Claudia Ludwig · January 12, 2023

What To Consider When Adding a Glass Extension to Your Home

Glass-based extensions are not new. There are reports of some fairly basic designs back in the 1600s, but they really took off in the Victorian era as glass became more widely available, the tax on glass was abolished and improvements in metal meant that designers had more scope to free their imaginations. Initially use was fairly limited to the growing of exotic plants and fruits coming back from warmer climes around the British Empire, but as that use has fallen away, other uses have surged forward. 

We now have garden rooms, conservatories, orangeries and other glass-based extensions in a variety of architectural styles. Clients generally want to add a glass extension to their home to create more space and bring more light into their homes.  It is a good way to increase the footprint of a home and improve the client’s enjoyment of a space, whilst also adding value to the property.  They are particularly popular in England and other Northern European countries where the summer is relatively short and clients get more out of a light filled but weather proof space than a large garden. 

A glass extension creates a light-filled space where the family can all gather at any time of the year. It draws the garden into the house.  It is also a multi-functional space – can be used for eating as well as for sitting, working etc.  Brightness in winter is one thing, but even in spring/summer it can be a great space for breakfast when it is too cold to sit outside, but you want to be among the flowers and enjoy the burst of energy a bit of sunlight can give.

What type of glass extension should you choose?

The architecture of the existing building and the intended use for the new glass-based construction are key factors to take into account when deciding which type of extension to go for. A client’s budget is another factor. A garden room which needs very limited foundations and is usually built from relatively cost-efficient materials can a much more budget friendly solution than an extension to the existing house where planning laws, foundations, isolation etc play a much larger role.

Another factor to consider is the aspect of the existing house and planned extension.  More or less glass may be appropriate depending on whether the extension is north or south facing, and in particular how much sun will fall upon the extension. Too much sun in the summer can make the extension uncomfortably hot. 

How overlooked the extension is may also be a factor – because the extension can be a goldfish bowl too if not well thought through, with neighbours (possibly slightly envious neighbours) able to keep an eye on your every movement. 

In my own home, I have added a large glass-based extension to the back of an Edwardian terrace house to create an open plan kitchen dining room. However, my clients have created conservatories to add space for a light filled playroom, garden rooms to finally have a quiet space to work from home or as a music room at the end of the garden, an orangery as a connection between two buildings and an indoor garden (there is nothing quite like orange blossom to brighten a winter morning), a glass covered courtyard with a water feature, or a lantern roofed separate building to house an indoor swimming pool.  These examples show that a glass-based extension can be a possibility whatever amount of space you have to work with. 

While adding a Victorian style conservatory onto a Victorian country house can be the right solution, it can often be more visually appealing to use a bold new style to create the extension rather than trying to blend it in with the original build. However, it will be important to enhance the connection with the existing building through the use of similar or complementary materials, whilst adding modern touches which bring joy to the eye or the touch. An extension to a Victorian terrace house for example may well be made from the same material – traditional clay bricks – but in a contemporary architectural style with glass sliding doors, sky lights or a green roof. 

What factors do you need to consider in terms of decorating?

While floor to ceiling sliding doors or windows will bring a lot of light into a space and allow for an easy flow between the indoors and outdoors, it restricts where you can place your furniture. If a client needs wall space to hang art, wants to create a window seat or needs extra space for kitchen cupboards, an extension with large but not full height windows and maybe limited to one or two walls rather than a wraparound glass extension will be more suited. 

Whether you choose a traditional conservatory or a contemporary glass extension, it is very important to consider insulation against heat in summer and cold in winter. This starts with the choice of glazing – double or triple glazing will provide much better insulation than single and glazing with integrated UV filter will keep out some of the heat and colour damage to furniture in summer. 

In addition, I always recommend to my clients to provide for blinds or curtains. For a contemporary glass extension, automated roller blinds which are recessed into the ceiling protect against the sun’s rays in the summer, but also add a background and cosiness in the darker months.

For a traditional glass conservatory at a client’s house in St John’s Wood, I have recently installed linen Roman blinds all around the 3 sides of glazing to make the space, which serves as a play and TV room for the children, feel more cosy and less overlooked at nighttime. 

In winter, sufficient heating will be important. Due to the glazing, radiators may be tricky and underfloor heating an appropriate choice. However, for a large glass-based extension underfloor heating alone may not be sufficient and will have to be combined with some trench heaters or similar. 

I also always think sound is an important factor with conservatories – they are often echo-filled.  People don’t think about the soft furnishings and other tools such as choice of flooring, window dressing, type of lighting etc to reduce that.

Another important thing to consider when planning an extension is lighting. If the glass extension has large sky lights for example traditional ceiling lights are trickier and may need to be integrated into the architecture.

Do you need planning permission?

An extension to an existing house may fall within permitted development and not require a planning permission. However, there are still building regulations to comply with. Furthermore, there are different rules for conservation areas and listed buildings. Before embarking on any construction works, owners should consult the local planning law and for any major construction works involve an architect and/or planning consultant. 

Glass based extensions can add some real character to your property as well as enhancing both your enjoyment and the value of it. But there are a number of pitfalls to avoid which makes having an experienced interior designer cast an eye over the designs so important. There is nothing worse than having a beautiful living space which you are unable to use at certain times of year through a lack of foresight in the design or building of your extension. 

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