The Genesis Vertical Sliding Window – A New Chapter

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When Bison Frames, the PVC-U window specialist received a request to provide windows that were destined for a grade II listed cottage, the company realised it could be on dangerous territory.  In providing a solution, the Yorkshire based company  looked long and hard at the existing vertical sliding sash window profiles supplied by Spectus Window Systems with a view to improving the vertical sliding window so that it would stand up to the scrutiny of the local planning officials.

The legislation and processes that have to be adhered to when trying to make alterations, however minor, to a listed property can be at best complex. The replacement of wooden vertical sash sliding windows to PVC-U, at Russet Cottage, an 1830s grade II listed building in the Beardwood area of Blackburn, was never going to be easy.  Planning officers and committee’s across the country are generally not receptive to PVC-U products when it comes to grade II listed properties.  As Martyn Haworth, director at Bison Frames explained: “When the project first came to light, we immediately knew we could be faced with some tricky situations.  There has been a lot in the press recently regarding certain councils reluctance to accept PVC-U on listed properties and so what we hoped for was a sympathetic council and planning officer.”


The process was arduous and a full planning application to Blackburn and Darwen Council had to be made, completing an application for “listed building consent for alterations, extensions or demolition of a listed building.” In the case of the cottage project, it was decided to involve the planning officer from the outset.

“Our client found that by involving the planning officer from the start he had access to the right information, such as what pointers to follow to gain permission and what grounds there were for a possible refusal,” said Martyn. “From an initial site meeting with the planning officer it was quickly established what could be done by following their guidelines so that the significance of the listed building would not be harmed.”

In the case of the Russett Cottage, Bison Frames discovered that the planning officer was not keen on the cruder detail of the jointing around the sash horns on the standard PVC VS window and also that a wood effect lamination was a must to replicate natural wood; a “shiny” PVC finish was a definite no.


The answer to the problematic sash window was provided by Bison Frames utilising the Spectus VS Window System.  The Yorkshire based company had been working on a brand new feature that would enhance the vertical sliding window and solve the issues surrounding the authentic look that the planning officer was demanding.   After much investment and design work the Genesis VS was born.

As Martin Althorpe, technical director at Spectus Window Systems explained: “In the early days of PVC-U windows the options were limited.  Frames were bulky and unattractive. Colour options were either white or poor quality replica wood effect. The Industry now offers slim, elegant frames in an infinite variety of styles, shapes and opening configurations as well as full colour palettes and wood effects.

The products on today’s market are on the whole far more sympathetic.  We wanted to develop a window system that would satisfy the aesthetic requirements of conservation areas and listed buildings.  With Bison Frames further investment theories have been put into practice, producing a phenomenal result in the process.  The Genesis window utilises timber jointing methods on all joints.  No longer are there any welded corners, the windows really do look like their timber ancestors.  Added to this the window has period appearance high security cam locks and sash buttons, run through sash horns and deep bottom sash rail as standard, providing the all-important authentic look to enhance any period property.”

Bison Frames have developed a new and unique joint on the vertical sliding window that works mechanically like on a timber window and is not welded in place.

Martin Althorpe continued: “As with all Spectus products, the vertical sliding window is extruded to BS EN 12608 and provides enhanced levels of resistance to weathering.  The company has attained BS EN ISO: 9001, BS EN ISO: 14001 and BS OHSAS: 18001 and the vertical sliding window has full kitemark accreditation and has also been BBA assessed.”


Seeing that the vertical sash window ticked all the boxes Bison’s client Mick Ramsden, welcomed a second visit to his Grade II listed home from the planning officer, who this time was able to view a sample of the new vertical sash window. Mick was also able to show the planning officer a standard welded vertical sliding window against the new mechanically jointed sliding window, and prove how it tackled some of the potential areas for rejection.

As Mick picks up the story: “After seeing the vertical sliding window first-hand, the planning officer suggested that the application be submitted. The quality of the window undoubtedly swung the decision as the application was passed for the reason it was not detrimental to the listed building status of the dwelling.”

“Making alterations to listed buildings or buildings in conservation areas can be a minefield,” continued Mick Ramsden. “Experience has shown us that in-depth research should be undertaken before any application is filed and that any supporting argument is pertinent to the situation.”

It’s perhaps as well to remember that all applications will be dealt with on their own merits. But more examples like this will increase the precedent of using PVC-U in a listed building situation. Just ensure that potential objections by the planning officer are listened to and find a way to see if they can be addressed.”

Spectus Window Systems has seen a growing popularity for its new vertical sliding window. There is a rising demand to use it as a replacement in older properties, not just those that are listed or in conservation areas. As a result Spectus Window Systems is now displaying one of Bison’s Genesis vertical sliders at the Building Centre, Store Street, London.

As Martin Althorpe concludes: “The industry understands the reticence of planning officers and committees from across the UK when it comes to PVC-U and older properties. Over the past 20 years the PVC-U product has evolved into one that is aesthetically attractive and cost-effective. If proof is needed then there are projects, large and small, across the length and breadth of the UK that confirm PVC-U does not detract but rather enhances older properties.”