Earthbag Root Cellar

For the past few years I have wanted to build a root cellar to store root crops, canned goods, and fermented beverages. A good root cellar has a relatively high humidity (80 - 90%), cool temperatures (between 35F and 55F), and good air circulation. Other aspects to consider are its location relative to your home and its position relative to the sun. You don't want it heating up, but you also want to have access to it during the colder winter months. "Root Cellaring" by Mike and Nancy Bubel is a phenomenal resource to use when planning and designing a root cellar. I used this book exclusively to get all of the insight I needed to plan my own root cellar... the only problem for me was finding a location. Our basement was out of the mix since my wife runs a small bakery in one quadrant, I run a wood shop in another quadrant, and then there is a small pottery studio in another. We have a great hillside but our garden has been cut into it in a terraced set up, and it would be a trudge through the snow during the winter. Mounding up earth was definitely an idea but with the masonry work and the amount of soil we had to bring in it would have cost more than we were willing to spend. So, my criteria for a root cellar ended up being:

1 - It must be easily accessible for everyone in the family

2 - It must be affordable (under $400)

3 - It must meet the necessary requirements of a good root cellar (temp, humidity, etc...)

4 - It must have at least 48 sf of area and ceilings that are at least 7' high

So this left me in a bit of pickle (sorry for the pun). There was only one spot that seemed to hit all the marks on the nose... under our back covered deck. The deck is attached to the house and is covered by a roof, that should keep out the water and also help keep the temperatures higher during the winter since the foundation will radiate heat from the basement. It's attached to the house so it could be easily accessed. Since there is literally one wall already built and a roof over it already it should be affordable. And, if I dig into the ground I should be able to keep it at a respectable temperature and a good humidity. Plus, there is plenty of space to make something within my design needs. The only question was how to actually build the walls to this thing? Then I saw this awesome video where this couple in Alaska used earthbags to build their root cellar. Earthbags are literally just sandbags filled not with sand but the earth you remove from a hole that you dig. These guys had to build their's in an open area and had to contend with building a roof, pumping out excess water, and regulating temperatures. I figured I could take my Goldilocks set up and apply their earthbag idea to it!

All in all, this build cost me just about $400, and so far it is working out fantastic. This is the first winter it is going to go through, so all of the kinks and quirks have yet to be completely worked out, but I thought I would share my earthbag root cellar build to hopefully inspire you all during this crazy 2020 year!

Once I established the location of the root cellar I had to figure out where exactly I was going to put it under the back deck. I figured I could cut a hatch into the deck floor to allow quick, covered access to the root cellar so I had to make sure the hatch wouldn't be in the way but could be easily accessed without moving furniture. I decided to center the root cellar in the middle of the deck between the tree support posts you see in this picture. You'll need to get your arsenal of hand digging tools out for the next step. And oh what fun the next step is!

Digging the hole by hand was no easy feat. Not so much because it was a lot of soil to move (22 yards by the end of it!!) but because it was located under a deck with only 4' of space between the lower side of the joists and the soil. I am 6'4" so I had to do some unique maneuvers to dig out the space. What I started with is digging out a hole I could stand in under the porch. This was easy enough to do from the outside of the porch with a long handled shovel. As soon as I was able to stand in the hole without hunching over too much I then swapped to a short headed spade to start removing the soil. I piled it up directly in front of the porch and to the left and right of the soon to be root cellar. I dug down until I hit the foundation's sill, which was about 5' down. I couldn't go further than this since our french drain is directly in front of the sill. The upside to this is that the root cellar will never flood being both under the porch's roof and having a french drain going through it. After digging down to the sill I left a thermometer that reads both temperature and humidity levels. With an 85 degree day the temperature in the hole was 65 and the humidity was in the mid 80s. I figured that is a great start to a root cellar.

Just a note about the digging. I didn't do it all in one day. I broke it up into a few different days doing 2 to 4 hours each day. It is one heck of a good workout!

