Combination root cellar and chicken coop

[hykue]

My two big projects for the summer are to make a root cellar and to make a chicken coop. I want to someday build a straw bale house, so I decided to practice on a chicken coop. For this to be a true test of my straw bale construction technique, I need to give it a proper foundation. To get below the frost line here, one needs to go quite deep. This is why nearly all houses here have basements. Which got me thinking, I could build my chicken coop with a basement, and that could be my root cellar. So, I've been merrily toodling along trying to figure out how to do all of this. I have a root cellaring book that has building instructions, and I have straw bale construction books. For the most part, I think I've more or less got it covered. But some of the details are confusing me.

So, to sum up that bit, I'm building a straw bale chicken coop on top of a poured-concrete-walled root cellar.

The big thing right now is the roof of the root cellar/floor of the chicken coop. I'm looking at a size of 12 by 15 feet (exterior dimensions). The root cellar will probably be divided into two equally sized rooms. My root cellaring book recommends a concrete ceiling, as root cellars are supposed to be damp and wood will rot in such a space. Also, it would make an easily washed floor in the chicken coop (I would put a sealant on it). I ran this past a friend of my husband's who has construction experience, and he suggested that the walls (or maybe the ceiling?) would have to be very thick to hold up the weight of the ceiling AND the weight of the straw bale walls. He thought that it was a bad idea and we should just use wood. This isn't for my house or anything, so I don't want to hire a structural engineer. I just want to figure out if it would be feasible to use concrete for this application, because I think it's preferable functionally.

In case it's pertinent, I'll try to give a good idea of the overall plan. From the bottom up, the root cellar will be dirt-floored, with a gravel-filled sump to drain into if required. The walls will be built on a wide footing, and they will be poured into insulated concrete forms. The proposed concrete ceiling can sit on top of that? Or maybe only on top of half of the wall? The walls will stick up out of the ground at least a foot but under two feet. After addition of moisture barriers to prevent bale wetting, bales will be stacked up. They are going to bear the roof load. The roof plate will be tied down through conduits in the concrete under the bales. The bales will be stuccoed, probably with a concrete stucco. As you can see, I feel fairly confident in my root-cellar knowledge, and fairly confident in my straw-bale knowledge, but the interface between the two is kind of scaring me. The more input the better!

 

[k0xxx]

This seems like a very interesting project. Unfortunately I can add nothing helpful, but I am very interested and have a couple of questions.

Being totally unfamiliar with root cellars and straw bale buildings, will the cellar be accessed through a stair well in the coop, or from a stairwell outside of the coop? I am assuming from outside, due to the dust and manure issues. Also, is the cellar being built into the side of a hill, or dug out of the ground?

Keep us updated on your progress.

 

[hykue]

Ah, yes. I forgot to mention that (very important) detail. The root cellar will have an outside stairwell, so the two areas will be completely sealed off from each other - one reason for the importance of the concrete floor!

The only hills around our property are south-facing (ok, the only convenient hills, anyway), so it will probably be dug into the ground instead. Root cellars tend to nasty temperature fluctuations if located on south-facing slopes, not too surprisingly.

I have been hoping to spend a bit more time on this forum, so I might just be able to update here! I have to admit, I posted this question on about 10 forums that I've never been on before, hoping for a response, but on the building forums nobody cares (because it's just too weird, I think), on the chicken forum nobody knows (because they're not construction experts), and on the homesteading forum I haven't been approved by a moderator yet. I have looked at this particular forum a bit before, and it looks like a pretty good place to be. Thanks for your response, I'm happy even if it generates enough interest to get a response!

 

[big brown horse]

My goal this summer was to build a straw bale chicken coop. I'm going to have to wait till next year unfortunately.

I love your idea!!

Welcome to the forum, you should be getting some good advice soon, sometimes it is slow on the weekend.

 

[patandchickens]

Whoah, that's sounding expensive. Also sounding like something you would want good engineering specs for -- you do NOT want to either a) spend alllllll that money and effort just to have the root-cellar walls cave in which is what happens if they are not designed right, or b) spend alllllll that money and effort just to create something that drops a large chunk of concrete ceiling/floor onto your stored produce or onto YOU.

If you want to do it yourself then this sounds like a good occasion for a crash course in Learning A Bunch Of Engineering/Design Type Stuff, *first*.

