Excelsior

Well i made this custom house 3 lvls and 18x18 i got the first floor basicly done besides the back walls but my stairs wont let me up to the second floor, whats wrong??
And i have nuthing on the other floors whatsoever

Place the stairs, than place all floor tiles of the 2nd floor. The floor tiles above the stairs will show up in orange. Remove those and you're set.

FYI: any orange or red tiles indicate you have something misplaced. Correct or remove those before committing your design.