Understanding Permitted Development for Home Extensions:
Extending your home can significantly improve your living space. Before proceeding, it’s important to understand whether your proposed project falls under Permitted Development (PD) or requires Planning Permission. Below is a breakdown of what’s typically allowed under PD and what to consider for each type of extension.
Please follow the link below for the full criteria set for Householders by Ministry of Housing, Communities and Local Government
✅ Single-Storey Extensions
(Permitted Development Conditions)
A single-storey rear extension may be considered Permitted Development, meaning no planning permission is required, provided the following conditions are met:
General Criteria
- Designated Land Restrictions: No cladding allowed on the exterior if the property is on designated land (e.g. National Parks, AONBs, Conservation Areas, World Heritage Sites).
- Side Extensions: Not permitted on designated land.
- Rear Extensions: Must be single-storey only.
- Land Coverage: No more than 50% of the land around the ‘original house’. (as it stood on 1 July 1948) Can be covered by additions, including sheds and outbuildings.
- Front or Side Extensions: Not allowed under PD. should not extend beyond the the principal elevation
- Materials: Must be similar in appearance to the existing house.
Size and Height Limits
- Width: Extension must not exceed half the width of the original house.
- Max Height: Must not exceed 4m in height.
- Within 2m of a boundary: Eaves height must not exceed 3 metres.
- Depth Limits (from original rear wall):
- Detached house: Up to 4 metres (PD), up to 8 metres with Neighbour Consultation Scheme.
- Semi-detached/terraced: Up to 3 metres (PD), up to 6 metres with Neighbour Consultation Scheme.
https://interactive.planningportal.co.uk/mini-guide-type/extension-single-storey
✅ Two-Storey Extensions (Permitted Development Conditions)
Two-storey extensions can also fall under PD rights introduced in August 2020, provided the following criteria are met:
Conditions
- Designated Land: Not permitted in designated areas.
- Land Coverage: Same 50% rule applies as above.
- Height: Must not exceed the existing house’s eaves or ridge height.
- If within 2m of a boundary: Max eaves height must be 3 metres.
- Depth from Rear Wall: Must not extend more than 3 metres.
- Distance from Opposite Rear Boundary: Minimum of 7 metres.
- Roof Pitch: Should match existing house as closely as possible.
- Materials: Must match existing property.
- Windows on Upper Floors (Side Elevations):
- Must be obscure-glazed and non-openable below 1.7m from floor level.
- Balconies/Verandas: Not permitted.
https://interactive.planningportal.co.uk/mini-guide-type/extension-double-storey
✅ Porch Extensions (Permitted Development Conditions)
- Designated Land Restrictions: No cladding allowed on the exterior if the property is on designated land (e.g. National Parks, AONBs, Conservation Areas, World Heritage Sites).
- Land Coverage: No more than 50% of the land around the ‘original house’. (as it stood on 1 July 1948) Can be covered by additions, including sheds and outbuildings.
- Front : Under certain criteria PD.
- Materials: Must be similar in appearance to the existing house.
Size and Height Limits
- Width: Extension must not exceed 3m2 (measured externally).
- Max Height: Must not exceed 3m in height (measured from ground level).
- Within 2m of a boundary: Eaves height must not exceed 3 metres.
https://interactive.planningportal.co.uk/mini-guide-type/porch
✅ Loft Conversions (Permitted Development Conditions)
A loft conversion may also be permitted development, if the following are satisfied:
Volume Limits
- Terraced House: Up to 40 cubic metres additional roof space.
- Semi-detached/Detached House: Up to 50 cubic metres.
Note: Any previous additions must be included in this volume.
Conditions
- Designated Land/Listed Buildings: Not permitted.
- Front Roof Slopes: Alterations facing the highway are not permitted.
- Height: Must not exceed existing roof height.
- Materials: Must be similar in appearance to the existing house.
- Eaves Setback: Roof extensions must be set back 20cm from original eaves (excluding hip-to-gable).
- Overhanging Roof: Not permitted to project beyond outer wall face.
- Windows (Side Facing): Must be obscure-glazed and non-openable below 1.7m floor level.
- Wildlife: You may require an ecological survey if protected species are present.
✅ Garage / Outbuilding Conversions
You can convert garages or build outbuildings under PD provided:
Conditions
- Position: Not forward of the principal elevation (front of the house).
- Designated Land/Listed Buildings: Not permitted or significantly restricted.
- Land Coverage: Must be within 50% of total area around the original house.
- Height Limits:
- Max overall height: 4m (dual-pitched roof), 3m (other).
- If within 2m of boundary: Max height 2.5m.
- Use: Must not be a separate, self-contained dwelling.
- Facilities: Microwave antennae not permitted.
- Verandas/Balconies: Not permitted.
https://interactive.planningportal.co.uk/mini-guide-type/outbuilding
✅ Conservatories (Permitted Development Conditions)
A conservatory is considered PD if the following apply:
Designated Land Restrictions
- No cladding allowed.
- Side extensions not permitted on designated land.
General Conditions
- Land Coverage: Same 50% rule applies (must include all outbuildings).
- Height: Max overall height of 4 metres.
- Within 2m of a boundary: Max eaves height of 3 metres.
- Location: Not permitted at the front or side if fronting a highway.
- Rear Depth Limits:
- Detached: 4m (PD) or 8m with consultation.
- Semi/terraced: 3m (PD) or 6m with consultation.
- Eaves Height: Must not exceed existing eaves height or roof ridge height.
https://interactive.planningportal.co.uk/mini-guide-type/conservatory
❓ Is My Proposal Even Possible?
Before you begin, consider the following:
- ✅ How much garden space will remain? A full rear extension may reduce your outdoor area significantly, which could affect approval.
- ✅ Will your design affect neighbours? Overshadowing or privacy issues can reduce your chances of success.
- ✅ Is your extension within 50% of the original footprint? Total additions (including previous ones) must not exceed this.
- ✅ Ceiling Height: New extensions must have a minimum ceiling height of 2m. For sloped ceilings, 50% of the room must exceed 2m in height.
- ✅ Natural Light: Maintain light to all habitable rooms—this is a Building Regulation requirement.
- ✅ Internal Alterations: If converting to open plan with a conservatory, windows/doors may need to remain due to energy regulations.
- ✅ Design Impact: Choose styles and materials that complement your home and surrounding properties.
- ✅ Solar Gain: Good design can use roof overhangs or shading systems to improve winter warmth and reduce summer overheating.
⚠️ Important Notes
- These Permitted Development rules apply only to houses, not flats or maisonettes. (please contact me to request assistance with this)
- Properties on designated land or those that are listed may have restrictions or may not qualify.
- Some homes have had their PD rights removed via an Article 4 Direction. Always check with your Local Planning Authority (LPA) before starting.
- Even if your project qualifies under PD, Building Regulations Approval is still required.
- A Certificate of Lawful Development is strongly recommended for all PD projects for legal certainty and peace of mind.
✅ We Can Help
From your initial idea through to final construction, we offer:
- Site assessments and consultations
- Design and planning services
- Permitted Development guidance
- Applications for Planning Permission, Lawful Development Certificates, and Building Control
- 3D visualisations and technical drawings
Unique Design Creations Ltd 