For many years there was virtually only one way to make PVC-U frames, and that was with 45º angle corner-weld and groove. Whether you like the look or not, unless you polish the corners that’s how they come. Homeowners never much liked the look, but as they had no choice, they accepted it.

Now, there is much more choice and several different options are available to fabricators, including: 45º corner weld-and-groove, corner-weld-and polished, mechanical butt-jointed with or without glass bonding, the Graf/Seamless 45º corner weld, a timber-look butt-welded on the outside with a 45º corner weld on the inside, and now a total timber-look, butt-welded on the outside and inside!

What’s driving this explosion in choice? One explanation is the growth in timber-alternative vertical sliders and flush sash timber-look PVC-U windows and doors. A recent independent study by MRA Research found nearly half of the fabricators interviewed see flush sashes becoming as important as standard casement windows over the next 10 years. And a quarter of fabricators who don’t currently make flush sash windows expect to start making them within the next 12 months. Timber-alternatives and the flush sash look is a growth area for fabricators and installers.

The main target market for flush sash windows – the ‘Haves’ who are property-rich and willing to pay for what they want – care a lot about the appearance of their windows and doors. They have spending power because their housing wealth is rising strongly. They’re mainly low or mortgage-free over 55s who are growing in wealth and number as the value of their homes rises. They want, and can afford, beautiful looks and high-end products that last. They love the look of timber, but don’t want the maintenance headaches. The way their timber-alternative windows are jointed is a crucial element of the look.

For the purist, mechanically jointing the sashes to replicate the traditional look of timber windows (which were always joined mechanically) achieves the look but at a cost. While most of the fabricators who were interviewed love the look of the flush sash – especially timber-look butt joints – a significant number think mechanical jointing is ‘a pain to fabricate’. There is also productivity and cost to consider. While it may be practical to mechanically joint for a small niche market, it’s simply impractical at scale. If you plan to grow, welding is the answer. In the research, most fabricators welded or did both because it was less disruptive and allowed them to meet volume demand cost effectively. “Mechanical joining is slower to produce and holds up production,” said one.

The look they love

Looks are important, but what’s behind the look also matters. So, while mechanically jointed timber frames are solid, PVC-U profiles are not. PVC-U mechanical joints that are open ended allow water, draughts, flies and dust to get in to the building, which isn’t what people have in mind when they pay more for the look they love.

Weld strength and the robustness of mechanical joints haven’t been in the news for years, but what works in a mostly white-frames market in a temperate climate is being tested. Rising temperatures driven by a changing climate, with a growing demand for foiled and darker colours have put weld strength and integrity in the spotlight again. Fortunately, we have the technology to achieve perfect corners that can cope comfortably in a timber-look market where most flush sashes are sold as colour.

Authentic, robust, and cost effective

Timberweld® is a patented method of welding perfect corners to create an authentic timber-look butt-joint effect. Currently there are 10 Timberweld licence holders (see for the full list) for casement flush sashes windows and doors, plus Masterframe which has been using Timberweld technology on all its vertical sliders for the past two years to achieve the perfect mechanical butt-joint look on both sides of the window. That matters to homeowners who want their windows to look authentic on the inside too. Leading fabricators licenced to use the Timberweld technology include CWG Choices, Sidey, HWL, Aztec Windows, Fastframe UK, Window Tech Trade and John Fredericks, and some big names are in the pipeline.

Robert Wallis, Managing Director of  Window Tech Trade, explains why Timberweld is the answer to this growth market: “Creating the timber butt-joint effect on both sides of the window is a big plus for installers, but the main benefit of Timberweld is ease of manufacture and speed of installation. It eliminates production problems and is extremely cost effective when you scale up. Our manufacturing output has increased by approximately 30% using Timberweld.”


For further details on the research or to find out how you can obtain a license to manufacture Timberweld® call 01376 534126 or email and follow @Timberweld.

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