Replacing windows where an Article 4 direction applies

If an Article 4 direction covers your street, an article 4 window replacement usually needs planning permission before the old frames come out. The direction withdraws the permitted development right that would otherwise allow the alteration, so the council gets to judge the new windows on their merits. One exception matters more than any other: a genuine like for like replacement that does not materially affect the external appearance of the house is not development at all, and no direction can make it so.

That distinction is where most disputes with a conservation officer start, and it is worth getting right before you order anything.

What the direction takes away

An Article 4 direction is made under article 4 of the Town and Country Planning (General Permitted Development) (England) Order 2015. It withdraws named classes of permitted development in a defined area, which means an application is required for work that elsewhere would need none.

For houses, the class that covers windows is Class A of Part 1 of Schedule 2, which permits the enlargement, improvement or other alteration of a dwellinghouse. Directions in residential conservation areas commonly withdraw Class A along with Class C, which covers alterations to a roof, and sometimes Part 2 Class A for gates, walls and fences.

Two points that catch householders out. A direction applies to the land, not to the owner, so it survives a sale and nobody has to tell you about it. And a conservation area on its own does not remove window rights. Designation restricts some things, such as cladding and larger rear extensions, while leaving simple window replacement permitted unless a direction says otherwise.

Where permission is needed only because of the direction, no application fee is payable under the fee regulations. Councils sometimes miss this on their online forms, so check the current fee schedule and say in the covering note why the application is fee-exempt.

Finding out whether one applies to your house

Three checks, in this order.

1. Search the council's website for "Article 4 direction" and open the schedule and map, not just the summary page. The schedule names the classes withdrawn and the map shows the boundary, which often follows a rear boundary line rather than a street.
2. Check the national dataset at planning.data.gov.uk, which publishes article 4 direction areas supplied by authorities. Treat it as a pointer rather than the final word, because the council's own document governs.
3. Ask the council's planning duty service in writing, quoting your address, and keep the reply.

Some directions are property-specific and list addresses in an appendix. Others apply to a whole conservation area. Read which classes are named, because a direction aimed at loss of front boundary walls tells you nothing about windows.

Immediate directions take effect on the day notice is served and must be confirmed within six months, so a direction made recently may still be provisional. Non-immediate directions are consulted on first and take effect when confirmed. Either way, the relevant question is the position on the day you start work.

When replacement is not development at all

Section 55(2)(a) of the Town and Country Planning Act 1990 puts works of maintenance, improvement or alteration outside the definition of development where they affect only the interior or do not materially affect the external appearance of the building.

A true like for like replacement sits inside that exclusion. Same material, same opening method, same frame and glazing bar sightlines, same reveal depth, same glazing pattern. Replace a rotten timber sliding sash with a timber sliding sash of matching profiles and you have altered nothing an observer in the street could identify.

The trouble is that very little of the market offers that. Swapping timber sashes for white plastic casements changes the material, the opening method and the sightlines at once, which is plainly a material change to the external appearance. So is losing horns on a sash, thickening glazing bars to carry a sealed unit, or moving from six panes to a single sheet of glass.

If you think your replacement falls outside development, do not simply rely on that view. Apply for a Lawful Development Certificate for proposed use or development under section 192 of the 1990 Act. That is the only formal way to confirm the works are lawful, and it costs a fraction of putting windows back.

Slimline double glazing and what officers accept

Standard sealed units use a cavity around 16 mm, giving an overall thickness in the mid twenties of millimetres. That will not fit a traditional sash without fattening the glazing bars and deepening the rebate, which changes the elevation. Slim-profile units use a much narrower cavity and can often be accommodated in a rebuilt timber sash with the original profiles retained.

Officer positions vary by authority, and honestly there is no national rule here. What is consistent is what persuades them:

• The glazing bar and frame sightlines match the existing, dimension for dimension.
• The unit is bedded behind a putty or slim timber bead line rather than a chunky applied bead.
• Glass is drawn or cylinder glass where the street has it, with the reflection behaviour that goes with it.
• Sashes remain vertically sliding with horns, cords and weights, not fixed lights dressed to look like sashes.
• Secondary glazing is considered where the front elevation is sensitive, because it changes nothing outside.

For a house in a conservation area, the council will read the application as a design and heritage question. A short Heritage Statement explaining the contribution the existing windows make and why the replacement preserves it does more work than any amount of product literature. If the house is listed, listed building consent is needed as well as permission, and the material tests are stricter.

Drawings and evidence to submit

Councils refuse window applications for thin evidence more often than for bad design. The bundle below is what a conservation officer needs to say yes without a site visit.

Add a covering statement of three or four paragraphs. Say what condition the existing windows are in, what repair options were tested, why replacement is proposed, and how the proposed profiles compare with the existing. Where only some windows are failing, a mixed scheme of repair to the front and replacement to the rear often clears an objection that a whole-house replacement would attract. Our note on small projections such as bay windows and canopies covers the related detailing questions where a bay is involved.

Proceeding without permission, and the risk you take

Unauthorised window replacement in an Article 4 area is a breach of planning control, not a criminal offence, unless the building is listed. The council can serve an enforcement notice requiring the windows to be put back, and an appeal against that notice goes to the Planning Inspectorate.

The time limit matters. For a breach consisting of operational development, immunity has historically been reached after four years, and the Levelling-up and Regeneration Act 2023 provides for a move to ten years, so check the current position for the date your works were carried out. Immunity is not a defence against a listed building prosecution, where there is no time limit at all.

The practical cost is usually felt at sale. A buyer's solicitor asks for the permission, the answer is that there is none, and the transaction stalls while a retrospective application or a certificate of lawfulness is pursued. Retrospective applications for plastic windows in conservation areas are frequently refused, which leaves replacement of the replacement as the only route.

If work has already happened, get advice before applying. Sometimes the better route is a section 192 certificate on the basis that the change was not material, and sometimes it is a scheme to reinstate correct profiles on the front elevation while retaining what is at the back. Where the house also has chimney or roof alterations in the same bundle, our note on removing a chimney and when permission applies sets out how councils treat that combination.

PlanScope can draft the supporting statements for a window application in minutes, including a heritage statement structured to UK planning policy. Reports should be reviewed before submission, and we do not guarantee planning approval. To see which documents your address is likely to need, enter your postcode on PlanScope.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.