You already have a lot of stuff would need a new room that is not too crowded. If you are a Moshi Member you need to buy moshi monsters double room for a terraced house.
Use Map to visit Ooh La Lane then enter to NEW HOUSES! maximum you can buy up to 4 more rooms for your monster’s house. Every room you buy will make your house taller.
The price is quite expensive, the cheapest is standard version 2 floors about 400 ROX. For example below is my cheap house (Moshi Style):
On the main screen see the button under room costs , if you have more Rox you can CHOOSE A STYLE FOR YOUR HOUSE. Everything is composed of 7 house types, from standard to elegance.
Well, now you know that there are houses like that in Moshi monsters, right?