Please tell me how...

[McSqueaky]

How do you make 2 floors in your house?

[Dubber]

Not possible as far as I know. However, you do have your attic.

[Fireball]

There is a theory that, like new rods, you will be able to update your house in future catalogs. When I was new to test, they were testing estates. The houses were different in one way, there was a porch outside of every house. Then Disney changed it so we could eventually update when they released the catalogs. We also believe the highest update you can make will be a small mansion. Other high quality houses might have two or more floors.