Sonotube stand... Opinions needed

[fxpose]

I decided to build a small oven in a tight nook located just outside of the kitchen as my current concrete patio & planned WFO build has been put on hold for now.

I plan on pouring a smallish 48" round hearth over sonotube columns. I do not wish to break the tiles to expose the concrete slab underneath, as some day this oven may have to be removed from this location, thus the reason for going with concrete legs. There will also be a layer of felt paper between the bottoms of each column and the tiles underneath to prevent bonding.
However, I will drive 1/2" pins into the tiles and down into the slab for each tube column to prevent shifting in case of an earthquake.
I might also cut some construction joints in the slab at grout lines and regrout.

The question I have is whether to go with 3 tubes or 4 tubes. Each tube will be about 30" tall. Four columns are definitely more secure with almost no chance of a tip over, plus the weight will be distributed over a wider area in that corner of the nook.
But I prefer the look and the simplicity of using just three columns. My only concern is a tip over as the legs will not be truely anchored to the floor, just pinned. But with each 8" tube just 30" tall this may not be a problem. I don't know. I can spread the legs wider apart from one another, bringing them even closer to the round perimeter edge.

The sonotubes pictured below are not cut down to length so they look rather long, skinny, and unstable, holding up the 48" round plywood which I will use as form. The wine bottles indicate oven opening.

Which do you think I should go with?

[fxpose]

BTW, that nook has always been my hibachi/bbq area......but not any more...

[dmun]

I think either plan will work: come a major oven-tilting earthquake you'll have worse problems than re-assembling the oven. I do see a problem getting your chimney two feet above anything within ten feet: that looks like a tall wall it's placed up against.

[fxpose]

Thank you. Yes, I plan on using a 6" stove pipe straight up, secured with a couple of braces along the way to the top.

As far as tipping, I was more concerned with someone leaning up against the oven. Or perhaps I'm being overly cautious. Center of gravity will be low too, I suppose.

[ThisOldGarageNJ]

Hey FX,,
Sounds pretty solid with either 3 or 4 legs, Im sure your gonna end up with a TON of concrete and brick.. Will you rebar the top slab to the legs ?? You could also put a few straps from the slab to the house to make you feel more secure,,
Good Luck
Mark

[fxpose]

Mark, I decided to use just 3 legs and yes they will be tied to the top slab. But I will pass on the strap idea. Also, the pin beneath each leg will prevent the unit from shifting (during an earthquake) as that entire corner is well pitched toward that little drain hole.

I had to convince my wife that this entire unit (weighing about a ton) can be picked up and moved elsewhere if need be. How, I don't know...except by crane I guess... She didn't like the idea of a massive concrete/stucco structure sitting in that tight corner, which I tend to agree with.

Anyway, this spot was never my ideal choice for a WFO to begin with. But under the circumstance I really don't have another practical spot and I'm in desperation of building an oven ASAP. Therefore, I'm going to go ahead with it and keeping the entire enclosure within the 48" diameter, including the vent and arch. I'm thinking that might yield about a 32" max oven size.

[Neil2]

Three legs is "statically determinate". With four legs, one will have little or even negative loading and cracking is more likely.

I would strongly recommend lifting some tiles and extending the concrete legs down a couple of feet into the sub grade. If the holes you dig are firm and not falling in, you can fill them directly with concrete without sonotube support. Just use the sonotube where it will be visible.

http://www.fornobravo.com/forum/21/f...er-3033-2.html (Flying Saucer)

[fxpose]

Thank you for your sound advice Neil. Any advice is much appreciated.

I actually went ahead and poured the tri legs over the tile today. My rationale for this is that Forno Bravo sells their beehive ovens with metal stands which can be placed practically anywhere with all that weight, similar to what I'm doing with my 'free standing' concrete stand, except that my stand plus the oven will weigh a few hundred pounds more.

I will post pics tomorrow.

[fxpose]

I drove 1/2" rebars 5" deep through the tiles. I did not hit any dirt while I was drilling which was a good sign that the slab underneath the tiles were at least 4" thick.

The tubes were cut down to 29", plumbed, concrete poured, and rebars inserted. This was a very quick job as only 3.5 90lb bags of concrete were used.

[Neil2]

Looking forward to seeing your build progress. I think it is going to be a nice compact solution to your site and somewhat unique oven.