When you first start homesteading or living off the land, the last thing you think of is how to store your garden produce and preserves.
Designing your root cellar starts with some thought of what it will be used for. Wine and beer storage? A place to store your homegrown beets, carrots and potatoes? Or just a catch all for anything to do with food, like canned and bottled preserves, the jars themselves, or where you put all your wine making gear.
Whatever you decide for its purpose will dictate the shelves or racks you build or buy. The easiest construction technique is to use plywood for shelves, with two by four lumber to make racks to hold the shelves.
Measure whatever it is that you'll store here, and make the shelves deep enough to hold that item - nothing is worse than finding that your shelf is two inches too shallow for jars and bottles of wine and preserves.
If you live in a cold climate, snow cover alone may not be enough to keep it from reaching dangerously cold (freezing) temperatures in your root cellar.
A simple heater such as an electric light in a metal can can make all the difference.
It has to be an incandescent bulb to get warm - new fangled compact fluorescent bulbs don't give off any heat.
Check it periodically, especially during cold snaps, to make sure it's still working.
Another important feature of a root cellar is some way of dissipating excess moisture. This can be super simple, in the form of a chimney type arrangement, or a vent to the outside through the door.
I find that the heat in the root cellar is quite high at times, and a vent through the roof helps cool it down.
The vent itself is a length of six inch sewer pipe, which is pushed through a cross shaped cut in the rubber liner and wood roof.
This seals, and has never leaked, even though the soil is right up against it. The pot on the top helps keep rain out (there is no hole in the bottom of the pot).