Overlooking, privacy and separation distances for garden plots

What are separation distances?

Separation distances are the minimum gaps councils expect between the windows of one home and the windows or walls of another, to protect privacy and outlook. They are set locally, usually in a design guide or supplementary planning document, so the exact figures depend on your council.

Many councils use around 21 metres between facing back windows of habitable rooms, such as living rooms, kitchens and bedrooms, and around 12 to 15 metres between a back window and a blank side wall. Your council’s own guide decides, and some vary the figures for different heights, ground levels or house types.

On a garden plot these distances usually decide how far down the garden the new home has to sit, and therefore how much plot is left for its own garden. They are the first thing a designer measures.

Why do separation distances matter so much for backland homes?

They matter because a backland home is usually surrounded by other people’s gardens, so it can affect several neighbours at once, not just the house in front. Rear gardens are where people expect the most privacy, and councils protect them carefully.

In England, national policy now says extra homes in gardens should maintain acceptable living standards for residents and neighbours in terms of daylight, sunlight, privacy and outdoor space. In Wales, Planning Policy Wales says the planning system must safeguard amenity, and that where amenity impacts cannot be overcome satisfactorily, development should be refused.

How do window positions reduce overlooking?

Window positions reduce overlooking by pointing the main views of the new home away from neighbours’ windows and gardens. Good layout often solves privacy problems that distance alone cannot.

• Put main living rooms and their large windows facing along the plot or towards the new home’s own garden.
• Keep first-floor windows facing neighbours to bathrooms, landings and stairs, which are not habitable rooms.
• Use high-level windows where light is needed but views are not.
• Avoid balconies and raised terraces that look into neighbouring gardens.
• Angle bay or oriel windows so the view runs past, rather than into, a neighbour’s space.
• Check ground levels, because a floor raised even slightly above a neighbour’s garden can make a fence ineffective.

When is obscure glazing acceptable?

Obscure glazing is acceptable for windows that serve bathrooms, landings or secondary windows to a room that already has a clear main window. It is rarely accepted as the only window to a bedroom or living room, because the people living there need a proper outlook.

Councils commonly secure it by condition. A useful benchmark comes from national permitted development guidance for house extensions in England, which expects upper-floor side windows to be obscure-glazed and non-opening unless the opening parts are more than 1.7 metres above the floor of the room. The same guidance says privacy glazing is normally rated from 1 to 5, with a minimum of level 3, and that one-way glass does not count.

Planting is a weaker answer. Councils are often wary of relying on trees or hedges for privacy, because they can be cut back or die, so treat landscaping as a bonus rather than the solution.

Which roof forms help on a garden plot?

Low, sloping roof forms help most, because they reduce the bulk neighbours see and the shadow the building casts. Many approved backland homes are bungalows or storey-and-a-half homes with rooms in the roof.

A hipped roof slopes away on all sides, so less wall faces each neighbour. Low eaves with rooflights give first-floor rooms light without windows looking out. Dormers can be placed on the side facing the new home’s own garden rather than the neighbours. Where a full second storey is acceptable, keeping it to the middle of the plot and dropping to single storey near boundaries often makes the difference.

For example, a two-storey house with large rear bedroom windows facing a row of back gardens is likely to fail several tests at once. The same floor area as a bungalow with a hipped roof, rooflights over the bedrooms and the living room facing its own garden may pass all of them.

What are the BRE 25 degree and 45 degree tests?

They are quick rules of thumb from the Building Research Establishment guide, Site layout planning for daylight and sunlight: a guide to good practice (BR 209, 2022 edition), which many councils use to screen for loss of daylight to neighbours’ windows. They show whether a more detailed calculation is needed; they are not pass-or-fail rules in law.

The 25 degree test applies to new buildings opposite existing windows. You measure the angle to the horizontal from the centre of the lowest window in the existing home to the top of the new building. If the whole of the new building sits below 25 degrees, a substantial effect on the daylight reaching that window is unlikely. If any part rises above it, a more detailed check is needed.

The 45 degree approach is for extensions or buildings next to, and at right angles to, an existing window. Lines are drawn at 45 degrees on the plan and on the elevation. If the centre of the window falls on the extension side of both lines, the extension may well cause a significant reduction in the skylight reaching it. The guide says this rule does not apply to windows directly facing the building or to buildings opposite.

The BRE guide itself says its advice is not mandatory and that its numerical values are advisory, to be interpreted flexibly. Where a quick test fails, a daylight consultant can run a fuller calculation, known as the vertical sky component, to measure the actual loss.

How do you judge overshadowing of gardens?

You judge overshadowing by working out where the sun is through the day and year, and how far the new building’s shadow reaches. Where the new home sits on the compass matters as much as how far away it is.

A new home to the north of a neighbour’s garden casts its shadow away from that garden. A new home to the south or west of a garden will shade it at some point in the day. The BRE guide also includes a check for sunlight to existing gardens and open spaces.

For example, at midday on 21 March in the Midlands, the sun sits about 38 degrees above the horizon, so an eaves line 5 metres high casts a shadow of roughly 6.5 metres. On 21 December the sun is only about 14 degrees up and the same eaves throw a shadow of around 20 metres. Further north the shadows are longer, which is why low roof forms and careful siting matter even more there.

Does the existing house need privacy from the new home too?

Yes, the existing house is a neighbour like any other, and councils judge its privacy and garden space with the same care. Owners selling part of a garden sometimes forget they will be the ones living closest to the new home.

Councils also look at the outlook and privacy of the new home’s own occupants. A new bungalow whose garden is overlooked by the upstairs windows of every house in the street may be refused even if the neighbours are well protected. A good layout gives both the old and the new home a private area of garden.

What can you do if the distances are tight?

If the distances are tight, change the shape, height or orientation of the new home before giving up on the plot. Small design moves often recover several metres of effective separation.

• Turn the new home side-on, so a blank or bathroom side wall faces the existing houses rather than main windows.
• Drop to a single storey, or to rooms in the roof lit by rooflights, so there are no upstairs windows to overlook anyone.
• Move the footprint sideways on a wide plot, so windows face a gap between neighbouring houses rather than a house directly.
• Set the floor level as low as drainage allows, especially where the ground rises towards the back of the garden.
• Ask the council for pre-application advice on a simple sketch before paying for full drawings.

Can neighbours object about loss of light and privacy?

Yes, neighbours can object on loss of light, privacy and outlook, and councils must consider those comments because they are planning issues. Objections about the effect on house prices are not.

There is a separate legal right to light, which a neighbour may hold over a particular window after long use. National guidance in England says the loss of private rights to light is not a material planning consideration, so planning permission does not cancel a legal right to light. Where a scheme comes close to a long-standing window, take legal advice as well as planning advice.