What follows assumes an ordinary detached timber house of roughly 80 to 120 square metres. These are orders of magnitude, not estimates, and they exclude the purchase price and its associated costs. Real figures move a great deal with condition, structure, location, specification and contractor.

Around five million yen

This is the floor for making a house liveable. It reaches the fittings and the surfaces. It does not reach the structure.

What this budget cannot include: roof and exterior wall work, insulation, seismic strengthening, full replacement of supply and waste pipework, replacement of termite-damaged members, or repair to the foundation or frame.

None of the work that extends the life of the building is in reach at this level. The result is a house that looks better and has the same problems. Cheap property plus cheap renovation frequently means paying again a few years later, that time for the structure.

Around ten million yen

Here the structure comes within reach, but not all of it. This budget is about choosing.

The decision that defines this budget is roof or exterior walls. Both determine the life of the building, and doing both properly at this level is difficult. Take the one in worse condition and leave the other for its next cycle.

Seismic strengthening and insulation rarely both survive that choice. Which of them matters more depends on the building, and which structural rules it was built under is where that assessment starts.

Around twenty million yen

This replaces everything inside the frame. It is close to what people mean by a full renovation.

Even here it is not equivalent to a new house. The foundation, columns, beams and parts of the sill remain as they were. Where decay or termite damage means structural members have to be replaced extensively, twenty million can be insufficient, and the honest conclusion is sometimes that building new would be more rational.

Establishing which of those two situations you are in is the job of investigation before purchase, not after demolition begins.

There is a procedural point at this level as well. Since April 2025, work on a two-storey timber house that extends to more than half of a principal structural part, such as the walls, floors or roof, requires building confirmation before it starts. That brings in an architect, drawings, fees and time, and the work is checked against current rules. Whether a given scope crosses that line is a question to settle with the contractor and the municipality before the budget is fixed. On a plot with frontage problems the consequences go further, as set out in the land you can never build on again.

Five things that move the number

The second is the one that cannot be forecast. Open a wall and the insulation is wet. Lift a floor and the sill has been eaten. These are not unusual findings in an old building; they are what old buildings contain. They do not appear in a quotation, because nobody could see them when the quotation was written.

What commissioning work from abroad adds

Beyond the work itself, an overseas owner carries costs that appear in no quotation.

• Language. Quotations, contracts and specifications are in Japanese, and so are the meetings. Signing without understanding is a real risk.
• Site presence. You cannot attend during the work or at completion, so you are judging the result from photographs.
• Decisions on variations. When a wall comes open and a cost appears, an answer is wanted immediately, across a time difference, through translation, on the basis of a photograph and a paragraph.
• Payment. Deposit, interim and final payments, each with international transfer timing and fees.
• Choosing the contractor. Judging who is reliable, from another country, with limited means of checking.

Not being in Japan does not change the price of the work. It changes how the work is managed, and that requires somebody on the ground.

Order matters more than budget

This is the part worth taking away from the whole article.

A new kitchen under a roof that admits water is a new kitchen that will be damaged. New wallpaper over a subfloor that is damp lifts within a few years. The same money buys a completely different outcome depending on the order in which it is spent.

1. Structure first. Repair leaks, treat termites and replace damaged members, repair sills and foundation.
2. Then water: roof and exterior. Until the water is stopped, everything repaired inside continues to be destroyed.
3. Then services. Pipework and electrical, because they are behind everything else.
4. Then insulation and strengthening. Most efficient while walls are already open.
5. Finishes and fittings last. What you can see comes at the end.

Most buyers start at five. The impulse to fix what is visible is entirely understandable. The correct order puts the invisible first, and how the invisible parts fail is set out in by the time it shows on the ceiling, the wood has been wet for a while.

Know what needs doing before you ask what it costs

The number that matters is not the renovation budget. It is the purchase price plus the transaction costs plus the work, and the work cannot be scoped from a listing. What else sits outside the purchase price is set out in what a cheap Japanese house actually costs, and our cost estimator covers the transaction side.