What premises can become a Sakoju? The reality of 25 m² per unit and barrier-free design

In short: the skeleton of premises that can register as service-provided housing for the elderly (Sakoju) is four things — each unit 25 m² or more in principle (18 m² if the shared areas are ample); a kitchen, toilet, washbasin, bath and storage in each unit or the shared areas; barrier-free corridors, level differences and handrails; and at least a status-check (safety-confirmation) and a life-consultation service. These are the registration standards under the Elderly Housing Act; design/renovation and the rules on contracts and operation are asked together. Existing buildings can meet them, but floor area and the design of the shared areas decide feasibility.

"Can I turn a vacant apartment into a Sakoju?" is a question we hear more and more. But a Sakoju is not a title you can freely adopt — it is a registration scheme under the Elderly Housing Act. This article is for real estate owners and operators in Tokyo considering a Sakoju: the property and building conditions for registration, set out in order from the Act on Securing Stable Living for the Elderly and the guidance of the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and the Ministry of Health, Labour and Welfare. Final confirmation of feasibility and figures rests with the registering authority — the prefecture, designated city, etc.

What are the minimum conditions to register as a Sakoju?

A Sakoju is rental housing for the elderly registered under Article 5 of the Act on Securing Stable Living for the Elderly (Act No. 26 of 2001). The registering authority is the prefectural governor (or the head of a designated/core city); the registration has a term and is renewed every five years (accessed 25 August 2026).

The skeleton of the standards splits into "the housing itself," "the services provided," and "the contract."

Category	Skeleton of the standard
Scale	Each unit 25 m² or more in principle (18 m² if the living/dining/kitchen shared areas are of ample size)
Equipment	A kitchen, flush toilet, storage, washbasin and bath in each unit (where these are suitably provided as shared facilities, some need not be in each unit; but a toilet and washbasin are basically per unit)
Structure	Barrier-free (corridor width, removal of level differences, handrails)
Services	At least a status-check (safety-confirmation) service and a life-consultation service; involvement of care professionals
Contract	A written contract with the residential portion specified; no money collected beyond rent, deposit and service consideration; return rules and safeguarding for prepayments; the residential portion is not changed and the contract not terminated without the resident's consent

Note that the floor-area and equipment figures are housing standards, and together with the service and contract rules they make up the "registration standard." Getting the building right alone will not register it if the service framework or the contract falls short. What matters first as a property matter is the floor area, barrier-free, and how the shared areas are built.

Can 25 m² per unit, shared equipment and barrier-free be met in an existing building?

Sometimes yes, but the older the building, the more floor area and the design of the shared areas divide feasibility.

First, floor area. The principle is 25 m² or more per unit; even units that fall short are eased to 18 m² or more where the shared areas — living/dining/kitchen — are of ample size. So it becomes a design choice: "widen each unit" or "thicken the shared areas." Converting an existing one-room apartment, the first hurdle is where to secure that shared area.

Second, equipment. In principle each unit has a kitchen, toilet, washbasin, storage and bath; but where these are suitably provided as shared facilities, some need not be in each unit (kitchen, bath, storage). A flush toilet and washbasin, however, are basically per unit. How you use this easing greatly changes the scale of renovation.

Third, barrier-free. You must meet structural standards on corridor width, removing level differences, handrails and the like. In existing buildings, corridor width and the presence of stairs/lifts are the dividing line for whether renovation can meet them.

Confirm before signing	Why it matters
Each unit's floor area and layout	Can it meet 25 m² (18 m² eased)? Units may need combining
Floor area available for shared areas	Governs whether the floor-area / shared-equipment easings apply
Corridor width, level differences, lift	Governs the scale of barrier-free renovation
Plumbing, electrical capacity	Affects shared kitchen/bath and status-check equipment
Use and structure	Bears on the need for a use-change confirmation and seismic work

Floor area, barrier-free conformity and whether a use-change confirmation is needed are matters of building confirmation and design. We (the real estate agent) assist with the groundwork of whether the property can meet the Sakoju standards, and with negotiating the acquisition/lease terms. Design judgement and conformity itself are handled by an architect. How care-facility premises get stuck is at why care-facility premises are hard to find; which parts of the lease to read, at reading a lease.

Who handles registration, building confirmation and care-service designation?

A Sakoju involves several professionals. The roles split.

What to do	Who
Property investigation/acquisition, brokerage and contract	Licensed real estate agent (us)
Preparation of the Sakoju registration documents	Administrative scrivener
Barrier-free conformity / use-change design; building confirmation	Architect
Long-term-care insurance service (specified-facility care, etc.) designation	Separate procedure (application to the designating authority)

A Sakoju is a registration of "housing"; whether care services are provided within it is a separate scheme. If you provide long-term-care insurance services to residents, a separate designation or notification may be required. Confusing the housing registration with the care-service designation misreads the opening sequence.

Preparation of documents submitted to public offices, such as the Sakoju registration, is undertaken by Yotsuba Administrative Scrivener Office. The registering authority, forms and the operation of the standards (add-ons under a prefecture's own elderly-housing plan, etc.) vary. Check the page of the registering authority directly at the outset. Business property in general is at investment and business real estate; the link between offices and permits, at company formation and choosing an office. How the use zone and floor-area ratio move pricing is at why Japanese land prices change with the floor-area ratio.

How much do cost and time roughly run to?

