22 Westminster Road: A Worked Example of UK Planning Permission and Permitted Development Rules

Property addresses like "22 Westminster Road" turn up in planning enquiries, appeal decisions and neighbour disputes all over the country, because Westminster Road is one of the most common street names in England and Wales. If you own, are buying, or are simply researching a house at this address, the chances are you are trying to work out one thing: what can be built or altered without a full planning application, and where does permitted development stop and a formal application to the local planning authority begin?

This guide uses 22 Westminster Road as an illustrative case study to walk through the rules that actually decide what you can do to a typical UK house: single-storey and two-storey extensions, loft conversions, upward extensions, and the curtilage coverage limits that catch people out. Every rule referenced here is grounded in the current permitted development framework for houses in England. If you own a genuine 22 Westminster Road (there are several, in different towns and cities), you should still check your own council's planning portal and any conservation area designation before relying on general guidance, because the position varies depending on whether the property sits on what planning law calls "article 2(3) land".

Why a Single Address Raises So Many Planning Questions

A house numbered 22 on a road called Westminster is, statistically, more likely than not to be an Edwardian or interwar terrace or semi-detached property, the kind of housing stock built in huge numbers across English towns between the 1900s and the 1930s. That build period matters enormously for planning purposes, because several permitted development rights, including the right to add extra storeys, only apply to houses built within a specific window of time.

Before spending money on architect's drawings or a structural engineer, any owner of a property like 22 Westminster Road needs to establish four things:

1. Whether the property is a house (as opposed to a flat or maisonette), since most of the permitted development rights discussed below apply only to houses.
2. Whether the site sits within a conservation area, National Park, Area of Outstanding Natural Beauty, the Broads, or a World Heritage Site, collectively known as article 2(3) land.
3. When the original house was built.
4. How much of the garden and curtilage is already covered by outbuildings, garages, sheds and previous extensions.

Get these four answers right, and most of the rest of the analysis follows logically.

Step One: Check Whether the Property Sits on Article 2(3) Land

This is the single biggest factor that changes what is possible at a property like 22 Westminster Road. Article 2(3) land covers conservation areas, National Parks, AONBs, the Broads and World Heritage Sites, and it triggers a much tighter set of permitted development restrictions than apply to an equivalent house on an ordinary residential street.

You can check this in minutes using your council's online planning portal or interactive constraints map. Search the address, and the map layer will show whether the property falls inside a designated conservation area boundary. Many town-centre and Victorian/Edwardian suburban roads, particularly those with the sort of uniform brick terraces you often find on streets named after historic figures or places (Westminster Road being a good example of a Victorian-era naming convention), do sit within conservation area boundaries, precisely because local authorities want to protect that uniform streetscape.

If 22 Westminster Road is on article 2(3) land, three restrictions bite immediately:

• Cladding the exterior in stone, artificial stone, pebble dash, render, timber, plastic or tiles is not permitted development. Any change to the external finish of the walls needs a planning application.
• Extensions beyond any side wall of the house are not permitted development at all. Side extensions, even modest ones, require planning permission.
• A rear extension of more than a single storey is not permitted development. Two-storey rear extensions need planning permission in a conservation area, even where they would be allowed without permission on a non-designated site.

In short, if the address sits in a conservation area, forget rendering the front elevation, forget a two-storey side return, and forget a full-height rear extension without going through the council. Single-storey rear extensions within the normal size limits generally remain possible under permitted development, but always check the specific depth and height limits with the local authority before assuming so.

Step Two: Understand What "Beyond the Principal Elevation" Means

Regardless of conservation area status, one rule applies to every house in England claiming permitted development rights under the extensions class: nothing is permitted forward of the principal elevation.

In practice this means an extension is not permitted development if it would project beyond the wall that forms the front of the original house, the elevation that faces the road, or beyond a side elevation that fronts a highway. The rule is interpreted generously against the homeowner: "beyond a wall" includes the whole area in front of an imaginary line drawn from the end of that wall out to the property boundary, not just the strip directly in front of the wall itself.

For a typical terraced house at an address like 22 Westminster Road, this rules out porches or bay window extensions that project forward of the existing front wall without planning permission, and it becomes especially restrictive if the property sits on a corner plot, where a side elevation also fronts a road. Corner properties face an additional restriction to the side elevation that fronts the highway, on top of the usual side extension rules, which is one reason corner houses on Westminster Road type streets often need full planning applications for changes that would sail through as permitted development on a mid-terrace equivalent.

