Complete semi-detached house with a granny flat. Base height and eaves height?

For our parents, we wanted a granny flat. 2 residential units are allowed. yes that is exactly the question :-)

What I haven’t said yet... the other half is inhabited by my brother, so we both have halves for the granny flat... if that helps

For our parents, we wanted a separate apartment.

Oh dear. If the separate apartment is also supposed to be age-appropriate, then "on one level" is of course required.

Post some drawings of the property (excerpt from the cadastral / development plan), then there is a basis, and you don’t have to speak blindly.

What I haven’t said yet... my brother lives in the other half, so we would have both halves for the separate apartment... if that helps

No. A residential unit cannot extend across a property boundary.

For your plans, you need a plot of land on which a multi-family house with 3 units can be approved.

Um, no, I didn’t mean unwanted external links here. Definitely not to such thick tomes. But rather simple JPEGs of what concerns the mentioned plots. That means I see there in WA1 and WA2 – by the way, only with 6.5 m eave and 12 m ridge height – unfortunately without plot dimensions, but with about 8m house width.

For your plans you need a plot on which a multi-family house with 3 units can be approved.

That would be cheaper, but not a must. A semi-detached house with two residential units and one with only one are conceivable here – only no residential unit may extend beyond the plot boundary. With a semi-detached house on just one plot that would be possible – but I would rather make apartments stacked vertically than standing upright.

Okay, you have already helped me there ;-)
I will discuss that then... Thank you very much