okay so a long terrace is where you have lots of houses that are all roughly the same size in a long row, which is what most terraces are. Which is English should be 'a house in a long terrace' because the terrace is long, not the house. It could also mean the shape, as most terrace houses I have lived in are narrow, but go back quite a way (are deep), then there is also confusion with longhouses. This is the fun of languages trying to translate between two completely different ways of describing a house.