I work in the construction field and regularly deal with things that require a great deal of load-bearing capacity. I would be happy to
answer these questions for you to the best of my ability; however, I would recommend double-checking my answers against multiple sources to confirm their accuracy (as you should with any advice you receive from anyone
)
Lotus Raber wrote:So I am a newbie looking to build a very basic and small root cellar from a cinder block.
Few questions
1-I have read the roof should be arched for condensation issues. It's extremely dry here in the desert. Does this still apply?
Applying an arched roof in a root cellar not only sheds
water more efficiently but also provides additional strength in the construction. Arches are far stronger than your standard flat roof or even a pitch, and because route cellars are typically buried, this is going to be of paramount importance so you do not have any collapses that occur.
Lotus Raber wrote:
2-Are there any concerns I should be aware of in keeping the dirt floor?
Any moisture in the soil can bleed up through a dirt floor. Dirt floors are not bad; however, it would be wise to monitor humidity levels within the root cellar. It may also be wise to consider the possibility of radon infiltration and provide some ventilation to protect yourself and your produce. Lastly, leaving a dirt floor in a space that stores food does allow for the introduction of pest species capable of tunneling. If you are going to leave a dirt floor, it may be wise to rent a compactor and try to mimic the compacted dirt floors used in some European green buildings, as this will provide a solid layer that could prevent the presence of pests species. It will mean you’ll need to purchase a fair amount of linseed oil, though lol.
Lotus Raber wrote:
3-Most people are building on a homestead and leaving the top of the cellar’s exposed works out there. Still, mine would be in my small backyard, and I wanted to bury it enough so that the space above it could still be used for either a patio or even just being able to walk over it. So the goal is not to hide it but still have use of the space on top. What do I build the roof out of?
Most of the builds and advice I see are for natural roofs or a big cement pad, and I was trying to figure out what other options I could do where I wouldn’t have it cave in, but I’m also not driving a car over it.
If you do a good job building it out of
concrete block with an arch you can simply cover the concrete block wall that you’ve constructed with black
pond liner before burying the structure under several feet of soil. If you engineered the arch correctly this would be sufficient to allow for the ground above to be used for a patio, raised beds, etc. there are a lot of great
art calculators and engineering schematic generators
online for Quansett hut style arches which would be more than sufficient for your job.
Lotus Raber wrote:
4-Is there a target depth that the roof should be under the ground surface to maintain the integrity of the roof and surface on top?
I appreciate everyone’s experience in kicking me if I’m way off track
I believe that if you are going to be utilizing the space above the arch ceiling on your root cellar it would be wise to have a minimum of 3 feet of soil above the root cellar. This will serve you in a couple of ways: first, the dirt will help evenly distribute the loads placed on it by your patios raised beds etc. the weight will compress the soil which will evenly distribute that weight through the concrete arch and to the side walls of the Quonset hut style root cellar. Second, having 3 feet of soil over the top of your roof seller will provide a solid thermal barrier and thermal battery keeping the structure at a more even temperature. and lastly having the roof buried under 3 feet of soil will provide an excellent moisture control seeing as the water flowing onto the soil above the dome will have a chance to percolate around the dome more easily as opposed to coming into almost immediate direct contact. I think it should go without saying that whatever you are going to do with the location above the root cellar this should not ever include a tree because no matter how good your construction job is a tree will scarf at it and quickly and mercilessly destroy your root cellar.
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