If your 'source' rootcellar plans have the whole thing buried, with earth on top, that is almost certainly the main reason for the plans calling for a concrete ceiling; with a chicken coop on top, I do not see any obvious reason why one could not do a conventional (just well-insulated) floor of wooden joists. Which would be simpler and usually cheaper, and I do not see any obvious disadvantages.

I would worry a bit about a coop-atop-root-cellar being a one-stop feeding station for vermin though. You would want REAL good verminproofing.

Good luck, have fun,

Pat

 

[k0xxx]

...I have looked at this particular forum a bit before, and it looks like a pretty good place to be...

Well Welcome!

It is always great to have someone new join us!

 

[lorihadams]

I agree with Pat, you're gonna need a good cat!

It sounds doable, have you looked in Mother Earth News? I saw an article in there several months back where they did a root cellar type thing but it wasn't with straw bale, I think it was with sod. That may be a good option to get around the concrete issues, you could do it large enough to have two rooms, one for your root cellar and one for your chicken coop.

Where do you live?

 

[lorihadams]

here's that link for the mother earth news article

http://www.motherearthnews.com/Do-It-Yourself/Earthbag-Building-Garden-Shed.aspx

 

[hykue]

Sorry about the delay, I've been dealing with goats and a cursed fox eating my chickens. One by one. My system is getting progressively more fox-proof, but at each step I find the new problem by LOSING A CHICKEN. ARGH! Anyway, I'm going to be getting some electric poultry net any day now . . .

If you want to do it yourself then this sounds like a good occasion for a crash course in Learning A Bunch Of Engineering/Design Type Stuff, *first*.

If your 'source' rootcellar plans have the whole thing buried, with earth on top, that is almost certainly the main reason for the plans calling for a concrete ceiling; with a chicken coop on top, I do not see any obvious reason why one could not do a conventional (just well-insulated) floor of wooden joists. Which would be simpler and usually cheaper, and I do not see any obvious disadvantages.
Pat

I agree wholeheartedly with the first bit of this - can anyone tell me *where* I can get information about engineering specs? I'm happy to learn a whole whack of it, happy to do the calculations, but I just can't seem to figure out where one acquires such knowledge. Other than taking a university course or three.

As for the concrete ceiling, it seems to me that the moist earth on top is one of the major reasons for the concrete ceiling. The other is condensation - the root cellar will be dirt-floored to produce high humidity for my produce - this will cause condensation on the ceiling and tops of the walls, which will be sticking out of the ground, and therefore be the coldest part of the cellar. Condensation in root cellars can really wreak havoc - the book recommends that wood shelving (not in contact with any moist earth) will need replacing about every 3-5 years. I don't want my ceiling to be that. That doesn't mean a joist floor wouldn't work - it just means that it would have to be not only well-insulated but also have good vapor barriers to protect the wood - and keep all that chicken "dust" away from my veggies.

And the rodent issue: I imagine I will be fighting mice regardless of whether the two buildings are combined or separate. I'm hoping the chickens will help to keep them under control "upstairs", and one advantage of the ICF and concrete-ceiling method is that as long as I screen my vents, the mice won't be able to get in anywhere except the door.

You also mentioned expense. It does seem to be an expensive proposition. I'll outline my goals below, and maybe you can all help me brainstorm something perfect.

But first - k0xxx - thanks for the welcome. Big brown horse - we also were going to build this last year, but it got put off until this year! Lori - thanks for the link. My MIL loves the idea of earthbag building, I'm more interested in straw bale for now. I'm pretty sure (having read an earthbag building book) that straw bale fits our needs better (and our soil type), but thanks for the link. Good reading anyway.

And to answer your question, I live in Saskatchewan, Canada.

So, goals.

1. Make a chicken coop and a root cellar.
2. Practice straw bale design and building.
3. Get done before the snow flies in about 3 months.
4. Don't spend the moon in the process.

I'm still open to doing these buildings separately, but I want to do a cost analysis of the two methods first, not just assume that one way will work better. I've made a list of the advantages and disadvantages of the two methods (stacked vs not-stacked). It's really long. It would be really helpful to me if others would read it and give me an idea of what they thought, though.

Disadvantages of stacking:
1. The big one in my mind is that this is going to be one enormous root cellar. Really. I could probably store enough potatoes in a 12x15 root cellar to last the whole winter for everyone in the RM (rural municipality, our equivalent to a county). It's probably twice as big as we could ever possibly need, even in the most extreme scenarios. I was considering splitting it in two, a front (cold) half and a back (warmer) half, with the cold half acting as the airlock for that frigid winter air. It would be good for keeping things that wouldn't suffer too much from a light freeze, like hams and such. Assuming we have hams. Regardless, it would be enormous. This means more materials than would otherwise be required. One way to deal with this is to have the root cellar be half of the foundation for the coop, and build a rubble trench as the other half.

