Combination root cellar and chicken coop

[yardfarmer]

I'm new to this forum also; one reason I joined was to responsd to your construction project.

I've been working on bridges for 25 years now and know a little about concrete. Not familiar with ICF 's, but the concrete roof is something that needs some carefull thought.

How thick does the roof need to be for your application? Most bridge decks are 8 inches deep, but since you won't be driving trucks over it, it could be thinner, unless insulation is the issue.

The concrete roof will need reinforcement. Probably 1/4" to 5/8" rebar. (sorry i'm in the US don't know metric conversions) the rebar should be spaced at 8" or so. The main concern with rebar is clearance to the surface. Usually a minimum of two inches from external surfaces is needed to protect the bar from corrosion. Concrete is pourous, so water will penetrate. I would not count on a sealant for protection; also the rebar needs to be encased around the concrete for load transfer.

Considering the weight of concrete at about 150 lbs. per cubic foot, you will need to be able to support this weight until the concrete cures (hardens), which will take about one week to reach strength. If your roof is 12' x 15' by 6" the total weight would be around 13,500 lbs. or about 7 tons, counting the rebar.

You may need support beams also for the 12 or 15 foot spans. If you put in a seperating wall that would help support the roof.

It may be a good idea to ask a structural engineer to advise you on the roof, if that is an option. I would hope that if you showed them some drawings of your plan they would be able to quickly calculate the necessary rebar spacing and supports you would need for this roof.

Good luck, looking forward to reading more about your project.

 

[freemotion]

Dumb question, maybe.....does the root cellar have to be the same size as the coop? Can it be smaller, to avoid the big headaches of a large cement "ceiling/floor" and have the cellar be centered under the coop, with a stairway and maybe a bulkhead leading into the cellar?

I see a root cellar...a wine cellar....and.....drum roll please....a CHEESE CAVE!!!!! Ooo-la-la, now I am really jealous.

 

[justusnak]

After reading this post...I sat and pondered...sometimes this is a good thing, sometimes its not so good. So, you decide... LOL
If you were to use concrete block, ie:cinder blocks, for the walls...you could fill them with the soil from the dig..and since faceing the south, build a wall in front of the doorway...and face it towards the east. This should help...with the heat issue. Now, for the ceiling....you could use Marine plywood. It is waterproof. This might be the solution to your roof. You could use linoleum in the coop floor which would make it easy to clean, and stop the dust from coming through to the root cellar. As for the shelving....maybe you can find some sort of thick plastic shelving?? Like they use in those outdoor kid playhouses? Just an idea....

 

[xpc]

A concrete roof for what you what won't be so hard, a bit pricey and time consuming but doable. I already designed a storm shelter for under my house and will relate the info I found using your measurements.

adding to what Yard farmer already said:

12'x15' = 180 sq.ft. @ 6" thick and would be about 90 cubic feet or 3.4 yards and could be quite costly because you're gonna need high tensile strength low slump? concrete mix. You will also need a fair amount of rebar rerod and mesh not to mention the initial 12 sheets for the plywood under form. It will almost always crack even with relief joints and may even buckle because it isn't tensioned or pre-stressed, if you make it on a slight angle then the floor can drain over the wall via the relief cuts. They make these slabs in sections and if you have money and close to a big city could buy what you need in sections.

Run all your courses of "non-insulated block" you do not want to hold heat in or out and want the earth to regulate the temperature. I would run straight block without mortar using a surface bonding cement instead (or both) I didn't see your location so don't know what your frost depth is but few places in the US are below 60" at most. If you want to go 7 feet deep then you will need about 400 blocks, running vertical rebar and filling courses as needed - don't forget the lintel for the doorway header.

Once your block is all up and cured and you left rebar sticking up through the top solid course you can form the ceiling, you can built a 2x4 frame that would fit just inside and below the top course minus the plywood thickness also a 2x6" frame on edge around the perimeter. Think of it as a floor joist system with many screw jacks or king posts to hold things up, slather the plywood with release agent so it can be removed later. I would also leave a I-beam of lam-ply down the center for under support. If you want to add tie down anchors put them in as the concrete is poured but not on top of the existing rebar - they are usually L-shaped with all threads. This is also the time to stub in any conduit or pipes for future use (use PVC sleeves).

You will need many runs of rebar and wire mesh on top of the plywood centered in the slab and best to use pre-made wire chairs if available or bend your own but is time consuming and a pain (don't use rocks). Remember at no time can rebar stick out of concrete, trim the bar that is sticking up from your walls to be inside the floor before the pour - or it will allow moisture in and rust your entire system. I know this because I was turned down on an inspection for that very same reason plus it makes sense.

You should check with the concrete provider about the mix and application but 3.5 yards of low slump usually can't be pumped and should be done in one fell swoop so as not to leave any demarcation cracks, broom finish so you can apply a sealer or tar paper later.

If it were me I would build the ceiling/roof with 2x8 pressure treated lumber with a high percentage of chemical for direct earth burial, I think they rate it as 0.6 or higher. Outdoor fence lumber is around 0.25 me thinks. You can then cover with 1x12" PT planks and 2 rows of 90lb felt crisscrossed leaving the edges droop over the walls. Slather it with a bucket or 2 of cold tar sealant and back fill with a layer of sand.

You mention installing a sump and is a good idea but as an extra precaution and for good measure install drain tile along your footer foundation and run it out as far as you can while the back hoe is there, its cheap and easy then. I would still separate and make the projects in different locations, the straw bale coop can float on grade in a sunny area and root cellar in a shaded area near the house that can double as a storm shelter with fresh air vent tube. I did all this kind of back breaking work for several summers while putting myself though school but things may have changed since 1980.

In a nutshell that about sums it up.

 

[tortoise]

I'd make friends with a structural engineer and barter if necessary. I worked at an engineering firm and the guys would do free stuff for friends.

 

[patandchickens]

I honestly see no conceivable sensible purpose for having a concrete ceiling/floor if you stack the coop on the root cellar. You only need that if you are burying the root cellar under a layer of earth. Insulating the bejeebers out of a conventional wood-joist ceiling/floor is EASY PEASY, as is making it quite sufficiently dampproof and sealing it against chicken dust sifting thru from the upstairs (which is the only 'leakage' you'd have to worry about). FAR easier and more straightforward and more affordable than the whole concrete ceiling thing, if you want the coop on top anyhow.

Seriously, given that you do not NEED that big a rootcellar, I think that your attempt to combine the two is going to end up being a really big money pit.

Engineering tables (for spans, foundation wall specs, concrete, etc) are fairly readily available, online or by talking to friends in the construction industry. Immerse yourself in them, figure it all out, then get someone to check your work.

Good luck, have fun,

Pat

 

[pronab2011]

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