How To Add Glass Extensions To Listed Buildings: All You Need To Know

Are you thinking about adding a glass extension to your listed building but are worried about planning restrictions spoiling your fun? Read on to find out exactly what you need to do to make your dreams of extending your home a reality…

Glass extensions to listed buildings are becoming increasingly popular and it’s not hard to see why; adding a glass extension to your home is the perfect way to create a larger light-filled space which can be used in many different ways. Glass extensions are often the go-to on contemporary homes, but can also be stunning additions to older homes in a way that a matching extension might not be. However, if you are lucky enough to live in one of the UK’s 500,000 listed buildings, you might find you have to plan your glass extension with a little extra thought.

A building is given listed status when it is deemed to be of architectural or historical significance. The listed status acts to protect the building from being altered and it is illegal to make changes without approval first. Since approval is granted by your local authority’s conservation officer, the rules around what can and can’t be done to a listed building are considered to be somewhat subjective. This means it always pays to consult a local professional (be it the conservation officer or an architect/designer with experience of the local planning authority).

So, if you are planning on adding a glass extension to your listed building, below are some key questions you need to consider.

What style of property is it?

There are dozens of styles of property that receive listed status. However, it is safe to say that the style of glass extension which is aesthetically acceptable on a Georgian townhouse might be totally different to that on an oak-framed barn conversion. It is essential to take this into consideration and, if possible, find examples of extensions to properties similar to your own.

Why was the property listed?

It is important to know why the property was listed. Was it a feature of the building or was it primarily because it was in a block of housing in a conservation area, where the property didn’t have any specific individual features but was deemed important to the area as a whole? If there are features in the listing, then it is essential that the proposed work doesn’t cover up or interfere with those features. Further information on properties in conservation areas can be found here.

How large is the property and how large is the proposed extension

A basic rule of thumb is that the proposed new work should be subservient and proportionate to the size of the existing property. A significantly larger extension is unlikely to be approved on a small listed property.

Is the proposed work to be attached to the original listed building or a more recently built extension?

A proposed glass extension or oak conservatory is more likely to be approved if constructed off an extension, rather than off the original listed building. In some cases, the proposed new work will only be approved if accessed via a small glass link, so that the extension itself is independent of, and not fixed to, the wall of the house. There do appear to be some very subjective restrictions such as maintaining a 300mm-wide glass panel between the new work and the house, so check with your local conservation officer before design work takes place. 

Will the proposed work cover any interesting historical features?

If the answer to the above question is ‘yes’ then don’t even consider it. However, one must first ask ‘what is an interesting historical feature?’ Some conservationists will claim the whole wall of a house is of historical significance, so always get clear and precise definitions ahead of works.

Will the proposed work be visible from a public highway or footpath?

The fact that none of the proposed work will be visible from anywhere, by anyone, except you, doesn’t mean that there will be no objection to the work by your conservation officer. However, low visibility of the additional structure may help when considered alongside other factors.

Will the proposed extension affect my neighbours?

Any development work you carry out on your home has the potential to affect your neighbours in one way or another. An extension to your home may block some light from their property or obstruct their view. You need to be aware of what the law says in such cases and what rights your neighbours have over you. For example, if your extension significantly overshadows your neighbour’s window and the window has been there for 20 years or more, you may affect your neighbour’s ‘right to light’ and be taken to court. 

Informing your neighbours about any work you have planned before it goes ahead is always recommended, as they will naturally have concerns about how any development work to your property might affect them. Even things like heavy equipment temporarily blocking the road or noise pollution from the build should be mentioned beforehand so they can plan ahead if necessary. You should also consider whether or not you (or your builders) will need access to your neighbours’ property or garden to carry out some of the work and seek permission to do so beforehand. 

If there is something of particular concern to your neighbour, you may be able to change your plans so you are both happy with the outcome. If changing your plans is not possible, your neighbours will still appreciate being consulted; it helps to have them on your side when applying for planning permission! Remember, the local authority will consult your neighbours over your development plans anyway so it’s best to speak to them first.

Neighbour Consultation Scheme

If you are planning a large, single-storey rear extension to your home (between four and 8 metres for detached houses and between three and six metres for all other houses) you will be required to go through the Neighbour Consultation Scheme. This basically means that you will need to inform your local authority about your plans for an extension and they will then consult your neighbours to see if they have any objections to the proposed work. If they do, the local authority will make a decision regarding whether or not their objections reveal any impact on the amenity of the neighbouring properties, and if your development can go ahead or not as the case may be. 

Party Wall Agreements

When planning your glass extension, you may need to have a Party Wall Agreement written up between you and your neighbour. Put simply, it is a private agreement between both of you and has nothing to do with your local planning authority. You will need to have such an agreement put in place if your new extension is attached to your neighbour’s wall, built right up to the boundary or built within 3 metres of your neighbour’s house footings.

