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Replacement or Repair of Windows in listed buildings?

The replacement or repair of windows in listed buildings is a controversial topic. Each case scenario is different, and the below should be considered general guidance.

Some homeowners might think the condition of their windows is so awful that they better ask for replacement rather than repair the windows in their listed building. While lack of maintenance may make windows look worse than they actually are, a localised repair combined with other improvements could save the historic value of your property.

Choosing the right window strategy

You are concerned about the condition of your windows and you are considering a replacement. You might think they have reached their lifespan, and it is time to install new windows. This is how some of my clients felt in the past. During the home consultation, I saw that the windows lacked maintenance, but they generally appeared in good condition. Should you replace or repair them?

In the case of a Grade I or II* star listed building, we should keep the timber windows and their single glazing to preserve as much of the original fabric as possible. This might also be the case for grade II listed, whose windows are highly significant.

Another aspect to consider is the window’s location and if the type of works proposed had already been approved for other windows in your house or neighbouring houses of similar style.

Also, it is unlikely for the conservation officer to grant permission for new windows where localised repairs would do the job.

Nevertheless, you decide what you would be comfortable asking for on a planning application. The following guidance may help you decide on the best strategy for you.

Timber sashes should not be removed for repair without consent. Talk to your local authority first.

The repair of windows: avoid the need for replacement

This is the easiest route for planning and guarantees the preservation of the existing windows. Like for like, repairs might not need a listed building consent, but you should check with your local authority. A practical approach is to ask a window repair company to come home and provide you with a quotation for the works needed. You should include that list of works as part of the conversation with your local authority. That will give the council certainty of what you intend to do.

  • General window maintenance: external joinery should be painted every three or five years, depending on their exposure to the sun and predominant winds. That way, the timber is protected from the weather. In most cases, water ingress is caused by the failure of putty (the paste that holds the glazing against the timber). Cracked and loose putty are indications that this needs to be renewed.
  • Timber repair: can be done to localised areas where the timber is rotten. There is no need to change the whole window, but just cut and replace the part in bad condition. Resin can also be used to cover cavities.
  • Draughtproofing: brush seals are very easy to install and make a massive difference in the thermal and acoustic performance. It allows for a smooth close/shut movement and stops air from flowing through.

Alternative to replacement in listed buildings:
Window repair + Secondary glazing

Secondary glazing is an accepted method for thermal and acoustic upgrades in listed buildings. Acoustically, it can perform better than double glazing, thanks to the air cavity created in between the existing and secondary glazing. An alternative to replacement can be the combination of repair to windows and additional secondary glazing. Rather than planning permission, a listed building consent might be required to install new secondary glazing.

  • Where there is currently outdated secondary glazing: it could be upgraded without the need for listed building consent.
  • The conservation officer might request a listed building consent if there is no precedent of secondary glazing in the building.
  • Slim aluminium secondary glazing should fit behind the window frame. 
  • Double-glazed secondary glazing is possible. But because of its weight, it would be a casement window.
Repair and secondary glazing avoids replacement of window in listed building
Details sash window with secondary glazing avoids replacement of window in listed building
With the right product and design, secondary glazing can become barely invisible.

Replacement of the glazing rather than windows

Adapting the existing sash windows to add double glazing could be considered, but it is not always possible. It depends on the space allowed by the section of the glazing bars. A measured survey will help you to assess if this is possible with your windows.

  • This could be an expensive exercise, and you should consider it only following a detailed analysis of your architect.

  • In this case, you could maximise the reuse of the existing sashes while achieving a thermal and acoustic upgrade with no need for secondary glazing.

Complete replacement of listed windows

This route is riskier, in terms of planning, especially for windows on the main façade. A precedent of replacement of windows on houses of similar style in your street would help assessing the risk of your application.

  • The proposal could consider new sashes rather than the complete window replacement. This way, the main window frame is not removed, saving damage to the walls.
  • Replacement of full windows is damaging as the existing sash box should be removed from the wall affecting plaster, architraves, etc.
  • Replacement of full windows is unjustified unless they appear beyond repair.
  • Of the shelf, new sashes with double glazing are deeper than your current windows and would not work within the space available. Bespoke might be designed to suit to some extent.


The solution for the replacement or repair of windows will vary for each historic building. Is it listed? Is it in a conservation area? You should find the best solution for you and your building. Consult specialists to understand the condition of your windows fully. Remember, you can achieve improvement with repairs and localised interventions. This might also be the most cost-effective solution. If in doubt, consult your local authority before carrying out any work.

Still not sure what you should do with your windows? Contact me via email or book a free 15 minutes consultation.