The pen of end lines in Floor Plan are set in the Profile Manager palette. Select the fill and under the Component - Selected panel, below the surface setting you can set the end line pen.
Hi,
thank you for your comment but the real problem is not about the line weight of the wall-end. My problem is that the line weight of the core ( which is set stronger in the Profile Manager than the other parts) is incorrect on floorplan ( only one side of the core is stronger, the other is lighter, as if it were covered by the other fills- changing the display order doesn't help).
Here is another version of the same floorplan-detail after that I pulled away the finish layers from the core in the Profile Manager. Amy other option is the same