Survival Shelters: Snow Caves & How to Build One

By Ian Kershaw
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There’s no argument that shelter is one of the most important needs for survival. The worse the weather is outside, the more important good shelter is. This can be said to be especially true in the wintertime, when temperatures can drop below zero and draw the heat out of our bodies.

But wintertime can be a difficult time to build a shelter. If snow covers the ground, it can make it hard to find the necessary materials. Building a debris hut when all the debris you might use are covered with a blanket of snow can be nearly impossible; and the deeper the snow gets, the worse it is.

If snow covers the ground, it can make it hard to find the necessary materials

There are also places where you couldn’t build a debris hut anyway, no matter what you do. While we all tend to interpret wilderness survival as surviving in the woods, the fact of the matter is that there’s a lot of wilderness out there where trees are few and far between. Building any of the shelters we are accustomed to thinking of as survival shelters can be difficult in those cases because they basically all depend on wood.

Historically, mankind hasn’t depended on just wood for construction materials. Our ancestors used whatever materials they had at hand. We still see this today in various parts of the world where they don’t have the luxury of trucking in building materials.

So, what materials do you have available to you in the midst of a snowstorm? Why, snow, of course. You probably have more of it than you want.

The Snow Cave Shelter

Surprisingly, a snow cave shelter could actually be warmer than many other types of emergency survival shelter, especially if it is below freezing outside.

Basically, the snow cave shelter – like the igloo – takes advantage of the basic laws of thermodynamics. Hot air rises and cold air will fall. Because water freezes at 32°F and won’t get any colder than that, the inside of a snow cave can be kept at 32°F, or even a little warmer if the only air inside is air that has been surrounded by the ice and snow. The key to making any snow cave work is to ensure that the air inside it can’t be replaced by the colder air outside.

A basic snow shelter

This is accomplished by ensuring that the top of the entrance door is below the floor of the cave. That way, while the entrance way may get colder than 32°F, the inside of the shelter should stay warmer than freezing. Granted, that’s not exactly warm; but when it’s below zero outside, it’s warm enough to keep you alive.

In order to dig a snow cave, you have to start out with a well-established snow drift or snow bank. By “well-established,” I mean one that has been there a while; not a fresh one. Fresh ones will be made of powder snow and won’t be stable. Established ones will probably have undergone some melting and re-freezing, causing them to be considerably stronger. You’ll need that strength.

The snow bank needs to be at least five feet high, if not higher. You have to have the floor of the cave a minimum of two feet off the ground to provide space for the door. The cave itself needs to be two feet high and then you need at least a foot of packed snow above it for the roof.

While it would be theoretically possible to make your own pile of snow to work with, it would take a lot of work. The snow you piled up would have to be tightly packed, so you’d need to pile up five to ten times the amount of snow depth you end up with. This job would probably take up a whole day.

There is one thing I want to mention here that is very important. I’ve seen some diagrams of snow caves where there is an air vent shaft going vertically up from the main part of the cave to the outside. Don’t do this! Adding such a vent would negate the thermodynamic advantage of the shelter and ensure that the inside of it is as cold as the ambient air outside. The only time when this might be practical is when it is above freezing outside.

Building the Shelter

The snow cave is made by digging. If you can, you want to start digging at the downwind side, which is the ideal location for the doorway. Since most places have fairly consistent predominant winds, this shouldn’t be a problem as the wind should keep coming from the same direction. This will have made the high side of the drift downwind anyway.

If you can, you want to start digging at the downwind side, which is the ideal location for the doorway

If it’s still daylight, you can probably build your shelter without artificial light as enough light will filter through the snow to make it possible to see and work. Be sure to wear gloves or mittens at all times so that your hands don’t get frostbite.

Ideally, you don’t want to be removing material but rather packing it in place. However, a lot will depend on how firmly packed the snow drift you are working with is. If it is already firmly packed, you’re not going to be able to pack it much more; but if you’re working with snow that is not firmly packed, packing is going to give it the structural integrity it needs.

Make the main part of the snow cave large enough to lie down in but not any larger than necessary

Obviously, the work starts at the doorway. You need to dig in one to two feet and then make a ramp that angles up to the actual cave. This ramp should be at roughly 45 degrees – any steeper and you’re likely to break the top of your doorway. Press the snow both up and down to provide a solid floor and a strong ceiling.

It is important to ensure that the floor of the main cave is higher than the top of the door to maintain the interior temperature. If you find that your floor is too low, it is easy to raise it up by simply adding more snow and packing it down.

Make the main part of the snow cave large enough to lie down in but not any larger than necessary. Your body heat will warm it slightly, perhaps raising the interior temperature as high as 35°F or 36°F. The larger the space is, however, the harder it will be to do this.

A snow cave entrance

Additional heat can be brought into the snow cave by lighting a candle. You want to be careful with this though, and ensure that the candle doesn’t melt the roof of the cave. Not only could you melt through the roof, but you could also cause water to drip on you, which would increase the risk of hypothermia. If you have a tarp, wrap yourself in it to keep your body heat from melting the snow and getting you wet.

Putting your pack in the entrance way provides protection from roaming animals as well as helping to block the wind.

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