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Old 04-03-2014, 06:58 AM
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Default Re: Base on existing Cement, is this recommended?

It depends on the condition of the slab. It's age and subsiqent condition will tell you a lot about the quality of it. Most standard pours are at least 3000psi, which is plenty to support the oven...even without rebar or screen. If the pour was there before he owned the property, and nothing is known about the pour, or it can't be assessed with any confidence, then it would be prudent to cut out a footprint and pour a thicker pad. However....l


I've got my current oven on no concrete footing, just 6" of granite dust, that was compacted in lifts. It has had full weight ( all the finishes except the shingles ) for almost a year, the weight of the base for a 1.5 years. I have been watching the vault for any sign of cracks, there are none. The base has not settled at all. The foot print is big on these outdoor ovens, and the weight is well distributed. Mostly all of the builds on here are framed with metal ( a few wooden ones, like mine) and clad with a light weight finish. The slab isn't supporting a sky scraper.


There are variables that put limitations on 4" slabs...like the desired finished dimension. But in general even a 4" is more than sufficient to support an oven. The one exception would be if the final finish like full thickness stone Was being used...stuff like stucco or manufactured stone will be significantly lighter. It would be a good idea to cut reliefs all around the footprint to isolate any cracking.

To conclude, if there is any shred of doubt, then why not pour a new pad. But if it was me, I'd have to see some settlement and cracking before I worried about a 4" pour. My words aren't here to coax anyone into building something they aren't confident in.
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  #12  
Old 04-03-2014, 07:19 AM
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Default Re: Base on existing Cement, is this recommended?

You live in a warm area, frost heave is not much of a concern. The concern is crushing your existing slab. I would suggest pouring a reinforced 6 inch slab on top of your current slab and take it out a foot or so past the weight bearing walls of your oven, spread the weight out. People float slabs all the time in areas that do not have frost heave, they tamp the earth, put down a few inches of gravel and pour a floating slab that is strong enough to bare the weight of the oven or what ever. A six inch pour with half inch re-bar cross checked on one foot squares will serve your needs. This method is common when installing masonry chimneys in houses that are being retrofitted with a new chimney that is being built on top of an existing basement slab.
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Old 04-03-2014, 07:48 AM
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Thumbs up Re: Base on existing Cement, is this recommended?

Quote:
Originally Posted by stormy View Post
......I would suggest pouring a reinforced 6 inch slab on top of your current slab......... A six inch pour with half inch re-bar cross checked on one foot squares will serve your needs. This method is common when installing masonry chimneys in houses that are being retrofitted with a new chimney that is being built on top of an existing basement slab.
This is where my mind was going as I read your thread. Even if you build on the existing slab, you can put an extra block wall directly under the center of the dome, that would spread the weight quite a bit.

I built an oven stand for a barrel oven, then switched to the pompeii oven. In my view, the barrel oven is more specialized than the dome oven. Was a good decision. No second thoughts. HTH
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Old 04-03-2014, 08:40 AM
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Default Re: Base on existing Cement, is this recommended?

Quote:
Originally Posted by stormy View Post
You live in a warm area, frost heave is not much of a concern. The concern is crushing your existing slab. I would suggest pouring a reinforced 6 inch slab on top of your current slab and take it out a foot or so past the weight bearing walls of your oven, spread the weight out. People float slabs all the time in areas that do not have frost heave, they tamp the earth, put down a few inches of gravel and pour a floating slab that is strong enough to bare the weight of the oven or what ever. A six inch pour with half inch re-bar cross checked on one foot squares will serve your needs. This method is common when installing masonry chimneys in houses that are being retrofitted with a new chimney that is being built on top of an existing basement slab.
This won't help if the 4" slab is iffy. It may be done all the time, but it's not best practice.
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Old 04-03-2014, 09:09 AM
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Default Re: Base on existing Cement, is this recommended?

I strongly recommend you don't pour a slab over your existing slab. If someone is unsure of the base/strength of your existing slab, why in the world would someone even consider placing even more weight on it, then building on it?
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Old 04-03-2014, 10:13 AM
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Default Re: Base on existing Cement, is this recommended?

Since we are bashing the barrel oven design, I started my oven quest with the barrel style oven, then someone on this forum convinced me to switch to the Pompeii. So glad I listened to him, (whoever it was). After gaining some experience with my oven, I now understand the benefits of the Pompeii dome over the barrel vault.

Go Pompeii !!!!, you will never regret !
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