Building a Cave

I started with a converted refrigerator, and subsequently I built a real one.

There is a room in my basement, about four feet by ten, with cement walls on three sides. I have never worked out why the house was built that way. It’s a strange little space that had no obvious purpose — and it turns out to be very close to a purpose-built cheese cave before you touch it.

I put up a vapor barrier, framed and finished the remaining wall, and hung an old wooden commercial walk-in cooler door on it. Temperature, humidity and airflow follow the numbers and the New England Cheesemaking approach.

It works great.

Why three cement walls is the whole thing

That detail sounds incidental and is actually the reason the room performs.

A below-grade basement wall is in contact with the ground, and the ground a few feet down doesn’t care what the weather is doing. It sits near the local annual mean temperature and moves through the year slowly and by a few degrees — in Michigan, that lands remarkably close to the 45–55 °F window a cave wants. Concrete has enormous thermal mass as well, so the room resists swings rather than tracking them.

Then the second gift: masonry below grade is naturally damp. In any other room in your house that is a problem to be solved. In a cheese cave, where you’re trying to hold 85–95% relative humidity, it is the assignment.

So a basement corner with three concrete walls starts out cool, stable and humid, which is three of the four things you need. Everything I added was to keep those conditions in, and to be able to walk into them.

This is why I’d tell anybody thinking about this to look at what the building already gives you before you buy equipment. A room that’s naturally 55 °F and damp needs a modest amount of help. A room that’s 70 °F and dry needs a machine fighting physics all year, and you’ll pay for that in electricity and failures.

The vapor barrier is not optional

This is the part I’d emphasise most to anyone copying the build, because it’s the step where a cave either lasts or quietly destroys the wall it’s built into.

You are deliberately running a room at 85–95% humidity. That water vapour will move toward anything cooler and drier, and if it can get into a framed wall cavity it will condense in there, and you will have mould and rot inside a wall you can’t see. A cheese cave is not a normal room and cannot be detailed like one.

A word of caution rather than instruction: exactly where the barrier goes depends on your climate and on which side of the assembly is warm and humid — and a cheese cave inverts the usual arrangement, because the cold, wet side is the inside of the room rather than the outside of the house. I’m not going to hand out confident building-science prescriptions I haven’t verified for your situation. What I will say plainly is: treat it as a wet room, decide the vapour detail deliberately, and don’t improvise it. Getting this wrong is expensive and invisible until it isn’t.

The door

An old wooden commercial walk-in cooler door, salvaged.

I recommend this route strongly if you can find one. A commercial cooler door is engineered for exactly this job — insulated, properly gasketed, heavy, with hardware designed to pull it closed and hold it sealed against a cold humid room. Trying to achieve the same thing with a domestic door and weatherstripping is a lot of fiddling for a worse result, and the seal is what your humidity actually depends on.

They also turn up secondhand, because commercial kitchens refit and the doors outlive the coolers. Mine is wooden, which dates it — the modern ones are metal-skinned.

One safety point, since this is a room you walk into and pull shut behind you. Modern walk-in cooler doors are required to have an inside release so a person can never be shut in. On a salvaged door — particularly an old one — check that it has a working one, and if it doesn’t, fit something before you use the room. That applies whatever you’re storing in there. It’s the one part of this build where a mistake matters more than a ruined cheese.

Cave versus fridge, honestly

Having built both, they’re not really competing.

The converted fridge is the right first move. It’s cheap, it’s reversible, it fits in a corner, and it teaches you what holding a temperature and a humidity actually involves. If you’re making one wheel at a time, it is genuinely enough, and I made cheese in mine for years.

The cave is what you build when the constraint stops being knowledge and starts being volume. Forty square feet holds a different order of quantity, and — this is the part I hadn’t anticipated — it changes the work. In a fridge you handle wheels in a crouch through a small opening. In a walk-in you stand up, see everything at once, and reach the back shelf without moving the front one. Turning a dozen wheels stops being a chore you put off.

The other honest difference is that the cave is far less fussy about holding its numbers, because the building is doing most of the work. The fridge is a small box fighting its own thermostat, and it needed more intervention than the room ever has.

If you’re building one

The ladder, cheapest to most committed:

A mini fridge with an external temperature controller and a dish of water. Under a hundred dollars, and it will age a wheel.
A wine cooler. Already runs warmer than a fridge and often has less aggressive dehumidifying — less to fight.
A full-size fridge or chest freezer, controlled, with a humidifier. This is the converted-fridge build and it is where most people should stop.
A built room, if the building offers you one. Look for below grade, masonry, and a corner nobody wants.
A purpose-built insulated room with refrigeration, which is a different project with a different budget.

The thing I’d underline from having gone from 3 to 4: the jump is worth it only if the space is already halfway there. I did not build a cave. I found one and finished it.

And rung 5, in pieces on the floor

For completeness, because it’s where this is going: I have an 8×8 walk-in cooler, bought off Facebook Marketplace, currently disassembled.

It needs putting together, and it needs the compressor confirmed working, which is the real risk of buying refrigeration secondhand — the panels are just panels, but a dead compressor turns a bargain into a large object you now own. I’m aiming to have it together and running by next summer.

Which will make the full progression converted fridge → found room → purpose-built cooler, climbed one rung at a time across thirty years. That’s slower than the ladder above makes it sound, and I think that’s the honest way to present it: each step happened because the previous one had become the constraint, not because I planned a path.

Next: the converted refrigerator that came first — including the one modification I’ve not found published anywhere else.

Sources

Temperature, humidity, airflow and shelving practice follow New England Cheesemaking Supply Company’s “How to Make a Cheese Cave”: https://cheesemaking.com/blogs/learn/how-to-make-a-cheese-cave
The room, its dimensions, the three concrete walls, the vapor barrier, the framing and the salvaged wooden commercial cooler door are my own build, described from my own account of it.