Updated for Version 1.3.2
Buildings form the core of Spaces and are quick and simple to create.
Make sure you are on the Building Tool:
Then, sketch the outline of the proposed building
Once you have drawn a "closed" shape, Spaces will automatically create a Building.
Automatic creating of items is controlled via the Drawing Settings in the bottom right:
A Building will be created based on the current Default Settings.
If you have Create items automatically disabled, you can create a Building by, again, drawing the outline and then using your finger to tap inside the enclosed shape.
With the Usage Palette open you can also drag a specific Usage Type, and drop it within the enclosed shape. Again, a Building is created based on the current Default Settings along with setting the Building Usage based on the Usage Type that you dragged.