If you want to make sure your Sims can actually use the basement space you’ve built when you’re finished, you’re going to need to make sure that you add stairs in as a part of your decorative plans. Tip One:- Always add stairs as soon as you can. The only thing you should be aware of is that there’s no point putting in exterior windows or exterior doors. You can change the height of the walls, add furniture, and decorate it as you please. Once you’ve built the basement area, it can be worked around like any other room in your house. This means, if you want a tall house, you can have a total of six floors. When you build a basement in The Sims 4, you can only go two floors down. Who else loves building basement bars? from Sims4