Snow Based Survival Shelters

Building a shelter in the snow presents additional dangers that you need to be aware of. Obviously the cold can result in frostbite in your fingers, but melting snow can soak your clothes which will suck the heat out of other body areas. And if there's no way to quickly dry off, you will find yourself in serious danger of hypothermia.

There are two forms of shelter you make using snow. The choice of shelter will depend largely on the terrain and the depth of the snow.

Tree Pit Shelter
The tree pit shelter is one of the easier snow shelters to build largely because it makes use of the cover provided by a trees branches.

1. Find a tree such as a Douglas or grand fir. The key is to find one with multiple lower branches that provide adequate overhead cover. For the most part, pine trees will provide little protection and are not a good choice.
2. Break away the lower branches until there is enough room for you. Note that the branches will be low enough for this because there will be several feet of snow “raising” the height of the ground.
3. Incorporate the broken branches into the structure of the tree to provide additional protection from the elements.
4. Dig down in to the snow until you hit bare ground if possible. This will depend of course on the depth of snow. This area should be big enough for you and your gear.

The snow around you will provide insulation while the tree will provide some structural support and cover over your head.

Building a Snow Cave Shelter
A snow cave requires an area of firm snow that is at least 6 feet deep. Ideally, a steep slope like that found on a riverbank or on a snowdrift will work best. Be sure the location you choose isn't at risk of an avalanche. Once you've found a suitable location, proceed with the following steps:

1. Dig an entryway into the slope 3 feet deep to be used as a tunnel. The hole will need to be big enough for you to fit in to it as well.
2. To take advantage of the fact that cold air sinks, construct a snow platform 2 to 3 feet above the entryway. It should be flat, level, and large enough for you to comfortable lie down on.
3. Using the entryway as a starting point, hollow out a domed area that is large enough for you and your equipment. To prevent the ceiling from settling or falling in on you, create a high domed roof.
4. To prevent asphyxiation, make a ventilation hold in the roof. If available, insert a stick or pole through the hole so that it can be cleared periodically.
5. To further protect the shelter from the elements, place your pack in the entryway. If you don't have a pack, you can use tree branches such as pine which will still have their needles attached.

When you're in the snow cave, you will have few clues about what is going on outside. For this reason, check the entrance periodically.

Snow A-Frame Shelter
The snow A-frame is a little harder to be built, but if you can't find a suitable location for a tree pit or a slope in which to build a snow cave, it is a good alternative. You'll need to find a flat area with snow that is at least 3 to 4 feet deep. It should be clear of trees and underbrush as well.

1. Start by stomping out a rectangular area wide and long enough to accommodate your body.
2. Let the snow pack itself and harden for at least thirty minutes.
3. Then dig a 3 foot deep entryway just in front of the rectangular area.
4. Now it gets tricky. Cut multiple 3 foot square blocks that are 8 to 10 inches wide from the rectangular area. You'll need a tool such as large machete, stick, or ski to accomplish this.
5. The blocks will form the roof of your shelter. That is, each block should be placed against another to form an A-frame above the rectangular area.
6. Fill in any gaps in the roof with surrounding snow.

WARNING: The temperature must be well below freezing to ensure that the walls of the cave will stay firm and the snow will not melt. In addition, once the snow shelter is built, never get the temperature above freezing inside; if this happens, it will lose its insulation quality and you will get wet from the subsequent moisture. A general rule is that if you can't see your breath, it's too warm.

References:
Wilderness Survival by Gregory J. Davenport