What obscure glazing means in a planning condition

A condition requiring obscure glazing means the glass itself must be obscured. Applied film stuck to clear glazing does not comply, however good it looks, because film is not glazing and it can be peeled off in an afternoon. The second half of the usual condition matters just as much: the window must be non-opening below 1.7 metres above the floor of the room it serves, which is the height at which a person standing in the room can no longer see out through the opening part.

Most householders meet this on a side-facing first floor window, either as a condition on a planning permission or, more often than they realise, as a condition built into permitted development rights.

Where the condition comes from

Two sources, with the same wording and different consequences.

The first is permitted development. Classes A and B of Schedule 2, Part 1 to the General Permitted Development Order 2015, covering extensions and roof additions, carry a condition that any upper floor window in a wall or roof slope forming a side elevation must be obscure-glazed, and non-opening unless the openable parts are more than 1.7 metres above the floor of the room. That condition applies automatically. Nobody imposes it, and failing it means the work was never permitted development at all.

The second is an imposed condition on a planning permission, used where a window would overlook a neighbour's garden or windows. Here the condition is drafted by the officer, which is why the wording varies between authorities and why some conditions are much easier to enforce than others.

The planning purpose is privacy, not daylight. A window that lights a landing and overlooks a neighbour's patio is the archetype, and the condition exists so the light can be kept without the view. Overlooking from terraces and balconies raises the same issue in a different form, which is covered in Juliet balconies, terraces and overlooking.

The obscuration scale and the level to specify

The glass industry uses a five-point obscuration scale, where level 1 is barely obscure and level 5 admits no recognisable image at all. Conditions commonly specify a minimum of level 3, and some authorities ask for level 4 or 5 where the relationship is close.

The differences in practice:

• Level 1 and 2 blur the view but leave shapes and movement readable, which does not achieve the planning purpose.
• Level 3 prevents recognition of detail at normal distances and is the usual compromise between privacy and light.
• Level 4 and 5 remove outline information almost entirely and are appropriate where windows face each other directly across a short distance.

Obscuration is achieved in the glass by texturing one face during manufacture, by acid etching or by sandblasting. All three are permanent properties of the pane. Within a double glazed unit the obscured face is normally placed inside the cavity so that it cannot be cleaned off or damaged.

Where a condition says "obscure glazing" with no level, ask the case officer in writing which level is expected before ordering the units, and keep the reply. A fabricator will supply exactly what the order says, and a glazing unit is not something you can adjust afterwards.

Why applied film does not comply

Three reasons, and officers will give all of them.

Film is not glazing. The condition describes a property of the glass, and a layer applied to the surface of clear glass leaves the glazing clear. Film is removable without tools and without trace, so it offers no durable control, and conditions of this kind are almost always drafted to be retained in perpetuity. And film degrades: it bubbles, discolours and lifts at the edges within a few years, particularly on a south-facing elevation.

The same applies to frosted spray coatings, adhesive privacy panels and internal blinds. A blind can be opened. That is the whole objection.

If the window is already installed in clear glass, the fix is to replace the glazing unit. On a standard casement that is an hour's work for a glazier and the cost of a unit, which is considerably less than the cost of responding to an enforcement notice.

The 1.7 metre opening restriction

The second limb stops the privacy being defeated by opening the window. The datum is the floor of the room the window serves, measured to the bottom of any openable part, and 1.7 metres reflects the sight line of a person standing inside.

Three practical consequences:

1. A standard casement with a side-hung opening light will not comply, because the opening light reaches well below 1.7 metres. Either the window is fixed throughout or only a top-hung vent above the 1.7 metre line opens.
2. Ventilation has to come from somewhere else. Trickle ventilators, mechanical extract, or an opening window in another elevation all work, and Part F of the Building Regulations has to be satisfied regardless of what the planning condition says.
3. Where the room is a loft conversion relying on that window for escape, a non-opening window creates a conflict with Part B. Resolve it with a rooflight or an openable window on another elevation before the planning drawings are finalised, not afterwards.

That tension between a planning condition and a Building Regulations requirement is common, and it is the same category of problem as the conditions attached to other permitted development rights, such as those discussed in air source heat pumps and the conditions attached.

Replacing the glazing later

Swapping an obscured unit for clear glass is a breach. Where the condition sits on a planning permission, the authority can serve a breach of condition notice under section 187A of the Town and Country Planning Act 1990. There is no right of appeal against such a notice, and non-compliance is a criminal offence.

Where the condition is the one built into permitted development, the consequence is different and sometimes worse. The extension or roof alteration ceases to benefit from the permitted development right, so the whole addition becomes unauthorised development rather than just the window.

Enforcement time limits are moving. The Levelling-up and Regeneration Act 2023 provides for a ten-year limit in England for breaches of planning control, replacing the earlier four-year rule for operational development and changes of use to a single dwelling. Check whether the provision is in force before relying on a time limit, because the transitional arrangements matter and the position has changed within the last few years.

Buyers' solicitors ask about this. A clear-glazed side window on a house whose permission required obscure glazing shows up on a conveyancing search and holds up sales, which is the reason most people eventually put it right.

Alternatives to an obscured window

Sometimes the better answer is not to have the window. Options worth drawing before you accept the condition:

• A high cill window, with the glazing starting above 1.7 metres, which can be clear because there is no view out from standing height.
• A rooflight in the side slope, which gives more daylight than a side window of the same area and no overlooking.
• Fixed external louvres angled away from the neighbour, which can be clear-glazed behind and read well architecturally.
• Relocating the window to the rear or front elevation and reorganising the room.
• A glass block panel, which admits light with no view and no opening.

A high cill usually costs the least to build and the easiest to live with, because the room keeps clear glass and a view of the sky.

Specifying it so it can be enforced

If you are drafting the condition, or responding to a draft, four elements make it workable: the obscuration level stated as a number, a requirement that the obscuration be integral to the glazing rather than applied to it, the opening restriction expressed as a height above the internal finished floor level of the room served, and a retention clause.

If you are the applicant, put the specification on the elevations and the window schedule so there is no argument later. A short Planning Statement explaining the privacy relationship, with a plan showing the sight lines to the neighbour's windows and garden, often persuades an officer to accept a high cill or a rooflight rather than an obscured window, which is a better outcome for everyone.

This is general guidance, not legal advice; 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.

To see which documents your proposal needs, enter your postcode on PlanScope and answer the guided questions. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.