obtaining professional advice or approaching the local planning authority through a pre-application service.
So, do I need planning permission?
For many modest residential extensions, the answer may be no, provided the proposal complies fully with Permitted Development requirements.
However, larger extensions, unusual designs, restricted properties and projects in sensitive locations may require planning permission.
The safest approach is to establish the planning position before progressing too far with the design.
CW Architectural Design provides architectural design and planning services for extensions, renovations and new homes across Staffordshire, Derbyshire, Leicestershire and Nottinghamshire.
Planning an extension? We can review your property, develop the design and advise on the most appropriate planning route before preparing the required drawings and application.
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