Listed Buildings and Windows

[A successful new timber sash window in a new development]

Windows are an very important part of a building’s history and can be invaluable to our understanding of historic properties. 

Above all, windows are a key part of the architectural composition of any building, and help us to establish the character of a house or building and sometimes a whole area.

Recently, there has unfortunately been an increase in window replacements in Listed Buildings with modern materials and mass produced windows in wood, PVC and metal. The result of this is that it has not only led to the destruction of valuable historic assets but can also greatly reduce the value of an individual property. The market now values period prope

rties which have not been modernised, in a recent television poll PVC windows in period properties were cited as one of the top 10 “improvements” that could substantially reduce the value of your home.

Do I need consent?

You need to apply for Listed Building Consent when:

• The windows are to be replaced with a new style of window, even if replacing unsuitable frames with more acceptable ones or
• There is a change in the materials used for the frames or
• There is a change in the type of glazing, e.g. single glazing to double glazing or
• If you wish to repaint existing windows a different colour to the existing or
• If you are proposing to reglaze involving the loss of original glass (particularly if you are fortunate to have original leaded or crown glass) Depending on the amount of works proposed the following may require listed building consent –
• Replace your windows even if it is on a like for like basis
• Repair and upgrade your windows

You need to apply for Building Regulations Approval when:

• Existing windows and doors are replaced (when more than 50% of the window or door is glazed)
• When new door and window openings are formed

Any listed building consent or building regulation approval required should be gained before work starts. If consent is not given and works are under way then you may be committing a criminal offence and may then be subject to enforcement action and/or penalties. It would also advisable to gain listed building consent and building regulations approval even at the planning stage and before ordering the windows in case any alterations are required by the council. Most reputable window companies will understand the need for these consents and should be able to advise you accordingly.

What replacement windows should I use?

Replacing original windows

The best option from a conservation point of view if your property retains its original windows is simply to have them repaired. Not only will this retain the historical integrity of the building it may also work out much cheaper than replacing them.  

If the existing windows are original or of special architectural interest but beyond repair then a specially made like-for-like replacement is the best alternative including like-for-like glazing.

If your reason for considering replacement windows is for draught proofing or thermal or noise insulation there are a number of ways of reducing heat loss and reducing noise through historic windows including secondary glazing and weather stripping.

Replacing modern windows

If you are replacing modern windows then you should seek to use windows which would have been used originally in the building. To find out which windows would be best for your property:

Try to find photographs or sketches with the original windows shown.
Look at similar properties to your own to see the style of window used.
Reputable window companies and agents should be able to advise you on the appropriate window style. A traditional timber sash window
If your still unsure contact the Conservation Officer who should be able to advise you on the most appropriate replacements.

Building Regulations now require that the energy conservation levels of the existing building are at least maintained, if not improved. Timber windows should be painted as they have been traditionally, normally white but other colours can be appropriate including black and shades of blue, green and grey. The replacement of modern windows in a listed building still requires Listed Building Consent and Building Regulation approval even if you are replacing them with more sympathetically designed windows.

What window replacements should I avoid?

With historic windows detail is of paramount importance. Windows using inappropriate modern materials should be avoided for example:

PVCu or plastic windows – the glazing bars are normally too thick and not detailed enough for historic buildings. Mouldings and mitre detailing is usually crude and frame sizes excessive and out of proportion. The visual affect of shiny modern plastic is also out of keeping with more traditional materials.  
Steel or Aluminium windows – again the modern appearance and detailing of these windows is incongruous with the historic fabric of most listed buildings. However these windows may be appropriate if your property is a more modern, many 20th Century listed building have used this type of window frame.
Mass produced modern style timber windows – as with the PVCu windows glazing bars are normally too thick without detailed mouldings which are important to retain the character of the property.
Applied glazing bars whether lead or timber - Traditionally glazing bars are part of the windows structure and historically small panes of glass were used as producing large sheets of glass was not technically possible. Replacement windows which use applied bars are historically incorrect and visually unsuccessful.
Double glazed windows – If your windows are not already double-glazed and this is the case in the vast majority of listed buildings, then double-glazing is unlikely to be appropriate over single-glazing as the size of glazing bars required is not consistent with historical glazing
Sealed units - In highly detailed sash and casement windows sealed units are unlikely to be appropriate as they cannot achieve the same level of detail as traditional windows.

What windows should I use in my new extension to my listed building?

Normally the best option for use in extensions is to use windows that match the existing house. However sometimes well designed contemporary extensions can work just as well on listed buildings especially if large amounts of glazing are proposed. You are advised to contact the conservation officer if you are considering extending your listed property and they will be happy to discuss window options as well as any other issues with you. Please note that all extensions to listed buildings require listed building consent, building regulation approval and may require planning permission.

[The window on the left is an example of a poor modern timber replacement]

Building Regulations and windows in listed buildings

Under Building Regulations all new and replacement windows require Building Regulation Consent. This can be done under either a building notice or a full plans application. There can be some apparent conflict between the building regulation requirements and listed building requirements, normally in terms of the use of single glazing. However if both the conservation officer and building control officer are consulted early on in the process these differences can normally be resolved.

In terms of replacing the windows within the listed building itself there is some flexibility under Building Regulations in terms of the use of single glazing and impact on heat loss in historic buildings. If there is conservation officer support for the use of single glazing over double glazing then the building regulations can be relaxed. In a scheme involving replacement windows and general refurbishment work it may be necessary to seek opportunities to improve sympathetically the insulation levels in other areas affected by the overall project. In all cases the long term integrity of the fabric of the listed building and protection of our heritage assets will remain as relevant factors.

The use of single glazing in extensions can be a little more problematic; it is however possible to fit single glazing in extensions and comply with Building Regulations. This depends on a number of factors including the size of the extension, the amount of glazing proposed, and the extent of other insulation. You are strongly advised to contact both the building control department and the conservation officer to discuss these issues early in the process.