Most home improvements don't need planning permission.

Find out if yours is one of them.

How_It_Works

Permitted development rights allow you to extend or alter your home without applying for planning permission - saving months of delay and thousands in fees. The legislation is dense, and getting it wrong carries serious penalties. We run your property and project details against the exact legal conditions. If your property is not eligible, we tell you immediately at no cost. If it is, you receive a formal assessment document to share with your builder or architect for £47.

Statement_of_Intent

The permitted development system is more complicated than it should be. After 10+ years working in architecture and the planning system - across the UK, with a particular focus on London - I've seen homeowners spend thousands on professional fees just to understand what they're allowed to do before they've even started. A professional PD assessment typically runs to £400-600. Pre-application advice from a council can cost even more. The rules are buried in legislation, the guidance is dense, and the advice online is often wrong or out of date. This tool exists because that shouldn't be the case. It takes what I know and makes it available to anyone who needs it, clearly and at a price that makes sense.

What_You_Get

Gate 1 eligibility check - free
Full project assessment - £47
Formal assessment document
Builder and council letter
Under 10 minutes to complete

Property Type

Is your property a house?

A house is a self-contained building on its own land with its own front door. Flats and maisonettes share a building with other homes. Converted buildings - barns, offices, warehouses, former shops - are also excluded from permitted development rights regardless of how long ago the conversion took place.
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.
Designated Areas

Is your property in a designated area?

Check in under 2 minutes: go to magic.defra.gov.uk, click Open Map, enter your postcode, and look for the Designations layer. Conservation area boundaries are sometimes drawn in unexpected places - your street may be included even if it does not feel particularly historic. Always check rather than assume.
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.
Curtilage Coverage

Roughly how much of your plot do all existing buildings cover?

Include all outbuildings, extensions, garages, and sheds - but not the original house itself. The 50% limit applies to the remaining garden/curtilage area only. This is a rough check - if you are near the threshold a professional measurement is recommended.
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. This is more common than most homeowners realise, particularly on newer estates.
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 LPA 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?

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.
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 enlarged or altered roof exceed the height of the existing roof ridge?

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 roof slope meets the top of the external wall - where the guttering sits. Measured from ground to this point - not to the ridge. The maximum permitted eaves height for any outbuilding is 2.5 metres - regardless of total height, roof type, or distance from boundaries. This is a standalone condition with no exceptions.
Outbuilding - Storeys

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

Outbuilding - Coverage

Will all outbuildings on your property combined cover more than 50% of the garden area?

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%.