root cellar specs

This question from RR regarding root cellar design; we repost here since the topic may be of more general interest:

Hi, I love reading your posts. You’re so generous with your information so I’m always a bit shy to ask for more… My partner and I recently moved into a 1750 farmhouse. It’s got a basement with a dirt floor, and we want to design a sweet root cellar within it. Lots of rodents, which we need to get rid of, so we need to make it rodent proof. Can you share the design of your root cellar? Floor, walls, ceiling? Size… ventilation… is it all passive? Things you’d want different? thank you!

Hi, R,
Thanks for the kind words! Your farmhouse sounds wonderful; where are you? Not a whole lot of the continent had houses on it in 1750 — particularly not houses that are still around. Is it stone, or brick? or something else really durable? We’re in the process of helping our former apprentice/now 5th son’s girlfriend to repoint the brick in her 1833 trading post/farmhouse, and it’s a really rewarding job. Best of luck with your project!

Our root cellar: You know, one of the things that makes us so ready to share information is that most of our projects have to fall into the ‘good enough is perfect’ category, because perfect generally costs a ton — and often turns out to be the wrong choice anyway. So anything we can do, other folks will find possible, too.

Our root cellar is no exception. It is where it is because there was room to fit it there, on our steep, rocky hillside, and because it’s where it is most accessible to the house and the people cooking. It’s right outside our basement door, just steps from the kitchen sink, so the cook never has an excuse for not including potatoes in the meal under preparation. But it is, consequently, on a south facing slope, with not a whole ton of earth over the roof; probably less than two feet. In addition, when it was built there was nothing to shade it from the south, so it tended to warm up a good bit in the summer. Now, 26 years later, there’s an apple tree and the shelter over our outdoor oven to give the root cellar a little shade, which no doubt helps keep it cool.

The build: Just after we bought this place in 1996 and discovered that the Amazon flowed through the basement when it rained, we had a backhoe operator with good nerves come out and ease his monster around our nearly vertical house place, digging french drains; and, since he was there, we had him dig the hole for a root cellar. I think we had a friend with some experience laying block do the walls; we then bought half a lumberyard of plywood and two-by’s to make a form for the poured ceiling, and prayed all the angels and saints into headaches while we mixed and poured concrete, I’m guessing (because I don’t remember) about six inches thick. The floor is pea gravel, several inches thick; this year we added a couple of inches of limestone (57’s to dust). Rodents have never dug in. There may be a french drain around the cellar; Shawn will remember, maybe, and if so I’ll let you know.

There’s one four-inch PVC chimney in the roof at the back; it had a small fan in it at one time, but when the damp proved to much for the electric service to the cellar, we let it go. There should probably also be a vent at the bottom of the door, but we’ve never put one in. The door frame is 2×4’s bolted into the concrete; the door is built of 2×4 and plywood with rigid foam interior. A couple of times we’ve had to cover rodent holes with flashing. This year, for the first time, we replaced the door frame.

The cellar does a great job of keeping vegs from freezing in the winter; in summer it is not cool enough for aging cheese (in the 60’s farhrenheit, instead of low 50’s), but I have my doubts about keeping cheese in such a damp environment anyway. Potatoes and mangel-wurzels are very happy there; cabbages, the one year we tried, not so much. Carrots we grow in the high tunnel in winter, but when we used to cellar them they did fine, only growing feeder roots a bit.

Oh, yes, size! Eight by twelve, or as near as makes no difference. We store potatoes in plastic milk crates and stack them; when we run out of crates we use plastic mesh feed sacks (friends save them for us). Mangels used to just get dumped in a corner, but now we grow a great many so they are bagged in the same way and stacked. We don't seem to get any significant rot or damage from piling them high.

Onions, garlic, and squash go in a drier environment in the basement.

Good enough is perfect.