Balconies, terraces and raised platforms

A balcony, verandah or raised platform cannot be built under householder permitted development. Class A of Part 1 of the Town and Country Planning (General Permitted Development) (England) Order 2015 expressly excludes development that consists of or includes the construction of a verandah, balcony or raised platform, and the interpretation provisions define a raised platform as one with a height greater than 0.3 metres. So a ground level patio is outside the planning system, a deck 250 millimetres above ground is a hard surface, and the same deck at 350 millimetres is a raised platform requiring planning permission.

Once you are making an application, the technical limits stop mattering and one question takes over: what will the occupants be able to see, and from where. Everything else in the submission is supporting material.

Why balconies are excluded from the right

Permitted development rights were drawn to cover changes whose effects on neighbours are predictable from their dimensions. A balcony is not predictable in that way. Its effect depends on what it looks at, which varies house by house in a way that a projection limit cannot capture.

Two consequences follow. There is no size below which a balcony is permitted, so a 900 millimetre deep balcony on a rear elevation still needs permission. And an element that would otherwise be lawful loses the right if a balcony is included, which is why a rear extension with a terrace on its flat roof falls outside Class A as a whole rather than just as to the terrace.

Flats have no householder rights at all. Part 1 applies to a dwellinghouse, so any balcony, terrace or platform on a flat or maisonette requires an application, and in most cases the freeholder's consent and the agreement of other leaseholders as well.

The raised platform definition

The 0.3 metre figure is measured from the ground level adjacent to the platform, which on a sloping plot gives a different answer at each corner. A deck that steps down a garden can be within the definition at the house end and outside it at the far end, and the measurement that governs is the highest point.

Practical points that decide whether a garden structure needs permission:

• a timber deck at 0.3 metres or below is not a raised platform, so the usual hard surface considerations apply instead
• a platform at any height forming part of an outbuilding or extension takes that structure outside its permitted development class
• steps and a landing giving access to a raised deck are part of the platform
• a hot tub on a plinth, a raised seating area and a garden room with a wraparound deck are all caught by the same definition
• designated land and Article 4 directions can narrow the position further

Keeping a deck at or below 0.3 metres is the simplest way to stay outside the planning system, and on a level garden it is usually achievable.

Overlooking and privacy assessment

Officers assess overlooking by geometry and by use. The geometry question is what a person standing at the balustrade can see of a neighbour's habitable room windows and of their private garden. The use question is whether the space will be occupied in a way that creates a sense of being watched, which is why a balcony is treated more seriously than a window at the same position.

Many authorities' design guides apply separation distances between directly facing habitable room windows, with a figure in the region of 21 metres common across published householder design guidance, and a shorter distance to a blank elevation. Those are local standards rather than national rules, so take the figure from the authority's own guide and say in the application which document you have used.

Oblique views matter as much as direct ones. A balcony on a rear elevation of a terraced house usually looks along the row rather than straight ahead, and the neighbour who objects is often two doors down rather than immediately adjoining. Draw the sightlines that exist, as you would for a rear dormer on a semi-detached house.

The depth of the balcony is the most useful design variable. A shallow balcony of around a metre supports standing and a chair, generates little dwell time, and produces narrow oblique view angles. A three metre terrace becomes an outdoor room, and it will be assessed as one.

Screening and obscure glazing

Screening is how most balcony applications become acceptable, and it needs specifying rather than offering in principle.

What works:

1. Solid returns at the sides, in the same material as the building, taken to a height of about 1.7 metres above the balcony floor so that they block seated and standing views along the row.
2. Obscure glazing in the side panels, specified by obscuration level rather than described as frosted, and fixed rather than openable.
3. Angled timber or metal louvres set to block the view along the elevation while leaving the outward view open.
4. Setting the balcony back behind the building line so the flanking walls do the screening.
5. Planting as a supplement rather than as the mitigation, because it is seasonal and it can be removed.

Obscure glazing to a height of 1.7 metres above floor level is the standard that Part 1 itself applies to side-facing windows, which is why officers reach for it. The reasoning behind obscure glazing conditions on side-facing windows transfers directly to a balcony screen, and a condition requiring the screen to be installed before first use and retained thereafter should be expected.

Juliet balconies and door openings

A Juliet balcony, meaning a guarding across a door opening with no platform projecting beyond the wall and no space to stand outside it, is a different proposition. There is nothing to occupy, so the overlooking effect is the same as that of a window of equivalent size.

Inserting French doors with a Juliet guarding into a rear elevation is generally an alteration rather than the construction of a balcony, and many authorities treat it as permitted. The caution is that the position is a matter of fact and degree. A guarding set forward of the wall plane with a shallow standing area is capable of being a balcony, and an inset balcony recessed into the building with a floor you can stand on is a balcony even though nothing projects.

Where the answer matters, apply for a certificate of lawfulness of proposed use or development under section 192 of the Town and Country Planning Act 1990. It is the only formal way to confirm the position, and on a property you intend to let or sell it is worth the fee.

Flats and shared structures

On a flat, three regimes stack up. Planning permission is needed for any balcony or terrace. The lease will almost always require the landlord's consent for an alteration to the structure or the external appearance. And where the balcony is formed in or through a party structure, the Party Wall etc. Act 1996 applies and notice has to be served on the adjoining owner.

Building Regulations add two more. Approved Document K sets the guarding requirements, including the height of the barrier and the limits on openings in it. Approved Document B restricts combustible materials in the external walls of taller residential buildings, and balconies fall within the scope of those restrictions, so check the current threshold and the material requirements before specifying a timber deck or a composite soffit on a block of flats.

Access and drainage are the details that cause trouble later. A terrace formed over habitable accommodation needs a waterproofing and drainage design, a threshold detail that keeps water out while meeting accessibility requirements, and a maintenance route for the outlets.

Evidence that overcomes objection

The submission that gets approved contains drawings that answer the objection before it is made:

• existing and proposed plans and elevations at a measurable scale, with the balcony depth dimensioned
• a sections drawing showing sightlines from the balustrade at eye height to the nearest habitable room windows and to the neighbouring garden, with distances annotated
• a site plan showing separation distances to all affected properties, including oblique relationships
• photographs taken from the proposed balcony position, from a platform or an upstairs window at the correct height
• the screen specification: material, height, obscuration level, fixing and whether it is openable
• a short statement referring to the authority's own design guidance and the separation standard it sets

A Planning Statement setting the proposal against the local design guide, and a Design and Access Statement where one is required, carry the argument that the drawings illustrate. PlanScope drafts both from your answers about the property and flags the facts it does not hold, and you can enter your postcode on the home page to see what else a householder application 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. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.