Bivouacs and snow shelters
Purpose-made snow shovels and cut-down grain shovels are best for digging in snow. At a pinch, ice-axes, billies and plates can be pressed into service. Dry snow is an excellent insulator, though perhaps as cold as -12 °C. Wet snow maintains a temperature of 0 °C.
Choose a steep, avalanche-safe snow slope and dig a tunnel sloping slightly upwards into the slope. In lee slopes and wind scoops, avoid the bottom of the dip, where snow will build up in the next storm. At about two metres in, start widening out to form a sleeping bench. The floor of the room should be a little below the top of the entrance to maintain some warmth, but low enough to allow the occupants to see what is happening outside, observe if the entrance tunnel is being buried by drifting snow and allow some ventilation. If the slope is not very steep, be careful that you do not make the roof too thin. Dome the ceiling perfectly smooth to prevent drips. Insulate the floor with sleeping mats and other gear. Be prepared to get very wet when digging the snowcave.
Beware of carbon monoxide build-up and preferably cook outside the entrance. In very bad weather, close the entrance with packs if you must.
Snow trenches and snow mounds
Snow trenches can be dug in an emergency. Dig a trench just wide enough to work in, two metres long and 1.5 – 2 metres deep. Hollow it out sideways and at one end of the trench, forming a ceiling 50cm below the surface, until you have enough room to accommodate everyone. Dig a set of stairs down to one end. Cover the original opening with snow blocks if the snow is in suitable condition, or a groundsheet covered with 30 cm of loose snow.
In shallow snow, make a packed snow mound over a pile of packs. Tunnel into the packs and extract them, leaving an empty space to occupy. You can further hollow the floor out to make more room.