A bulky concrete apartment appears to hover above the glass roof of a patisserie at this combined home and workplace in Japan by architect Yuko Nagayama.

But these new apartments — known as three-tatami rooms, based on how many standard Japanese floor mats would cover the living space — are pushing the boundaries of normal living.

Dribbles of gold fill the cracks in the floor of this Kyoto apartment, designed by architecture studio TANK to replicate the traditional Japanese pottery technique of kintsugi. TANK principal ...