Maybe as a child you tried to dig into the snow to make your own little snow cave. If so, you probably noticed that snow that was deep but not fresh was more stable than you expected. It is also much warmer than you may have expected. Being surrounded by snow can make for a very well insulated shelter.
There are several things you must keep in mind when building a safe snow shelter, all of which relate to the stability, entrance, and airflow of the structure. All you need is a lot of snow, a camp shovel and maybe some sticks to get started.
Make a BIG pile of snow
Gather up a large pile of snow. This pile of snow should be a minimum of five feet high and five feet in diameter. This will allow for the one foot thick walls with room to get inside. If you can make or use a bigger pile of snow, you can make a snow shelter that will be even larger inside. Once you have your snow pile, let it sit for at least 24 hours for the snow to harden up. Before you dig out your shelter, the snow layers need time to settle together for stability.
Dig out the entrance Find the downwind side of your shelter, and begin digging out a 2 foot wide hole to go into the shelter there. It is up to you if you would like the entrance right at the ground or about half way up. Think about what will be the most convenient for your shelter and the people using it.
place depth sticks in the top of the snow pile The walls for your snow shelter should be between 1 foot and 2 feet thick. Since you create the shelter by hollowing out a snow pile, you need way to know when you have hollowed out to the right thickness. Without a way to tell, you could create walls that are too thin or have a lost opportunity for space inside. By placing sticks about 2 feet apart, pushed in to the proper depth, you will know when your walls are the right thickness as you will hit the sticks when hollowing out the inside.
Dig out the inside
Now take that camp shovel, or any other good snow digging tool and hollow out the inside. A bucket can be helpful at this point to move all of the extra snow outside of the shelter. This part gets easier the longer you work at it. You create room to work as you go. Dig all the way around, reaching your depth sticks in every direction.
Create a chimney/secondary entrance
Moisture from breathing can build up very easily in a snow shelter. Excess moisture on you means you will get cold. It is also a good idea to have a secondary entrance in the event the shelter collapses. Thick snow walls are very stable, but this precautionary step is still wise. The unlikely but possible event of collapse should be accounted for.
The secondary entrance should be put at an outward upper angle, at about 45 degrees from the ground headed outward. Going straight up means that heat will escape too easily. Dig the hole out to about body width for the people using the shelter. Place a blanket over the hole to keep the inside warm.
Enjoy your shelter
You have created a place where you may be able to sleep outdoors, or to have a wintertime play fort. Be sure to use appropriate winter camping gear when staying inside the shelter for any length of time. Above all, enjoy the work you put into your shelter!