Winter that lasts five months changes the drawing

A house that would be unremarkable in Tokyo becomes a maintenance problem in Kutchan. Three numbers explain most of the difference, and two of them are fixed by regulation before a designer draws anything.

Snow load: 230cm in Kutchan and Niseko

Hokkaido sets a design snow depth for every municipality under Article 86 of the Building Standards Act Enforcement Order. Kutchan and Niseko are both designated at 230cm. Sapporo is 140cm, Otaru 150cm, Furano 130cm. Anything at or above 100cm counts as a heavy-snow region, which changes how the structure has to be calculated.

In practice, a roof in Niseko is sized to carry well over one and a half times the snow a roof in Sapporo carries. Get this wrong and you are paying someone to clear your roof every few weeks for the life of the building.

Frost depth: the foundation has to sit below it

The prefecture publishes a standard frost depth for each municipality as well: 60cm for Kutchan, Niseko and Sapporo, 50cm for Otaru, 70cm for Furano. Foundations have to sit below that line, or the ground freezes underneath them and the house moves with the seasons.

Hokkaido attaches a warning to its own table that is worth repeating. These are standard figures only. Within a single municipality, air temperature, soil, groundwater level and elevation all shift the real depth, so it has to be set for the specific site rather than read off the list. This is the most common shortcut we find in buildings bought second-hand by owners from overseas.

Where the melt water goes

Snow that slides off a roof lands somewhere. If that somewhere is your entrance, your neighbor’s fence, or the only parking space, you will be rebuilding it within two winters. Kutchan publishes its own guidance on how far snow travels when it comes off a roof, and it is further than most people expect.