Masonry knee wall possibly load-bearing?

Do you mean whether the rafters rest on this wall? It is hard to judge because the wall was either built up to the rafter or the rafters were laid on the masonry wall. I don’t know how to tell the difference between these two options. However, it would be strange if this wall supports the rafters, because it is not continuous in the attic. More precisely, it exists only in the large living room, about half the length of the attic. In the adjacent rooms, the knee wall is much further back or not present at all, so that the room is used almost up to the last corner.

A static calculation or other documents – apart from the construction drawings – do not exist.

Structural engineers also make a living by checking existing buildings for their static stability, e.g. whether the masonry knee wall plays a role in the bracing.

What is your opinion on this?

Opinions about the static stability of your house are truly misplaced here, no matter how much is written.

In the house that I have owned for about three years (built around 1970), I would like to make a small change in the attic. It is about the following: In the large living room of the attic (which extends across the entire width of the house), the knee wall (is that the correct term?) has been set so far inward that behind it lies a huge unused area. Presumably so that there is almost no roof slope in this room. I would like to install a 70 cm wide door in this side wall, whose height is just under 160 cm, so that the space behind can at least be used as storage.

Of course without guarantee, I have no concerns about that. A masonry knee wall certainly would not be suitable as a ridge purlin. It could brace, but I do not see your desired small door as "suitable" to significantly impair this possible function.

P.S.: but always remember with such cavity openings, finding corpses is reportable *ROTFL* *SCNR*

P.S.: but always remember with such cavity openings, finding corpses is mandatory to report *ROTFL* *SCNR*

LOL ;) Nothing can happen, I've already been in that cavity. In the adjacent room (kitchen) there is a tiny door through which you can also get in there. However, not for long, once the new kitchen is installed, this small door will be history.

I have already been in that cavity. In the adjacent room (kitchen) there is a tiny door through which you can also get in there.

Oh, and you had no insight there that would have answered your question?