For homeowners in England
A decade in the planning system Featured in Architects' Journal

Most home improvements don't need planning permission.

Find out if yours is one of them

Answer a few questions about your project. Get a dated, referenced document you can share with your builder and council. Under five minutes, nothing to install.

FreeUnder 5 minutes
No accountNo card
Every rule checked against your specific project
A plain-English audit you can share with your builder
Free consultation if anything's unclear
Fig. 01 · Specimen assessment
for a rear extension
Assessment
Rear extension
Ref PDA-1428
15 Apr 2026
Qualifies
Subject property
Address- - -
PropertySemi-detached
ConservationOutside
Article 4None
Proposal
Depth3.8 m
Height2.9 m eaves
MaterialsBrick, match
Legislation
GPDO 2015 Sch.2 Pt.1 Class A
A.1 Development not permitted
A.2 Conditions
A.3 Interpretation
Fig. 01 Specimen Dated
01The problem

Two ways this quietly goes wrong.

Most homeowners fall into one of these without realising. Both are expensive. Both are avoidable with thirty minutes of the right checks.

Issue 01
Paying for permission you never needed.
You file a planning application to be safe. Council fees, drawings, the statutory eight weeks of waiting (often longer). Then the letter comes back to say the project was permitted development all along. No application required.
Typical cost: hundreds to thousands of pounds in fees, drawings and time.
Issue 02
Skipping it, then a neighbour complains.
Everyone assumes it's fine. Work starts. One condition turns out not to be met: a measurement, a material, a previous extension nobody counted. The council issues an enforcement notice and you are asked to undo the work.
Typical cost: the work itself, plus the cost of removing it.
This tool is for
+Houses in England (detached, semi, terraced)
+Freehold owners
+Standard residential projects
This tool isn't for
–Flats, maisonettes or shared ownership
–Listed buildings or national parks
–Scotland, Wales or Northern Ireland
02How it works

Two stages. Both free.

A thirty-second property check first, then the full assessment. Every question is in plain English and nothing is stored unless you finish.

Stage / 01 Free
Property check
Thirty seconds of questions tell you whether your house has standard permitted development rights, or whether something about the property (a conservation area, a previous extension, a local restriction) changes the picture.
30 seconds · no sign-up
Stage / 02 Free
Project assessment
Every rule that applies to your house, checked against your specific project: dimensions, position, materials, height. You get a dated, referenced document you can share with your builder and your council.
Under 5 minutes · dated document
03What you receive

A document you can actually use.

Three parts in one document. Written for people outside planning, so your builder reads it in a minute and your council recognises the format immediately.

Part 01 · Determination
Cover
Qualifies
RefPDA-1428
Date15 Apr 2026
PropertySemi-detached
ProposalRear extension
ConclusionPermitted Dev.
ClassGPDO A.1
Owner- - -
01 / 09Dated
Part 01
The determination
The headline result: qualifies, needs prior approval, or needs planning permission. Referenced against the specific class of the GPDO 2015 that applies to your project.
Part 02 · Audit
Every rule checked
Class A.2
Extension design conditions
  • Depth within limit
  • Eaves height does not exceed existing
  • Overall height below ridge
  • Materials match existing
  • No balcony or raised platform
  • 50% curtilage rule
04 / 09Checked
Part 02
Every rule, one by one
A plain-English audit of every condition that applies to your project, with how yours measures against each one. If anything needs attention, it's flagged with what to change.
Part 03 · Requirements
Before work starts
01
Building Regulations
Separate submission required before work begins.
02
Lawful Development Cert.
Recommended. Fee £274 via planning portal.
03
Party Wall Act 1996
Notice required if work is near a shared wall.
08 / 09Action required
Part 03
What to do next
A practical checklist of the things that apply outside permitted development: building regs, LDC, party wall, covenants. Straight to the point, with fees where relevant.
Not sure yet? Start with the property check. Thirty seconds, no sign-up, and it tells you whether the full 5-minute assessment is worth running.
04How it compares

How most homeowners try to find out.

And why none of it is specific to your house.

