Planning and building

Historic window guidance

This 'Design and Conservation Guidance Note' is a very brief overview for those seeking good practice guidance when caring for historic windows and considering change; we've also provided a selection of references and links for detailed guidance.

Historic windows overview

When referring to 'historic windows' this normally means:

  • aged timber windows of traditional design and construction
  • windows that contribute to the building's special interest

The term can also include more recent authentic replacement timber windows that also contribute to the building's special interest, and can also include early steel framed windows.

The term 'historic glazing' refers to glass produced before modern float glass; this usually predates the 1950s. Signs of this glass include mild visual distortions.

In 'Traditional windows, their care, repair and upgrading' (published February 2017), Historic England say:

The loss of traditional windows from our older buildings poses one of the major threats to our heritage. Traditional windows and their glazing make an important contribution to the significance of historic areas.
 

They are an integral part of the design of older buildings and can be important artefacts in their own right, often made with great skill and ingenuity with materials of a higher quality than are generally available today. The distinctive appearance of historic hand-made glass is not easily imitated in modern glazing.

Therefore, loss of historic windows needs careful consideration and may not be supported. Section 3 of 'Traditional Windows, their care, repair and upgrading' gives brief guidance for different types of work.

Care, repair and upgrading of historic windows

Regular care and maintenance reduces the need for costly interventions at a later date.

A well-maintained window with good draft proofing will also perform better for thermal comfort.

Try to be objective about thermal performance and carbon reduction, so decisions can be based on facts and not assumptions.

For instance, adding internal secondary glazing can reduce heat loss comparable to some new double glazing. As another example, the embodied energy of uPVC windows and the need to replace these units over time, can have a worse carbon impact compared to retaining single glazed timber windows in good condition when introducing other window upgrades. Historic England's Know Your home, Know Your Carbon is a good guide on this subject.

Changes to windows can impact on condensation and damp throughout the building. Glazing should be the coldest part of an external wall. If replacing windows improves their thermal efficiency and reduces airflow in damp buildings, condensation can be transferred to other parts of the building -potentially hidden within walls. This can lead to rapid decay of historic fabric. Therefore, proposals for windows might need to be considered together with other building changes to avoid problems.

Different types of change to windows have different degrees of carbon benefits and different degrees of impact, thus an optimal balance between these factors should be sought. This usually means retaining existing fabric and minimising interventions, where possible.

Works to historic windows

Read about common scenarios and approaches in relation to works to historic windows.

See key points on:

Then see: references and links for detailed guidance

Painting historic windows

For painting historic windows:

Impact: low

Permissions:

  • where the property is not a listed building but located in a conservation area this will not normally require permission
  • where the property is a listed building, houses or commercial buildings this will also not normally require permission, particularly if using the same colour or muted tones
  • painting shopfronts will not normally require permission, more flexibility is generally considered for colour choice

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Repairing windows on a listed building

For repairing windows on a listed building:

Impact: low

Permissions:

  • replacement of small timber elements such as a rotted sill with quality new timber, matched profiles, and a good standard of work will not require permission
  • repair of broken or cracked glass will not require permission when replaced with similar glass, that is single glazing replaced with single glazing
  • draught proofing does not usually require permission

Comments:

  • often windows look in worse condition than they actually are
  • repairs should seek minimal intervention

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Adding internal secondary glazing to listed buildings

For adding internal secondary glazing to listed buildings:

Impact: low

Permissons:

  • a good design choice and frame position are important
  • conversely, bad choices can cause unacceptable harm
  • for a clear recommendation on permissions, seek advice from the Local Planning Authority (LPA)

Comments:

  • secondary glazing is usually a preferred method of improving thermal, sound, or comfort performance of single glazed windows because if well designed, it will only have limited impacts on historic fabric
  • secondary glazing can achieve comparable performance to replacement new double glazed timber windows with correct design choice (including Low-E glass type)
  • if subdivision of secondary glazing is needed, the proportions or frames should align with the external windows, for example, glazing bars should 'line through'
  • there are rare exceptions where internal secondary glazing is not recommended, such as unacceptable impacts on internal shutters or historic joinery

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Replacement of existing glazing whilst retaining window frames on listed buildings

For replacement of existing glazing with slimline or vacuum double glazing whilst retaining existing frames on listed buildings:

Imapct: medium

Permissions:

  • will require listed building consent unless replacing panes within a clearly modern window

Comments:

  • when permission is required, this proposal is usually acceptable if windows are not leaded lights or don’t contain historic glass and/or window frames can accommodate any additional rebate necessary to install replacement glazing in the same outer face position
  • these types of units are thicker and heavier and should not compromise the long-term stability of existing frames, including a consideration of the need for future intervention and replacement

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Replacement of existing windows with double glazed windows on listed buildings

For replacement of existing windows with double glazed windows on listed buildings:

Impact: high

Permissions:

  • highly likely to require listed building consent

Comments:

  • when permission is required, an application will consider the contribution existing windows have on the building's special interest
  • for instance, if the windows are recent and don't contribute to a building's special interest then their replacement in double glazing with an appropriate design can be neutral or positive
  • alternatively, windows that contribute to a building's special interest are important to retain rather than replace, and replacement will not usually be supported
  • where a replacement is agreed in principle then design, detail and materials will be important, for example, expect uPVC not to be an acceptable material for windows in a listed building

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Replacement of existing historic windows in a Conservation Area

For replacement of existing historic windows with double or triple glazed windows, not a listed building, but in a Conservation Area:

Impact: medium

Permissions:

  • the need for permissions vary
  • as a guide, they are generally more permissive than those for listed buildings
  • most unlisted houses have permitted development rights to replace windows if considered by the LPA (not the owner) to be a like-for-like replacement
  • checking with the LPA what like-for-like means in detail is recommended, as it is subject to interpretation
  • regardless of standard permitted development rules, some houses might be in an area that have certain rights removed by an Article 4 direction
  • permitted development rights afforded to houses do not apply to other building types like flats or commercial buildings

Comments:

  • good practice guidance for maintaining historic windows in listed buildings is also useful to inform proposals for historic windows in unlisted buildings, regardless of the need for permissions
  • when permission is required, replacements are usually supported, subject to good design
  • one guiding consideration will be the impact the proposal has on the special interest of the conservation area
  • for instance, if traditional timber windows contribute to the special interest of the area and are the dominant window type, then a replacement window should also be a traditional design type
  • this usually means a window of timber construction (uPVC is usually unable to replicate the design detail and glazing bar proportion of traditional timber windows)
  • double or triple glazing will usually be supported

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Detailed guidance on historic windows

Please refer to guides containing more detailed information on the general care of historic windows.

Guidance from Historic England

Guidance from Historic Environment Scotland

Guidance from Department for Communities, Northern Ireland

Also see

Planning Enquiries

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