Tokyo Mansion Renovation — 管理組合 Approval, 一級建築士, ¥5K-¥1M per sqm

Most AskBaily markets share a common shape: a homeowner owns their unit, hires a licensed contractor, pulls a permit, and starts work. Tokyo runs differently in one way that English-speaking foreign owners get wrong with remarkable consistency. In Japan, mansion — マンション — does not mean a luxury single-family house. It is the Japanese real-estate term for a reinforced-concrete condominium building, almost always governed by a management association (管理組合 / kanri kumiai) whose consent must be obtained before you move a wall, change a floor, or replace a window. The single-family detached house is called 一戸建て (ikkodate) — a different regulatory animal entirely.

This pillar is written for the Tokyo expat homeowner, the bilingual Japanese real-estate professional advising foreign clients, and the foreign investor who owns a Tokyo mansion unit. Baily's position here is narrow: one verified team consisting of a Class 1 Architect (一級建築士 / ikkyū-kenchikushi) who can stamp the drawings your 管理組合 will actually accept, and a Construction Industry Act (建設業法)-licensed contractor whose license grade and specialty categories match the scope. Angi sends your information to twelve strangers. Baily sends it to one Japanese-licensed kenchikushi-and-contractor team that handles foreign-investor-friendly mansion renovations and has actually done the paperwork dance with a Tokyo management association before.

The regime is not punitive. It is unforgiving if you fail to understand which walls you own, which you merely use, and which of your neighbours have standing to object in writing.

What "mansion" means in Japan (and what it doesn't)

A マンション is a concrete or steel-reinforced-concrete multi-unit residential building, used interchangeably with "condominium" in English-language Tokyo listings. A typical Tokyo mansion ranges from a 1970s four-storey Setagaya low-rise to a fifty-storey Toranomon tower. The legal structure is governed by the Act on Building Unit Ownership, Etc. — 建物の区分所有等に関する法律, usually shortened to 区分所有法 (kubun-shoyū-hō) — enacted in 1962 and amended materially in 1983 and 2002.¹

Do not confuse this with 一戸建て (ikkodate), the single-family detached house on its own plot with no management association. Also worth knowing: 分譲マンション (bunjō-manshon) is a for-sale condominium as distinct from 賃貸マンション (rental). A foreign investor buying a Tokyo mansion unit is almost always buying into a bunjō-mansion, meaning a management association exists, meaning the renovation conversation starts there.

Before you talk to an architect or contractor, read the 管理規約 (management rules) of your specific building. Every bunjō-mansion has one, typically based on the MLIT model rules but customized by each association, covering permitted hours, approval procedure, soundproofing rating required for flooring changes, and consent thresholds for touching common parts.²

Common parts vs exclusive parts under 区分所有法

The Condominium Act makes a distinction that does not map cleanly onto the English concept of "my apartment." Under the Act there are 専有部分 (sen'yū-bubun / exclusive parts) and 共用部分 (kyōyō-bubun / common parts), and the line is narrower than most foreign owners assume.

Exclusive parts (専有部分). Your title extends to the interior surfaces of your unit only: finished face of walls, upper surface of floor finish, underside of ceiling finish, interior side of entry door, and everything inboard. Interior non-loadbearing partitions within your unit are typically exclusive, as are plumbing and electrical downstream of the riser connections.

Common parts (共用部分). Everything else: structural concrete walls (including those forming your unit boundary), floor and ceiling slab, exterior windows and sashes, the balcony (exclusive-use right, not ownership), entry door exterior face, plumbing risers, electrical risers, ventilation ducts, corridors, lobbies, lifts, rooftop, building exterior.

The practical consequence: the wall your bathroom backs against is almost certainly a common-part structural wall containing a common-part plumbing riser. You cannot cut into it, re-route its plumbing, or even drill an anchor without management association consent. The exterior window you would like to replace is common — and typical Tokyo mansion rules categorically prohibit individual owners from replacing windows at all.

Article 17 of the Condominium Act sets the consent threshold for modifying common parts at a four-fifths majority at a general meeting.³ This is why experienced Class 1 Architects start by pulling the original 確認申請 (kakunin-shinsei) permit drawings from the building management office and marking every wall by classification before concept design begins.

Management association (管理組合) approval process

Every Tokyo bunjō-mansion is governed by a management association (管理組合) which all unit owners belong to automatically. The association elects an executive committee and typically delegates operations to a 管理会社 (management company).

