JapanHow is unit owner's common area share determined?
A unit owner's common area share in Japan is determined by the floor area of their exclusive unit relative to the total floor area of all units in the building, as set out in the Condominium Act.
What the Law Says
The Condominium Act (Act on Land and Building Leasing and Ownership, etc.) governs how common area shares are allocated among unit owners in Japan. The law establishes a clear, objective method based on physical floor area.
Under Japanese law, each unit owner’s share of the common areas — such as hallways, elevators, stairwells, and roofs — is not decided by agreement or negotiation after purchase. Instead, it is fixed at the time the condominium is established and is tied directly to the size of the owner’s exclusive unit.
The share is calculated as a ratio: the floor area of the individual unit divided by the total floor area of all exclusive units in the building. This ensures proportionality and fairness across all owners.
This allocation method applies automatically unless the condominium’s original regulations (set at establishment) specify a different method — but even then, any alternative must be clearly stated in the registered regulations and cannot override the statutory default without unanimous consent.
Statutory TextThe share of the common parts shall be determined in proportion to the floor area of the exclusive parts owned by each owner.
— Condominium Act, s. 14(1) — Allocation of Share of Common Parts
What to Do
Review the registered condominium regulations (shoyū kisoku) to confirm whether s. 14(1) applies or if an alternative method was validly adopted.
Obtain the official floor area measurements for your unit and the building’s total exclusive floor area from the registry office (houmukyoku) or management association.
Calculate your share: (Your unit’s floor area ÷ Total exclusive floor area of all units) × 100 = Your % share of common areas.
Verify that maintenance fees, repair contributions, and voting rights align with this calculated share.
Sources
Not legal advice. This article is general information based on publicly available sources, written for educational purposes. Laws change and individual situations vary. Consult a licensed attorney in your jurisdiction before acting on anything you read here. Last reviewed: 2026-06-08.