Criterion
Google itFree
Call the councilFree
This assessmentFree
Specific to your property
General rules only
Sometimes
Every condition checked
Formal document
None
Verbal only
Dated and referenced
Accessibility
Open, but impersonal
Hard to reach
Instant, 24/7
Turnaround
Hours of reading
Days for a callback
Under 5 minutes
Share with your builder
Nothing to share
"They said it's fine"
Something in writing
Supports council application
Not included
Not included
Included
Google it
Free
  • Specific to your propertyGeneral rules only
  • Formal documentNone
  • AccessibilityOpen, but impersonal
  • TurnaroundHours of reading
  • Share with your builderNothing to share
  • Supports council applicationNot included
Call the council
Free
  • Specific to your propertySometimes
  • Formal documentVerbal only
  • AccessibilityHard to reach
  • TurnaroundDays for a callback
  • Share with your builder“They said it’s fine”
  • Supports council applicationNot included
This assessment
Free
  • Specific to your propertyEvery condition checked
  • Formal documentDated and referenced
  • AccessibilityInstant, 24/7
  • TurnaroundUnder 5 minutes
  • Share with your builderSomething in writing
  • Supports council applicationIncluded
05Who built this

A decade of watching homeowners get this wrong.

The rules aren't the problem. The rules are fine. It's the way they're hidden, cross-referenced and easy to miss. This tool exists to give homeowners a clear answer before they commit to anything.

Gian Virdi
A decade in the planning system · London

Two patterns come up again and again on residential projects. Homeowners paying for planning applications their project never needed, when a quick check would have saved them months and thousands of pounds. And homeowners starting work on something that quietly breaches a condition nobody thought to check, only to find out when an enforcement notice lands.

The legislation isn't secret, but it's genuinely hard to read. It cross-references itself, shifts with each amendment, and trips up anyone opening it for the first time. This tool does the reading for you and produces something you can actually use: a dated, referenced document checked against the current rules.

Experience
A decade in the planning system, focused on residential projects in London
Featured
Architects' Journal
Recognition
International architecture competition winner Nominated for a national architecture award
Legislation
Official national legislation: GPDO 2015 (as amended 2026)
06Common questions

Before you ask.

Q.01 Can't I just Google this?
Free guides explain the general rules. They can't check your specific property, your previous extensions, local restrictions your council may have added, or how the rules interact with your exact proposal. One missed condition can invalidate your permitted development rights entirely.
Q.02 My builder says I don't need planning permission. Do I still need this?
Your builder is probably right. This gives both of you formal documentation to prove it. Most builders appreciate having something in writing before they start work, and it protects everyone involved if anything is ever questioned later.
Q.03 Can't I just call the council?
You can, and planning officers are helpful. They're also busy and can only give general verbal guidance over the phone. They won't assess your specific project in detail, and verbal advice doesn't carry legal weight. This gives you a formal document you can keep and share.
Q.04 What exactly do I get?
A dated, referenced document in three parts: the determination (qualifies or not), a plain-English audit of every rule checked against your project, and a checklist of the additional requirements that apply before work starts. Plus a free thirty-minute call if you'd like to talk it through.
Q.05 Is this really free?
Yes, completely free during beta. The full assessment will be £47 after beta, and the property check will remain free. If you complete an assessment while we're in beta, you keep the document at no cost.
Q.06 What if my project doesn't qualify?
You're told exactly why and what to change. Most issues are simple design adjustments: reducing a dimension, changing a material. You can amend and reassess as many times as you need. Knowing you need planning permission before you start is worth far more than finding out after.
Q.07 What happens if I get it wrong?
If you build something that doesn't comply, your council can issue an enforcement notice requiring you to undo the work at your own cost. This is exactly what this assessment is designed to avoid: knowing before you start, against the actual legislation, instead of finding out after.
Q.08 Is this legal advice?
No. This is a professional assessment checked against the legislation, but it's not a Lawful Development Certificate issued by your council. If you want formal legal confirmation, the next step is to apply to your council, and the document you receive here supports that application.
Start here

Don't start work until you're certain.

It starts with a thirty-second property check, then the full assessment if it's worth running. Most homeowners know where they stand in under five minutes.

Knowing before you commit costs nothing.
Finding out after can cost thousands.
Free Under 5 min No account needed
Permitted development guides
Your Project

What type of project are you planning?

Select the type of project you want to check. This tool covers the three most common home improvement projects under permitted development.
Property Check

Before we assess your project, we need to check a few things about your property.

This takes about 60 seconds. We check whether your property type, location, and planning history qualify for permitted development. This part is completely free.
Property Details

Tell us about your property

We use your postcode to check designated area boundaries and identify your local council. Your postcode is not stored.
Your postcode is only used to check designated area status and is not stored.
Listed Status

Is your property a listed building?

Check the Historic England National Heritage List at historicengland.org.uk or search your council's website. Listed status is also flagged in your solicitor's report on title. If you live in an older or characterful property, always check before assuming.
Previous Extensions

Has your property been extended before - either by you or a previous owner?

