ᐅ Patio doors/windows with no central mullion – with or without a low-profile threshold

Hello everyone,
our window installer offers us the choice of having the patio doors or floor-to-ceiling windows (with mullion) either with or without a low threshold.
The threshold is only 2cm (1 inch) high and costs 80 euros more per window unit. What bothers me, however, is his comment: "It is worth mentioning that with a mullion design, at the point where the two sashes meet, during heavy rain and wind blowing against the window, some water may be pushed into the room. This design is essentially like having two patio doors side by side, whereas previously only one sash was planned."
I don’t quite understand the last sentence, but water getting inside would be a problem, right?

What are your thoughts on this?

Is the neighbor’s balcony accidentally located above your terrace?

Either way, I would do it like this, with a French door and a flat threshold.

We have "level thresholds," which so far has been a very good decision. Up to now, no water has entered the interior. As cautious people, we installed external drainage channels (the excavation contractor thought they were unnecessary, but the authors of the relevant standards insist on them).

Hendrik007 schrieb:
Den letzten Satz verstehe ich nicht,

I feel the same!

The terrace is only slightly covered by the neighbor’s balcony and otherwise open.
I need to inquire whether a drainage channel is planned.

We also have a flat threshold and have had water in the living room before.

In 2 years, maybe around 100 ml (3.4 fl oz) once. Not an issue with tiles, but carpet, laminate, or hardwood flooring don’t really like that.

toxicmolotow schrieb:
We are also using a flat threshold and have already had water in the living room.

Do you have an external drainage channel?