see this example

The attached file gives a schematic of your house:
- foundation level 60 cm = 2 ft
- 1st floor
- deck around 1st floor
- 2nd floor

Check out the heights of the levels by double-clicking the tabs at the top of the 2D design window.
In the 3d preview window, do a right-click and select Display ALL Levels or Display SELECTED Level to change between two views. This is what you need to see the house without a roof (once a roof has bee added on its own level).

Download and install the plugin Roof Generator to experiment with the roof.