Do I Need Planning Permission for New Windows?

The direct answer

There are two separate legal steps, and people routinely confuse them. Planning permission controls how the building looks and is usually not required for replacement windows. Building Regulations control how the window performs, and they apply to every replacement window, everywhere, with no exceptions. Apex Glazing is a FENSA-registered installer (Reg 40373), so the Building Regulations side is self-certified and notified to your council for you.

The law it actually rests on

Most guides skip this, which is why so much of the advice online is wrong. Replacing a window is only ever a planning matter if it counts as "development" in the first place.

Under section 55(2)(a) of the Town and Country Planning Act 1990, works of "maintenance, improvement or other alteration" that "do not materially affect the external appearance of the building" are not development at all. A genuine like-for-like window swap therefore needs no permission because there is nothing to permit.

If the change does materially alter the external appearance, it becomes development, and you then look to permitted development rights. For a house those sit in Schedule 2, Part 1, Class A of the Town and Country Planning (General Permitted Development) (England) Order 2015, "the enlargement, improvement or other alteration of a dwellinghouse". Class A carries condition A.3: the materials used in exterior work must be "of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse".

One correction worth making, because it is repeated all over the trade press: Class C is not the windows class. Class C covers "any other alteration to the roof of a dwellinghouse", so it is relevant to rooflights and dormers, not to a window in a wall.

Four questions that decide it

Work down the list. A "yes" on any row means you need to apply before the windows are ordered.

All four "no"? You are almost certainly clear to proceed. If you want that in writing before you spend money, apply to your council for a Lawful Development Certificate. It is not planning permission; it is formal confirmation that what you propose is lawful without it, and it is the document a buyer's solicitor will ask for later.

When permission is not required

Typical scenarios that need no planning application, assuming a house that is not listed and not covered by a relevant Article 4 Direction.

When permission is required

These need Listed Building Consent, householder planning permission, or both. Fees shown are the statutory England fees from 1 April 2026. Starting work without the consent you needed risks an enforcement notice and having to put it back at your own cost.

Conservation areas: the part everyone gets wrong

Being in a conservation area does not, on its own, mean you need planning permission to replace your windows. That is the single most common misconception we meet at survey. What removes the right is an Article 4 Direction that specifically covers windows and doors at your address, and most conservation areas do not have one.

"Conservation area consent" no longer exists in England. It was abolished on 1 October 2013 by the Enterprise and Regulatory Reform Act 2013; what used to need it is now dealt with as planning permission for "relevant demolition". So if you are searching for conservation area consent for replacement windows, the thing you are actually looking for is either nothing, or a householder planning application under an Article 4 Direction.

Two caveats that do apply everywhere in a conservation area. Cladding the exterior in stone, render, timber, plastic or tiles is excluded from Class A, and councils generally take a harder line on materials and detailing, so an officer will look closely at sightlines, glazing bars, opening method and frame colour even where no application is needed.

How to check your own address, properly. Search it on the national Planning Data service (planning.data.gov.uk), which publishes conservation area and Article 4 direction area datasets, then confirm on your own borough's planning pages, because the national dataset is not yet complete for every authority. If in doubt, a Lawful Development Certificate settles it.

Verified examples of London Article 4 Directions that do control windows and doors, so you can see what a real one looks like:

That list is deliberately short. There are many more Article 4 Directions across London and we will not guess at the scope of ones we have not read. Anything on this page that we could not verify against a council or legislation source has been removed rather than softened.

Listed buildings and secondary glazing

Listed Building Consent is required for any works that affect the character of a listed building as a building of special architectural or historic interest, under the Planning (Listed Buildings and Conservation Areas) Act 1990. It applies to Grade I, Grade II* and Grade II alike, to internal windows as well as external ones, and there is no application fee. Carrying out unauthorised works to a listed building is a criminal offence, not merely a planning breach.

In practice, full replacement is often refused on a listed building, and the useful route is secondary glazing. The Building Regulations recognise this directly: where windows cannot meet the normal thermal standard "because of the need to maintain the character of the building", Approved Document L allows either a centre-pane U-value no worse than 1.2 W/m²K, or single glazing supplemented with low-emissivity secondary glazing. That is the compliance path most conservation officers will accept, and it is why secondary glazing is usually the right answer for a listed London property rather than a fight over replacement.

Flats, leases and freeholder consent

Householder permitted development rights come from Part 1 of the GPDO, and Part 1 applies to a "dwellinghouse". The Order's own definition of that word excludes "a building containing one or more flats, or a flat contained within such a building". So a flat has no Part 1 rights at all. If the window change materially affects the external appearance, it needs planning permission, whichever elevation it is on.

Planning is only half of it. Almost every London flat is leasehold, the windows are usually demised to the landlord or form part of the structure, and the lease will typically require the freeholder's or management company's written consent before anything is altered. Getting planning permission and then discovering the lease forbids the change is a common and expensive order of operations. Check the lease first, get the licence to alter, then apply.

If your building is owned by a company, an estate or a corporation and you are being told to seek "freeholder consent", that is a separate private-law permission running alongside the planning system. Neither substitutes for the other.

Already fitted them? Retrospective applications

If windows have gone in without the permission they needed, the position is recoverable. Section 73A of the Town and Country Planning Act 1990 allows a planning application to be made for development already carried out, commonly called a retrospective application. The fee and the assessment are the same as if you had applied first; the council simply considers the finished work rather than a drawing.

On timing, the old "four-year rule" is gone in England. The Levelling-up and Regeneration Act 2023 amended section 171B so that a single ten-year time limit now applies to all breaches of planning control. That change took effect on 25 April 2024, with transitional protection where operational development was substantially completed before that date.

Unauthorised work to a listed building is on a different footing entirely. It is a criminal offence, and there is no equivalent immunity to sit out. Take advice before doing anything else.

Fees and timings

Statutory fees for England from 1 April 2026, and the statutory determination periods. Pre-application advice is charged separately by each borough under its own scheme, so check your council's current fee list rather than a national figure.

Plan your installation around 10 to 12 weeks after validation, not after submission. Apex Glazing prepares the window schedule, elevations and material specification as part of the job when we are supplying the windows.

Building Regulations always apply

This is the part that catches people out. Even when no planning permission is needed, replacement windows are controlled work under the Building Regulations, and the standards are specific.

Note that the 2026 edition of Approved Document L has been published but does not take effect until 24 March 2027, so the 2021 edition incorporating the 2023 amendments is the standard in force for work today. If you are weighing up glazing specification, our guide to window U-values sets out what the numbers mean in practice.

Does double glazing specifically need permission?

No, not as a category. Double glazing is a specification, not a planning class. On a house that is not listed and not under an Article 4 Direction, swapping single-glazed units for double-glazed ones in the same openings is not development, so no application is needed. The question only becomes a planning question when the visible result changes: heavier frames, lost glazing bars, a sash window replaced by a casement, or a horned Victorian sash replaced by a flat-topped modern one.

Where appearance is the sticking point on a period property, the fix is usually specification rather than permission. Slim sightlines, correct glazing-bar layout, run-through horns and the right frame colour are what an officer looks at. See double glazing in London for the sealed-unit options, or heritage-profile uPVC and steel-look aluminium for period-appropriate frames.

Frequently asked

Sources

Every legal and regulatory figure on this page is taken from primary legislation, statutory guidance, or a named local planning authority. Nothing here is estimated.

This page is general guidance on the law in England, not legal advice on your property. Always confirm with your local planning authority before ordering.