Can this root cellar be saved?

I will be returning to live on my family farm soon. While walking the property last weekend I was saddened to find the state of the root cellar to be much worse than I had hoped. (See images below)

I would appreciate any advice I can get regarding repairs or if repairs are even feasible at this point. Safety would be my major concern since I will have my children there with me and I'm sure they will be playing on it often just like I did as a child.

Thanks in advance!

I haven't seen it from upclose, so can't really say if it's safe. I take it it's not in danger of immediate collapse. Ask a professional. Where i to fix it i'd seal the cracks with a cement/sand mix, first from the inside, so make it thick and sticky. Wait for it to harden and fill it from above with a sloppy mix. Push it in with a small stick.Fill it completely. Wait a day for it to harden. That will keep the water from coming in and worsening the problem. Then phase 2 bang the loose render of the wall with a hammer and render the walls. Phase 3 lock on the door so kids can't come in. Phase 4 keep a close eye on the repaired bits, if cracks don't open i wouldn't worry too much about it being unstable.
If you're unfamiliar with what i'm saying call in a expert to do the job.  

You could also have a metal i beam on the sealing with studs and build pillars under it for support.

Hugo Morvan wrote:You could also have a metal i beam on the sealing with studs and build pillars under it for support.

I had considered this. Maybe a steel box frame inside for support.

Yeah even better. Is there metal in the concrete slab? Or has it completely rotten?

Hugo Morvan wrote:I haven't seen it from upclose, so can't really say if it's safe. I take it it's not in danger of immediate collapse. Ask a professional.

Thankfully I'll have a brother-in-law and nephew nearby who are both pretty knowledgeable.

Where i to fix it i'd seal the cracks with a cement/sand mix, first from the inside, so make it thick and sticky. Wait for it to harden and fill it from above with a sloppy mix. Push it in with a small stick.Fill it completely. Wait a day for it to harden. That will keep the water from coming in and worsening the problem. Then phase 2 bang the loose render of the wall with a hammer and render the walls. Phase 3 lock on the door so kids can't come in. Phase 4 keep a close eye on the repaired bits, if cracks don't open i wouldn't worry too much about it being unstable.
If you're unfamiliar with what i'm saying call in a expert to do the job.  

Sounds like solid advice. Thanks! One downside of the old home place is tight clay soil with a high shrink–swell capacity. Over time it can beat up underground structures pretty viscously. This is probably a 1940s era structure. There are also two remaining underground cisterns that I need to check to see if they will hold water.

Hugo Morvan wrote:Yeah even better. Is there metal in the concrete slab? Or has it completely rotten?

I believe it's concrete over brick around the sides. I don't see any evidence of rebar or wire in the curved top.

Might be worth the time to figure out what is the cause(s) of those cracks. Concrete/masonry typically does not just  crack on its own. It may be due to an inadequate foundation, or the walls bowing out from the load, or other things (those are just the first things which came to mind). Best time to do this investigation is before you fill/repair the cracks, when more details will be visible.

Once the causes are identified, you can do something about them perhaps at the same time as fixing the cracks (thinking of cross bars here).  If you don't resolve the root cause of the cracks, they will likely just reappear.

As a Civil Engineer, I would say the foundations have suck and that is causing the movement and cracking.
The whole thing could be repaired by underpinning the structure with new foundations.
I expect there will be none, the dome may be sitting on earth.
Under pinning can be researched, but basically you did small sections one at a time, deep under sections of the dome and fill with mass concrete.
Do it in sections leaving the original foundation in-between and then go back and replace the bits left between.

Then I would put a new layer say 4 inches think with reinforcement over the top.

I personally don't like the look of that at all. And you say there will be kids potentially in and on it.

I would probably take a sledge hammer to it, and bash out the old roof. Then you can do any needed repairs to the walls in safety, and install a fresh ferrocement arch roof. Ferrocement is very strong under compression, so you could potentially berm the roof up with soil as well. DIY ferrocement is pretty cheap and not too tricky. Just need some careful thought about how to make your form.

Phase 3 lock on the door so kids can't come in.

 I'd put this as phase 1.  It sort of goes with the First Aid mentality of ensuring no further hazards or danger before starting.  

Get your brother-in-law and nephew there, and wrap their brains around the project.  It sounds like your clay situation might be combining with an inadequate foundation/drainage situation to create instability in your walls and thus seriously compromising your arched roof.  

The thing to consider most, is, after a thorough mental assessment, is the cellar worth salvaging cost-wise, in relation to the costs of building a new one (that might function a lot better and a lot safer for a lot longer)?  You might be better off smashing this one up for urbanite and saving yourself the headache of time-intensive repairs/upgrades to something that has so many (potential) inadequacies.  It's like opening a can of worms.  You might repair it now, and spend a bunch of time at it, and then, if you don't manage to do it exactly right, then your grandkids will be doing it again, (possibly cursing your name).  Is it worth repairing?  

A new one can be built with a deep rubble trench with drain pipes on it's outside, a properly reinforced concrete footing, and sufficient quantities and engineered grids of rebar in your walls and arches to support the varied forces that you will be expecting.  Considering the years of service that such a structure can provide, the relative high cost should be calculated as spread out over decades of budget.  If you are planning a long-term investment in this family property, then it is probably best to simply suck of the cost, dissolve yourself of the nostalgia, and rebuild.

Three things to consider with building a proper root cellar are humidity, temperature, and air flow.  There is a balance that must be met between these factors, depending on the types of food you are trying to store.  Building the cellar with the idea of burying it with a good layer of dirt and sod (say a couple or three feet), would go a long way toward moderating your temperature.  It looks like your old structure has a vent pipe, which is good.  You need at least one, and best to have them set up so that they do not collect water, and so that insects and rodents can not go in them. These vents help with all three factors.  Additionally, shelves should be set up and food set up on them such that you have good ventilation.  Most cellars have a dirt floor, or at least one that is not solid, so it could be graveled or cobbled but shouldn't be concrete; this helps maintain humidity.  You do not want it to be wet, but you do want it to be damp looking.