Windows are one of the integral parts of a house. They go beyond their functionality; they can tell a story as well. Windows are well-known to regulate the weather to keep the draught or rain out; the windows got it literally covered. However, they do not only serve that purpose. They also carry a significant architectural history, especially if you live in a listed building. So, whether you own a listed building or are interested in the preservation of historic windows, read on and find all you need to know about it.

Listed buildings

Listed buildings are structures or areas of historical importance. These are not just for houses or buildings but may also pertain to certain structures such as bridges and monuments, or parts of your house such as your windows. As long as they are deemed historically significant, they can be a listed structure. Listed buildings or structures have special laws that protect them from unauthorized or improper handling, helping preserve its national heritage. Thus, any repairs, alterations, or demolitions are subject to scrutiny and approval from the local authority.

Listed buildings are classified according to their heritage significance, decided upon based on several criteria that consider it as a part of history. These are heritage values that serve as standards, based on its role in the development in the location’s architecture, the community, and so on.

Grade I

There are three grade classifications for listed buildings. Grade I is considered to be the highest grade, labelled as buildings of “exceptional interest.” This grade is also the rarest due to its high standard, comprising of around only 2.5% among all listed buildings recorded.

Grade II*

Grade II* is the second-highest rating, labelled as buildings of “particularly important buildings and of more than special interest.” Grade II* buildings comprise of around 5.8% of all listed buildings.

Grade II

Grade II is the lowest rating and is the most abundant among the three grade levels. They are labelled as buildings of “special interest, warranting every effort to preserve them.” They comprise the majority of the listed buildings, at around 90% of the overall recorded listed buildings. Chances are if you live in a listed building, it is of this grade.

To find out if you do live in a listed building, you may check out Historic England’s list here.

Listed building windows

Listed buildings are known for their historic significance, especially in architecture. This holds true in the structures that come along with the building. Windows also preserve a part of history, and these are part of what makes a listed property unique and valuable. In this section, we’ll focus more on the common types of windows in listed properties.

For a more extensive explanation on period windows, you may check out this PDF from Historic England.

Traditional windows in listed buildings

There are two common window styles used in heritage houses: (1) wooden sash windows and (2) cottage style windows. These windows have been on houses for long, and if you have one, then you might be looking at a period building.

Sash windows

Wooden sash windows have been present for more than three centuries; the earliest ones dated around the 1670s. They go very well with period buildings, often on Victorian or Georgian style houses. They are windows with glass panes divided by glazing bars and have “sashes” that may either be movable or stationary. Single-hung sash windows have the upper sash stationary while the lower sash is able to move up and down and double-hung sash windows have both upper and lower sash as movable parts.

Cottage style windows

Cottage style windows are also a popular pick, as its design is meant to be flush with the window frame, creating a simple look for the house. These are also common in period buildings. A usual problem with this type is that it usually suffers from warping due to moisture and heat from consistent exposure to changing weathers. However, modern solutions for warping wood are now available, so warping is now a rare occurrence.

Materials used for old windows

The material used for the window itself reflects the timeline of your property. This is why special rules are in order when making changes or repairs to listed structures, to ensure that the durability and longer-lasting structures will not be at the expense of the historical values.

Window frames

Frames of period windows are typically made from timber, a durable hardwood. In the medieval period, most of the windows were unglazed and were open, separated by either plain or moulded mullions, and taller windows further subdivided through transoms. This was because glass was rare and very expensive at the time. In turn, shutters made of timber or oiled fabric stretched over the frame were used for security and draught-proofing

Glass panes

Glass was mainly imported within the continent during the early medieval period, and thus was a very expensive fixture for windows. It was only popularized around the 17th century, when it was mass-produced, making it a common fitting on windows for homes. There are different types of glass used for windows such as broad glass, crown glass, and cylinder glass, among others. Crown glass is rare in the modern era but was widely used for windows until the 19th century.


Shutters were originally made for its functionality, preventing the entry of draught or intense light, and for privacy. As such, English buildings have internal shutters which are opened and closed from the inside. However, some shop fronts have their shutters as external features of their buildings. These are usually made of plain boards in the early designs but have since changed to frame and panel look, or a series of narrow leaves arranged in a column.


These fixtures can also be of interest as the evolution of windows can be seen through these fittings as well. The early 17th century had used iconic H- or HL- shaped hinges and spring catches made from wrought-iron. As sash windows were introduced, plenty of fixtures were present as well such as brass or hardwood pulleys, lead weights, and shutter hinges and knobs.

These materials are part of what make the property a listed building. The history that lies into its creation and evolution is a contribution to the architectural heritage of the building. If you live in an unlisted building and see these special features in some of your windows, you may want to consider having it checked, to see if it can make the list.