Look at your house from the garden. Does the back of the house look like anything has been added - a flat-roof extension, a side return, a conservatory? Even extensions built by previous owners count against your permitted development allowance. The allowance does not reset when a property is sold.
Planning Conditions

Are you aware of any planning conditions on your property that may restrict permitted development?

Search your address on your local council's planning portal (free and public). Click on any previous planning applications and read the decision notices - conditions are listed at the bottom. If your property was built after 1970 or is on a newer estate, this is especially important to check. Search your address on your council's planning portal and look at the decision notice for any conditions restricting permitted development.
Important Information

Your property has passed the eligibility check.

Before continuing, please note that the following may affect your PD rights and cannot be checked automatically by this tool.
Article 4 Directions
Checking Article 4 data for your area...
Planning Conditions on Original Approval
Check your council's planning portal for decision notices on any previous applications at your property. Conditions restricting permitted development are listed at the bottom of each decision notice.
Restrictive Covenants
Check your property's title deeds or contact your solicitor. Restrictive covenants are private legal restrictions that exist separately from planning law and can prevent alterations even where planning permission is not required.
Your Project

Which project are you planning?

Select all that apply.
Extension - House Type

Is your house detached, semi-detached, or terraced?

Detached - stands alone with no shared walls. Semi-detached - shares one wall with one neighbour. Terraced - part of a row of three or more houses. A pair of two houses joined together are both semi-detached, not terraced. Corner plot note: If your property is on a corner plot with two road-facing elevations, check with your local council's planning department which is the principal elevation before proceeding.
Extension - Storeys

Is the extension single storey or two storey?

Extension - Position

Where is the extension positioned?

Extension - Materials

Will the materials used on the extension visually match the existing house?

The rules require materials of similar visual appearance to the existing house. This is a condition of permitted development - not a preference. If your house is red brick, use red brick or a very close match. Highly contrasting materials would fail this condition.
Extension - Balcony or Raised Platform

Will the extension include a balcony, veranda, or raised platform?

This refers to any raised platform forming part of the extension itself - for example a flat roof used as a terrace, or a balcony projecting from an upper storey. A raised platform is any structure more than 0.3 metres above ground level that can be stood on. These are never permitted development. Note: a Juliet balcony with a fixed guard rail and no external standing platform is not covered by this condition and is generally permitted development. A separate garden deck is covered under Class E, not this question.
Extension - Eaves Height

Will the eaves of the extension be at the same height or lower than the eaves of the existing house?

The eaves is where the roof slope meets the top of the external wall - where the guttering sits. For a flat roof extension, this is the top of the parapet wall or the flat roof edge. The eaves of the extension must not exceed the eaves height of the existing house. This applies to both single and two storey extensions. For single storey extensions within 2 metres of a boundary, the eaves height is further capped at 3 metres. A single storey extension cannot have eaves higher than the ground floor ceiling level of the existing house.
Extension - Overall Height

Will any part of the extension be taller than the highest point of the existing roof?

No extension can exceed the height of the highest part of the existing roof - this means the ridge line or the highest point of a flat roof. Single storey extensions must also not exceed 4 metres in total height. Two storey extensions must match the roof pitch of the existing house as closely as practicable.
Extension - Boundary

Will any part of the extension come within 2 metres of a boundary?

Your legal boundary is not necessarily your fence line. Download your title register from the Land Registry at gov.uk/search-property-information-land-registry for £3 to confirm your exact boundary. If in doubt, assume your boundary is closer than you think.
Extension - Two Storey Rear Boundary

Will the two storey rear extension be within 7 metres of the rear boundary?

This condition applies to two storey extensions that extend beyond the rear wall. Measure from the outside face of the rear wall of your proposed extension to your rear boundary. This rule does not apply to side extensions. Use your title plan to confirm the boundary position.
Extension - Side Width

Will the side extension be wider than half the width of your original house?

Note: a side extension must also not extend beyond the wall that forms the principal elevation of the original house (usually the front wall). If your side extension projects forward of the front of the house, it will require planning permission.
Measure the full width of your original house from outside wall to outside wall (not including any existing side extensions). Halve that number. Your side extension must not exceed that figure. Example: 8 metre wide house = maximum 4 metre side extension.
Extension - Depth

How far does the extension extend beyond the original rear wall of your house?

