Allotment shed root cellar - advice wanted

[gregorach]

Right well... My allotment shed is rapidly approaching the end of its current incarnation - it's certainly well-ventilated, but unfortunately it's also composting itself, not to mention listing rather dramatically... I'm hatching plans for a replacement, and I want to put a small cellar in under it, to store veg through the winter and beer through the summer. I've got Mike & Nancy Bubel's classic Root Cellaring, but it doesn't really contain much guidance on exactly the sort of thing I have in mind. I'm thinking of something roughly along the lines of their buried box cache, but since it's going in under the shed, it needs to last.

I currently have two options bubbling around in my brain. The first, and probably easiest, is to bury a large tea crate. I'm thinking I'd want to surround it with a layer of hard-core for drainage, and wrap it in plastic film to stop it from rotting, and chicken wire to keep the rodents out. The main problems I see with this design are (a) keeping the humidity inside high enough, and (b) stopping it from rotting due to the humidity inside.

The other option is to build an earth-floored box using bricks, paving slabs or breeze blocks. That should eliminate the humidity and rot issues, but it's more work and I'm a lousy brick-layer... Again, there will need to be some drainage and rodent-proofing, at least around the edges.

Either way, I'll be putting in both inlet and outlet vents (PVC piping), with a view towards possibly using forced ventilation when I get the solar power system installed. (Yeah, I get a bit carried away sometimes... ) The inlet vent will exit above ground on the north side of the shed (rodent-proofed, of course), while the outlet vent will probably exit inside the shed.

So - anybody got any experience of this sort of thing? Any ideas? Anything I haven't thought of?

[Green Aura]

Do you need to be able to walk on it?

I've seen lots of plans for making root cellars out of old frdiges or chest freezers - they're already water-proofed and insulated and, I'm guessing, fairly rodent-proof. You just need to remove all the mechanical bits and shelves then bury them lid/door up, of course.

Then you just need to work out some method of flooring to go over the top.

[gregorach]

Do you need to be able to walk on it?

No, the plan is just for a trap-door. There's no way I'm hand excavating deep enough for a walk-in cellar! I don't think the soil's even deep enough anyway...

I've seen lots of plans for making root cellars out of old frdiges or chest freezers - they're already water-proofed and insulated and, I'm guessing, fairly rodent-proof. You just need to remove all the mechanical bits and shelves then bury them lid/door up, of course.

Then you just need to work out some method of flooring to go over the top.

Yeah, I've thought along those lines... But I don't have an old fridge or freezer handy (and if I did, it would probably get made into a temperature-controlled fermenting cupboard for my brewing), whereas I do have a couple of large wooden tea chests, a few paving slabs, and the folks on the next plot have a large pile of bricks in one corner. And there's still the question of maintaining proper humidity and fitting the ventilation...

Flooring over is no big deal - I'll be completely rebuilding the shed, with proper 2x4 joists under the floor. Working a trap-door into that shouldn't be much of a problem.

[oldjerry]

This might work,dig a hole say 4'' wider,and deeper then your t chest,stick 2'' of decent size chippings at the bottom covered with another2'' ofconcrete with a bit of quick dry liquid in it.Let that set then stick the tea chest on the top,and pack the gap between the chest andthe sides of the hole with concrete using the chest as a mould(If it's not strong enough fill it with chippings,if it gets trashed use an identical sized one when it's all dried.Then when it's driedthe tea chest should fit it and it'll be easy to make a lid for.I'm not sure that makes much sense,but it's made my brain hurt. best wishes.

[gregorach]

Yeah, that's pretty much the sort of thing I was thinking of, except I'm not convinced that it actually needs the concrete - well packed hardcore should do the job. But I'm not sure about maintaining the proper humidity inside it, and it'll be a bugger to replace should it start to rot... Looks a good deal easier than bricklaying though.

[oldjerry]

The probs got to be sealing the hole to keep it completly dry so YOU can create the humidity you need.If you concreted the bottom and sides you could then tank them,and that would seal it ..... maybe?... Best wishes

[gregorach]

From reading the Bubel's book, they reckon earth-floored cellars are the way to go if possible, because that naturally tends to keep the humidity in the right range. Achieving and maintaining 90%+ humidity in a properly ventilated box doesn't sound too easy if it's otherwise completely impermeable. Not that concrete alone would achieve that - there's a reason houses need damp-proof courses...

And if I were going to all that trouble with concrete (bearing in mind that there's no way I can get any kind of machinery in, probably not even a cement mixer, and all materials will need to be barrowed in) then I might as well go down the masonry route. In fact, I'd be better off, as it would involve mixing less concrete. You ever tried to mix a large amount of concrete by hand? Believe me, it's not fun...

It looks to me like the concrete + box option has all of the downsides of both approaches, without the benefits of either.