I ended up finding the best deal for the sandbags from www.sandbaggy.com. We ordered 500 14"x26" sandbags knowing that we wouldn't use them all but also making sure we would definitely have enough. Unfilled sandbags don't take up much room so I figured storing any unused sandbags wouldn't be a bad thing and at 31 cents per bag we weren't breaking the bank. The bags came in a massive box and were neatly put into groups to easily pull them out. They have nice sturdy ties (we didn't break one during this whole project!) and they were easy enough to fill just with a shovel. We could have made a funnel or even bought one but honestly I didn't see the point since we were filling bags faster than I could lay them. You literally use the soil dug out of the hole to fill the bags, so other than the bags the material to build the walls is free! Obviously the number of sandbags will depend on the size of your root cellar. We had one wall completed since it abuts the basement's foundation.

Once filled the sandbags are easy enough to move but they do weigh about 50-60 pounds each, and there are literally 100s of them to move. I figured we could let gravity do the majority of the work and employed an old slide as the sandbag depositing device. We repositioned the slide as needed and just let the sandbags slide down to the bottom of the cellar hole. I would drop ten or so down the slide, hop into the hole and then stack them along the basement wall, then repeat the process.

Sandbags kinda have a slippery surface. When building an earthbag structure you need to make sure that the bags stay nicely stacked on top of one another. Gravity definitely does a great job keeping the heavy bags "stuck" to one another but any lateral force could possibly displace and weaken the stack. One way to counteract this is by alternating the stacking pattern. Similar to laying bricks or concrete block, don't let your joints line up. This is not as easy as it sounds since the sandbags are not something you are going to cut in half to make a smaller piece. You can definitely fill some of the bags up less than others, which will allow for a nice alternating pattern. I ended up just altering the arrangement of the bags from first laying the long wall and then the short walls to then laying the short walls and then the long walls. This did the job really well and allowed me to keep the joints mostly out of line. Other than gravity the other thing you will need to use to keep the bags from translating on top of each other is some barb wire. The barb wire kind of acts like the "cro" in velcro with the barbs biting into the bags both below and above, locking them into place. A couple of disclaimers; the barb wire is wrapped under tension and will unravel itself most annoyingly while you are using it. I pounded a metal stake into the ground to keep the barb wire in place and prevent it from unravelling. Also, the stuff is springy. Use good puncture resistant gloves and be careful laying it along the bags, the stuff hurts when it jumps up and bites you. I have war wounds to prove it. Use rocks to hold down the lines, using two lines per row. I set up a quick cutting area for the wire with two posts. One post represents the short wall an the other post represents the long wall.

Now that you have the barb wire skillset down and your soil bagged, or at least started, you can start to build your walls. To make a truly solid earthbag structure you need to tamp the sandbags so that they are compressed to nearly the greatest point. I bought a $20 tamper from our local co-op and would encourage you to get one too. At this point you put the bag in place, tamp it with the tamper, butt the next one up to it, tamp it, and continue down the line. Get all of the bags for the first row tamped and then lay your barb wire down on top of the bags, place your next bags and tamp them. I had to switch to a 4x4 to tamp once I got closer to the bottom of the deck floor. I would tamp the bag as much as I could on the ground, lift it into place and then finish tamping it.

Once you have built all of your walls with sandbags you should... take a break for God's sake, you've gotta be exhausted! Admire your work and get ready for the next stage... as long as you can get out of there (don't forget the ladder).