Cost and time vary greatly with the property's state (new build or existing renovation) and the local operation. There is no nationwide fixed price. Here, without asserting figures, we set out what costs money and time as "items."

Item	How to think about it	Who
Building/renovation cost	Varies greatly with floor area, barrier-free and shared-equipment design; the biggest variable	Architect / contractor
Design / confirmation application	If a use-change confirmation is needed, the period extends	Architect
Registration application	Document preparation to the authority's form; fees depend on the authority	Administrative scrivener
Registration term	Five years (renewal required)	—
Status-check / life-consultation framework	Staffing and equipment as operating cost	Operator

The period moves by months with the scale of renovation of an existing building and whether a use change is needed. The specific amounts, periods and authority-specific standards cannot be fixed in this article, so treat them as unverified and confirm individually with the registering authority and the architect. Grasping the variables and planning around them is safer than forcing a figure.

Who should you consult?

Investigation, acquisition/lease brokerage, and the sale or lease contract are handled by Yotsuba Real Estate Co., Ltd. (licensed real estate agent, Tokyo Governor (1) No. 113304). Preparation of documents submitted to public offices, such as the Sakoju registration, is handled by Yotsuba Administrative Scrivener Office. Barrier-free conformity and use-change design and building confirmation are handled by an architect; the care-insurance service designation is a separate procedure.

These two (the real estate agent and the administrative scrivener office) are independent business entities. You engage each directly. We neither pay nor accept referral fees or introduction commissions. Design/building confirmation goes to an architect, registration to a judicial scrivener, tax to a tax accountant, and labour matters to a certified social insurance labour consultant (opening planned September 2026) — each engaged by you directly. Consultation is free of charge.

Frequently asked questions

Q. Can a unit of 18 m² still register as a Sakoju?
A. It can, in some cases. Each unit is 25 m² or more in principle, but where there are shared facilities of ample size for common use by the elderly — living/dining/kitchen — it is eased to 18 m² or more (the registration standard under the Act). How the shared-area floor area is taken changes feasibility, so confirm at the design stage with the architect and the registering authority.

Q. Can I convert an existing apartment into a Sakoju?
A. Yes, if it can meet the floor-area, barrier-free and shared-equipment standards. But if corridor width, level differences, the shared-area floor area, or the plumbing fall short, renovation or a use-change confirmation may be needed. In existing buildings, the starting point is to confirm each unit's floor area and the floor area available for the shared areas.

Q. Does a Sakoju automatically let me provide care services?
A. No. A Sakoju is a registration of "housing," and providing a status-check (safety-confirmation) and life-consultation is the registration standard. To provide long-term-care insurance services to residents, a separate designation or notification is needed. The housing registration and the care-service designation are separate schemes, so sequence them separately.

Q. Can I ask a real estate agent to file the Sakoju registration?
A. No. Preparing the registration documents submitted to public offices is administrative-scrivener work, undertaken by Yotsuba Administrative Scrivener Office. Property investigation, brokerage and the contract are handled by Yotsuba Real Estate Co., Ltd. Barrier-free conformity and use-change design and building confirmation are handled by an architect. Each is an independent business entity, engaged directly.

Sources (primary)

• e-Gov "高齢者の居住の安定確保に関する法律" (Act on Securing Stable Living for the Elderly) — Act No. 26 of 2001. Art. 5 (registration of the Sakoju business by the governor etc.); Art. 7 (registration standards — scale, structure, equipment, services, contract); the registration term (five years) and renewal. Accessed 25 August 2026.
• MLIT, "Act on Securing Stable Living for the Elderly (housing)" — overview of the Sakoju registration scheme; each unit 25 m² or more (18 m² if shared areas ample), unit equipment, barrier-free, status-check/life-consultation services, safeguarding of prepayments. Accessed 25 August 2026.
• Sakoju information system (MLIT), "About the scheme" — registration standards, the registering authority, information provision. Accessed 25 August 2026.

The specific figures for floor area, shared-equipment easing and barrier-free, and any add-on standards under a prefecture's own elderly-housing plan, are set by MLIT/MHLW ordinance and each local government's operation, and differ by locality. This article does not assess any individual property. Confirm with the registering authority and the architect at the outset. Whether a use-change confirmation is needed and seismic/barrier-free conformity vary with the property's floor area, structure and zone designation; final judgement rests with the architect and the specified administrative authority. Specific cost and time vary greatly with the property and authority operation and are not fixed here (unverified).

This article is general information. It does not judge or guarantee the feasibility of any particular property or acceptance of a registration. Investigation and brokerage, and the sale/lease contract, are undertaken by Yotsuba Real Estate Co., Ltd. (licensed real estate agent); preparation of the registration and other documents submitted to public offices, by Yotsuba Administrative Scrivener Office — independent business entities, engaged separately and directly. We neither pay nor accept referral fees.

About the author

Joji Uramatsu — licensed real estate transaction specialist (Tokyo Governor registration No. 293544) and administrative scrivener (registration No. 25087022). Representative Director, Yotsuba Real Estate Co., Ltd. (licensed real estate agent, Tokyo Governor (1) No. 113304); principal, Yotsuba Administrative Scrivener Office. Kohinata, Bunkyo, Tokyo, about five minutes' walk from Myogadani station. Property and paperwork are put on the same table. Full profile: author page.