Re: Building a deck on top of a deck
@misterNYCmodel Your home is beautiful! Decks can only be different heights if they don't actually connect. You adjust the foundation separately on each deck by making sure each is traced properly to make it an 'official room' (then you can delete the walls afterward with the wall tool) then highlighting/selecting the room and dragging the 'plumbob' in the center up or down when highlighted. Then you can join them via stairs.
I made a build where I have two decks at different heights, and you are welcome to download and play with that aspect a bit to get a feel for the dynamics. Can you share the video link and the point in the video where the person shows this technique that you are trying to use? https://www.ea.com/games/the-sims/the-sims-4/pc/gallery/2300886DA06111E989B3D5D7447C5F1D