Obscure glazing: which privacy level to specify

Most councils that ask for obscure glazing will accept level 3 on the five point obscurity scale, and a good many specify level 4 or 5 for a window looking directly into a neighbour's garden at close range. The scale runs from 1, which is barely textured, to 5, which prevents any recognisable image passing through. Choosing the obscure glazing privacy level is therefore a judgement about distance, angle and what is being overlooked, and it belongs on the drawing rather than in a condition somebody writes later.

Get it wrong in either direction and it costs. Specify level 2 on a side window three metres from a bedroom and the officer will condition something heavier. Specify level 5 on a bathroom that needs some daylight and the client will replace it within a year.

How obscurity levels are graded

The scale used across the glass industry runs from 1 to 5 and measures how much visual information passes through the glass, not how much light. Level 1 gives a light texture through which shapes and movement are clear. Level 3 is the common middle ground, where movement and colour are visible but detail is not. Level 5 diffuses to the point where nothing beyond vague light and shade registers.

Councils almost always express the requirement as a minimum, not as a fixed value. A condition requiring glazing to at least level 3 permits level 4 or 5 as well, which gives the client room to choose a pattern they like.

Applied films are a different product from manufactured obscure glass. They can achieve comparable obscurity, but they can be removed by anyone with a scraper, and councils know that. Where the privacy is doing real planning work, specify the obscurity in the glass itself and say so.

Where the 1.7 metre restriction comes from

Two permitted development classes carry the same condition. Class A of Schedule 2 Part 1 to the General Permitted Development Order 2015, covering extensions to a dwellinghouse, and Class B, covering roof extensions, both require that any window in a wall or roof slope forming a side elevation is obscure glazed, and that any part of the window which can be opened is more than 1.7 metres above the floor of the room in which it is installed.

Read the second half carefully, because people misquote it. The measurement is from the finished floor level of the room, not from ground level outside, and it applies to the openable part rather than to the window as a whole. A window with a fixed lower pane and a top hung opening light whose lowest opening point sits above 1.7 metres complies. A tilt and turn unit whose whole sash opens does not.

The figure is a permitted development condition. Where a council imposes the same restriction on a full planning permission, it does so by condition and may choose a different height, so check the wording rather than assuming 1.7 metres.

Writing the specification on the drawing

Put it in three places so that nobody has to interpret it.

On the elevation, hatch or tone the obscure glazed panes so they are visible at a glance. On the window schedule, give each affected opening a reference, the obscurity level, whether the pane is fixed or openable, and the height of the lowest openable part above finished floor level. And in the notes, state the standard being met in the same words the condition is likely to use.

A note reading "W12: obscure glazed to a minimum of level 3 on the 1 to 5 obscurity scale; lower pane fixed shut; lowest openable part 1.75 metres above finished floor level" answers the officer's question before it is asked. It also survives into the construction package, which is where these specifications usually get lost.

Section drawings earn their place here. A sill height on an elevation tells you nothing about the floor level inside on a split level plan.

Conditions requiring retention

The standard condition requires the window to be obscure glazed and fixed shut below the stated height before first occupation, and to be retained in that condition thereafter. Many authorities add wording removing the permitted development right to replace the window with clear glazing.

That last part matters. Replacing a window like for like is often not development at all, so without express wording the client can, in practice, swap the glass. A condition drafted to require retention notwithstanding the relevant provisions of the General Permitted Development Order closes the gap.

Check the drafting on issue. Conditions requiring obscure glazing "in accordance with the approved plans" are only as good as the plans, which is another reason to put the obscurity level on the drawing.

Where the condition as drafted is unworkable, for instance because it requires a fixed pane in a room that needs an escape window, raise it during the application rather than applying under section 73 afterwards.

Obscure glazing against fixed screens

Obscure glass is not the only answer, and it is sometimes the wrong one. A fixed privacy screen, a brise soleil, angled fins or a solid balustrade upstand can protect a neighbour's privacy while leaving a clear view in another direction.

For balconies and terraces the screen is usually better, because obscure glazing does nothing for somebody standing outside. For a stair or landing window, obscure glazing is proportionate. For a habitable room, think harder: a bedroom whose only window is obscure glazed has no outlook, and outlook is part of the residential amenity the council is assessing.

Angled or oriel windows facing away from the boundary are the third option. They cost more, they look deliberate, and they often resolve an objection that obscure glazing only mutes.

Daylight lost through obscure glass

Patterned obscure glass reduces visible light transmittance, but far less than clients expect. Heavier levels of obscurity and applied films cut more, and the loss varies by product rather than by level.

The effect worth modelling is not the transmittance but the room's overall performance. Where a Daylight and Sunlight Assessment is being prepared, use the actual transmittance figure for the specified product rather than a default clear glazing value, because the difference shows up in marginal rooms. The current approach to assessing new interiors is set out in our note on the 2022 changes for new interiors.

The other loss is diffuse rather than measurable. Obscure glass scatters light, so a room lit through it feels flatter and loses the sense of orientation a clear window gives. On a small extension that is a fair trade. On a principal living space it is not, and the layout should change instead.

When clear glass is fitted later

Breach of a planning condition is enforceable. The council can serve a breach of condition notice, and failure to comply with one is an offence, with no right of appeal against the notice itself.

Time limits for enforcement action were changed by the Levelling-up and Regeneration Act 2023, so check the period currently in force before advising a client that a historic breach is beyond reach. The safer assumption is that it is not.

In practice these breaches surface at sale. A buyer's solicitor compares the approved drawings with the building, finds a clear glazed window where the condition required obscure glass, and asks for it to be regularised. Retrospective applications and indemnity policies both cost more than the glass would have.

Advise clients at handover, in writing, which windows are conditioned and what the condition says. The detail of how authorities word these conditions, and what the wording actually binds, is covered in our note on how councils word obscure glazing conditions.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. Enter your postcode on PlanScope to see which amenity and daylight documents an application is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.