What materials have been used in the construction of the existing property?

This is an interesting question. In most cases it is safe to say that use of similar materials such as reclaimed bricks, slates or roof tiles, oak framed windows, vertical sliding sash or flush, conservation casement window styles will be conditions of approval. 

However, there is a movement requiring that the new extension is constructed of totally dissimilar material and appearance to demonstrate that it was not part of the existing structure. This is another reason why the use of a frameless glass structure is continuing to grow in popularity. That said, it helps to merge the old with the new by taking aesthetic cues from the existing structure to design the new extension.

Why do you want an extension?

This question can be asked of any home extension but becomes more important when considering glass extensions to listed buildings. Firstly, it should be noted that work on listed properties can cost upwards of XX per cent more than the equivalent work carried out on non-status properties. Secondly, clearly demonstrating a need can provide the necessary justification for adding a glass extension to your listed building. 

Leading to the question:

Is the amenity and the proposed work essential and the adequate function of the property?

In other words, does the property deserve the proposed amenity? If it can be demonstrated that the property – and not just you - deserve the proposed work to function properly as a home, it is more likely to be considered favourably by the local planning authority. 

But what does this mean?
A large home, with a disproportionately small kitchen, could justify a glass extension to the kitchen in order to provide a facility which is better suited and proportionate to the requirements of the home. Why? Well, it can be argued that the house requires the amenity to attract a buyer who can afford to live in, and fund, the costlier maintenance of a listed property. The Listed Property Owners Club is a great source of advice for anyone looking to have work done to their listed home and can help you understand this element of the argument for extensions further. ​

What style of Glass Extensions to Listed Buildings will be deemed acceptable?

There is no simple answer to this question, as, despite claims to the contrary, there is a deal of subjectivity demonstrated by conservation officers. Even within the same planning district, there will be differences amongst conservation officers and what they will approve.
So, which should you choose? Well, it will also come down to your personal taste and preferences, but you can get lots of ideas and inspiration for your build by researching examples of hardwood glazed extensions on listed properties. This will enable you to see the type of extensions which may have been added to homes similar to your own.

Window Frame Material

It is unlikely you will be allowed to use any material other than wood. Sometimes you can use aluminium, but it is extremely unlikely you will be able to use uPVC. Timber framed windows are usually more expensive, requiring flush frames with conservation casements and dummy casements on each of the fixed glazed areas. 

Oak glazed extensions are a popular choice as oak is an indigenous material which has been used for many centuries for window and door construction. It is often preferred by conservation officers and is thus a sound choice for glass extensions to listed buildings.

Whilst adding double glazing to the main house might be a no-no for listed buildings, it is important that the new glass extension is efficient at keeping the heat in on a cold day. Always specify double glazing to ensure heat loss is kept to a minimum. Equally, it is important that the glazing in the roof of the new work is efficient at keeping the heat out on a hot day, preferably using automatic opening roof vents to ensure any hot air in the interior can escape and create a cooling draught.

It’s also important to note that whilst hardwood glazed extensions – such as those built from oak – will require some maintenance, this should not put you off as an extension made from any material will require some upkeep to ensure it stays in pristine condition. Simply rubbing down the oak lightly with fine wire wool and applying a few coats of wood finish or paint will have it looking beautiful again for years to come.

Lastly - and this is extremely important - you need to consider how to filter light back into the room which will eventually be covered by the new work. Get this wrong and you’ll end up in a situation where the room behind has minimal natural light, making it dark and unappealing. 

What should Glass Extensions to Listed Buildings look like?

The design of the extension needs to be aesthetically pleasing and congruent with the design of your home. An oak-framed, tiled-roof garden room is unlikely to look right on a Georgian house and an orangery is equally unlikely to suit an oak converted barn. Whilst they sound the least exciting, a traditional conservatory has nearly always been of a lean-to, mono pitch design, and therefore often a safe and cost-effective solution for a listed building application.

It may also be that a gable or hipped roof oak conservatory or timber-framed garden room might be a more suitable solution. Hardwood orangeries may suit certain styles of listed property but in many cases are less likely to be approved.

Who can design Glass Extensions to Listed Buildings

The final recommendation is to take advice from a specialist wooden conservatory supplier with a proven track record of obtaining Listed Building Consents. A reputable company will have experienced designers who can provide 3D visuals of your building project as well as a support team capable of dealing with your planning permission, listed building and building control applications where required.
More information on applying for listed building consent can be read here.

With over 40 per cent of our oak extensions in the last 10 years being added to listed buildings, Richmond Oak is well placed to provide specialist advice regarding additions to these special homes. 

Do you have a question? Request a callback with our design team who will contact you to talk through your project