Thanks JACANT. I will try to answer your questions. Hopefully it is a little bit clear because my language is Dutch and I'm writing this in English.
Yes, I'm considering to print this item. Before I decide, there are a few challenges.
I'm very curious about your workaround. First I will explain why I chose this method. I read the book about Sketchup and 3D printing and some forums on the internet. They adviced, when you want to hollow your design in Sketchup, for example a cube, create the cube, and use the offset-tool to create walls. Because the advice on this forum, I using now the tape measuretool instead of extra lines. Hopefully this prevent too much lines that causes errors in the design. At this moment, I only need to add windows and doors. I'm also considering to delete the roof and cut the roof from special plates you can by in modeltrain-stores.
Because I have a copy of the genuine architectural drawings of this building it is quite easy to draw.
It sounds like the way you describe is a little bit easier. Because I'm not familiar with that workarround I need to learn again and need to redraw the design. That will cost a lot of work and time. I have also concidered to only draw the walls one by one and print them separate and stuck them together when printed.
It will be indeed expensive but for me, it could be worth (depending on the final price). Please keep in mind there will be much more windows what will help to reduce the price. It is a long term project.