I was reading the FAQ and I dont know if it have an error or I understand bad. Basically in the shop we have 5-story basements, but in the FAQ can read: Are there different size basements? Basements will come in the three basic sizes, just like the lots: Village, Town, and City. Each size also comes in single or multiple floor options (up to 4 stories) as well as different layouts.
The official FAQ hasn't been updated, which is why I maintain an unofficial FAQ. Mine mentions new castle lots and 5 story basements. Check my sig.