What Are Stick On Glazing Bars?
Stick on bars, bonded astragals, applied bars and any other variation you can think of are relatively new types of jargon for the joinery trade. We've been working with this method for over 20 years, which in the world of joinery, is a blink of an eye!
In basic terms, stick on bars are small sections of wood or composite material that are bonded to double glazed units to look like traditional solid glazing bars.
So why do joiners use stick on glazing bars? Double glazing needs to be set into rebates with a minimum upstand of 15mm with enough wood left to form a joint, support the glass and secure the glazing beads to it. This means a solid glazing bar can easily end up being between 40mm to 50mm thick. A quick thank you to Coastal Ironmongery who kindly provided the very useful image. We use Coastal for a variety of our ironmongery needs and the quality is always great.
Are stick on glazing bars just a cost cutting exercise? From my perspective, no. It does reduce the cost of the window but not by cutting corners. One of the main reasons windows with solid bars are so expensive is that double glazing has to be purchased as a minimum square meterage, normally about 0.25sqmtr. You can imagine that a window with multiple small panes soon becomes quite expensive. We find glazing solid bars takes longer as there are so many small glazing beads to deal with. It is also very difficult to use drained and vented dry glaze methods with solid bars. Drained and vented systems are preferred as they tend to extend the life of the double glazed units.
What looks better, stick on glazing bars or solid glazing bars? In the majority of cases when using double glazing, stick on bars look best to my eye. They are finer, ours are around 23mm thick. They look neater as there aren't lots of edges of beading converging on a central section. With the stick on bar, everything is neat and tidy.
Do stick on bars fall off? It is possible, however it is very rare. Because we have been working with the system for a long time we have ironed out the issues. The main reasons for a bar coming loose is natural timber twisting and bending over time, coatings not being renewed or a bar that's be cut a little to long here in the workshop. It's an easy fix as the bars we use are not part of the structure of the joinery.
How are stick on bars bonded to the glass? We apply our bars with a black proprietary glazing tape. This tape has a very strong grab. How strong? I can't tell you in scientific terms but I know from experience that removing one due to a misalignment is a nightmare. They don't come off in a hurry.
Do stick on bars weaken a window? The bars we use offer no structural strength. They don't need to, after all, we make windows with no glazing bars and they hold up fine.
Are stick on bars suitable for listed properties? In our experience no, they are not acceptable for listed buildings. Listed buildings unique heritage is protected, windows have to replicate existing designs and are subject to a listed building application. On occasions, double glazing is used in extensions to listed building or a change of use. These situations must be carefully approved with the listed building officer in your area.
From my perspective, I like applied bars and have them on my joinery at home. They give the look of individual panes and slim glazing bars. It isn't a traditional method, but is pragmatic and is part of how joinery is made these days.