Thickness of concrete?

[trout valium]

Here's my situation.  We need rabbit barns, about 20 x 50.  In order to keep them cool in the summer, and above freezing in the winter (zone 3 here in vermont) I was entertaining the idea of poured concrete walls, backfilled 6' for a heat sink to the ground.  Not having a lot of direct experience with this medium, I was wondering how thick the wall should be to 1.  hold back the dirt  and 2 to support the roofing structure.  I would be putting in footers and leaving the floor dirt for now.

Any good rule of thumbs out there?

[harry51]

Hey, Trout,

Check out the pics at http://countryplans.com/smf/index.php?topic=5473.0 and you will see how I learned that concrete walls are about the most expensive you can build in terms of both labor and material. There's more on the subject at Mike and Michele's Bigger House in Owner/Builder Projects as well.

If you are resolved to build them, using reinforced cement blocks is likely the least expensive way to go, but ICF's may work for you in the cold climate, even though the interior walls should be finished with a fireproof material like sheetrock. If you're not familiar with insulated concrete forms (ICF's), there's been some discussion on this forum, and Googling ICF will bring up lots of info.

Other alternatives, if properly designed, likely could do the job without the earth shelter/backfill, might include earth rammed walls, straw bale walls, or highly insulated wood framed walls.  Probably the design of the roof and ventilation systems will be at least as critical to achieving your goals with this building as the walls will be, so please keep us posted as your plans evolve.

G/L!

[Squirl]

Many Owner builders like to use concrete blocks.  Blocks can be done over time and by one person.  Poured concrete takes forms (expensive), a concrete truck, and normally more than one person.

[John Raabe]

One of the concerns you will have with concrete block, poured concrete or PT Wood walls is that 6' of backfill amounts to quite a bit of pressure wanting to push the wall over. You likely need to design these as retaining walls which often rely reinforced walls tied into large wide concrete footers that counteract the toppling forces. This is expensive and compounded by the fact you want to do a dirt floor.

If you are willing to pour a floor slab and build the walls of PT wood, that might be the least expensive solution. The floor slab would equalize the pressure from the two sidewalls at the bottom of the walls. (I assume both sidewalls are backfilled.) Then you could do a gable truss roof with metal brackets to the walls which will lock the upper wall forces through the triangulated truss.

I have good design information on PT below grade walls in the Universal Cottage Plans.

[trout valium]

I appreciate the input.  If we build one of the concrete structures, it will have a foundation below the frost line.  This way the bottom of the wall will have 4 feet of dirt holding it back (below the dirt floor)

i have been looking into a pole barn style also.  My biggest problem is the rabbits peeing on the walls, and animals (weasels, etc.) getting in.  The insulation should take care of heating problem.  It's hard to figure the best way, as I am looking at total cost, including operating the building) over 5 to 10 years, not just building costs..