Planning Permission vs Permitted Development: What You Can Build

Understanding the Difference: Planning Permission vs Permitted Development

When you’re planning a home extension, conversion, or major renovation, one of the first questions you’ll face is: “Do I need planning permission?” The answer isn’t always straightforward, and getting it wrong can be costly.

In the UK, there are two main routes for building work: planning permission (a formal application to your local council) and permitted development rights (work you can do without applying). Both still require compliance with Building Regulations, which is a separate approval process entirely.

As plasterers working across Kent since 2008, we’ve seen countless homeowners confused by this distinction. Some delay projects unnecessarily thinking they need permission when they don’t. Others crack on with work that clearly needs approval, only to face enforcement notices and costly remediation.

What Are Permitted Development Rights?

Permitted development rights are a national grant of planning permission that allows certain building work and changes to your property without needing to apply for planning permission. These rights are set out in the Town and Country Planning (General Permitted Development) (England) Order 2015, which has been amended several times since — most recently expanding rights for rear extensions and loft conversions.

Think of permitted development as a set of rules that say “you can do X as long as you stay within Y limits.” Stay within those limits, and you’re free to proceed (after Building Regs approval). Go beyond them, and you’ll need to submit a planning application.

Key Permitted Development Categories for Homeowners

• Class A: Extensions and alterations to houses
• Class B: Additions to the roof of houses (dormers, skylights)
• Class C: Other alterations to the roof (roof height increases)
• Class D: Porches
• Class E: Outbuildings (sheds, garages, summer houses)
• Class F: Hard surfaces (driveways, patios)

What Can You Build Under Permitted Development?

Here’s where the rubber meets the road. The specific limits vary depending on your property type and location, but these are the general rules as of 2026:

Single-Storey Rear Extensions

Single-storey rear extensions are the most common project we see on sites, and the rules are relatively generous:

Important conditions: The extension cannot cover more than 50% of the land around the original house (excludes original footprint). The roof pitch must match the existing house if within 2m of the boundary. Side-facing windows above ground floor must be obscure-glazed.

Larger Single-Storey Extensions (Prior Approval Route)

Since 2013, you can build single-storey rear extensions beyond the standard limits under a “prior approval” process:

• Detached houses: Up to 8m depth (same as standard permitted development)
• Semi-detached and terraced: Up to 8m depth (2m more than standard)

You must notify your local planning authority and adjoining neighbours. Your neighbours have 21 days to raise objections. The council then has 42 days to decide whether the impact on amenity (light, privacy) is acceptable. If approved or no response, you can proceed. This costs around £116 in 2026 compared to £462 for full planning permission.

Two-Storey and Side Extensions

Two-storey extensions have tighter restrictions and often need full planning permission:

• Maximum depth: 3m beyond the original rear wall
• Cannot extend beyond the side of the original house
• Maximum eaves and ridge height cannot exceed the original house
• No verandas, balconies, or raised platforms
• Materials must be similar in appearance to the existing house

Most side extensions require full planning permission because permitted development rights are very limited for work that extends beyond the original side wall. After working on dozens of extension projects across Kent, we always advise clients to budget for planning permission when extending sideways.

Loft Conversions and Roof Extensions

Loft conversions are popular because they add valuable space without expanding the footprint. Under permitted development, you can add:

Key restrictions for roof work:

• No extension beyond the plane of the existing roof slope on the principal elevation (street-facing)
• Materials must be similar in appearance to existing
• No verandas, balconies, or raised platforms
• Roof extensions must be set back at least 20cm from the eaves
• Side-facing windows must be obscure-glazed and non-opening unless 1.7m above floor level

Roof lights (Velux windows) on the rear slope are usually fine under permitted development as long as they don’t project more than 150mm from the roof plane.

