If I purchase a detached house, am I solely responsible for all maintenance responsibilities, such as exterior walls and roof?

Exactly, in simple terms, that's how it is. When you buy a detached house (一戸建て), essentially, from the roof tiles down to the foundation, and from the exterior paint to the weeds in the yard, all maintenance responsibilities and costs fall 100% on you, the homeowner.

Think of it this way: an apartment (マンション) is like everyone living together in one building, so you collectively pay (management fees and repair reserves) to hire a "caretaker" (management company) to maintain the common areas, like the exterior walls, roof, lobby, elevators, etc.

A detached house, however, means you're the master of your own domain. The entire house and the land it sits on are your private property. Naturally, there's no one else to share these responsibilities with. This is freedom, but it also comes with a significant responsibility.

Specifically, the main areas you'll need to be responsible for and consider include the following:

1. The "Face" of the House: Exterior Walls and Roof

This is the biggest expense and the most crucial maintenance item.

Exterior Walls (外壁): Generally, they need repainting every 10-15 years. This isn't just for looks; it's vital for protecting the wall materials, providing waterproofing, and preventing cracks.
Roof (屋根): Maintenance cycles and methods vary depending on the roofing material. Tile roofs may need inspection and replacement of broken tiles, while metal or composite roofs might require complete recoating or renovation. This also typically happens on a 10-20 year cycle.

If you neglect these, leaks can occur, leading to much more troublesome and expensive repairs.

2. The Internal "Core": House Systems and Appliances

These things are easy to overlook until they break, causing major disruption.

Water Heater (給湯器): These typically last about 10 years and need replacing when they fail.
Kitchen and Bathroom Fixtures: Things like range hoods, faucets, toilets, bathroom ventilation/drying units, etc., can wear out or break over time.
Air Conditioning: Even though you install it yourself, it's part of the house systems. Cleaning, repairs, and replacement are your responsibility.

3. The Invisible "Enemy": Termite Control

This is often overlooked but critically important, especially in Japan where wooden structures are common.

Termite Inspection and Prevention (シロアリ駆除・予防): It's generally recommended every 5 years. If you wait until you see termites, the wooden structure of your house might already be severely damaged, leading to significant losses.

4. The Surrounding "Environment": Yard and Exterior Structures

Yard (庭): If you have a yard, mowing the lawn and trimming trees become regular tasks.
Exterior Structures (外構): Things like fences, gates, driveway/parking surfaces, etc., also need repair if they become damaged or rusty, and you pay for it.

A Tip for You:

So, what does an experienced homeowner do? They set up their own "maintenance reserve fund" (修繕積立金).

While not mandatory, this is a very wise practice. You can follow the model of apartment repair reserves: based on your house's condition, set aside a fixed amount each month (e.g., 10,000-20,000 yen) specifically earmarked for these major future repairs. This way, when you need hundreds of thousands or even a million yen to renovate the exterior or roof 10 years down the line, you won't face a huge financial burden.

In summary, the benefits of buying a detached house are greater freedom, more space, and no restrictive building rules. The trade-off is that all maintenance responsibilities and costs rest solely on your shoulders. Planning ahead and factoring future repair costs into your regular budget is key to living there comfortably and for the long term.