Got it done again, thanks to your help - and the link you wrote for another dumbo like me ;-)
Must honestly say: the way to do it is far from user-friendly. Too many clickclickclicks... Especially the trim from top/bottom is a real trap!
A few hurdles made the run extra complicated:
1. The outside walls of my new home are seen by TFP as INSIDE walls. My own mistake: when I made the initial layout of my terrain I used 'walls of 1 cm' to create a road, a rice irrigation canal, borders of my terrain. Even if these 'walls' are almost invisible, TPF treats them as walls - thus the outside walls of my home will be inside walls. - What other option would I have head initially, to determine the rough structure of the building site?
2. Because I had to add wainscots to interior walls, the question was: left or right interior. It always was a guess. What is left and what is right?
3. On long walls the wainscots I applied are interrupted where another interior room 'touches' the wall(s) I want to modify. How can I give these 'sides' of interior walls the same look?
As to the tower: I managed to get a small hip roof with 3 pending sides. But the front of the rectangular 2x2m tower remains flat. How to get the 'four sided church tower roof'?
Another question coming, in a new post.
Stop if you get bored... :-)