Roof terraces on a flat roof extension

A roof terrace on a flat roof extension always needs planning permission. Class A of Part 1 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015 excludes any development that includes a balcony, veranda or raised platform, and the Order defines a raised platform as one more than 0.3 metres high. A flat roof over a ground floor extension is well above that, so the moment you add a door, a guarding and an intention to stand on it, roof terrace planning permission is required.

The same exclusion appears in the classes covering roof enlargements and other alterations, so there is no route round it within Part 1. And flats have no Part 1 rights at all.

Why terraces are excluded from permitted development

Permitted development rights are drawn to allow changes whose effects are predictable. A terrace is excluded because its effect on neighbours depends entirely on where it sits, how high it is and what it looks over, and none of that can be regulated by a dimensional rule.

The exclusion is about the platform rather than about the roof. Building a flat roofed rear extension within the Class A limits is fine. Building the same extension and using its roof as amenity space is not, because the raised platform and any guarding around it fall outside the right.

A question that comes up constantly is whether simply walking out onto an existing flat roof through an existing window needs permission. No physical works means no operational development, and a householder occasionally using a flat roof is unlikely on its own to amount to a material change of use. Install a door, a balustrade, decking or a planter arrangement, and you have carried out operational development that needed permission. In practice councils treat the works as the trigger, and so should you.

Also check for a condition. Newer houses frequently carry conditions removing permitted development rights or specifically preventing use of a flat roof as a terrace, and those conditions are enforceable regardless of the Order.

Overlooking and the privacy assessment

Privacy is what the application will be decided on. The officer's question is simple: from the terrace, what can you see that you could not see from ground level.

A raised standing position changes the geometry in two ways. You can see over boundary fences and hedges that screen views from a garden. And you can see down into neighbouring gardens and through first floor windows at an angle that a ground floor window never achieves.

The conventional separation yardsticks, around 21 metres between facing habitable room windows and around 12 metres to a boundary or blank elevation, are applied more strictly to terraces than to windows, because a terrace gives a person time, movement and a wide field of view rather than a glance from inside a room. Where a design guide gives no figure for terraces, expect the officer to reason from first principles and to be cautious.

Screening heights and obscure glazing

Three mitigations do most of the work, and they are worth offering in the application rather than waiting to be asked.

A privacy screen along the boundary sides of the terrace, typically 1.7 to 1.8 metres above the terrace surface, which is above standing eye height for most adults. Obscure glazed screens are the usual solution where a solid screen would look heavy or would block light to the neighbour, and the obscure glazing levels and conditions that apply are worth getting right on the drawing rather than leaving to a condition.

Setting the usable area back from the edge, with a planted zone or a fixed planter between the balustrade and the standing area, which increases the effective distance to the boundary.

Limiting the terrace to part of the roof, with the remainder left inaccessible and shown as such on the plan. A condition will usually secure that, and the condition will be enforceable.

Do not propose a screen you would not build. A 1.8 metre screen on three sides of a small terrace produces a space nobody wants to sit in, and officers have seen enough of them being removed after approval to be sceptical.

Juliet balconies compared with a walk out terrace

A Juliet balcony is a guarding fitted to a door opening, with no platform projecting beyond the face of the wall. Because there is no raised platform outside the building, it sits in a different position in planning terms, and on many houses it is treated as an alteration rather than as a balcony.

The practical difference for neighbours is that a Juliet balcony gives the same view as an ordinary window at the same height, since nobody stands outside the wall plane. That is why it is so often the answer where a terrace is refused, and the distinctions are set out in more detail in Juliet balconies, balconies and the overlooking test.

Anything with a projecting floor, however shallow, is a balcony and is assessed as one.

Access arrangements and the room behind

Officers look at what the terrace is attached to, because it tells them how it will be used.

A terrace accessed from a landing or a hallway reads as occasional use. A terrace accessed from the main bedroom reads as private and lightly used. A terrace accessed through bifold doors from a kitchen or living room reads as an outdoor room that will be used every evening in summer, and it attracts the most scrutiny.

Show the internal layout on the submitted plans rather than leaving the room unlabelled. A plan that hides what is behind the doors invites the worst assumption.

Consider the guarding early as well. Building regulations require guarding to a height of 1.1 metres on a balcony, and a 1.1 metre balustrade plus a 1.8 metre privacy screen on the same edge is a design problem to resolve on paper, not on site.

Noise, evening use and neighbour relations

Terrace objections are frequently about noise rather than about being seen. Voices carry from a raised surface, hard surfaces reflect sound, and a terrace directly above a neighbour's rear bedroom window produces a real problem at eleven o'clock on a summer night.

There is not much a condition can do about ordinary domestic use, and councils rarely impose hours restrictions on a householder terrace. What does help is the physical design: locating the terrace away from the shared boundary, using a soft surface, and keeping the area modest. On a terraced street, the honest advice is to talk to both neighbours before you submit, because a neighbour who has seen the drawings and understands the screen is far less likely to object than one who first learns about it from a site notice.

Drawing sight lines for the application

The drawings decide the case, and most refused terrace applications were refused on drawings that did not answer the question.

1. A plan showing the terrace, the standing area, the screens, and the distance to each neighbouring boundary and to the nearest neighbouring windows.
2. A section through the terrace and the neighbour's garden or window, taken from an eye height of about 1.6 metres at the terrace edge, showing what is and is not visible over the screen.
3. Elevations showing the screen height, its material and its opacity, with the obscure glazing level annotated where glass is used.
4. A roof plan marking any area that is to remain inaccessible.

A short Planning Statement explaining the mitigation in sequence turns those drawings into an argument. Where the flat roof was not designed to carry people, a Structural Survey is also worth commissioning early, since an imposed load that the existing joists cannot take will change the whole proposal.

This is general guidance, not legal advice. Councils apply different separation standards, so check the position with your local planning authority or a qualified professional before relying on it. A Lawful Development Certificate is the only formal way to confirm that works are lawful.

Enter your postcode on PlanScope to see which documents your application is likely to need. Reports should be reviewed before submission, and we do not guarantee planning approval.