Houseplan is a 3D modeling and real-time rendering programme that has useful 3D tools and features, enabling architects, urban planners, amateurs, etc. to present building ideas easily and efficiently.

How to access the tool

Open your drawing file, then find Home tab > Building panel > Show Floor, shown as below,

Draw a plane to specify the area of the stair well, and dig a hole from floor 1 to 6,

Open Floor 1 and find Home tab > Building panel > Stairs tool, shown as below,

Select the Stair Match tool and draw the stair, then adjust its direction

You can also make the stairs of Floor 2 by selecting the plane and convert it directly, then, Complete the rest of the stairs with the Stair Formation tool

You can also add curved stairs by defining 2 polylines

Check out the Step by step video tutorial