Every akiya buyer underestimates renovation. The rough rule of thumb — budget 30-100% of purchase price for renovation, and double-glazing is non-negotiable — conceals a thousand local variations, and the Japanese contracting market is opaque to outsiders by design. This is the field guide we wish we'd had on our first house.

Budget rules of thumb, by decade

House structures built between these dates require these levels of work:

  • Pre-1980 — assume full systems replacement (water, electric, gas, septic, heating). Budget 50-100% of purchase price.
  • 1981-1995 — "new earthquake code" (shin-taishin) houses, structurally fine. Often need updated insulation, double-glazing, kitchen and bath. Budget 30-50% of purchase price.
  • 1996-2005 — usually liveable with cosmetic refresh. Budget 15-25% of purchase price.
  • 2006+ — should be move-in ready, possibly with appliance updates. Budget 5-15%.

The five non-negotiables

Whatever else you do or don't do, these five are not optional in any year-round-liveable snow-country house:

  1. Double-glazing. Single-pane glass + Japanese winter = freezing condensation + mold. Budget ¥30,000-¥60,000 per opening.
  2. Insulation. Most pre-1995 houses have none. Floor and ceiling insulation alone changes the house's habitability.
  3. Water heater (kyutoki) replacement. The standard kyutoki has a 12-15 year life and degrades silently. ¥200,000-¥400,000.
  4. Gas piping inspection. Required by law before reconnection. Almost always identifies one or more issues. ¥30,000 inspection + variable repair cost.
  5. Septic / sewer connection. Many rural akiya use a johkasou (private septic). Servicing required annually. If the previous owner stopped servicing it — budget ¥800,000-¥1.5M to replace.

What to leave alone

For kominka in particular, the temptation to "open up" the floor plan can destroy what makes the house valuable. Some things to leave intact:

  • Daikoku-bashira — the central load-bearing column. Often centuries old, structurally critical, and aesthetically irreplaceable.
  • Engawa (the wooden veranda) — if it is structurally sound, it is the kominka's signature feature.
  • Original sliding panels (fusuma, shoji) — pricier to replicate than to restore.
  • Tatami flooring in main rooms — can be refreshed for ¥15,000-¥25,000 per mat (8-10 mats per room); replacing entirely is rarely worth it.

Contractors, ranked by what you should hire them for

  • Kominka specialist (kominka senmon kosha) — for traditional carpentry, shoji/fusuma, raised hearths, post-and-beam structural work. Concentrated in Hida (Gifu), parts of Nagano, and rural Tohoku.
  • General contractor (komuten) — for kitchens, baths, modern flooring, plumbing, electrical. Every town has one or two.
  • Renovation specialist (rifomu kaisha) — for whole-house refreshes by a general contractor with a designer on staff. National chains include LIXIL, Panasonic Living.
  • Direct trades — for single jobs (gas, electric, roof). Cheaper than going through a general contractor, but requires you to coordinate.

Reading the quote

Japanese construction quotes (mitsumorisho) follow a predictable structure: itemized line items, with the "materials" (zairyo) and "labor" (sho-rin) costs broken out separately. Look for:

  • Demolition (kaitai) — often missing from rough quotes and a real expense.
  • Disposal (sanpai shobun) — required for asbestos-containing materials, expensive.
  • Scaffolding (ashiba) — needed for any roof or two-storey exterior work.
  • Consumption tax (shohi-zei, 10%) — often quoted as "excluded" until final invoice.

Get three quotes. They will vary by 40-80%. The middle one is usually right.