ᐅ Double doors with or without a mullion — what’s the difference?

We have French doors, triple-glazed, slightly wider than 2 meters (6 ft 7 in).

hausnrplus25 schrieb:

I don’t understand why triple glazing wouldn’t be possible either

Because large panels become really heavy, and the hardware often can’t handle the weight properly—in plain terms: the door (or window) warps.
I’ve seen it myself with my old windows from the 1980s. Window sashes about 150cm (60 inches) wide (2-leaf). They hang terribly crooked. The new windows will be triple-leaf. No one even offers me a two-leaf option.

We also have French doors. One panel with triple glazing weighs about 90 kg (total width 1.8 m / 6 feet). Over the past 8 years, I had to adjust the fittings on the patio door twice.

nordanney schrieb:

Because large elements become really heavy and, if in doubt, the fittings won’t handle the weight well—in plain terms: the door warps (or the window).
I see it myself with my old windows from the 1980s. Window sash about 150cm (60 inches) wide (double-leaf). They hang terribly crooked. The new windows will be in three parts. No one offers me a two-part option either.

Okay, I probably just can’t imagine your huge windows. We also have a single-leaf window in our apartment that sags due to the weight, but a double-leaf window should have been planned there... although a double-leaf window that wide... well, we’re just not building a glass house.

11ant schrieb:

... I recommend width 226 if you prefer a classic symmetrical division. A rough opening width of only 1 meter (3.3 feet) is a bottleneck with a tray or laundry basket, at best inconveniently narrow. If the width is only 2 meters (6.6 feet), I suggest an asymmetrical division so that the first sash to open can be made 113 cm (44.5 inches) wide. I recommend sliding doors only from a width of 251 cm (99 inches) onward. I’m happy to give more specific advice if the entire situation (whole room with all windows) is shown here.

I have no idea how big your laundry baskets are. We had a situation where a 1 meter (3.3 feet) wide patio door was defective. The entire unit was replaced with one having a door only 89 cm (35 inches) wide now. I consider a 1 meter (3.3 feet) wide sash extremely impractical. It either extends far into the room or outwards onto the terrace, which then can’t be used as well. We had that direct comparison. If necessary, the laundry basket can be carried lengthwise instead of sideways.

Was there not also a clear recommendation from @11ant to use large elements only made of aluminum due to this issue (weight, warping, etc.)?

superzapp schrieb:

Wasn’t there a clear statement from @11ant to use large elements made only of aluminum precisely because of this issue (weight, warping, etc.)?

“Clear statement” is a strong expression; violations are not punishable.
I would rather call it a “strongly emphasized recommendation,” which generally applies to large frame elements such as lift-and-slide and folding door systems, as well as entrance doors. I don’t actually apply this recommendation to tilt-and-turn windows, but I recently learned that PVC frames without steel reinforcement are now increasingly offered (which also explains why the supplier does not want to use triple glazing). Although there are also double-glazed units with satisfactory thermal insulation values, I generally prefer triple glazing: fundamentally, the insulating effect is more influenced by the space between the panes than by the glass itself. From that perspective, it would actually be more accurate to speak of double-interspace or single-interspace glazing rather than double or triple glazing.

The reasons for my recommendation are multifaceted: with entrance doors, it’s the overall weight and the resulting forceful closing impact even when closing quietly, combined with the often underestimated frequency of use; for lift-and-slide doors, the lighter frame helps compensate somewhat for the weight of several large glass panes; and folding door systems simply have so many joints, guides, and suspension points that the added stiffness is worth the extra cost, since in such a system any imbalance tends to multiply (which is also why only the best suppliers are chosen for fittings). But as I said: if the original poster provides detailed information, my recommendation can become more specific.

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