Converted couch? A sofa that used to be something else? Hmm, perhaps not.
Maybe you meant "converted church", meaning a building that was, at some tim, a church, and is now a house?
Anyway, a few types of house:
* bungalow: A house with one storey.
* terraced house: One house in a long row of houses all attatched to one another. Commonly made of red brick.
* Semi-detatched house: A house that is attatched to one other house.
* Detatched house: A house that is not attatched to any other houses.
* Cottage: A cute house in the countryside (commonly with a thatched roof).
* Flat: Un piso
* Two up two down: A small house with A kitchen, living room, 2 bedrooms and a bathroom.
* Converted [building]: A house that used to be something else before being turned into somewhere to live. "converted barn" is very common.
* Townhouse: A small house in a town.
* Mansion: A huge, expensive, detatched house in the country.
* Houseboat: Una casa flotante.
* Bedsit: A one-room, rented (and often rather grotty) house.
I think what you mean is a "convertible couch",
also known as a "convertibe sofa."
That's the kind that opens up and becomes a bed.
It's convertible, because by day it's a couch, and at night it can convert into a bed.