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tngabe 01-07-2011 05:51 PM

Concrete/block free foundations?

I've searched the forum for information on ston foundations, but the questions previously asked seemed to get ony speculative answers. If those that asked did eventually try foundations without poured concrete, I haven't found how it turned out. Has anyone built an oven, or anything else for that matter, on a stone foundation laid on top of aggregate or anything else?

I dug about 3' deep and filled the hole with sand mixed with pieces of concrete i have sledged up. After compacting that, I am planning on capping it with limestone that is about 10" or a foot thick with mortar filling the spaces in between the pieces of limestone.

How much do I need to worry about this foundation settling and causing my stone stand and oven to list and possibly crack?


Lburou 01-07-2011 06:43 PM

Re: Concrete/block free foundations?
No doubt the experts here will be asking you what kind of soil you have and how thick your mortar/limestone layer will be and if you plan any reinforcement in it.

My speculation: Probably very little settling, depending on your original soil, thickness of limestone/mortar layer, reinforcement of that layer AND the design (shape) of your block stand for the hearth.

dmun 01-08-2011 06:41 AM

Re: Concrete/block free foundations?
I think you can't find specific information about your situation because in my reading, (and I've read pretty much everything on the FB forum), it's unique. Hardly any of us would have access to such a slab of stone, or if we did, would have any way of moving it. The only stone foundations I know about is a couple of builders who built on bedrock outcroppings.

That said, I don't think it would behave any differently than a similar concrete slab. My only caution would be to thoroughly compact the underlying stone before placing your slab, but that much weight is pretty much going to compact it anyway.

Good luck with your project. Keep us posted with pictures. We love to see big rigging projects.

tngabe 01-08-2011 07:07 AM

Re: Concrete/block free foundations?
The soil here is mostly clay, at least once I dig down through the topsoil. The stone I am planning on using for the foundation is mostly 10 to 12" thick. I'm not planning on reinforcing the rocks, I have no idea how I would if I were. According to the Google, I'm looking at 160 lbs or so per cubic foot so if I build a 6' x 8' foundation a foot thick, it should be over 7500 lbs. Gosh, now that I've done the math, I'm starting to think I've already started to enter the realm of wood fired oven madness. I'm planning on fitting them as close together as I can and bridging the gaps with mortar. I'm hoping this is a good project to get me started on learning about stone construction.

As I mentioned in my introductory post (if anyone other than dmun who is reading this saw that one) I'm lucky enough to have a good bit of stone here already and to live around the corner from my in-laws, who have an old limestone quarry on their property. Although the quarry is now a pond, there is a ton (figuratively speaking, literally more) of limestone I have access to. My father in-law had also been buying things he didn't need for several years before I entered the picture, so I have a dump bed chevy and small tractor with a front end loader to move all this stuff with, otherwise I wouldn't be considering it in the first place. I'll be sure to post pictures when I have some. The only ones I have so far are of a hole in the ground and the same hole filled with sand and rubble. Which is now covered in snow, or I'd be out working on it instead if inside and online. :(

Tscarborough 01-08-2011 07:22 AM

Re: Concrete/block free foundations?
So long as you have your base below the frost line and achieve sufficient compaction, you shouldn't have any issues.

Lburou 01-08-2011 07:31 AM

Re: Concrete/block free foundations?
As Peter Sellars once said in a movie, "I like to watch". I'll be cheering you on! It sounds like you have good sense and will make it happen. :)

Neil2 01-08-2011 10:02 AM

Re: Concrete/block free foundations?
"I dug about 3' deep and filled the hole with sand mixed with pieces of concrete i have sledged up. After compacting that, I am planning on capping it with limestone that is about 10" .

Put a 4 inch reinforced concrete slab down then your limestone paving blocks on top. Work on the premise that all structures will settle. The slab just ensures even settlement.

dmun 01-08-2011 10:24 AM

Re: Concrete/block free foundations?

limestone paving blocks on top.
I think Tngabe is talking about a unitary slab of limestone, not chunks or pavers. A slab of concrete underneath would be gilding the lily. It will settle, of course. My bet would be that it would settle as uniformly without concrete as with it.

Faith In Virginia 01-08-2011 11:00 AM

Re: Concrete/block free foundations?
All things settle. I'm not sure I completely follow your process. I do suggest that after you compaction of the sand stone and hard stuff you put a thin layer of sand or sand like material before you put down your paving blocks. This is what you do when you build a house footer that has sections of rock that pass through your footer. The premise here is that if you have one section that can't settle more (rock) with disturbed earth on the rest of the foundation then the sand layer over the rock will allow the foundation to settle as one piece rather then snapping on the un-giving rock. So this is why a small layer of sand will help regulate any settling issues.

Tscarborough 01-08-2011 11:54 AM

Re: Concrete/block free foundations?
I have built some pretty heavy structures on some pretty dodgy foundations. So long as the dirt is compacted well and evenly, it is generally not a problem. This little playhouse was built with CMU, then stuccoed. The sole foundation is 2-1/4x8x16" soaps placed on well compacted clay dirt (It cost $12,000 to fix the foundation of that house when I lived there). It is still there, no cracks 15 years later. It is now the prettiest doghouse in the neighborhood.

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