Building where the road closes in winter
A cabin above the snow line is built in the short season between thaw and the first storm, often with every material trucked up in one or two loads. That is the reason to count everything first: a forgotten box of fasteners is a day's drive. This one is a single room with a bathroom partition, one outside door and five modest windows facing the view.
Frost runs deep at altitude, so the trench goes to 1.5 m (about 5 ft) here; your building official will name the depth for the site, and the backfill row follows it.
Foam in a 2×6 frame
Closed-cell spray foam fills the full 5 1/2 in (140 mm) cavity of 2×6 studs. It insulates, seals against the wind that finds every gap in a timber cabin, and slows vapour by itself, so the page will not add a polyethylene sheet over it: two vapour-closed layers can trap water between them. The foam row is an area at the cavity depth; get the yield from your installer.
Board-and-batten siding suits the setting and is counted across the whole outside face: boards around a door or window are cut from full-height boards, so the count does not deduct the openings, and the row says so.
A 12 in 12 roof
A 45° roof sheds a heavy snow load instead of holding it, and its slope factor of about 1.41 means the shingles cover far more than the plan. Generous 600 mm (2 ft) overhangs on every side protect the siding from drip and drift. The ice-dam strip runs up both eaves, which on a roof this steep is a narrow band of the slope.
Before the truck goes up
The slab is 125 mm (5 in) here rather than the usual 100: thicken it only on an engineer's word, because a slab under a snow-loaded roof is a structural question this page does not answer. And count a few spare sheets of plywood for the loft deck, which no row here includes.
Ask, too, how the materials get up the last stretch of track. A full pallet of shingles can weigh more than a light pickup should carry on a washboard road, and foam is sprayed by a rig that needs power and a dry day; book the sprayer before the windows go in, so the cavities are open and warm enough to take it.