Privacy distances and where the separation rules come from

The privacy distance planning officers apply to your extension is not in any statute. There is no national separation standard, nothing in the Building Regulations, and no paragraph of national policy that sets a number. The familiar figures come from local supplementary planning documents and residential design guides, most of which trace back to council design standards written decades ago and carried forward through successive plans.

That matters, because a figure from a design guide is a starting point for a judgement rather than a threshold you either pass or fail.

Where separation distances come from

Councils publish residential design guidance, and most of it contains a section on privacy and overlooking with distances in it. That document is a material consideration, and a scheme that meets its figures is much harder to refuse on overlooking grounds.

What the guidance cannot do is bind the decision. The test in policy terms is whether the proposal would cause unacceptable harm to the living conditions of neighbouring occupiers, and an officer can conclude that a scheme meeting the stated distance still causes harm, or that one falling short does not.

Check the actual document rather than relying on the number everyone quotes. Authorities vary, some have withdrawn prescriptive distances entirely, and a few apply different figures in different character areas.

The familiar figures and what they assume

The most widely adopted figure is 21 metres between directly facing habitable room windows, with a shorter distance, commonly around half that, between a habitable room window and a blank flank wall or a boundary. Many guides add distance where buildings exceed two storeys.

Three assumptions sit underneath those numbers and all three fail regularly in practice.

The first is that the relationship is direct: two windows facing each other squarely across level ground. The second is that the windows serve habitable rooms on both sides. The third is that ground levels are broadly equal, so neither party looks down into the other.

Where any of those does not hold, the number stops being useful and the assessment has to look at the actual sightlines.

Oblique relationships and the angle that matters

Most real cases are oblique, and the assessment is about what can be seen rather than how far apart the buildings are.

Draw the sightline. From the centre of the proposed window, at the proposed floor level, show what is visible of the neighbour's window and of their private garden space. An angled view that catches the edge of a neighbouring window at 30 degrees is a different proposition from a square view into the room.

For extensions, many councils also apply a 45 degree test measured in plan and sometimes in section from the nearest edge of a neighbour's habitable room window. It is aimed at loss of light and outlook rather than privacy, though the two tend to be argued together, and the outlook question is set out in outlook and the overbearing test in amenity cases.

Present the sightline on a drawing. An officer with a plan and a section showing the angle can make the judgement in minutes. An officer with a paragraph of assertion has to visit the site.

Upper floor windows, balconies and terraces

Balconies and roof terraces are treated more strictly than windows, and for a sensible reason: people stand on them, stay on them, and look around.

A first floor rear window gives a glimpsed view while someone crosses a bedroom. A terrace at the same level gives a sustained one, over a wider arc, at the times of day when neighbours are using their gardens. Officers who would accept the window often refuse the terrace, and appeal decisions have repeatedly taken the same view.

Where a terrace is proposed, expect to need privacy screens of a specified height along the flanks, obscure or solid balustrades on sensitive elevations, and sometimes a reduction in depth so the usable area sits further from the boundary. Planters are not a screen unless the planting is evergreen, maintained and shown on an approved plan.

Dormers and high level windows raise the same question in a milder form. A window with a cill set high enough that a standing adult cannot look down into a neighbouring garden answers most objections, and it is worth dimensioning on the section.

Obscure glazing and fixed lights

The standard response to a problem window is a condition requiring it to be obscure glazed and non-opening below a stated height, commonly 1.7 metres above internal floor level.

It works on flank windows serving bathrooms, landings and secondary spaces. It works much less well on a window serving a main habitable room, because obscure glazing removes outlook from that room and officers are increasingly reluctant to approve habitable accommodation that depends on it. A bedroom lit only through obscure glass is a poor room.

The condition also has to be enforceable in the long term, and obscure glazing is the item most often quietly replaced by a later owner. The drafting, and the practical limits, are covered in obscure glazing conditions and when they work.

In conservation areas the glazing choice interacts with appearance as well, which narrows the options further, as with rooflights and glazing in conservation areas.

Screening, planting and level differences

Level difference is the factor most often left out of an objection and most often decisive.

Where the proposed building sits above the neighbouring land, a separation distance that would be comfortable on level ground allows a clear downward view into a garden and through ground floor windows. Where it sits below, the reverse applies and the overlooking concern may disappear. Show existing and proposed levels on the section, taken from a topographical survey rather than assumed.

Boundary treatment helps within limits. A 1.8 metre fence screens a ground floor relationship and does nothing at first floor. Evergreen planting screens if it is maintained, which nobody can guarantee for the life of the development, so officers give it limited weight unless it is secured by condition with a replacement obligation.

Retained existing planting is weaker still, because the neighbour who owns it can remove it the week after permission is granted.

Making or answering an overlooking objection

If you are objecting, be specific. Name the room, state its use and the floor it is on, give the distance measured rather than estimated, describe the view that would be gained, and attach a photograph taken from inside the affected room looking towards the site. General statements about loss of privacy carry very little weight.

If you are the applicant, deal with it before it is raised. Show the distances on the plan, show the sightlines on a section, offer the obscure glazing condition yourself where a flank window is unavoidable, and explain the levels.

And be clear about what is not a planning consideration. There is no right to a view, loss of property value is not material, and a civil right to light is a separate matter from the planning assessment of daylight, which is what a Daylight and Sunlight Assessment addresses.

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.