here is the map layout for the courthouse building. I can't remember exactly what we built as we rushed through building all the tables in one sitting and didn't write some of them down as were just learning the parts locations etc. This image will be updated when I remember what parts go onto this table and what gadget it built again.
The tables and chairs in this building can cause a bit of an obstacle when there is a lot of zombies inside as there is not much room to manoeuvre. I would suggest not staying in here past about round 6 or 7, and you should open the front doors to get out into the main street and give yourself some more breathing space.
You can get into the courthouse from the doors at the front of it, or if from the tunnels you started off in when you fell underground, can work your way through them until you emerge on the balcony upstairs.
Here is the map layout below:
Thanks for reading guys and I will list the parts and update the image when I remember what goes on that build table.