21st Century Manufacturing & Performance

At Roseview we do things differently. We take the most traditional of window styles – quintessentially British sash windows – and enhance them with 21st century manufacturing and performance. The result is a thoroughly modern, energy efficient window that maintains all the classic style and elegance of its period counterpart.

We’re renowned for innovation, product excellence and staying one step ahead of the game, and we’re proud of the reputation that the Roseview and Rose Collection names have earned. It’s the result of more than 40 years of dedication, knowledge, experience and independence.

Sash Windows

Sash windows have been an important part of British architectural heritage since the late 17th century. Initially only within the reach of the richest gentry, sash windows took off in the regency period, becoming a staple part of Georgian architecture. 

Huge sash windows, set back from the face of the building to protect them from the weather, and featuring the classic six-over-six or nine-over-nine bar designs, were all the rage in Georgian Britain. Because they weren’t hinged they could be much larger than the casement windows of the time, and by opening both sashes half way they provided better ventilation and air circulation – important factors for health at the time.

While the original design of sash windows remained largely unchanged, ever-improving glass technology allowed for larger panes. As a result Victorian sash windows featured fewer astragal bars – often using just one vertical bar per sash. Window sizes started to shrink, to match the less grand architecture of the time. 

Beyond that Edwardian windows didn’t need bars at all, but often included them – in increasingly ambitious designs – purely as a decorative feature. Later in the 20th century sash windows started to fall out of favour, partly through fashion and partly through the need for cheaper, simpler casement windows. However, this trend started to reverse in the late 20th century as more emphasis was put on conservation and architectural heritage.

Today sash windows are popular again, but in a format that provides all the charm and elegance of the classic sash window, but with the benefits of modern performance built-in.

225 Projecting


Modern sash windows are a high-tech affair, using modern computer-controlled cutting and machining to ensure precision and consistency. But windows built entirely by machine lack the finesse and craftsmanship of traditional windows. So a carefully balanced mix of new and old is required.

If you ever visit our 50,000 square foot factory in Olney (which you’re more than welcome to do – just give us a call to arrange a visit!), we think you’ll be surprised by the sheer scale of the operation. 

We have two state-of the art sash window machining centres, plus three bespoke CNC millers, all dedicated to ensuring that every cut and milling process is clean, accurate and consistent. You need this as the foundation for a high-quality sash window. But once profiles are cut, machined and ready for assembly, the emphasis switches to hand built. There’s no substitute for experienced, dedicated staff when it comes to making sure that every window is built properly; that joints are tight and square, sashes run smoothly, glass is glazed properly and astragal bars applied accurately.

Underpinning all of this is state-of the art software and product scanning that tracks every part and window through the factory, onto delivery vehicles and into our customers’ hands, ensuring traceability at every step of the process.

Modern sash windows are a careful mix of classic style and modern performance. Manufacturing those windows follows the same principle: a mix of state-of the art technology with traditional, hand-crafted, joinery-style finesse. We call it #TraditionRedefined.

Trade Glaze Sash Windows


When designing and manufacturing classic sash windows, subtle details make all the difference. They take a standard modern window and elevate it to full traditional and conservation-grade authenticity. 

We’ve been dedicated to manufacturing sash windows for more than forty years. It takes that level of focus, knowledge and experience to find new and better ways of replicating classic features without compromising modern performance. One of the first things you learn is that it’s not just what you add to a window, what you take away is just as important.

Since 1985 we’ve been developing ways of introducing classic features to modern windows. The following are just some of the features that Roseview has developed, and which – in many cases – remain unique to us.

Trickle Vent In Head
seahorse sash horn sash windows

Seahorse Sash Horn

Roseview launched the first true run-through sash horn many years ago. It was unique in that it didn’t use an unsightly wraparound cap that instantly identified it as uPVC. Since then we’ve taken that further, to the point where we’re the only uPVC sash window manufacturer that can offer seamless horns in different designs – our latest being the ultra-authentic ‘seahorse’ horn.

Seamless Technology

Typically uPVC windows are easy to spot because of their caps, joins and unnatural shadow lines. We develop seamless technology to allow us to manufacture windows that look exactly like solid timber. Sometimes it’s not what you add, it’s what you take away.

Astragal Bar Carrier

A key feature of sash windows is their astragal bars. On modern windows these bars are usually fixed on the glass using a mixture of tape and clips. Not only can these be visible behind the bars, they aren’t particularly secure. That’s why we developed our own system, using a solid, full-length aluminium carrier that provides a rock-solid join between the bars and glass.

low u values with ThermoVFlex


The nature of sash windows means that they will never seal as tightly as compression-based casement windows, meaning that they can’t reach the same peak levels of energy efficiency. However, our latest development allows us to build sash windows with an unrivalled u-value of 1.2 w/m2K, without the need for triple or vacuum glazing (both of which have serious shortcomings and limitations).

Chalk Textured Foil

Simple woodgrain finishes provide an approximation of painted timber. Our textured chalk foil option both looks and feels like a true painted timber finish.


Chamber Filler

One of the biggest giveaways on a uPVC sash window is the visible external balance chambers, which the top sash slides up and down in. Our unique two-part chamber filler profile fills this gap without interfering with the sash sliding.

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Ultimate Rose
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