Measure from the outside face of the original rear wall - not from any existing extension. The original rear wall is where the house was first built. If a previous owner added an extension, measure from where that original wall was. For visual guidance see the government's official technical guidance (pages 4-12 cover rear extensions).
Loft - House Type

Is your house detached, semi-detached, or terraced?

This determines your permitted volume allowance. Detached and semi-detached - up to 50 cubic metres additional roof volume. Terraced - up to 40 cubic metres. This is cumulative and includes any previous loft additions by previous owners.
Loft - Previous Alterations

Has the loft been converted or enlarged before - by you or a previous owner?

Check your loft space - does it look like a standard untouched roof space? Also search your address on your local council's planning portal for any previous loft conversion applications. The volume limit is cumulative - any previous additions count against it.
Loft - Dormer Position

Where do you want the dormer window or roof enlargement to be positioned?

Front dormers facing a highway are never permitted development regardless of size. If you want a front dormer, a full planning application is required - but removing it from the design and keeping it rear-facing may bring the project back within PD. Rooflights (Velux windows) that sit flush in the roof slope are subject to different, simpler rules.
Loft - Ridge Height

Will the highest point of the loft conversion be at or below the existing ridge line?

The ridge is the highest horizontal line of your roof - where the two slopes meet at the top. No part of a permitted development loft conversion can exceed this height. Chimneys and parapet walls above the ridge line are not counted when establishing the limit.
Loft - Balcony

Will the loft conversion include a balcony, terrace, or any outdoor platform?

Balconies and roof terraces are never permitted development on a loft conversion. A Juliet balcony with a fixed guard rail that does not allow access to an external platform is generally acceptable. Removing a balcony from the design may bring the project back within PD.
Loft - Side Windows

Will there be any side-facing windows in the dormer?

If yes, they must be obscure glazed to level 3 or above (frosted/patterned glass) and non-opening below 1.7 metres from finished floor level. Both conditions must be met. This protects the privacy of neighbouring properties.
Loft - Eaves Setback

Will the dormer be set back at least 0.2 metres from the eaves?

Measured along the roof slope from the outside edge of the eaves. Most well-designed dormers naturally achieve this. Exception: this rule does not apply to hip-to-gable conversions or where the dormer joins the original roof to an extension roof. A hip roof has four sloping sides - a hip-to-gable conversion replaces one sloping side with a vertical gable wall.
Outbuilding - Position

Where in the garden will the building be positioned?

Outbuildings are only permitted development if positioned behind the principal elevation - the front face of your house. A building in your back garden is fine. A building to the side is fine as long as it does not extend forward of the front wall. A building in the front garden is never permitted development.
Outbuilding - Roof Type

What type of roof does the building have or will it have?

Dual-pitched - traditional shape with two slopes meeting at a ridge: maximum 4 metres total height. Flat or mono-pitched - maximum 3 metres total height. Any type within 2 metres of a boundary - maximum 2.5 metres. The boundary rule overrides everything else.
Outbuilding - Height

What will the maximum total height of the building be?

Height is measured from the highest adjacent ground level - not from inside. If your garden slopes, measure from the highest point next to the building. Critical: if any part of the building is within 2 metres of a boundary, the maximum height is 2.5 metres regardless of roof type - this overrides all other limits.
Outbuilding - Boundary

Will any part of the building be within 2 metres of your legal boundary?

Your legal boundary is not necessarily your fence line. Download your title register from gov.uk/search-property-information-land-registry for £3 to confirm. If any part of the building - including roof overhang or guttering - is within 2 metres, the maximum height drops to 2.5 metres with no exceptions.
Outbuilding - Use

What will the building primarily be used for?

Outbuildings must be incidental to the enjoyment of the house. A home office, gym, or hobby room is fine. Occasional guests sleeping there is generally acceptable provided there is no separate kitchen. Permanent living accommodation or rental use requires planning permission.
Outbuilding - Eaves

Will the eaves height of the building exceed 2.5 metres?

The eaves is where the wall meets the roof. For a flat roof building, the eaves height and total height are effectively the same measurement. The maximum eaves height for any outbuilding is 2.5 metres. If you selected a total height of 2.5 metres or less earlier, your eaves will automatically comply with this condition.
Outbuilding - Storeys

Is the building single storey with no mezzanine or upper floor?

Outbuilding - Coverage

Including this new outbuilding, will the total area of all buildings (excluding the original house) cover more than 50% of your garden?

Include all existing sheds, garages, and outbuildings plus the proposed new building. For most standard gardens with one or two outbuildings you are very unlikely to be near 50%.