Building a cave into a hillside

I'm not sure if this is the right forum, but it seems closest.  We are planning earthworks projects on our farm right now and one of our long term goals is to create a Kentucky version of Iberico ham, and we'd like to have a cave to age it in.  Our land does not have any natural caves, and after the recent tornado activity in the area, we are even more enthusiastic about having a place to ride out storms should the need arise.  

The use case for the cave would be to age hams, potentially age cheese, be a place to store some wine maybe, and I wouldn't mind being able to use it as a root cellar if it was possible.  We are expecting that we would have a few different zones that may be walled off, and to ensure the climate conditions, we'd probably have some sort of either minisplit or air conditioning unit.  The problem here is we don't really know where to start.  We expect that you cut away a portion of the hill, build the cellar out of concrete or similar, and then replace the excavated dirt over the top of your cellar,  however the rest of this is kind of a mystery.

Do you have any personal experience building something like this, or any resources I should be reading?

I want to do something similar, and build a cave into one of the big ridges on my land. I just don't know how to tell if I'm doing it safely, and how to avoid a cave in.

i’m in the process of hand-digging (verrry slowly) a root cellar into the side of a quite steep hillside here. i don’t know a whole lot about cave-aging meat, but for more root-cellary things i worry a little bit about your mini-split plan. that seems like something that would effect the humidity levels in unfortunate ways.

greg mosser wrote:i’m in the process of hand-digging (verrry slowly) a root cellar into the side of a quite steep hillside here. i don’t know a whole lot about cave-aging meat, but for more root-cellary things i worry a little bit about your mini-split plan. that seems like something that would effect the humidity levels in unfortunate ways.

Fair.  The hope would be that we won't need to use the minisplit system often if at all, however being able to maintain a consistent temp/humidity may require a minisplit and humidifier just to keep things consistent, but maybe it wouldn't be needed?  Thats what I'm here to learn!

Trace Oswald wrote:I want to do something similar, and build a cave into one of the big ridges on my land. I just don't know how to tell if I'm doing it safely, and how to avoid a cave in.

We do not believe that we can safely and effectively just tunnel back and expect no cave-ins.  We are expecting to excavate, pour a bunker essentially out of concrete, and then move the dirt back over the bunker to hide it in the hill.

I've seen a youtube video or two of exactly that, excavate into a slope, put a durable roof/wall material in place, trench drainage around the base, then backfill over it all. If you get several feet of soil back over it all, then you should be close to the average annual soil temperature of the area. Many mention 50-55F but it can vary a good deal, my annual average is 70F for example being zone 11-12. If you dig into a hill, in addition to protecting against a cave-in you'll need to see how water flows at different times of year and you may need to manage humidity. If tornado protection is desired, I would build where a tree isn't nearby, so if it is pulled over the roots don't damage the building, or so it can't fall on top and pin you inside. Same reason to be careful camping under widow-makers in the woods.

If you really want to make a DIY cave so yourself a favor and let some expert do a ground survey and calculate the statics accordingly.

Watching YouTube Vids are sure helpful but there are many lunatics out there constructing things and might have killed people with their loose opinion planning and building, because in reality they lack any professionalism.

Keep in mind how many people are getting killed year by year due to collapsing self-made quarries, ditches and trenches.
Many more had a close call and were still able to breathe until help was digging them free.
In a cave that collapses you will NOT stand any chance of surviving this !!

Once completed it looks more than solid and you feel it is made for a lifetime, but during a rain all can change dramatically.

“Dripping water hollows out stone, not through force but through persistence.” is a wise saying.

The cut-and-cover method you describe is the easiest and fastest way to go about building an underground space if you have access to the right equipment. It does eliminate the danger of cave-ins, and if you slope the sides of your excavation back away from the work area, it should be perfectly safe to work in the site. You probably do not need an engineer to design a couple of small rooms, but I would personally start to feel iffy about anything with a clear span of over 6 to 8 feet or so if you were to just put a flat concrete slab lid on it. Curved roofs are inherently stronger, but will be a lot harder to form up, and without an engineer you would not know if it was going to be strong enough. The drawback of cut-and-cover is that you will need to move a lot of material, twice! Also, unless you have a massive excavator, you will be a bit limited in how much depth you can get. A really deep trench can be as dangerous as an unsupported tunnel, so you need to slope the sides or else put in horizontal shoring. Even 3 feet of earth on top of a structure will even out the temperatures quite a lot, and if you are going to use AC anyway, this might be the way to go.

Now, if you really want an adventure, I will say that tunneling is a fun way to pass the time :) A lot will depend on your local soil, and the minimum size of cavern you are willing to get away with. Soils are a complex material, and the interactions with groundwater have to be taken into account. There are some materials like soft sandstone that can be dug by hand, yet will yield acceptably stable tunnels. I would not risk my life in an completely unsupported tunnel in anything but the best ground conditions. You will know you have those conditions if there is a local tradition of digging tunnels, and they are still there hundreds of years later. All you really need to dig a safe(ish) tunnel is a soil with enough stand-up time to get a liner in place (and a basic grasp of how to design an adequate liner). Then you dig, and line, dig and line. It takes forever, but it is also a lot of fun. I am almost done with my root cellar project, and I will post some video of what I have been up to at some point soon. It does have the advantage of letting you go a lot deeper without disturbing any of the soil. I have about 12 feet of cover over my tunnel now, and i am pretty sure it is in under my garden now. At some point I want to go deeper, mostly just to see what is down there :) My attempt at drilling a core through the floor hit something hard about 6 more feet down, so I kinda want to check that out at at some point.

I see a lot of root cellars that are made by burying culverts, and then adding front/back walls to them.

When I was a child, the root cellar was a cinderblock room, with proper footings, and a slab of cement poured over it. It was built to code, and is still standing.

Have a look at this chaps videos, they may help

You can research for books on the topic. Look for bunkers, underground storage etc

Joseph Lofthouse wrote:I see a lot of root cellars that are made by burying culverts, and then adding front/back walls to them.

When I was a child, the root cellar was a cinderblock room, with proper footings, and a slab of cement poured over it. It was built to code, and is still standing.

Thanks.  We've considered going with some "non conventional" materials but it seems like many of them do not breathe as well as concrete which seems like the ideal material in this situation.

Right now we are trying to weigh the options between ICFs, concrete blocks, and prestressed concrete slabs, or a combination of them.

Pre-streesed slabs are a very good product

A timbrel vault roof is an economical way to span a cut and cover space. Those things will hold a lot of weight when done correctly.

I'm watching this...just posted in the tornado/high wind thread and now found this! I have a small backhoe to do the digging and the more I think about it, should probably prioritize getting mine built before the spring storms come.