The National Heritage List for England estimates that there are around 500,000 listed buildings currently in the country, with a listed building being anything from a place of worship to a row of terraced houses. Their status plays an essential role in protecting England’s rich architectural history, giving us insight into the many beautiful buildings that have been constructed through the ages.
When it comes to the restoration of windows in grade-listed buildings there are a number of challenges that need to be overcome. Like many other materials used in these types of properties, they can usually only be repaired rather than replaced to retain the original character. To help you learn more, our grade-listed windows restoration guide covers everything you need to know.
What is classed as a listed building?
When a building is ‘listed’ it is done so to celebrate and mark its special architectural and historic importance. Once it becomes a listed building it then falls into a protected category that means only certain alterations can be made to ensure the original look and feel is maintained wherever possible. As a result, there is a number of limitations on what sort of work can be carried out on a listed building.
In general, any building built before 1700 that is still standing and close to its original condition is likely to receive listed status. This also applies to buildings constructed up to 1850. Buildings constructed after World War II can also be listed, although they are put under closer scrutiny.
A building will either be classed as Grade I, Grade II, or Grade II* – the star annotation denotes the building is of more special interest than other Grade II-listed buildings.
What windows repairs can you carry out in a listed building?
Permission is required for extensive work, but for minor restoration repairs such as painting and draught sealing planning permission usually doesn’t have to be secured. As long as there are no replacements or major works carried out timber frames can be repaired, while new glazing can be installed if it is a similar thickness to the original. To be safe always check with the local authority before making any changes to windows on a listed property.
When is the best time to restore listed windows?
Like any normal windows, there are always developing signs that will indicate the windows need to be restored. This includes things such as:
- Changes to the structure
If there is difficulty in opening or closing the windows, it is likely they have slowly moved over time. This will eventually lead to damage being caused to the frames, so this needs to be addressed in order for the right level of repair and restoration to be carried out.
- Pointing failure
Window pointing is the finish seen between the stone or bricks. When this starts to fail a larger quantity of moisture will seep into the window frames. Over time this leads to draughts and lower energy efficiency in the property. The earlier this is fixed, the less costly it will be.
- Wet rot
This needs to be dealt with as quickly as possible to avoid it becoming a larger problem. Signs include flaking and bubbling paint, gaps in the joints, peeling and degrading paint. Remove standing water that is on the window sill as this can seep into the wood and lead to the rotting of the timber.
When should sash windows be repaired?
Sometimes it isn’t the window frame itself that is causing the issue. The mechanisms inside a sash window also need to be maintained and repaired because just as with any other window they will deteriorate without proper care. This can include things like:
- Frayed cords
If there are frayed cords it is usually a sign the sash window requires renovation. It could also be a reason for the window not opening as the cord becomes frayed due to the pressure coming from the bottom sash.
- Seized pulleys
Sticking windows can be a result of loose joints, overpainting, or a seized pulley. This prevents the window from opening and will require lubrication to loosen it up again.
- Heavy glass
Incorrect glass installed into a sash window can make it difficult to open. This is often due to glazing that is too heavy being installed, so the rest of the window is unable to operate correctly.
- Swollen frames
When water is allowed to get into the frames (it may need to be re-varnished for protection) water gets inside to swell the frames which prevent the window mechanisms from doing their job.
General repairs on grade-listed sash windows
It is to be expected that over time grade-listed sash windows will need to be repaired due to general wear and tear.
If you are replacing things such as broken glass, lubricating stiff windows, repainting surfaces, repointing, or fitting new sash cords, it is unlikely you will need to get planning permission. This is because they could be viewed as minor faults that will not alter the original character of the building.
However, you must ensure the glazing matches or is as close as possible to the original. And it is always advisable to check with the local authority before starting any work, regardless of how minor the repair work may be.
Is it better to repair or replace listed windows?
It is always preferred that historic windows of interest are repaired and maintained wherever possible, rather than replacing them. Replacements should always be seen as the last resort. In most cases a professional and experienced restoration company should be able to restore the window to a good level, avoiding the need to replace them.
Houses that are listed or in an Article 4 Direction will likely require permission to make any changes to the windows, whereas with like-for-like repairs you will not usually need to get consent from the local authority. However, this should also be checked, just in case.
Can grade-listed properties be double-glazed?
One of the main issues facing grade listed properties is energy efficiency, as they were originally built some time before recent technology enabled us to manage indoor energy more effectively.
Double glazing is one of the best ways to reduce heat loss in a grade listed property, although care must be taken over the type installed. uPVC windows are not acceptable on these types of buildings as they will instantly alter the architectural character.
However, installing slim profile double glazed units that reflect the original heritage of the building is an acceptable alternative. The best option for this is Fineo glass. In particular, Fineo 8 can be retrofitted into existing single sash windows without affecting the historical value, as the thickness of the glass is only 7.7mm.
Before slim profile, double glazing can be installed drawings usually have to be provided to the local authority so they can check they match the original windows. The regulatory guidelines around this tend to be quite complicated, but working with a company that has in-depth knowledge and experience with working on grade-listed buildings should make all the difference.
Is double glazing allowed in a conservation area?
If the property is located in a conservation area then it should be less complicated to make the required changes. This is mostly because slim profile double glazing is not required for properties in a conservation area, and a single double glaze unit can be installed.
However, planning permission could be needed if the property is subject to Article 4 Direction, or is situated above a shop. Also, if the window is not facing the street there is a chance that planning permission may not be a requirement. The best thing, as always, is to err on the side of caution by checking with the local authority before any work begins.
Can you draught-proof windows on grade listed properties?
One of the best ways to reduce energy usage on historic windows is to ensure they are draught proofed. It will also help with reducing noise, rattling, and dust – all without making barely any change to the appearance of the building.
Windows in grade listed buildings can be upgraded in this manner with a number of weather-stripping systems available to use. This can include things such as parting beads and those that include brush seals of woven polypropylene pile.
Other solutions feature rout slots in the side of the frames and meeting rails to create a push-fit, V strips, flexible Z or different shaped brushes, which are not visible once the window has been closed.
Before draught-proofing takes place any required repairs should first be carried out, so make sure to identify these before work begins. Even the most straightforward of repairs can have an effect on air infiltration and heat loss, which will make the draught-proofing process much faster and easier to complete.
When choosing draught-proofing products, you should try to consider the following:
- How big are the gaps in the window you want to seal?
- How variable is the width of the gaps in the window?
- Does the draught-strip need to be hidden – even when you open the window?
- How much allowance has to be given for seasonal contraction and expansion?
- Should the draught-strip be the same colour as the frame? (painting it should be avoided)
You will also need to ensure the draught-strip meets regulatory standards. Products that meet BS7386 are suitable for this purpose, as they will offer the sort of performance levels required.