Underground Root Cellars in the PNW: What You Need to Know

Posted on by Parker Concrete
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Can You Build an Underground Root Cellar in the Pacific Northwest?

The most straightforward answer to this question is yes. However, the more complicated answer is: it depends. Many factors contribute to whether your land or property is suitable for a root cellar. Here in the Pacific Northwest, the humidity and heavy rainfall present challenges for property owners looking to build a root cellar. There are a few things to consider before hiring an excavating contractor to dig out your new root cellar.

Root Cellar 101

People use root cellars to keep perishable food from both freezings in the winter and spoiling in the summer. Most often, gardeners and farmers put vegetables in the root cellar after an autumn harvest.

What is a Root Cellar?

A root cellar is any storage system or location that uses the earth to naturally cool, insulate, and humidify the space. Root cellars date back to before refrigeration. Before refrigerators, the only way to store root vegetables such as turnips, beets, parsnips, and potatoes was to use the earth. Otherwise, much of the harvested produce went bad before it could be useful.

Ideal Conditions for a Root Cellar

Root cellars work the best under certain conditions, which is why there’s no easy answer to whether or not a root cellar is the right choice for your property. However, consider the following when deciding on if and where to install a root cellar:


For a root cellar to properly store raw and pickled vegetables, it must hold temperatures between 32 degrees Fahrenheit and 40 degrees Fahrenheit. This temperature is critical to keep vegetables from freezing over the winter. Typically, the weather here in Hillsboro and the surrounding Portland metro area is suitable for storing vegetables over the winter, but the moisture may present issues. To regulate temperature, it’s good practice to incorporate a ventilation system in the root cellar. This process helps especially in the autumn to let cold air into the root cellar and bring the temperature down.

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Root cellars must be humid to properly store root vegetables such as potatoes and carrots.


Root cellars must have a humidity level between 85 and 95%. The moisture prevents the vegetables from losing water through evaporation, which also prevents the withered look of dried out carrots and potatoes. No one wants to eat a sad potato. The high humidity in the PNW is excellent for root cellars, but the amount of rain can make maintaining a root cellar without cement reinforcement nearly impossible.


Most experts recommend that outdoor root cellars are at least ten feet deep (more on that next) and twenty feet away from the house and any large trees. Some sources suggest using foundation walls as part of the root cellar, but that may compromise the integrity of the foundation itself. It’s not worth the risk. However, some people can successfully convert a corner of their basement into a root cellar. Cement works well for insulation, and it may be the best choice (over earthbags, etc.) for root cellars in the Pacific Northwest due to the heavy rainfall.


In most areas, the temperature of the earth is consistent at ten feet deep. The root cellar must be deep enough into the ground to keep food from spoiling in the summer and to protect food from freezes. Some properties may not have enough available depth due to rock, utilities, and other municipal and landscaping concerns. Additionally, keep in mind that you may need a permit to install a root cellar in your backyard. Hillsboro City ordinances state that if the structure is less than 200 square feet and ten feet high and not attached to the home, it doesn’t need a permit. However, any electrical work or plumbing may require electrical or plumbing permits. Check your local ordinances.


The organization of the root cellar is crucial to the preservation of stored food. Installing a thermometer and a hygrometer (to measure both temperature and humidity) is best practice when it comes to maintaining a root cellar. Someone should check the temperature and humidity every day (or as often as possible) to ensure that they’re both in an acceptable range.

Wooden shelves are the best choice for root cellars as they don’t conduct temperature in the same way as metal. The shelves should be at least an inch away from the wall to improve air circulation and prevent airborne mold. When storing vegetables, remember that grouped vegetables can gather heat. Grouped vegetables or roots in a pile will expedite the spoiling process. Make sure to store vegetables in a way that gives them plenty of room and rotate the shelves periodically.


The easier it is to get into the root cellar, the more useful the cellar will be. When planning the root cellar, keep in mind that the more manageable the root cellar is to clean, the better as well.


Root cellars need to be dark. Light negatively affects some vegetables in storage. A single bare lightbulb is more than enough light for a root cellar, but it should be kept off between visits.


It’s critical to protect the root cellar from pests, especially rodents. Rats and gophers love to eat stored produce, so be sure to close all spaces as tightly as possible around the root cellar. Make sure all vents are properly screened and sealed to prevent a little critter from coming in and eating all of those potatoes!

Alternatives to Root Cellars

If digging a root cellar isn’t possible on your property, there are a few alternatives to consider:

  1. Consider picnic coolers as a food storage alternative. The coolers can be outside in the winter. Just cover them with a blanket or move them to the garage to regulate their temperature.
  2. Clamps are another food storage alternative. All that’s required is digging a hole below frost level (about one square yard) and filling it with straw, then produce, then additional straw and plastic or some other heavy cover.
  3. Cargo containers are an excellent option for property owners that cannot dig out their root cellar but have enough space for a large storage area. Partially bury it and surround it with hay bales to insulate it.

Ready to Dig? Hire Parker Concrete

If you have the space for an underground root cellar, skip the hard work, and call Parker Concrete to excavate the area for you. The knowledgeable staff can help answer any questions about your project, including whether or not the cellar will hold on your property. Call today to get started!