Seen a corner of glass in someone else’s extension and started dreaming about one of your own? Corner glazing can transform a room, bringing in more natural light, opening up views and creating a striking architectural feature. But getting it right takes more thought than simply adding another window.
Compared with other types of windows, corner windows are more complex and raise a few important questions. What type of glass should you choose? How will you ventilate the room? Should the glazing be fixed or opening? And how will the design affect structure, privacy and cost?
We asked the experts what you need to know before committing to a corner window, including where they work best, what to consider when specifying one and how to make the most of the light and views they can bring to a home.
What are the benefits of corner windows?
"Corner windows can completely change the feel of a room," explains Allan Reid, uPVC specialist and Founder of Art Windows and Doors. "They bring in loads of natural light and can make the most of a nice garden view, so they work particularly well in extensions, open-plan spaces and rooms that look out onto the outdoors."
Adam Randall, co-founder of Fluid Glass, agrees, adding: "Where homeowners need to bring extra light into a dark space (often the kitchen), a corner window allows light to flood in from two sides and keeps the room bright all day rather than for a couple of hours."
Expanded views are another obvious draw. "If the best bit of your garden, a big old tree or a long view sits off the corner of the room rather than straight ahead, a corner window is ideal," Adam explains. "That's why we see frequently see them on rear extensions to terraces and semis, on garden rooms, and on upstairs bedrooms."
Allan Reid is the founder of Art Windows and Doors, a uPVC window and door specialist. He works with self-builders and renovators across the UK, helping homeowners choose the right glazing for their projects.
Adam Randall is co-founder of Fluid Glass, a UK structural and architectural glazing company. Since 2022, he has helped design and deliver bespoke glazing for architects, developers and homeowners.
Which types of home suit corner windows, and when should you avoid them?
Corner windows are a natural fit for contemporary new builds, where clean lines and uninterrupted glass are part and parcel of the look. But don't assume you need a brand new house to pull one off. A corner window as part of a glass extension can look just as striking on a period property, giving you a sharp contrast against a traditional façade.
Terraced and semi-detached houses are where Adam Randall sees corner windows most often, usually tucked into the back of a rear extension. These are the spaces with the most to gain – like a dining room crying out for more light or a garden room with a view worth framing.
Of course, not every property is suited to one. According to Adam, a tight urban plot "where the corner would look straight into a neighbour's property" would not be appropriate. Nor would a house where the structure can't take it without a chunky beam, or a post set back in the room. "At that point you've paid for the frameless look and lost it," he says.
Similarly, if you live in a conservation area, it's worth checking with your local planning authority or architect before you get your hopes up, as alterations like this can be restricted.
Frameless or framed corner glazing?
What to know about frameless options
The appeal of a frameless glass corner is easy to understand. “A frameless corner wins on one thing – the view – and on the right room that's worth everything,” says Adam Randall. With no post at the corner, you get the uninterrupted expanse of glass that many people picture when they think of corner glazing.
But frameless doesn't necessarily mean better. Removing the post doesn't remove the need for structural support, it just means that support has to be provided elsewhere.
“The building still needs to be supported around the glass, so the structure has to be properly planned,” says Allan Reid. This could mean steelwork or another form of support, depending on the project. The architect, structural engineer and glazing company should agree on the solution early in the design process. Leave it too late and you could end up with design changes and extra costs.
When does a framed corner make more sense?
A framed corner can be the more practical option in demanding locations. On an exposed site, such as a coastal or hilltop property, or on an upper floor, a slim post can provide the extra support needed to deal with wind loads. It can also be a better solution where the glass is particularly tall (above around 3m, for example).
There are some practical benefits, too. Framed corners are more forgiving of small differences in how the building is constructed, and replacing the glass in future is generally more straightforward
The difference in costs
Frameless glazing is typically more expensive than a framed corner of the same size and Adam suggests allowing around 30-40% more for the glazing itself.
The extra cost comes from several areas. The glass may need to be larger, thicker or laminated, with polished edges and manufactured to very tight tolerances so the two panes meet neatly at the corner. You'll also need the structural steel that replaces the post, plus a structural silicone joint between the panes.