Porches

You can add a porch without planning permission if:

• Ground floor area doesn’t exceed 3m²
• No part is more than 3m above ground level
• No part is within 2m of a boundary with a highway

Outbuildings (Sheds, Garages, Garden Rooms)

Outbuildings are permitted development provided:

• They’re single-storey with maximum eaves height of 2.5m and overall height of 4m for a dual-pitched roof or 3m for any other roof
• If within 2m of a boundary, maximum height is 2.5m
• Buildings and ground area don’t cover more than 50% of land around the original house
• Not used as separate living accommodation

What Always Needs Planning Permission?

Regardless of size, certain types of work always require planning permission:

• Front extensions (beyond minor porches)
• Significant side extensions that extend beyond the original house width
• New separate dwellings (including converting a garage into a granny annexe)
• Changes of use (residential to commercial, single dwelling to HMO)
• Work affecting a listed building (you’ll also need Listed Building Consent)
• Work in designated areas (conservation areas, National Parks, Areas of Outstanding Natural Beauty)
• Satellite dishes on chimneys or exceeding size limits
• Any work affecting protected trees (those with Tree Preservation Orders)

Building Regulations: The Other Essential Approval

Here’s where many homeowners get confused: Building Regulations approval is separate from planning permission and applies to almost all structural work, even if it’s permitted development.

Building Regulations ensure your extension or conversion is structurally sound, thermally efficient, safe, and accessible. Administered by your local council’s Building Control department (or an Approved Inspector), the regs cover:

• Part A: Structure (foundations, walls, roof design, load calculations)
• Part B: Fire safety (escape routes, fire doors, compartmentation)
• Part C: Site preparation and resistance to contaminants and moisture
• Part E: Resistance to sound (between dwellings)
• Part F: Ventilation (trickle vents, extract fans)
• Part L: Conservation of fuel and power (insulation, U-values, air tightness)
• Part M: Access to and use of buildings

For a typical single-storey extension, you’ll need Building Control to inspect at key stages: foundations, damp-proof course, drains, insulation, and final completion. They’ll issue a completion certificate when satisfied. Without this certificate, you’ll have serious problems when you come to sell.

Building Regulations Costs in 2026

These fees vary by council and whether you use the local authority or a private Approved Inspector. Some approved inspectors charge slightly less but may be less familiar with local nuances.

Special Cases: When Permitted Development Gets Complicated

Conservation Areas and Article 4 Directions

If your property sits within a conservation area, many of your permitted development rights are automatically removed. You’ll typically need planning permission for:

• Any extension to the side of the house
• Roof extensions or alterations
• Cladding the exterior with render, stone, or artificial materials
• Installing satellite dishes on chimneys or front elevations

Article 4 directions remove specific permitted development rights in designated areas where the council wants tighter control over changes. These often apply to terraced streets or estates with distinctive character. Your council’s planning department can confirm if one applies to your property.

Flats and Maisonettes

Permitted development rights are significantly restricted for flats. You generally cannot build extensions to flats under permitted development. Roof terraces, balconies, and external staircases also typically require planning permission.

Listed Buildings

Listed buildings receive special protection due to their historic or architectural interest. No permitted development rights apply to listed buildings. You’ll need both:

• Listed Building Consent for any internal or external alterations affecting character
• Planning permission for extensions or new structures

This includes seemingly minor changes like replacing windows or removing internal walls. Historic England provides comprehensive guidance on listed building consent requirements.

The Planning Permission Application Process

When your project exceeds permitted development limits or falls into a category requiring consent, you’ll need to submit a formal planning application. Here’s how it works:

Step 1: Pre-Application Advice (Optional but Recommended)

Most councils offer a pre-application service (£100-£300) where a planning officer reviews your proposal before formal submission. This isn’t mandatory but can save months of time and thousands in fees by identifying issues early.

Step 2: Prepare Your Application

You’ll need:

• Completed application forms (available on the Planning Portal)
• Site location plan at 1:1250 scale showing the property outlined in red
• Existing and proposed drawings showing floor plans, elevations, sections
• Design and Access Statement (for most applications, explaining your design choices)
• Supporting documents (heritage statements, tree surveys, flood risk assessments as needed)

Most homeowners hire an architectural designer or architect to prepare these drawings and submit the application. Costs typically range from £1,500-£4,000 depending on complexity.

