How do you build 10 story house on sims 2 for PC?

You need to have Sims 2 University in order for this to work.

Open the cheat bar (Ctrl + Shift + C) and enter the following cheat;

SetHighestAllowedLevel [level]

E.g. in your case it would be

SetHighestAllowedLevel 11

Add one on to the number you want, so that you can add a roof too.

Or You could add a dormer to your top floor and get an extra level if that doesn't work (It didn't work for me). In case you do not know a dormer is like a small part of a roof that has a wall and is commonly used for Windows on loft rooms

- The reason why it didn't work was because the cheat was entered wrong -