The workflow: the unit owner submits a written renovation application (リフォーム工事申請書) including scope, architect-stamped drawings where required, flooring-change specifications with sound-insulation rating, contractor's Construction Industry Act license number, insurance certificates, and proposed construction hours. Depending on scope, approval is either delegated (interior-only, exclusive-parts-only), committee-level (most mid-scope renovations), or requires a general meeting vote (anything touching common parts). A written approval letter is issued with conditions attached.

Review runs 30 to 90 days. Light scopes clear in two to three weeks; general-meeting scopes can take three months because meetings are often scheduled only once or twice a year. A foreign investor buying in late autumn and targeting a spring move-in should plan around the association meeting calendar.

The application requires the contractor's 建設業許可 number and copies of 労災保険 (workers' compensation) and general liability certificates. A contractor without a Tokyo Metropolitan Government prefectural license or national license will be rejected at this stage by most Tokyo management offices.

Soundproofing LL-45 / LL-40 floor rating requirement

One of the most universally enforced management rules in Tokyo concerns floor sound insulation. The reference is the Japan Industrial Standards floor impact sound insulation rating expressed as LL-45 (acceptable), LL-40 (higher standard), or LL-50+ (inadequate for most buildings). Lower LL number equals better impact insulation.

Most Tokyo mansions built from the late 1980s forward require LL-45 minimum for any flooring change; many newer buildings require LL-40. The classic violation is the foreign owner who rips out original carpet to install hardwood without an acoustic underlay. The downstairs neighbour files noise complaints within weeks, the association serves a formal notice, and the owner is required to re-rip the hardwood, install an LL-45-or-better underlay or floating-floor system, and re-install. Re-doing this averages ¥800,000 to ¥2,000,000 for a typical 60 sqm 2LDK.

Acceptable solutions include direct-bond LL-45 rated flooring products (Daiken, Asahi Woodtech, Eidai), floating-floor constructions with resilient underlayment, or carpet-over-resilient-pad installations. The specification is shown on the renovation application at submission; a product certificate is included in the completion handover pack.

Building age matters: pre-1981 旧耐震 vs post-1981 新耐震

Japan is a high-seismicity country and its Building Standards Act (建築基準法 / Kenchiku Kijun Hō) has been revised after each major earthquake event.⁴ The most consequential revision for mansion ownership is the 1981 amendment, introducing what is now called the 新耐震 (shin-taishin / new earthquake standard).

Pre-1981 (旧耐震 / kyū-taishin). Buildings with permit applications approved before 1 June 1981 were designed to the old seismic code. Over-represented in central Tokyo (Shibuya, Shinjuku, Minato, Chuo) because of location in prewar-established districts. Domestic banks restrict mortgages on kyū-taishin buildings, typically requiring a seismic-retrofit certificate (耐震基準適合証明書) before financing. Insurance premiums are higher. Foreign buyers financing through specialized providers may face LTV caps of 40 to 50 percent.

Post-1981 (新耐震 / shin-taishin). Required buildings to withstand a magnitude-6-upper earthquake without collapse. Financing is conventional, insurance standard.

Post-2000 reinforced. The 2000 amendments tightened connection details, concrete cover, and reinforcement anchorage following the 1995 Great Hanshin-Awaji Earthquake.

2024 amendment. A further round through 2024-2025 tightened concrete cover and connection detailing for newly permitted structures — does not affect existing mansions directly but applies to major reconstruction.

A pre-1981 Azabu mansion priced 30 percent below a comparable Akasaka shin-taishin unit may look like a bargain, but financing constraints, insurance costs, and the association's likely near-term demand for collective 耐震診断 (seismic assessment) can absorb the discount. Flag seismic status in pre-acquisition due diligence.

Class 1 Architect (一級建築士) — when required

The Architect-Engineer Act (建築士法) establishes three classes of kenchikushi.⁵

• Class 3 (木造建築士). Wood-only. Not relevant for mansion work.
• Class 2 (二級建築士). Buildings up to 300 sqm and two stories, residential. Covers small ikkodate but not mansion work.
• Class 1 (一級建築士). Unrestricted by size, height, or type. Required for any building over 200 sqm or over two stories — capturing essentially every Tokyo mansion.

The Class 1 license is a national license administered by MLIT. It is not the same as a US state-licensed architect (AIA / NCARB) and the two do not reciprocate. The licensing exam runs notoriously rigorous, with pass rates under 15 percent in recent years.

