two-story house
Refers to a house with two floors. The term is straightforward and commonly understood.
彼は郊外に二階家を建てた。
He built a two-story house in the suburbs.
Standard kanji spelling.
Alternate kanji spelling using 屋 instead of 家.
Compound of 二階 (にかい, 'two stories') and 家 (や, 'house').