The level of measurement of the number of rooms in a single-family house is ratio scale.
A ratio scale has measurements where the difference between values is meaningful. In other words, the differences between points on the scale are measurable and exactly equal. For example, the difference between 2 rooms and 4 rooms in a single family house is 2 rooms and is equal to the distance between 3 rooms and 5 rooms.
Also the ratio scale has has a meaningful zero. The zero in a ratio scale means that something doesn’t exist. For example, there are 0 rooms in a single family house means that there is no room in the house.