A Class 1 Architect is required whenever scope includes modification of structural elements, any change requiring a building permit (確認申請) under Article 6 of the Building Standards Act, or any scope the management association requires architect-stamped drawings for. In practice, every mansion renovation involving wall modifications, plumbing re-routing, or structural-adjacent work passes through a 一級建築士's stamp before it reaches the management office.

Class 1 Architects are listed on MLIT's national register and through the Japan Institute of Architects (JIA).⁶ Baily's Tokyo partner architect network is built from this list. We verify license currency before introducing.

Construction Industry license (建設業許可)

The contractor side is governed by the Construction Industry Act (建設業法 / Kensetsugyō-hō).⁷ Any contractor undertaking work valued over ¥5 million (¥15 million for building construction) requires a Construction Industry license — either a national license (国土交通大臣許可) for multi-prefecture operators, or a prefectural license (都道府県知事許可) issued by the prefectural governor. For Tokyo, the prefectural license is issued by the Tokyo Metropolitan Government (東京都知事許可).

The Act defines 28 specialty categories (業種). Those relevant to mansion renovation include 建築一式工事 (general building), 内装仕上工事 (interior finishing), 管工事 (plumbing), 電気工事 (electrical), and 防水工事 (waterproofing). A full mansion renovation prime contractor should hold 建築一式工事 or 内装仕上工事, with subcontractors holding relevant specialty licenses.

Two trade-specific licenses sit alongside. Electrical wiring may only be performed by workers certified as 第二種電気工事士 (Class 2 Electrical Engineer) or higher under the Electrical Engineer Act (電気工事士法).⁸ City gas installation may only be performed by certified 都市ガス工事士 under the Gas Business Act. Many Tokyo management associations require copies of these certifications for the tradespeople on site.

Working hours + neighbor notification (ご挨拶) cultural requirement

Most Tokyo mansions set permitted construction hours at 09:00 to 17:00 Monday through Friday, with no Saturday, Sunday, or public holiday work. Some older buildings permit Saturday morning work; some newer luxury buildings restrict to 10:00 to 16:00 weekdays. Buildings with a resident superintendent (管理人) enforce this by not allowing contractor staff access to the service lift outside posted hours.

The cultural layer that surprises foreign owners is the 挨拶 (aisatsu / greeting) obligation. Before construction begins, the contractor on behalf of the homeowner makes a door-to-door visit to the immediate neighbours (unit above, below, and on either side) to notify them of the upcoming construction, provide schedule and contact information, and present a small customary gift — typically a box of wrapped sweets or a towel set worth ¥500 to ¥1,500 per neighbour. Not a legal requirement; a strongly-enforced cultural norm. Skipping it is the fastest way to generate noise complaints and management association friction on day one. Baily's partner contractors run this visit as a matter of course; it is not a line item on the quote.

Asbestos in pre-1995 buildings

Japan did not comprehensively ban asbestos until 2006. Mansions with permit applications approved before 1995 — a substantial share of central Tokyo housing stock — commonly contain asbestos in fireproofing sprays on structural steel, in some ceiling tile products, and in vinyl floor tile backing.

The regulatory framework is the Air Pollution Control Act asbestos provisions as amended in 2022, which requires a pre-demolition asbestos survey (石綿事前調査) on any building part subject to demolition or substantial renovation, registration of survey results with the local ward, 14-day advance notification for any abatement work (石綿除去作業), certified abatement contractors, and disposal through licensed hazardous-waste routes.

Budget ¥300,000 to ¥2,000,000 for survey and remediation, add two to six weeks for notification and abatement, and do not allow demolition until the survey is in hand. A contractor who suggests skipping the survey will expose you to personal liability.

Foreign-owner financing reality

Japan imposes no restriction on foreign individuals or entities owning Tokyo real estate. A foreign passport holder can buy, hold, rent, and sell on the same legal footing as a Japanese citizen. There is no equivalent of Singapore's Additional Buyer's Stamp Duty.

The constraint is financing. Domestic banks (MUFG, SMBC, Mizuho) rarely extend mortgages to non-resident foreigners. Resident foreigners with permanent residency (永住者) can typically access domestic-bank financing on terms similar to Japanese citizens. Non-residents typically access financing through specialized domestic banks with foreign-client desks (Tokyo Star Bank, SBI Shinsei Bank) at 50 to 60 percent LTV and 2.5 to 4 percent APR, through international banks with Japan branches, or all-cash — the most common route for foreign investment purchase, particularly for trophy properties in Hiroo, Roppongi, Azabu, and Shoto.

