In creating a house with a basement, you need to pay a closer attention to the elevation options. This option refers to the level of the house in parallel with the ground. To set the program to always show elevations, go under View Properties > Visibility > Design option tab > select the design option that you want. In this process, you should also make sure that you properly select the wall direction. This can be done by selecting the Wall button from the upper tab, and go to Location Line. This option will determine the position of the exterior wall regarding the drawing line that you use to create the wall. Any incompatibility in this area could lead to errors, like the one you encounter. I suggest that you use the following tutorial website in the learning process.