Juliet balconies, terraces and overlooking on an extension

A balcony on a house always needs planning permission. Class A of the General Permitted Development Order 2015 excludes any enlargement that includes a verandah, balcony or raised platform, and Part 1 defines a raised platform as one more than 0.3 metres above ground level, so a first-floor terrace on an extension roof is outside permitted development whatever its size. A true Juliet balcony is different. Where the guarding sits flush in a door opening with no platform to stand on and nothing projecting beyond the wall face, there is no balcony in the Order's sense, and the work can fall within the ordinary Class A right to alter a dwellinghouse.

That distinction is doing a lot of work, and it is the first thing to settle with your designer.

Why balconies and terraces sit outside permitted development

The exclusion is deliberate. A raised platform creates a new vantage point over neighbouring gardens and windows, and the Order's drafters treated that as a matter for case-by-case judgement rather than a right.

The same exclusion appears in Class B for roof additions such as dormers. So a rear dormer that would otherwise be permitted development stops being so the moment a small terrace or a cut-in balcony is included in it.

Flat roofs are the version of this that catches people. Building a single-storey rear extension under Class A is one thing. Adding a door from the first-floor bedroom onto its roof is a separate development, and it needs an application even though the extension underneath did not.

How overlooking is assessed from a raised area

There is no national numerical standard for privacy. Officers make a judgement about whether the proposal would cause an unacceptable loss of privacy, and they do it by standing in the neighbour's garden and looking at the proposed vantage point.

Most councils publish a separation guideline in a householder design guide. A longstanding rule of thumb of around 21 metres between directly facing habitable room windows appears in a great many of them, often with a shorter figure to a rear boundary. The figure varies between authorities, so read your own council's guide rather than assuming the number.

What matters more than the raw distance is the geometry:

• The height of the vantage point above the neighbour's ground level.
• Whether the view is oblique or square-on to a window or a sitting-out area.
• How much of the neighbour's private garden falls within easy view, particularly the part closest to their back door.
• Whether existing boundary treatment, a change in level or an outbuilding already interrupts the view.
• Whether the overlooking is from a room in casual use or from a standing platform where people linger.

That last point explains why a bedroom window at first floor is usually accepted while a terrace at the same height often is not. A window gives glimpses. A terrace gives an occupied position.

Screening, obscure glazing and how far they get you

Screens work, within limits. A solid or louvred screen at around 1.7 to 1.8 metres above the terrace surface, returning along the flanks, blocks the standing sightline into a neighbouring garden. Officers will want it shown on the drawings, dimensioned, and secured by condition.

Three cautions. A screen that solves overlooking can create an overbearing element close to a boundary, so the amenity gain has to be weighed against bulk. Timber screens weather and get removed by later owners, which is why a condition requiring retention matters. And obscure glazing works for a window but not for a terrace, because nobody stands behind a fixed obscured panel to enjoy a roof garden.

Where a side-facing upper-floor window forms part of the scheme, Class A already imposes conditions requiring obscure glazing and restricting opening below 1.7 metres above floor level. That is a condition on the permitted development right, not a design choice.

Juliet balconies compared with projecting ones

The middle row is where disputes arise. If a client wants doors rather than a window and the detail includes anything projecting that a person could step onto, treat it as a balcony and apply. A Lawful Development Certificate under section 192 of the Town and Country Planning Act 1990 is the only formal way to confirm that a flush Juliet arrangement is lawful without permission.

Conditions preventing use of a flat roof

Where an extension has a flat roof reachable from a first-floor window, councils frequently impose a condition that the roof is not to be used as a balcony, roof garden or sitting-out area. It is a standard condition and it is enforceable, provided it meets the tests in the national guidance on the use of conditions: necessary, relevant to planning and to the development permitted, enforceable, precise and otherwise reasonable.

Two practical points for a homeowner. The condition binds future owners, and it shows up on a solicitor's search, so ignoring it creates a problem at sale rather than a problem next summer. And varying it later means a section 73 application, which is a full assessment of the overlooking question you avoided first time.

If the roof is never intended for use, some designers prefer to design out access altogether: a window with a restrictor rather than a door, or a parapet upstand that makes the roof visibly not a terrace. That removes the need for the condition and the argument.

Design alternatives that keep the outlook

Clients usually want the view and the light rather than the platform, and there are ways to give them that without the overlooking problem.

High-level glazing above 1.7 metres from finished floor level gives sky and daylight with no downward sightline. A full-height fixed panel next to a Juliet arrangement does the same. Angled fin screens let a person look out along the garden while blocking the square-on view of a neighbour. Setting a terrace back from the boundary by a couple of metres with a planted zone in front does more for privacy than a taller screen at the edge. And on a wrap-around extension, moving the first-floor opening from the flank to the rear elevation often removes the objection entirely.

Small projections are a related question worth checking, because the rules on bay windows, canopies and similar projections turn on whether anything extends beyond the original wall.

What the application needs

For a balcony or terrace, submit existing and proposed plans and elevations, a section through the terrace showing the standing height and the screen, and a drawing showing sightlines to the nearest neighbouring windows and garden areas. That sightline drawing is the single most useful thing you can provide, because it answers the officer's question before they have to visit to form a view.

A Design and Access Statement is required only for certain categories of development, and a householder application is usually not one of them, though many councils ask for a short design note through their local validation list. A Planning Statement earns its place where a previous scheme was refused on privacy grounds and you need to explain what has changed.

PlanScope can produce an AI-assisted draft of either document from your postcode and a few answers about the project. Reports should be reviewed before submission, and PlanScope does not guarantee planning approval. Enter your postcode on PlanScope to see which documents a first-floor extension or terrace is likely to need. This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it, and use a Lawful Development Certificate where you need certainty.