Domestic-bank renovation loans (リフォームローン) are generally not available to non-resident foreign owners. Renovation is typically funded at closing (if the lender permits scope uplift), through a separate loan from the foreign-client bank, or from the owner's capital. Baily does not provide financing; financing is a pre-condition you arrive with.

Cost bands: ¥5K-¥1M per sqm by scope + finish

Tokyo mansion renovation cost is quoted per square metre and varies by roughly two orders of magnitude. 2026 pricing:

Light — ¥50,000 to ¥100,000 per sqm. Paint, wallpaper, flooring swap (LL-45), fixtures, minor kitchen-cabinet refresh. No plumbing or electrical re-route. Typical 60 sqm 2LDK: ¥3M to ¥6M.

Mid-range full reno — ¥150,000 to ¥300,000 per sqm. New kitchen, new bathroom with waterproofing membrane and LL-rated floor, interior partition modifications within exclusive parts, electrical refresh, interior-window (内窓) retrofit. Class 1 Architect involvement. Typical 60 sqm 2LDK: ¥10M to ¥20M.

Premium full reno — ¥300,000 to ¥600,000 per sqm. High-end kitchen (Miele, Gaggenau, Subzero), full stone bathroom with Japanese-style soaking tub, structural reconfiguration requiring executive committee approval, underfloor heating, smart-home integration. 80 sqm 3LDK: ¥25M to ¥50M.

Luxury trophy — ¥600,000 to ¥1,000,000+ per sqm. Roppongi Hills, Azabu-Juban, Hiroo, Shoto, Akasaka tower-residence territory. Full interior design by name practice, bespoke millwork, fine stone. 120 sqm units routinely clear ¥100M.

These bands exclude consumption tax (10 percent), architect fees (8 to 12 percent of construction cost), and management association fees.

Timeline: 5 to 12 months total

Full-renovation timeline from first architect contact to handover:

• Management association pre-consultation and rule review — 1 to 2 weeks.
• Schematic design — 3 to 6 weeks.
• Design development and contractor tendering — 4 to 8 weeks.
• Management association approval — 30 to 90 days.
• Building permit (確認申請) if structural scope — 4 to 12 weeks. Most interior renovations do not trigger 確認申請.
• Pre-construction aisatsu — 1 week.
• Asbestos survey and abatement if pre-1995 — 2 to 6 weeks (can overlap).
• Construction — 8 to 24 weeks. Light 6 to 10, mid-range 10 to 16, premium 16 to 24.
• Completion inspection, final sign-off, defects handover — 2 to 4 weeks.

Foreign investors planning a spring move-in should engage the architect by the preceding autumn. The association calendar drives the pace more than the construction schedule.

What Baily verifies before any Tokyo mansion match

Before introducing the homeowner to any architect or contractor, Baily verifies:

• Class 1 Architect license (一級建築士登録番号) current on the MLIT national register.
• Construction Industry license (建設業許可) current on the Tokyo Metropolitan Government prefectural register, with specialty categories covering the scope.
• Workers' compensation (労災保険) and general liability insurance valid through construction.
• At least one prior Tokyo mansion renovation delivered in the past 24 months, with the management association approval letter and completion certificate available on request.
• For pre-1995 buildings, contractor specialty license for asbestos pre-survey and abatement.
• English-language communication capacity — in-house bilingual project manager or dedicated liaison.
• Cultural awareness of the aisatsu workflow as a matter of course.

We introduce one architect-and-contractor team per homeowner. The partner receives a single homeowner lead with full project context, not a broadcast enquiry shared with eleven competitors, and is expected to respond within one business day with a scoping call invitation.

Frequently asked questions

Can I knock down walls in my Tokyo mansion to combine rooms?

Maybe — depends on whether the wall is structural and whether it's in your exclusive part (専有部分) or shared common parts (共用部分). Under the Condominium Act (区分所有法), interior partition walls in your exclusive part can typically be removed with management association notification only. Load-bearing concrete walls, walls containing plumbing risers, and walls bordering common corridors are common property and require either a 4/5-majority owners' meeting vote or are categorically prohibited. Your Class 1 Architect (一級建築士) reads the original 確認申請 (kakunin-shinsei) drawings to confirm wall classification before design starts. The single most common foreign-investor mistake is assuming "interior wall = my wall" — Japanese mansion law does not work that way.

