Heritage Windows London
Heritage windows are a specific category — windows produced to match the character, profile and detailing of original historic joinery. In London, where a significant proportion of the housing stock dates from the Victorian, Edwardian and Georgian periods, getting heritage window replacement right matters both aesthetically and in terms of planning compliance.
At International Windows Group we manufacture heritage timber windows across the full range of historic London window types. Sash windows, casement windows, tilt and turn — all produced to profiles that reflect the original character of your property and, where required, satisfy the requirements of conservation officers and listed building consent.
Browse completed projects in our timber windows portfolio or read more about us on the About Us page.
What Are Heritage Windows?
The term „heritage windows” covers timber windows produced to match historic originals in profile, sightline width, glazing bar configuration and finish. The defining characteristic is that the design follows the original rather than a contemporary standard profile — which means narrower sightlines, more slender glazing bars and details that reference the joinery traditions of the period.
In practice, heritage windows are most often specified in three situations: replacing windows in a listed building, replacing windows in a conservation area, or restoring a period property where the owner wants to retain the authentic character of the original joinery even where planning doesn’t strictly require it.
For a detailed overview of the historic context, read our guide to Victorian sash windows in London — restoration, replacement and conservation.
Heritage Windows for Listed Buildings
Replacing windows in a listed building requires listed building consent. The replacement windows must match the originals in material, profile, sightline width and finish — and in most cases, this means timber. Aluminium or uPVC replacements are very rarely approved for listed buildings.
We have experience producing windows for listed properties across London. We work from existing window profiles, historic drawings or photographic evidence to establish the correct specification, and we provide supporting documentation — material specifications, profile drawings, finish details — to accompany listed building consent applications.
The process varies depending on the listing grade and the local planning authority. We advise on this at the consultation stage. Contact us to discuss your specific building.
Heritage Windows for Conservation Areas
London has over 1,000 designated conservation areas. If your property sits within one, replacing windows will typically require planning permission rather than being permitted development — and the approved replacement windows will need to match the character of the originals.
Conservation officers in different London boroughs have different specific requirements, but the general principle is consistent: replacements should match originals in material (timber), profile and appearance. We know what different London conservation officers expect and can advise on the right specification for your area.
Read our area guides for more specific information: sash windows in North London, bespoke timber sash windows in North London and wooden windows in Ealing.
Heritage Sash Windows
The timber sash window is the most common heritage window type in London. Victorian and Georgian sash windows have specific proportions — the ratio of sash height to width, the glazing bar width, the depth of the box frame — that define the character of the building’s facade. Replacing them with windows that don’t respect these proportions changes the character of the building and is rarely approved in conservation areas.
We manufacture heritage sash windows with profiles drawn from original examples. Glazing bar widths are matched precisely to originals. Sash proportions follow the historic pattern. Double glazing is available in slimline units that don’t significantly alter sightline widths.
See our timber sash windows page for full specification details and our timber sash windows London page for more on the installation process.
Heritage Casement Windows
In properties where the original windows were casements rather than sashes — common in Arts and Crafts, Edwardian and some Victorian properties — heritage specification means producing flush casement windows with slim sightlines and traditional ironmongery. We manufacture heritage casement windows to match original profiles and can advise on the right specification for your property type.
More detail on our casement windows London page.
Glazing for Heritage Windows
Modern double glazing is available for heritage windows using slimline units that keep sightline widths close to those of the original single glazed windows. This improves thermal performance substantially while maintaining the authentic appearance.
For properties near busy roads or railways, acoustic glazing is available. Read our guide to acoustic glazing in London for detail on performance levels and specification options.
For those weighing up double versus triple glazing for a period property, see our honest assessment: Double vs Triple Glazing in London.
Documentation & Planning Support
For listed building consent and conservation area planning applications, supporting documentation is important. We provide material specifications, profile drawings and finish details that can be submitted alongside your application. We can also advise on what information planning officers in specific London boroughs typically require.
Our compliance standards and accreditations are available on the certificates page. Technical drawings for our window profiles are available in the technical drawings section, and product brochures can be downloaded from the brochures page.
The Process
Free Consultation
We visit your property, assess the existing windows, discuss planning requirements and advise on the appropriate specification. No obligation. Arrange yours here.
Specification & Documentation
We agree the window specification — profile, glazing bar width, timber species, finish, glazing unit — and prepare any documentation needed for planning or listed building consent applications.
Precise Measurement
Our team takes exact measurements of every opening. Included at no cost with every order.
Manufacture
Your windows are built in our workshop to the agreed specification. Every detail confirmed before production starts.
Professional Installation
Our own teams handle removal of old frames and fitting of new windows. We make good around every opening and leave the site clean. See completed work in our portfolio.
Frequently Asked Questions
Do I need listed building consent to replace windows in a listed building?
Yes, in almost all cases. Listed building consent is required for any alterations that affect the character of a listed building, which includes window replacement. We advise on the application process and provide supporting documentation. Contact us to discuss your building.
Can I fit double glazing in a listed building?
In many cases, yes — using slimline double glazing units that don’t significantly alter the sightline widths. Approval depends on the listing grade, the local planning authority and the specific circumstances of the building. We advise on what’s likely to be approved for your property.
How do I find out if my property is in a conservation area?
Your local planning authority’s website will have a map of designated conservation areas. You can also check the Historic England National Heritage List for listed buildings. If you’re unsure, contact us — we can often advise based on the address and postcode.
What if I replace windows without consent in a conservation area?
Replacing windows without the required planning permission or listed building consent is a planning breach. Local authorities can require reinstatement of the original windows at the owner’s cost. It’s always worth checking requirements before proceeding. We advise on this as part of the consultation process.
Get in Touch
Call us on +44 20 3375 5535 or visit our contact page to arrange a free consultation. We’ll assess your property, advise on the appropriate specification and planning requirements, and give you a clear quote — no obligation. You can also download our technical documentation or browse the brochures before we speak.