Windows in Conservation Areas — What You Can and Cannot Do in London

London has over 1,000 conservation areas — and if your property is in one, replacing your windows requires careful thought. Get it wrong and you may face an enforcement notice, a requirement to reinstate the originals at your own cost, or difficulties when selling. Get it right and you'll have beautiful, thermally efficient windows that comply fully with planning requirements and enhance your property's value.

A&J Joinery has been working in London's conservation areas for over 20 years. This guide explains what you can and cannot do — and how we manage the planning process on your behalf.

What is a Conservation Area?

A conservation area is a designated area of special architectural or historic interest where the character and appearance of the area are protected by law. In London, conservation areas are designated and managed by each borough council. Changes to the external appearance of buildings within a conservation area — including window replacement — are subject to additional planning controls.

Key London conservation areas include those across Fulham, Chelsea, Hammersmith, Kensington, Notting Hill, Westminster and many others. If you are unsure whether your property is in a conservation area, check your borough council's planning portal or ask A&J Joinery during your free survey — we know every conservation area across South West and West London.

What Counts as Permitted Development in a Conservation Area?

Permitted development (PD) allows certain works without a planning application. In a conservation area, PD rights for windows are more restricted than for standard residential properties. Generally:

• Like-for-like replacement in the same material and design — usually permitted development, no application needed
• Timber sash windows replaced with timber sash windows — usually PD if profiles match the originals
• Double glazing within existing timber frames — usually PD as the external appearance is unchanged
• Draught-proofing — always PD, as it is maintenance work

What Requires Planning Permission?

• Changing material — replacing timber with UPVC, aluminium or any non-original material almost always requires planning permission in a conservation area
• Changing style — replacing sash windows with casement windows, or vice versa
• Altering proportions — changing window size, number of panes or glazing bar pattern
• Any works to listed buildings — Listed Building Consent is always required, regardless of what is being changed
• Front elevation changes — most London conservation areas apply heightened controls to front and side elevations visible from the highway

UPVC in a Conservation Area — The Honest Advice

We are frequently asked by homeowners whether they can fit UPVC windows in their conservation area property. Our honest answer: in most London conservation areas, UPVC windows require planning permission and applications are very likely to be refused. This is because:

• UPVC cannot replicate the slim profiles, sharp arrises and joinery details of original timber windows
• London borough conservation officers consistently refuse UPVC on visual amenity grounds
• UPVC cannot be colour-matched to the nuanced off-whites and creams of period properties
• Enforcement action for unauthorised UPVC windows can require full reinstatement at the homeowner's cost

Timber is always the right material for conservation area window replacement in London — and with Accoya® timber's 50-year rot guarantee, it is now also the low-maintenance choice.

How A&J Joinery Manages Conservation Area Planning

We manage the entire planning process for your conservation area window project in London — at no additional charge:

• Free survey and planning assessment at your property
• Confirmation of permitted development status or planning application requirement
• Preparation of technical drawings and heritage impact statement
• Submission of planning application to your borough council
• Liaison with conservation officer throughout the application process
• Manufacture and installation only after planning consent is confirmed

We cover all London boroughs and have a strong track record with conservation officers across Hammersmith & Fulham, Kensington & Chelsea, Westminster, Richmond and all other South West London councils.