Today, I designed a parametric model of a structural building with the functionality to increase the number of storeys. All the components (footings, columns, beams and slabs) of this building depend on only 4 parameters. They are the length of the footing, the number of footings in x & y-direction and the number of columns in the z-direction.
Certain expressions are used to set the dependent constraints. Refer this link for further readings: (https://www.freecadweb.org/wiki/Expressions)
The FreeCAD file of this model can be downloaded from this link: TestModel
Feel free to test and review this parametric model.