2. The earth is not insulating the cellar. This is a pretty good point, but I'm not sure it's significant. Here's why: last year, we went away from the start of January (our coldest month) until March. I left a max/min thermometer in our cold room, which has two uninsulated exterior walls. The walls project above ground about 1.5 feet. We use wood heat and have a drafty-as-heck old house, so it got cold fast, but the minimum thermometer read -4 (celsius, which is +25 farenheit) when we returned. The one I left in my garden read -40 (same in either system). I'm thinking this is some indication that only a little boost to insulation is needed. This boost would be provided in my design by the insulated concrete forms, and to a lesser extent by the chicken coop on top, acting like a relatively warm hat. The chickens should be able to keep their hyper-insulated straw bale coop reasonably warm, or at least warmer than our unoccupied house was.

3. The ideal location for these two buildings is not the same - the root cellar should be very close to the house and the chicken coop should not. I think this isn't too major, as there will be a good path through the snow to the buildings in the winter, as chickens need checking regularly. Also, we don't really have a great location for a root cellar that's much closer to the house.

4. Someone mentioned elsewhere that vermin will be more concentrated around such a delectable source of food - both chicken food AND root veggies! This is a pretty good point. I might have to train my chickens to catch mice . . . or get a cat to live in the root cellar. Or both. But I don't think the problem will be significantly worse than if the buildings were separate. Also, it should be hard for mice to get in, as they would have to make it through either concrete or plastered bale walls. The weak points will definitely be the doors.

5. If the floor cracks (even just little, non-structural-damage type cracks) or is otherwise not sealed, then we will have to stop using one of the buildings, because there will be poop on our food. Yuck.

Advantages of stacking:
1. We only have to dig one hole. I'm planning to get an excavator or something, but it really seems simpler (and cheaper) to me to just have one dig site. Maybe this is really a minor thing, but it seems like a big bonus to me.

2. We don't have to dig as deep - to bury a root cellar for earth insulation, you need to dig quite deeply, of course. If it's going to be sticking up, we don't have to dig as deeply, and the top will be insulated by warmed air and straw bales. This makes ICF's make sense (insulated concrete forms), because we need some way to insulate those sticky-uppy parts. ICF's are kind of their own advantage, because we will be spending less time on building and tearing down concrete forms.

3. The roof of the root cellar and the floor of the chicken coop are shared. This means we will be using less material, probably, as these two components are both combined. I'm not sure this balances out the amount of concrete required for the enormous root cellar, though.

4. The large roof overhang on the straw bale building (to protect the stuccoed bales) will transport water a little ways away, which will reduce the chances of cellar cave-ins. Don't worry, I'm not planning for that to be the only protection, I'm thinking also a gravel-filled sump and drainage gravel/pipe around the edges. But it can't hurt to have a bit of extra insurance.

5. This will be more like a house than any other way we could build a straw bale outbuilding, so it will give us more opportunity to learn. We want to make all of our mistakes on this building, so that when we finally build a straw bale house for HUMANS to live in, we'll have a clue.

I'm sure there are more on both counts, that I'm not thinking of. I'm good at taking an idea and running with it, MAKING it work. My husband (who is away at work and not reachable by phone or email or ANYTHING most of the summer) is good at what I call "looking for the holes". We complement each other well, but without him here I tend to latch onto harebrained schemes and then strive for them until I get exhausted. That's where you come in!

I guess I'm looking for two things right now. I need people to look at those lists of advantages and disadvantages, add to them, dispute them, or what-have-you, and help me see the options clearly. I'm also hoping someone can tell me how to figure out (I don't mind doing the math, but I don't even know where to start) how much concrete (and rebar, and decking, and such) I will need, so I can compare different options price-wise. In other words, I need to do the structural engineering thing, figure out my loads, how thick the walls need to be, how thick and how reinforced the floor needs to be, etc, etc. But I don't know where to look for the information that will guide me in how to do that.

Thanks for all the responses so far!

 

[SKR8PN]

Let me get this in my head correctly............
The root cellar is going to be concrete? and the chicken coop built on top is going to be straw bale construction? Am I on the right track?

I had to come back and edit......
Is the cellar going to be IN the ground or above ground?