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.

Step-by-step tutorial

Select Home tab > Building panel > Floor Hole, shown as below,

Floor Hole tool allows users to draw hollow areas on selected building floor. Altenatively you can just enter FLOORHOLE to open Floor Hole dialog box,

Select the Draw button and draw the outline on the floor, Close

Double click to select the outline and right click to Erase

Try to draw the floor holes from s specific floor to another

Then, convert a plane to the floor holes with the Define button

Download Houseplan free-trial here: www.gstarcad.net/houseplan

Check the following tutorial video and see how you can open holes on multiple floors easily and efficiently: