Topic 5: Building upwards
If you are looking to create multi-level buildings, or to add a roof to your rooms to create a bunker, you will first of all need to build your ground floor level using one of the methods described above, but do not immediately place the Caps on top of the Pillars.
Once your walls are all in place, you can rest a Connector on top of the Walls and add additional Pillars on top of the first level to create the frame for the second story. Add any Floor tiles you wish to have on the second level, slot in your Walls and top the Pillars off with a Cap, unless you are building even higher.
If you are topping the structure off with floor tiles, to allow your miniatures to stand on the structure, make sure you place Connectors on top of the Walls to rest the Floor tiles on. This avoids gaps and wobbly flooring.
Handy Hint:
Connectors can be used upside down to span a gap in place of a Wall. This allows you to have openings in the side of your structure or hollow areas within your buildings and bunkers without using an additional Wall piece.