Importance of windows on listed buildings

Windows alone serve a purpose; it not only regulates the ventilation within your home but also gives it character. Its design contributes to the beauty of your home, consistent with the other features that are in it. In a listed building, the purpose of windows is elevated to a higher value. They do not just make your house a wonderful sight, they make it a part of history. It is exactly this that makes windows an interesting subject for restoration. The window itself is a piece of evidence that survived the test of time, the craftsmanship that even surpasses modern takes on architecture. If normal windows help build character, then period windows share the story through its overall design, materials, and the skill of the craftsman with the quality.

Doing work on windows

Having known the importance of period windows, we now find out how to possibly renew them. Listed properties have stricter rules than regular properties, especially when it comes to the alterations that will be executed on the existing structures. In this section, we learn more about the alterations that can be made in the preexisting structures of your listed building, especially on the windows.

You might also want to check out: Listed buildings: regulations and permissions for restoration


Permissions are in order when attempting to change the structures within your listed home. For starters, all buildings, listed or not, requires Planning Permission. This is especially required when making big alterations to your home. To find out if your work requires Planning Permission, you may follow this link. Listed buildings have another special consent needed, which is the Listed Building Consent. If the work will affect the structures that make it of special interest, then you will need to apply for this as well. Repairing using like-for-like materials would usually not need consent, but it is still best to contact your local planning authority or conservation officer to ensure that all requirements are met.

Repairing windows

Repairs are done to reinforce the structures that have been worn out through time, so that it may serve its intended function without having to replace it. Repairs should be paralleled with continuous maintenance to ensure that it will have longer use. As much as possible, repairs are to be done in-situ, or within the original place where the windows are, especially those attached to the building. For sashes and casements which can be removed, it can be brought to the workshop if needed. Before doing any work or removing any parts, it is critical to record all components of the windows to make sure that they go back the way they were. Repairs should be mainly done by experts to ensure proper handling, and here are some of the repairs that may be in place

  1. Timber cills tend to decay and should be replaced with durable hardwood
  2. Rotten wood should be cut off and spliced by new inserts
  3. Wood fillers based on wood dust with polyester or epoxy resin can be used to fill in gaps
  4. Rust from metal windows can be repaired by acid pickling or flame cleaning
  5. Metal windows can also be brought to a workshop to be grit- or shot-blasted and galvanized or zinc-sprayed
  6. Historic glass such as a crown or cylinder glass should be retained as much as possible, the putty should be softened through solvent paint strippers or heating

Making it energy-efficient

Old windows can be made to be energy-efficient without having to replace them. The size of the window is a big factor in the exchange of heat within your home. A room may feel draughty even when the window is sealed shut, and this may be due to gaps within the window structures. Several solutions can be done to prevent this from happening.

  • Draught-proofing is done by sealing the gaps around the windows. This is a cost-effective and least-intrusive work that can be done to prevent draughts.
  • Secondary glazing installs a ‘secondary’ or supplementary window system from inside the room to prevent draught through insulation, while still having access to the original windows.
  • Double- or triple-glazing uses multiple glass layers to reduce heat transfer through the glass, through an insulation layer between the gaps, which can either be evacuated or filled with an inert gas such as argon, krypton, or xenon.

Replacement windows

Replacement should always be treated as a last resort, although it may be possible to need one. In case of replacement, it is important that an accurate copy is made. This will include the whole profile of the window, from the form, detailing, to the operation of the window. Components are also to be accurately copied to ensure it retains its character. Many companies can provide bespoke windows of the exact production, and it is better to rely on them to do the work for you.

Repair over replacement

In working with period windows repair should always be prioritized over their replacement. It is through these components that the building is of special interest. Historic glass such as those of the crown type is now very rare and not manufactured to date, and so replacing would not bring the same quality and value to the old window. Details of the windows also show its timeline, through the evolution of workmanship and designs. The age, although the source of the problem, is also the reason it is very valuable and irreplaceable.

Period windows are one of the defining features of a listed property. It holds a part of history, not just with its character, but the materials and the craftsmanship that went with it. Period properties should be preserved as much as we can, in that way, we can also preserve a piece of history.

This article was written on behalf of Boulton & Boyce by Pieter Boyce. Pieter has an intense passion for English Architectural history and has been specialising in the conservation of original wooden windows and doors for decades. His exceptional knowledge of timber windows and doors, both listed or non-listed, is attributed to his hands-on approach to learning all aspects of the complete restoration of original features as well as having personally surveyed thousands of items throughout his long tenure as a head surveyor for one of the largest window and door restoration companies in the UK. He now runs a boutique wooden window and door consultancy and fervently champions the retention of original windows and doors. To learn more of Pieter’s services, visit his website at

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