Draw the base area of a building

First of all, define the base area of the building. The simplest case is a rectangular base area.
The base area can also be traced from an imported image of a floor plan.

Steps

1. Select the Rectangle tool in the Getting started bar. 
    Alternativly press [R].
    
2. Click with the left mouse button on the zero point.
    This sets the starting point of the rectangle.
   
3. Move the cursor to the right.
    A rectangle is spanned and the direction is set.
4. Set the length and width, separate the values by semi-colon and press [Enter].
    For a rectangle of 9,50 * 8,00 type: 9,5;8 [Enter]
    You can enter the values directly using the keyboard.
    The rectangle is drawn with the dimensions entered.
   
5. You can continue drawing rectangles or press [Space].
    The spacebar ends the rectangle tool and activates the select tool.

Result

You created a rectangular area that can be used as base area for a building model.
Define the building height in the next step.