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Let's use the first solution, i.e. lowering the garage, although the procedure is basically the same, so you can create "combinations" of height levels freely.
The above example will be a descriptive model for lowering a part of the building.
Draw a view of the entire level. Then mark the garage walls and define a different base height for them, i.e. set the lower edge of the wall to -50cm. In this project, you do not align the walls (this would be the case for the project in the first picture), you only change the height of the location, and leave the height of the walls unchanged.
If you didn't do this at the beginning, set the garage door on 0cm from the floor, which you are about to insert.
Create the levels below, which will either be the level of the foundation walls only, or you will also introduce the foundations there, it is up to you. You should remember only one thing: if you have any displacement of the floor on the ground, it will, unfortunately, cover a part of the spot footing or strip footing in the cross-section. Therefore, in a case like this, it would probably be better to insert two levels and separate foundation walls and strip footings on them.
Assign the level below, in this case 120cm. Set the level cutting line to 60cm and copy the walls only (windows and doors will be copied automatically, but information about deleting them will appear soon). The created level may look strange in the 3D view for a moment, because the garage walls have been copied with all their parameters (i.e. lowered by 50cm and the height of the ground floor). You need to select them all again and adjust their height to the place you have left. The height of the walls in this case will be 70cm.
At this point, you can change the layers for the walls. After approval, we can modify the entire view, delete unnecessary partition walls and change external walls.
Now you will proceed to the most important step of placing the floor on the ground. As the floor on the ground is introduced from zero of the level and it cannot be lowered, in the described case you have to place it on the floor below, i.e. the currently active one. To do this, mark the frame from the garage room and enter the properties window.
If you cannot select the room frame, you probably forgot to change the cut height of the view when creating the level of the foundation walls. Therefore, enter the level properties and set the Cut height for projection accordingly.
After selecting the garage frame, enter the properties window. Mark the option Floor on ground and adjust the floor layers.
Then, move all the layers of the floor above the bottom boundary of level. When you select a layer, a blue arrow on the right hand side activates which allows you to move the layer upwards.
Now, increase the bottom layer of sand to such a height that the floor is 70cm high or add a layer, for example, plant soil and give it the appropriate height. The floor must be equal to the walls of the garage.
Finally, go to the ground floor and remove all layers from the garage room in the properties window so that they do not overlap on your new floor on the ground.
The sample project 4 included in the ArCADia BIM program has been described above. After opening it, you can accurately trace all parameters of the walls, floors and levels for a more accurate picture of this topic.