Step 3: Submit and Pay Fees

Planning application fees in England (2026):

• Householder applications: £462
• Full applications (new dwellings): £462 per dwelling up to 50, then additional fees
• Prior approval (larger extensions): £116
• Lawful Development Certificate: £258

Step 4: Consultation and Determination Period

Once validated, your application is made public. Neighbours are notified and can submit comments (objections or support) for 21 days. The council has 8 weeks to make a decision on householder applications, 13 weeks for major applications.

The planning officer will assess your proposal against local and national planning policies, considering:

• Impact on neighbouring amenity (loss of light, privacy, outlook)
• Design and appearance in context
• Impact on heritage assets
• Highway safety and parking
• Trees and landscaping

Step 5: Decision

The council will either approve (with or without conditions), refuse, or request amendments. If refused, you can appeal to the Planning Inspectorate, though this adds 6+ months to the timeline.

Certificates of Lawfulness: Proving Permitted Development

If you’re unsure whether your proposed work falls within permitted development rights, you can apply for a Certificate of Lawful Development (Proposed). This costs £258 and provides legal confirmation that your project doesn’t need planning permission.

This is particularly valuable if:

• You’re making a significant investment and want certainty
• Your project is borderline and neighbours might complain
• You’re in a conservation area but believe rights haven’t been removed
• You need proof for a mortgage lender or building insurance

The council must respond within 8 weeks with a certificate confirming lawfulness or refusing if they believe permission is required.

Common Mistakes Homeowners Make

Over nearly two decades in the trade, we’ve seen these planning mistakes repeatedly:

1. Assuming “It’s Small, So It’s Fine”

Size isn’t everything. A small front extension might need permission while a large rear extension doesn’t. The location, height, and boundaries matter as much as the footprint.

2. Not Checking the Original House Plans

Permitted development limits are calculated from the “original house” as it existed in 1948 or when first built (if later). Previous extensions count against your allowance. If the previous owner already built a 3m rear extension, you may not have any permitted development left.

3. Building Without Building Regulations

Even if your extension is permitted development, skipping Building Control is illegal. We’ve seen homeowners forced to partially demolish completed extensions because they didn’t comply with structural or thermal requirements. The completion certificate is essential for selling your property.

4. Ignoring Party Wall Requirements

Just because planning isn’t needed doesn’t mean you can ignore the Party Wall Act 1996. If you’re building on or within 3m of a boundary, you must serve notice to adjoining owners. This applies even in permitted development situations. Costs for party wall agreements typically run £700-£1,500 if neighbours appoint their own surveyor.

5. Starting Before Approval

It’s tempting to crack on while awaiting Building Regulations approval or prior approval decisions, but starting work before formal consent is granted puts you at risk. If consent is refused or granted with conditions requiring changes, you’ll face costly remediation.

Plastering After Planning: What Happens Next

Once approvals are in place and construction begins, the internal finishing trades come into play. Extensions require full first-fix (electrics, plumbing, insulation) before plasterboarding and skimming.

For extensions and conservatory conversions, we typically use 12.5mm plasterboard fixed to timber studs or battens, then skim with 2-3mm of multi-finish plaster. In high-moisture areas like wet rooms or bathrooms within extensions, moisture-resistant plasterboard is essential.

The plasterwork timeline for a typical 4m x 4m single-storey extension:

• Day 1: Fix plasterboard to walls and ceiling (one plasterer, one labourer)
• Day 2: Scrim and tape joints, bead corners and reveals
• Day 3-4: First coat skim to walls, second coat same day or following morning
• Day 4-5: Skim ceiling (typically done separately as it’s the trickiest surface)
• Day 5: Final trowel, clean down, protection

Allow 10-14 days for the plaster to fully dry before decorating. During this period, maintain ventilation but avoid excessive heat which can cause cracking. Read our guide on what to do after fresh plastering for detailed curing advice.