Do I need a 一級建築士 or can a 二級建築士 handle my mansion renovation?

You need a Class 1 Architect (一級建築士). Class 2 Architects (二級建築士) are licensed for buildings up to 300 sqm gross floor area and two stories — a small detached house, not a mansion building. Even if your unit is only 60 sqm, the building is almost certainly over 300 sqm and over two stories, and Japanese architect-license scope is tied to the building, not the unit. Most Tokyo management associations also explicitly require 一級建築士-stamped drawings as a condition of renovation approval.

As a non-resident foreign owner, can I get a Japanese bank to finance my mansion renovation?

Almost never from a domestic bank (MUFG, SMBC, Mizuho) if you are non-resident. Specialized foreign-client banks (Tokyo Star Bank, SBI Shinsei Bank) and international banks with Japan branches offer renovation-loan products at 50 to 60 percent LTV with 2.5 to 4 percent APR, but most foreign-owner renovations are funded either at purchase closing (with scope uplift included in the purchase mortgage) or from the owner's own capital. Baily does not introduce lenders. If financing is a constraint, arrange it before you engage the architect.

My building was built in 1978. Can I still renovate, or do I need to wait for a seismic retrofit?

You can renovate. A pre-1981 (旧耐震) mansion carries financing and insurance constraints on the unit, but individual-unit renovation within your exclusive part is legally permitted. Your Class 1 Architect will flag any interaction between your scope and a pending collective retrofit. Do not undertake interior refurbishment worth more than 10 to 15 percent of unit value in the same year the association plans to levy a special assessment for collective retrofit — the sequencing can leave you paying for finishes that are disturbed when the retrofit scaffold comes in.

How long before construction should I notify my neighbours, and what should I bring?

Seven to fourteen days before construction start is standard. The visit is typically made by your contractor's site supervisor, often accompanied by you on larger projects. Bring a written notice (工事のお知らせ) showing schedule, hours, and contact info, along with a small wrapped gift per household — a ¥500 to ¥1,500 box of confectionery or towel set is customary. Visit the units immediately above, below, and on either side at minimum; many contractors visit the full floor and the floor above. Not a legal requirement, but one of the most consequential soft-skill inputs to project success in a Tokyo mansion setting.

Sources

Footnotes

1. Act on Building Unit Ownership, Etc. (建物の区分所有等に関する法律), Law No. 69 of 1962 as amended. Text: https://www.japaneselawtranslation.go.jp/en/laws/view/3766/en and https://elaws.e-gov.go.jp/document?lawid=337AC0000000069. ↩

2. Ministry of Land, Infrastructure, Transport and Tourism (国土交通省) Mansion Management portal, including the MLIT Model Management Rules for Condominiums (マンション標準管理規約): https://www.mlit.go.jp/jutakukentiku/house/jutakukentiku_house_tk5_000058.html. ↩

3. Condominium Act Article 17 — common-parts modification consent thresholds. https://elaws.e-gov.go.jp/document?lawid=337AC0000000069. ↩

4. Building Standards Act (建築基準法), Law No. 201 of 1950 as amended. https://elaws.e-gov.go.jp/document?lawid=325AC0000000201. The 1981 amendment introducing 新耐震 and the 2000 and 2024 amendments are available through the same e-Gov portal. ↩

5. Architect-Engineer Act (建築士法), Law No. 202 of 1950 as amended. https://elaws.e-gov.go.jp/document?lawid=325AC0000000202. Establishes Class 1, Class 2, and Class 3 architect licenses. ↩

6. Japan Institute of Architects (公益社団法人 日本建築家協会 / JIA): https://www.jia.or.jp/english/. ↩

7. Construction Industry Act (建設業法), Law No. 100 of 1949 as amended. https://elaws.e-gov.go.jp/document?lawid=324AC0000000100. See also the Tokyo Metropolitan Government Bureau of Urban Development Construction Industry Licensing page: https://www.toshiseibi.metro.tokyo.lg.jp/kenchiku/kensetugyo/. ↩

8. Electrical Engineer Act (電気工事士法), Law No. 139 of 1960 as amended. https://elaws.e-gov.go.jp/document?lawid=335AC0000000139. ↩