In Vasari, the basic building block is called a mass. A mass is a wrapper for a form, or series of forms, which provides the ability to query certain appropriate properties. For example, once you create a mass, and add mass floors, you can query items such as floor area, surface area, and volume.
Masses can be at the scale of a building, the scale of a wing of a building, or even at the scale of a unit. They can be used to calculate gross floor areas, surface areas, and volumes, analyze solar radiation, and analyze energy use.
There are two ways to create a mass in Vasari. First, if you need to create a mass containing multiple types driven by parameters, you can create a conceptual mass using the external family editor.
To do this, you create your form, create types using parameters, and then load it into the project and place it using either the Place Mass button or by dragging it in from the project browser
Secondly, if you want create a mass that can be modified in context, click the Create Mass button. You can then start modeling immediately within the context. To finish, simply double click in a blank area of the view, or click the Finish Mass button.