Composite door tolerances remain subject of heated industry debate with call backs because of bowed slabs according to commentators, costing installers thousands each year.

“Building products have tolerances. That’s accepted”, says Steve Mines, Sales Director, Sliders UK. “In composite door manufacture, however, slab bowing tolerances seem to be being set completely arbitrarily. We’re being told by installers that some manufacturers argue that 8mm tolerances are simply ‘part of the course’.
“We’re not, however, dealing in what’s acceptable according to a technical manual. It’s about the reality on the ground and ultimately what’s acceptable to the end user.
“If a door won’t open or close properly, if the weather sealing fails or the locking mechanism sticks because the slab has bowed, installers are going to get call backs, plain and simple – and that costs, with the installer, not the manufacturer picking up the bill.”
Out of tolerance doors are a clear problem at point of installation. Bowing carrying significant potential to impact on the performance locking mechanisms and seals. This, according to Mines has become a more significant issue as slabs have been redesigned to include more timber to address security concerns.
“The trigger was PAS24 and particularly cut-through testing, which exposed a fundamental and underlying vulnerability in the make-up of composites”, says Mines. “This drove slab manufacturers to use more timber in their designs, addressing issues around cut through tests but creating others in the process.
“Timber swells, it bows and contracts, depending on humidity and temperature. And it’s this, which is leading to call-backs for installers, because it impacts on weather sealing and locking mechanisms.
“Doors can be adjusted, the problem is how do you adjust and set up a door correctly when its bowing 8mm or maybe more? It means installers are going out to the same job on multiple occasions.”
Steve argues call backs are costing installers ‘thousands’ each year. “You’re looking at time lost for a fitter to go back. That’s not simply a cost associated with time on site when they’re not effectively earning a fee but time lost when they could be”, he says.
“If you’re going back two or three times – which installers are – costs associated with bowing composite doors very quickly add up.”
He argues that this is just the tip of the iceberg, suggesting that reputational damage, although more difficult to quantify, should also be factored into the equation.
“You spend a huge amount on advertising and lead-generation but word of mouth recommendation and reputation are still critical”, Steve says. “If you’re a homeowner and your door is sticking and the supplier can’t seem to get it right, would you recommend them?
“An 8mm, bowing tolerance is simply too much – you can’t set the door right and you’re going to get call backs.”

The Ultimate Composite doors uses intelligent timber inserts and is supplied with a bowing tolerance of just 3mm

Sliders UK’s took a decision to launch a new composite door offer from Capstone last year. This uses ‘intelligent timber inserts’, manufactured from 15mm LVL, which are deployed to strengthen the slab at points historically vulnerable to attack in other leaf systems, giving it a PAS24 cut-through test approval.
It means that this technically advanced combination of timber inserts and thermally insulating foam used in Ultimate Composite Doors, delivers on security while balancing it with the core structural stability of the slab – giving it a maximum bowing tolerance of just 3mm.
“We needed a solution to PAS24 and we got it in the Capstone slab. What we have also been able to guarantee is performance. At a maximum of 3mm, movement in the slab isn’t going to impact on locking mechanisms or weather sealing.
“3mm is not something we aim for but it’s certainly not going to generate a call back. Six and 8mm tolerance is. And that’s the point.
“We wouldn’t want to be servicing doors with a 6mm or 8mm tolerance so why should we as a composite door manufacturer expect our customers to?”, argues Steve.
And Sliders UK is putting its money where it’s mouth is, underwriting this industry-leading 3mm bowing tolerance with a s guarantee, which writes off anything more, as a manufacturing fault. “If it bows beyond 3mm, we’ll replace it at our cost. It’s that simple”, says Mines.
The Ultimate Composite Door by Sliders UK also features a number of other efficiencies. Capstone’s patented three stage glazing cassette system, supports easy replacement of glass but also maximizes security.
Available in a choice of Eurocell or Duraflex framing options and arange of 36 premium finishes, with any RAL colour available through Sliders UK’s in house spray painting facility, the Ultimate Evolution also delivers u-values as low as 1.0Wm2.K.
Door furniture and hardware is Trojan, while standard hinges and locks are manufactured by Ingenious, with heritage and auto-locking options from Winkhaus.  Door cylinders are six-pin anti-drill and pick as standard with the UKAS accredited 3-star BSITS007 tested Ingenious cylinder, also available as an upgrade option.
According, to The Market for Domestic Entrance Doors by Palmer, composite doors now account for 50% of the market, the share rising to 54% by installed value with the inclusion of PVC/ABS faced doors. Going forward composites are forecast to see a 22% increase in sales through to 2020.
“It’s fair to argue that was a sense of panic when PAS24 cut-through tests exposed a failing in the design of composite slabs.
“The irony is that in addressing it and bringing in more timber into composite doors slab manufacturers introduced the same fundamental problem that has formed the foundation of the pitch against timber doors.
“This is that as a natural material, timber moves. It takes only the slightest ingress of moisture or a significant change in temperature for it to swell or contract and bow.
“Using intelligent LVL inserts, we can offer a highly engineered solution that brings new stability to slab design, while meeting all requirements under Part Q and PAS24 – include cut-through tests.”
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