The Mechanical Joint
In timber window frames, the corners are made by creating a mortise and tenon joint. Don’t worry about the words too much – simply imagine one side with a peg and the other with a slot. When the joint is put together well, there’s a thin vertical line on the frame, and the whole is either screwed or glued together.

When PVC-U windows appeared, it became the norm for the corners to be welded with a mitre type joint. Again, don’t worry about the jargon – it’s the diagonal you’ll see in the corners of frames. It’s strong, weatherproof and effective, but the ‘weld-line’ is a big giveaway that it’s a PVC-U frame. With sash windows, the true period aesthetic demands the look of a timber-type joint.

Naturally, we’ve solved the problem. Our PVC-U frames can have mechanically jointed corners on both the sliding sashes and the outer frame. No more obvious diagonal welds, just a neat vertical joint that’s just as effective as a weld but which replicates, exactly, the appearance of a timber joint.

We can’t deny that traditional timber sash windows are a thing of beauty. The craftsmen’s skills are evident in the smallest details, in the curve of a Georgian bar, in the grace of a sash horn and in the near-invisible joints in a frame.

Planning and conservation
In the past, planners have often refused applications to replace timber sashes with a PVC-U alternative. This has left many people with a dilemma – face the considerable expense of new timber sashes or continue living with the draughts, poor insulation, broken sash cords and maintenance burden of their old windows.

In some cases, it’s led to properties that look run down and which do nothing to enhance the special character of a conservation area. The Spectus Vertical Slider is the answer, and planning authorities are realising it. More and more approvals are granted when they hear it’s a Spectus sliding sash. Planners respect our faithful recreation of the traditional style and appreciate our use of easy to maintain, energy-efficient and recyclable materials.

Our Vertical Sliders respect the heritage of traditional windows and deliver the most advanced levels of performance, but they’re also very practical and easy to live with, right now.

They insulate, they’re secure, and they have the safety features you need. They’re simple to care for and a doddle to operate. There’s a choice of 28 beautiful, foiled finishes, including several that replicate the appearance of painted wood.

Operation and aftercare Instead of fighting with weights, pulleys and broken sash cords, Spectus Vertical Sliders use reliable spiral balance mechanisms. Use the sash lifts or pull rings to move the sash just as far as you want, and it will stay in position. If there are children at home, add safety restrictors which limit the amount the sashes can move. To ensure the sash is safely closed, simply engage the neat snail cam mechanism.

Tilt-open facility Because resources are precious, building things to last our Vertical Sliders have a handy tilt-open feature to both sashes. It makes cleaning the exterior glass from indoors easy.

Cleaning and maintenance Timber frames take a lot of looking after – sanding, painting, wood preservatives – even so, they still rot, warp and stick. To look after a Spectus Vertical Slider, simply wash the frames with soapy water, using a soft cloth and then dry them. Ensure drainage channels and pile seals are free of debris and lubricate the sliding mechanism with a bit of beeswax polish. Add a drop of light machine oil to the hardware. Job done.

Our Vertical Sliders respect the heritage of traditional windows and deliver the most advanced levels of performance, but they’re also very practical and easy to live with, right now.

Installation We’ve matched the dimensions of a timber box sash. With the same front-to-back depth, installation is straightforward. Add our precision manufacturing and superb engineering, and you’ve got a frame that’s easy to fit and no trouble once it’s in place.