Windows, Doors, and Sliders: How Big is Too Big?

2nd March 2018

As with all industries nowadays, technology marches on when it comes to the utility of glass in your home. Triple glazing is becoming more common-place, as is Alu-clad, a product which allows for greater longevity and reduced maintenance. Energy retention is increasing all the time in concert with the worlds increasing need for sustainability; making passive homes within reach for more and more people. However, as is also the case with other industries, as possibilities increase, so do customer expectations, and we are finding more and more clients seeking to maximize their views, and indeed the light in their home by installing oversize glazing. But what are the limits of today’s products? Whether it’s a fixed pane, a sash slider, or a sliding door, just how big can it be? We turned to Walter Power at Zyle Fenster Ireland to find out.

How often are you getting questions about over-size glazing these days?

In reality, it is almost every day at this stage. It is probably a bit more common for us than other suppliers as we have earned a reputation for being able to handle some of the larger bespoke jobs. Many companies will just downright refuse to get involved in it as it is generally a more complicated process from design, fabrication, and through to installation. It suits us though as we prefer to provide a personalised service to a limited number of clients, rather than chase volume and allow our standard to drop. We receive a lot of inquiries based on the fact that we are willing to produce and install some quite astonishing glazing, sliders in particular. In fact, as I speak, we are installing a ten metre, 4 pane slider, overlooking the bay of Kinsale.

Before I ask about the specific limits of glazing types, what kinds of issues do oversize products bring up?

So nowadays it is not just a matter of fabricating and installing, we also must have a good understanding of the energy retention implications of any glazing that we do, so design calculations have to be made from that perspective. Additionally, our production facilities tend to be set up for what the most common needs are so some creative engineering generally needs to happen there. The real attention to detail though, comes during the installation stage. We are sometimes dealing with multiple panes of glass, each weighing up to a quarter of a ton! This takes, experience, planning, and of course specialized machinery to make happen. The heavier a product, the more essential attention to detail is when installing, we have to ensure we take the time to get everything just so in order to maximize efficiency and functionality.

Size Limits


Fixed Panes

When it comes to single fixed panes, we generally max out at about three metres by two and a half metres. This size can be reached across products by increasing the density of the glass. Realistically, however, this limit is dictated by logistics. That is, the difficulty of transporting and installing anything larger than this. In truth, if a client has pockets deep enough to pay for bespoke logistical arrangements, this size could be increased.

Opening Windows

When it comes to the size of an opening sash, our Tilt & Turn system provides the most durability. This is essentially why I encourage all clients to avail of this system. Not only does it give you a variety of opening positions for airing, cleaning etc. But they are also a much more robust system than opening out, even if you are not going for a large size. A single opening vent can go up to two and a half square metres, although it is not wise to have a sash that is wider than it is high. When you talk about opening out, side hung sashes, you can reduce these limits considerably. For our products we max out at about seventy centimetres wide, although I know other companies do slightly more. I would bet though, that if you have any kind of large opening out window, you will be replacing those hinges before long.  As I said, we like to focus on the best products so we tend to favour Tilt & Turn jobs.

Sash Windows

With sash sliding windows we have done up to one and a half metres wide by three metres high. We haven’t really had cause to work out limits yet but with engineering, they are very durable. It’s all about the counterweights you put inside the frame and I’m sure we could figure out some quite large ones if they were needed, sash window technology is quite old after all. That being said, U-value wasn’t such a factor when they were first building Georgian houses. We recently did a massive job in the UK where the sash sliders were ‘curved on plan’. This means that the actual frames and glass were curved as you would look at them from above, to match the curvature of the old building.


So for our doors, we will guarantee anything up to one point two metres wide by two and a half metres high. We can do this across our range of products. We are finding a big increase in the interest in larger front doors like this and so they are tried and tested at this size by now. When we get into our more advanced aluminium systems like Schuco, we can increase the height to three metres. When it comes to double doors, you can simply double the size of the single ones and we can build them for you.


When it comes to an Aluclad or Timber slider, the largest two pane slider we can do is six metres wide by two point seven metres high. Overall width can be increased by adding fixed panes but we tend to max out at about ten metres wide like the one we are currently doing in Cork (see picture) When we get into more expensive products like Schuco, we can increase the height to three metres but overall width still generally maxes out at ten, although there are some more things you can do with Schuco also (see Schuco blog here).


All in all, there are limits to how big glazed products can be, whether it is down to gearing, transportation or the glass itself. However, Zyle Fenster have been found more willing than most to deal with bespoke oversize products as they are positioned for one-off high quality builds rather than mass production. Click here to download a brochure today.


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