Step Three: The 50% Curtilage Coverage Limit

This is the rule that catches out the most homeowners, because it is cumulative and easy to miscalculate. Under permitted development, you cannot cover more than 50% of the curtilage (the garden and grounds around the house, excluding the footprint of the original house itself) with buildings.

Crucially, this 50% cap counts everything: the existing shed, the garage, a previous extension, a summer house, and whatever new extension or outbuilding you are now proposing, even structures that were built before 1948. Homeowners frequently assume that because an old outbuilding predates the current rules it does not count towards the limit. It does. Only the footprint of the original house itself is excluded from the calculation.

For a property such as 22 Westminster Road with a modest rear garden, perhaps 8 to 10 metres deep, this limit can be reached surprisingly quickly once you add up an existing detached garage, a garden shed and a proposed single-storey rear extension. Before commissioning drawings, measure the plot, calculate the footprint of every existing structure other than the house, and work out what percentage of the curtilage is already built on. If you are close to the 50% mark, a planning application rather than a permitted development notification may be the only realistic route for further building work.

Step Four: Loft Conversions and Roof Extensions

Loft conversions are one of the most popular ways to add space without extending the footprint, but the rules differ sharply depending on the article 2(3) status established in step one.

Away from conservation areas, dormer loft conversions and roof enlargements can often proceed under permitted development, subject to volume and design limits set by the relevant class. However, roof balconies are never included within this permitted development right; if your loft conversion design includes a balcony, that element needs a full planning application regardless of location.

On article 2(3) land, the position is far stricter: roof extensions, including dormers and any other enlargement of the roof, are not permitted development at all. If 22 Westminster Road sits within a conservation area, any loft conversion that changes the shape or volume of the roof, dormer windows included, requires a planning application to the local authority. This is a common pitfall: homeowners assume a "standard" rear dormer is permitted development because that is true for millions of houses nationally, without checking that their own street has conservation area status, which removes that right entirely.

Step Five: Adding Whole Extra Storeys (Upward Extension)

Since August 2020, a further permitted development route has existed specifically for adding one or two entire additional storeys on top of an existing house, rather than extending outwards or converting the existing roof space. This is a genuinely useful option for a terraced or semi-detached property where garden space is limited but there is appetite for a substantial increase in floor area.

The rules are specific and worth checking carefully against the actual build date and construction of 22 Westminster Road or any similar property:

• The house must have been built between 1 July 1948 and 28 October 2018. Older Victorian and Edwardian terraces, ironically, are excluded from this particular right, even though they might otherwise seem like obvious candidates for a loft-style storey addition.
• Houses with two or more existing storeys can add up to two additional storeys; single-storey houses can add one.
• Each new storey must not add more than 3.5 metres to the height of the building.
• The whole extended house must not exceed 18 metres in total height.
• For a house that is not detached, such as a mid-terrace or semi-detached property, the resulting roof height must not exceed that of the neighbouring property's roof by more than 3.5 metres, which is designed to protect street scene consistency.
• This right does not apply on article 2(3) land or to listed buildings, mirroring the restrictions already covered above.

Importantly, even where a house qualifies, this is never an automatic right. It requires prior approval from the local planning authority, a formal process where the council assesses matters such as the external appearance of the extended house, the impact on neighbouring amenity (particularly loss of light) and the effect on natural light to neighbouring properties, before construction can proceed. This sits between full planning permission and the "just build it" freedom of some permitted development rights: you must apply, pay a fee, and wait for a decision, but the principle of the development itself is not usually in dispute if the technical criteria are met.

Practical Process, Timescales and Costs

Whether 22 Westminster Road ends up needing a full planning application, a prior approval submission, or nothing more than a permitted development compliance check, the practical process looks broadly similar:

• Pre-application research: Check the council's planning portal for the constraints map (conservation area, listed status, article 4 directions), and search for any planning history already recorded against the address. This is free and usually takes under an hour.
• Measured survey and drawings: A basic single-storey rear extension design typically costs somewhere in the range of £800 to £2,000 for drawings from a local architectural technician or architect, more for anything involving structural calculations or upward extension.
• Lawful Development Certificate: If you believe works fall within permitted development, applying for a Lawful Development Certificate provides written confirmation from the council, giving certainty for future sale or mortgage purposes. Fees are set nationally and the council typically has eight weeks to determine the application.
• Prior approval applications (for upward extensions under the relevant class): The council must be notified of the proposed development, and has a defined determination period, typically around eight weeks, to consider the specified matters and issue a decision.
• **Full planning applications