Planning Permission and Permitted Development: Cost Comparison

When to Seek Professional Advice

While straightforward rear extensions are often DIY-manageable from a planning perspective, professional advice becomes valuable when:

• Your property is in a conservation area or has listed status
• You’re planning significant structural changes like removing load-bearing walls
• The project is borderline for permitted development limits
• Your property has previous extensions and you’re unsure of remaining allowances
• There are restrictive covenants on your title deeds
• You’re converting a garage or outbuilding to habitable space

An architectural designer or planning consultant typically charges £600-£1,500 for a feasibility study and planning strategy. This upfront investment can save far more in avoided mistakes and rejected applications.

Frequently Asked Questions

Do I need planning permission to remove a chimney breast?

No, you don’t need planning permission to remove an internal chimney breast. However, you definitely need Building Regulations approval because it’s structural work. The chimney breast supports the stack above, so proper steel or concrete support beams must be calculated and installed by a structural engineer. You’ll also need to serve Party Wall notices if the chimney is shared with a neighbour. Expect Building Control fees of £400-£700 and structural engineer fees of £400-£800 for calculations and inspections.

Can I convert my garage into a living space without permission?

Converting an attached garage to living space (bedroom, office, playroom) is usually permitted development, provided you don’t alter the external appearance significantly and it remains part of the main dwelling. You’ll need Building Regulations approval for the insulation, heating, fire safety, and structural changes. Converting a detached garage into separate self-contained accommodation requires planning permission because it creates a new dwelling. Converting it to ancillary space (home office, gym) used by the main house occupants is usually permitted development.

How do I know if my property is in a conservation area?

Your local planning authority maintains a register of conservation areas and Article 4 directions. Most councils have online mapping tools where you can enter your postcode and see designated areas instantly. Alternatively, call the planning department or check your Land Registry title documents, which sometimes note conservation area status. When buying a property, your solicitor’s local searches should reveal this information. Remember that conservation area status applies to the land, not just individual buildings — even modern properties within designated areas have restricted rights.

What happens if I build without permission when I needed it?

Building without required planning permission is a breach of planning control. The council can issue an enforcement notice requiring you to either apply retrospectively or demolish the work. They have 4 years to enforce against building work (10 years for change of use). Retrospective applications cost the same as standard applications but have a higher refusal rate because existing works limit design flexibility. If refused, you’ll face either demolition costs (£5,000-£20,000+ for an extension) or expensive appeals. Unauthorised work also creates serious problems when selling — solicitors’ searches will reveal it, and mortgage lenders won’t lend on properties with planning breaches.

Can I build an outbuilding bigger than the permitted development limits?

Yes, you can apply for planning permission for an outbuilding that exceeds permitted development limits. The council will assess it on its merits, considering impact on neighbours, design, materials, and land coverage. Large outbuildings (over 30m² or 4m height) increasingly attract scrutiny because councils worry they’ll be used as separate accommodation. If you’re planning a large garden room, summer house, or workshop, expect the council to impose conditions preventing use as a separate dwelling (e.g., “shall be used only for purposes incidental to the enjoyment of the dwelling house”). Approval rates vary but are generally good if the design respects neighbouring amenity and garden character.

Do I need planning permission for internal alterations like knocking through walls?

No, you don’t need planning permission for internal alterations in a house, even major structural changes like creating an open-plan kitchen-living space. However, you do need Building Regulations approval if you’re removing or altering load-bearing walls, chimneys, or stairways. Structural engineers charge £350-£800 for steel beam calculations and specifications. If your property is listed, you’ll need Listed Building Consent for internal alterations affecting character. For flats, you may need landlord or freeholder consent under your lease terms, even though planning permission isn’t required.

Understanding the distinction between planning permission and permitted development is essential for any home improvement project. While the rules offer generous freedoms for most standard extensions, they’re designed to protect both your interests and your neighbours’. When in doubt, a quick call to your local planning authority or a consultation with a planning professional can save months of delays and thousands in remediation costs. And remember: regardless of the planning route, Building Regulations approval is virtually always required for structural work — it’s not optional, and cutting corners creates problems that will come back to haunt you when you sell.