I think that this was honestly my favorite part of this project. I love hidden things and you would never know that there is a root cellar under our back deck if you were standing right on the deck. I plan on landscaping around the whole deck to hide even the part you can see from the outside. To cut the hatch I first laid out where I wanted it to be located. I made sure to incorporate one of the joists in the location so that when I cut them they would all stay together and so that I could fit down the hatch without a problem (the joists are 18" on center). I also made sure to cut only whole deck boards, no need to make it looked all chopped up. Using a circular saw I cut the rough outline and then used a jigsaw and chisel to finish up the corners. From there I was able to free up the deck planks completely. To prevent the whole thing from falling into the hole when I cut the joist I put some support blocks screwed from the underside (I had to go back into the hole). These supports will be attached to the hatch once everything is cut and completed. To cut through the joist I used a demo saw (sawzall). After that I had to add some end-joist bracing to make up for the cut joist and then affixed the side pieces to the hatch as you can see in the second photo. I put a ladder down there and constantly warned the family to be careful around the trapdoor :)

After you have the hatch in place you can start working on the upper walls under the deck. Or you could build them without the hatch and never escape... your call. I used pressure treated 2x8 stock to frame the upper walls. I made short walls on the ground after measuring the space I needed to fill and then squeezed them into place. The outside of the walls are sheathed with rated PT plywood. The walls are screwed directly to the underside of the porch joists and the friction between them and the sandbags holds them in place. You could also use galvanized nails driven into the sill of the little walls, but I didn't see the value in it for the size of the walls.

I used rigid 4" insulation board to insulate both the walls and the ceiling of the root cellar. This stuff cuts easily with a knife on one side and then you flip it and snap it straight. I made sure that all of the pieces would fit tightly to make it more insulated and to friction fit them so I didn't need to use glue or anything like that. The ceiling pieces are pushed in to slope down to the outside so that any water that does get onto the porch from the screens or cleaning the porch floor flows down and out. I used spray foam to make up for any corners, gaps, or open spots. You are going to want to get it pretty tight but remember that you still need good air circulation which means you will be cutting two 4"- wide holes in the thing anyhow.

At this point you have walls, a hatch, some insulation, and a big hole in the ground! Congrats. You are going to need a way to make sure that the air circulates throughout the root cellar. You are also going to need to make an easy to use system that organizes your goods that you plan on storing for the winter.

Vents: I used 4"ID drainage pipe for my vents to the outside. One vent is the air exhaust and the other is the air intake. The air exhaust is just a short 8" long pipe. It needs to be flush to the interior wall and extends out like 4" from the exterior wall. I wrapped both it and the intake pipe in hardware cloth (metal grid fence stuff for anyone that doesn't know what it is) and then held it tight with some duck tape. This will keep the critters out of your root cellar. I then used a compass to draw a circle on the exterior wall and then used a jigsaw to cut the hole for the pipe to pass through. You can easily connect a damper to either pipe (which I might do once I see how this thing performs during the winter). The clean air intake has an elbow connected to it and then the pipe runs down to the floor of the root cellar. This "stack effect" should help pull in cold fresh air and exhaust hot stale air.

Shelves: I used pressure treated lumber and plywood to build the shelves. I made these extremely simple but sturdy. I attached them directly to the joists and to each other on all three walls. The back wall (the basement wall) is where I am putting our canned goods and the other shelves are for other root crops. I also found a free wine rack that I separated into two pieces where I can store a good number of our bottled hard cider, wine, and beer we make. The way you design your shelves really depends on the space you have made with your earthbag root cellar!

We have a great garden and it has gotten larger year after year. We've added a tall spindle orchard in the back of the garden just this year and claimed another 500 sf of gardening space for potatoes, corn, and so much more. We are aiming to be as self sufficient as possible and we are hoping that this root cellar is just one more step towards that goal. This is our first winter with this root cellar, so the jury is still out on what things we might need to tweak or fix. Overall I believe we have so many things going for us, but only time will tell. I love the fact that it is hidden, while being so close to our house. I love the fact that it was affordable and gives me so much space to store root crops and canned goods. By the way, we use mostly reusable "Tattler" canning lids. They are plastic and rubber so they can handle the high humidity in the root cellar. Speaking of humidity. The humidity in there is a constant 85% and the temperature since the vents were installed in September has been 55, even on 29 degree nights. I will post more details about how it performs as things move forward but if you have any questions please do not hesitate to reach out to me.

Happy homesteading!

Chris