Owners are always encouraged to seek to repair and where possible reinstate original features. Because many of the houses are within terraces, examples of original detailing can often be found on neighbouring properties and these can be used to recreate the original appearance of the house (although it is important to ensure that they belong to the same terrace grouping and you do not copy a detail that was not original to the house).
When considering upgrading original windows for thermal efficiency and or replacement because they are in part rotten, it is worth noting that Victorian pine is generally of a much higher quality than modern timber because the timber was grown for longer therefore has a much tighter grain and is more resinous, making it more resistant to rot. It is therefore always preferable to repair existing windows.
The thermal performance can be significantly improved by correctly balancing the window and installing draft strips or by installing secondary glazing. If windows do need to be replaced, the slimlite glazing system now allows for new double glazed sash frames to be installed inside existing sash boxes so that they do not have to be removed (therefore keeping the original high grade timber, avoiding waste).
If the materials and detailing of the window remain exactly the same in terms of the external appearance through only replacing the sash and not the sash box then there is no requirement to apply for planning permission as this will be considered a repair. However, the glazing pattern must replicate the original design.
Changing the design of the window will always require planning permission, although where it is proposed to change modern casement windows it is likely to be advantageous. It is important to remember that these planning applications will be free of charge.
The most important feature of the sash window is that it slides up and down (rather than being outward opening like the more modern windows) and that the window is set behind the ‘reveal’ of the brickwork. More modern windows that open outwards break up the architectural unity of traditional terraces.
Windows made out of uPVC and aluminium windows appear ‘chunky’ and untraditional and are often poorly fitted, looking out of place in historic areas and are unlikely to be acceptable. However as described above, the manufacturing of timber double glazed windows has significantly improved with ‘slimlite’ timber double glazing.
With regard to roofs, it is always preferable to locate roof lights and solar panels on rear roof slopes where they are not visible from the street. Conservation roof lights are available that have a lower profile so do not stand proud of the roof. Flush solar thermal panels (for water heating) rather than tubes are now also available that fit into the roof rather than proud of the roof, therefore reducing the overall impact on the streetscene. For slates roofs a new innovation designed for listed buildings and conservation areas are ‘solar slates’.