Managing Ageing Investment Property in Japan: Preventing Leaks and Blocked Drains

Published2026.11.0210 min read

The return on an investment property is not decided only by the price and yield at purchase. One water leak or blocked drain can bring repair costs, compensation to tenants, rent reductions and vacancies. And Japan’s buildings are now entering “middle age” in large numbers. Here is what owners of whole buildings and individual condominium units should know, based on MLIT and other official data.

Key points

Ageing stockCondominiums aged 40+ years: about 1.588 million units at the end of 2025, expected to double in 10 years and triple in 20
Common problemsLeaks (supply and hot-water pipes, drains, roof and walls) and blocked drains that spread damage to units below
Owner liabilityLandlords must repair; rent is reduced if part of a unit is unusable; owners are liable for damage caused by building defects
What to doMake statutory inspections, patrols and drain cleaning routine, and save to a repair plan

Japan’s housing has entered middle age

Point in time	Condominiums aged 40+ years	Built in
End of 2015	about 533,000 units	1976 or earlier
End of 2025 (now)	about 1,588,000 units	1986 or earlier
End of 2035 (10 years)	about 3,131,000 units (×2.0)	1996 or earlier
End of 2045 (20 years)	about 5,036,000 units (×3.2)	2006 or earlier

Source: MLIT estimate, as of end of 2025 ※1

The total condominium stock was about 7.236 million units at the end of 2025. Meanwhile Japan had 9,002,000 vacant homes in 2023, a vacancy rate of 13.8% — both record highs. ※2 With buildings ageing and supply plentiful, management quality decides whether tenants choose your property.

Common problems

Supply and hot-water pipes: corrosion and pinholes in old steel pipes, loose joints
Drains: ageing joints, backflow from blockages, detached washing machine hoses
Building envelope: worn roof waterproofing, cracks in walls, failed sealant around windows
From the unit above: bathroom or washing machine accidents damaging ceilings, walls and belongings below
Blocked drains: kitchen grease, hair and foreign objects build up; a blocked shared stack can cause backflow on lower floors

	Whole building	Single condominium unit
Repair scope	Everything (roof, walls, shared pipes, equipment)	Private area: owner; common areas: owners’ association
Pipes	Owner plans and arranges everything	Where the private section ends is set by the management rules
Funding	Owner saves independently	Association repair reserve + owner’s own funds

The owner’s legal responsibilities

Duty to repair (Civil Code Art. 606): the landlord must make repairs necessary for use (unless the tenant caused the damage)
Rent reduction (Art. 611): if part of the unit becomes unusable through no fault of the tenant, rent is reduced proportionally
Repairs by the tenant (Art. 607-2): if the landlord does not repair within a reasonable time after notice, or in an emergency, the tenant may repair
Liability for structures (Art. 717): if a defect in a building causes damage to others and the occupier took due care, the owner is liable even without fault

Check your building insurance and liability cover for cases like water damage to the unit below or falling exterior materials. ※3

Repair cycles (MLIT guidelines)

Part / equipment	Repair	Replacement
Steel painting (stairs, railings)	5–7 years	—
Water supply / drain pumps	5–8 years	14–18 years
Roof waterproofing	12–15 years	24–30 years
Exterior painting, sealant	12–15 years	24–30 years
Water tanks	12–16 years	26–30 years
Supply and drain pipes	19–23 years (lining)	30–40 years
Elevators	12–15 years	26–30 years
Review of long-term repair plan	Every 5 years	—

Source: MLIT long-term repair plan guidelines ※4. Actual timing depends on inspection.

Buildings around 40 years old are entering their second major pipe works (replacement). Always check the repair history and future plan before buying.

Statutory inspections

Fire safety equipment (Fire Service Act): regular inspections and reports to the fire department (every 3 years for apartment buildings)
Simplified water supply (Water Supply Act): buildings with water tanks over 10㎥ need an annual inspection by a registered body
Periodic reports (Building Standards Act Art. 12): required for certain buildings and for elevators

Five management habits

Regular patrols of common areas, drain pits and roof drains
Periodic high-pressure drain cleaning to prevent blockages and backflow
A first-response plan: contact point, shut-off, emergency fix, photos
Records and saving to match the repair cycles
Move-in / move-out checks of plumbing and equipment

FAQ

In a condominium unit, how much of a leak is the owner’s responsibility?

It depends on whether the cause is in the private area or common area, as defined by the management rules. Contact the management company first and identify the cause.

Who pays for a blockage caused by the tenant?

Repairs for damage caused intentionally or negligently by the tenant are generally the tenant’s responsibility, as MLIT’s restoration guidelines also state. ※5

Can I manage from overseas?

MYHOUSING manages properties for overseas owners from one unit, reporting repairs with quotes and photos for your approval. The management fee is 5.5% (tax included) of monthly rent including the common-area fee.