Do I Need Planning Permission? 10 Common Scenarios Explained

One of the most common questions we are asked as planning consultants is whether planning permission is required. The answer is rarely straightforward. This article explains ten common scenarios and outlines when planning permission is likely to be required.

1. house extensions

Do i need Planning permission?
Many house extensions can be carried out under permitted development, but this is subject to strict limitations on size, height, position and materials. 
Planning permission is likely to be required where:
The extension exceeeds the tolerences of permitted development size limits
The proposal involves a side or two-storey extension
The property is located within a conservation area or other designated land
Permitted development rights have been removed by condition or Article 4 Direction
Early advice is particularly important where neighbour amenity or character is a concern.

2. Loft conversions and roof alterations

Do I need planning permission?
Often no,  but there are important exceptions.
Many loft conversions fall within permitted development, provided they do not alter the overall height of the roof or introduce prominent features.
Planning permission is likely to be required where:
Dormer windows face a highway
The roof height is increased
The property is a flat or maisonette
The building is listed or within a conservation area
Even where planning permission is not required, building regulations approval will still apply.

3.outbuildings, gardens rooms and home offices

Outbuildings can often be erected under permitted development, provided they are incidental to the main dwelling and meet height and siting limits.
Planning permission is likely to be required where:
The building is located forward of the principal elevation
Height or coverage limits are exceeded
The outbuilding is used as independent living accommodation
The site is within designated land
Using an outbuilding as a self-contained unit almost always requires planning permission

4. Change of Use (Including HMOs and Short-Term Lets)

Do I need planning permission?
Often, yes.
Changes between different use classes may require planning permission, particularly where the intensity of use increases.
Planning permission is commonly required for:
Conversion of a dwelling to a House in Multiple Occupation (HMO)
Change from residential to commercial use
Use of a property as a short-term or holiday let in restricted areas
Local planning policies and Article 4 Directions can remove otherwise permitted changes of use, making early advice essential.

5. Barn Conversions and Rural Building5. 

Do I need planning permission?
Yes, in most cases.
While some agricultural buildings may benefit from permitted development rights, these are subject to detailed criteria and limitations.
Planning permission or prior approval is likely to be required where:
The building does not meet Class Q eligibility tests
Significant rebuilding or structural alteration is proposed
The site is within a sensitive landscape or heritage setting
The proposed use would harm the character of the countryside
A full planning application may provide a more flexible and robust route in complex rural locations.

6. Subdividing a House into Flats

Do I need planning permission?
Yes.
The subdivision of a single dwelling into two or more separate residential units constitutes a material change of use and requires planning permission.
Planning permission will be required where:
A single dwelling is converted into self-contained flats
Additional access, refuse or parking provision is needed
The proposal increases the intensity of residential use
Local planning authorities will assess such schemes carefully in relation to residential amenity, design, and parking standards

7. New Dwellings in Gardens or Infill Plots 

Do I need planning permission?
Yes.
The creation of new dwellings within residential gardens or small infill plots requires planning permission, regardless of scale.
Key considerations typically include:
Impact on the character and density of the surrounding area
Relationship with neighbouring properties
Access, parking and servicing arrangements
Early site appraisal can help establish whether a proposal is likely to be supported in principle.

8. replacement dwellings

Do I need planning permission?
Yes.
Replacement dwellings require planning permission but may be supported even in locations where new-build housing would normally be restricted.
Planning authorities will typically consider:
The scale and design of the replacement relative to the existing dwelling
Landscape and visual impact
Sustainability and energy efficiency
In some cases, a replacement dwelling can provide a policy compliant alternative to refurbishment.

9. works to listed buildings

Do I need planning permission?
Often and Listed Building Consent will almost always be required.
Listed Building Consent is needed for works that affect the character or significance of a listed building, including internal alterations.
Consent is typically required for:
Structural alterations
Changes to historic fabric or materials
Extensions or alterations affecting the building’s setting
Unauthorised works to a listed building are a criminal offence, so specialist advice should always be sought.

10. minor works commonly overlooked

Do I need planning permission?
Sometimes.
Certain small-scale works are frequently assumed to be permitted but can still require consent.
Examples include;
Boundary walls, fences and gates above specified heights
New or altered vehicular access points
External lighting in rural or sensitive locations
Solar panels in conservation areas or on listed buildings
These details are often picked up during enforcement investigations rather than at application stage.

Unsure Whether You Need Planning Permission?

If you’re considering development on a small or constrained site, early advice can significantly reduce risk. You may also find our Small Development Sites Planning Advice page helpful.

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⚠️ Common mistake
Assuming permitted development applies without checking planning history or Article 4 Directions.

💡 Planner insight
Many enforcement cases arise where garden buildings are later used in a way that was not permitted under permitted development rights

💡Planner Insight
Many properties in rural and no coastal area do not benefit from permitted development rights