Site access can add to the bill, too. Large fixed panes may need a crane to install them, which can be particularly costly on a terraced street if it means hiring the crane for a day and arranging a road closure.
The good news is that the extra cost isn't necessarily reflected in how the window performs once it's installed. “What doesn't cost more is living with it,” says Adam. He says to expect the “same U-values, same guarantees, and no moving parts to go wrong”.
Adam's advice when comparing quotes is simple: make sure the structural steel is included in both the frameless and framed options.
What type of glass do you need for a corner window?
According to Allan Reid, the right type of glass for your corner window will depend on your property. So, before you specify anything, he suggests thinking about how energy efficient the glass needs to be, how safe it will be and how much sun the room gets. "Things like low-emissivity coatings and safety glazing may all be worth considering," he says. "It's much better to get this right at the design stage than try to fix problems once the windows are in."
With so much glass meeting in one corner, the coating is where Adam Randall would start: "We'd always recommend solar-control glass (a neutral coating – you won't see a tint) that blocks the appropriate amount of heat," he says.
What about privacy with corner windows?
A room with glass on two sides can feel exposed, particularly if it faces a neighbour, footpath or somewhere people regularly pass by, says Allan Reid. “I’d recommend checking the view from outside as well as inside before deciding on the size and position of the glazing,” he adds. Blinds, curtains or privacy glass can help, but they may compromise the open feel you wanted, so it’s worth thinking about privacy before the work starts.
Being overlooked may be less of an issue than you expect, says Adam Randall, as corner windows are often fitted to extensions that sit forward of a neighbour’s second floor, giving the room some natural privacy. If you do need more screening, made-to-measure shutters can be fitted to corner windows. Ashley Weight, co-founder of ShuttersUp, says tier-on-tier shutters “allow views across the upper area of your window whilst maintaining privacy in the lower area”.
Ashley Weight – known to his team as ‘Mr Shutters’ – is a co-founder of ShuttersUp. Having joined the industry at 17, he's worked on every part of the process, from manufacturing through to installation.
How do you prevent a corner window from overheating?
"Large corner windows can make a room feel bright and spacious, but you do need to think about how the room will stay cool," warns Allan. "If there's lots of glass and not much ventilation, the space can get uncomfortably hot, particularly during the summer."
Orientation is the first thing to think about. "A corner has two faces – and a south face and a west face catch the sun at different times, so the room is being loaded for longer than a single window would be," explains Adam Randall. As a general rule, north- and east-facing corners are less prone to overheating, since they get less direct, high-intensity sun than a south- or west-facing corner.
This is where the solar control glass coating discussed earlier comes back into play. Adam recommends asking your glazier for a 70/35 specification, meaning the glass lets in 70% of natural daylight but only 35% of the sun's heat, giving you a bright room without the full thermal load of an uncoated pane.
Shading inside the room is another option. Ashley Weight says closed shutters can help reduce solar heat gain, and their adjustable louvres let you control light and airflow, "helping to keep rooms cool, shaded and naturally ventilated".
Should a corner window open or stay closed?
Whether a corner window should open depends largely on the house design, the space available and how you want to use the room, says Adam Randall. The architects he works with typically specify one of three set-ups:
A fixed glass corner: Best suited to a space for relaxing and enjoying the view. It offers the best thermal and weather performance, as well as the cleanest lines.
An opening corner: This brings in light from two aspects while allowing fresh air in and, in some configurations, access to the outside. To walk out through the corner itself, however, requires a sliding door with an open-corner configuration – a door system in its own right, rather than a frameless corner that simply opens.
A combination of the two: A fixed glass corner provides the view, while a minimal sliding door elsewhere in the room provides access and ventilation.
Whichever option you choose, ventilation needs to be considered. A corner window alone won't provide the same cross-ventilation as windows on two separate walls. Adam says rear extensions often combine corner glazing with a minimal sliding door or an opening rooflight, which he says, “does more for a hot afternoon than two windows on opposite walls ever did – warm air goes up and out and pulls fresh air in behind it.”
For a fuller picture of what your project might cost, see our guide to glass extension costs, or try our extension cost calculator to get a ballpark figure for your own home.
