Hallo rb,
you may have found your way yourself by now, but I have played a bit with your file. Maybe it can give you some input.
Test1_mod_025mm.dxfTest1_mod_050mm.dxfTest1_mod_050mm_1to50.dxfThe first is mostly left as is, just set most lines to 0.25 mm as standard, to start with, and put a grey fill into the walls.
In the second I made the walls' outline 0.50 mm thick. I also changed the settings in Options - Current Drawing Preferences - Dimensions according to a intended print scale of 1:100. This makes it easier to switch to a different scale later.
Number three is tuned to a 1:50 scale, and with a hatch instead of a fill for the walls.
When printing you have to set that scale in Print Preview.
You will see you have to consider the intended scale when drawing. For example the windows details are much to delicate and dense for 1:100, even for 1:50, they get clogged from line thickness.
I haven't tuned everything perfectly, just to give you some clues. Work left for you.
By the way, LC 2.1.3 doesn't like changing hatchings'/fillings' attributes properties afterwards, they disappear then. Better delete and redo. Version 2.2.0 RC is much improved in this respect.