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kebwi 09-01-2009 07:59 PM

Alternatives to concrete hearth
 
Bear in mind that I am building a 36" oven, pretty small. So, when considering my ideas below, factor in the weight of a 36" oven and associated infrastructure, not 42".

In an effort to minimize mixing and pouring concrete, I'm wondering if there are other ways to create the support slab for the hearth.

Idea 1:
Get one of those killer plates of steel that are placed on the street during construction. That would work, right? But is it feasible? Meaning, can individuals purchase that stuff in the first place, can we get it cut (or in a size that we can design around), is it an affordable option, and is it actually structurally sound for the purpose of support these ovens?

Idea 2:
Lay extra rebar but no concrete, maybe every 6". Wire it up tight so it won't shift. Lay a heavy piece of plywood across the top to form a flat base for the insulation layer. Would I need some plastic between the insulation and the plywood (does wood not like to have concrete laid directly on it? does it rot or something like that?) Same questions as above. Is this affordable relative to pouring concrete and is it structurally sound?

Idea 3:
Lay a bed of 4x4s or some other kind of thick timber across the cinder blocks. If one could groove them, one could even align rebar along the length of some of the beams. Same questions as above. Is this affordable relative to pouring concrete and is it structurally sound?

Problem with concrete is, frankly, I don't think I have "those kinds of friends" here, not yet anyway, so I'm going to doing most of this job truly on my own with *maybe* a little help from my wife.

As to the foundation, I haven't decided yet, I might have it done for me or use one of those small-jobs concrete deliverers.

Thanks, worried...unsure how to proceed.

Lars 09-01-2009 08:23 PM

Re: Alternatives to concrete hearth
 
Hey Worried!

My son and I poured the hearth base slab with an 'od-job' bucket. Basically, you pour in an 80lb. bag after a gallon of water. Roll it around a while, then pour it in the form.

You and your wife can do it! Especially in Seattle! Not so hot! There are many tricks to save you back and increase your capacity. You will need about 16 bags, but be sure to calculate and have plenty on hand. You can use up any extra in the holes of the block wall! ( and hey, concrete is cheap)

So, here's the tricks! Get your bags all on a ledge somewhere ( out the back of an SUV will work) put down the bucket, pour in a gallon of water, then slide the bag over across the top of the bucket. Get a cheap small wood saw. Cut the paper bag at the bottom and let it all go in the bucket.

Put on the top and roll it to the hod. Best if you can park uphill from your site. You will not believe how much concrete you can pour this way!

Lars.

kebwi 09-01-2009 08:31 PM

Re: Alternatives to concrete hearth
 
Ha! That's hilarious. I love it. God help me if the lid comes off and it dumps on the lawn. I'll think about it.

RTflorida 09-01-2009 08:39 PM

Re: Alternatives to concrete hearth
 
A heavy gauge steel framework could work along with a heavy steel plate or heavy gauge corrugated steel steel sheet. Exactly how heavy......not an engineer. We have had a few builders go this route, hopefully one of them will step in and give some advice.

ANY kind of a wood substructure is not a good idea. 1) wood rots & 2) would expands and contracts (more than you think) which can/will cause movement of your oven (not good for a mortared brick oven = cracks)

RT

Les 09-01-2009 08:41 PM

Re: Alternatives to concrete hearth
 
Keb, all bad ideas except the plate steel, but that is crazy expensive. Just follow the plans - it really is not that hard to pour your hearth. Do you have a United Rental in the area? - they will sell you a yard at a time - thats the route I went. I bought a yard , poured the hearth and filled every other core at once, well worth the price (my back thanked me)

Les...

kebwi 09-01-2009 08:47 PM

Re: Alternatives to concrete hearth
 
Thanks for the responses. I'm just brainstorming. Seems inevitable I would strike several misses in the process.

Cheers!

splatgirl 09-01-2009 09:04 PM

Re: Alternatives to concrete hearth
 
it won't be fun, but pouring a foundation or hearth slab or both, is defiinitely do-able with two people assuming one of you can lift 60 or 80 lbs repeatedly. Even moreso if you have small batch ready-mix or on-site mix places there. Then basically all you have to do is screed and trowel and that's an easy one person job.
Using bagged mix, we did my foundation slab with two people. Cool weather=no problem. We had a helper for the hearth slab, but it was like 95 degrees and blaring sun that day so time was a big factor. We used a gas powered mixer from the rental place both times, but I've mixed bags and bags using an OddJob for other projects. They're great. Another idea would be to hire someone from your local day laborer office...every city has at least a few of those places.

never use wood to hold up concrete, and definitely don't use it to hold up something relatively fragile like bricks and mortar.

using a steel framework stand (FB sells one) would get you around having to pour one of the slabs and lay block, but really the only way you'll have a support for the masonry that is stable enough is if it's concrete.

Neil2 09-02-2009 04:40 PM

Re: Alternatives to concrete hearth
 
"Keb, all bad ideas except the plate steel, but that is crazy expensive."

I agree with les.

Pouring conrete is not difficult. If you want to gain a little experience start with some sidewalk or stepping stones or something else on your yard.

dmun 09-02-2009 07:17 PM

Re: Alternatives to concrete hearth
 
If you go with steel plate, the place to go is a steel fabricator. There's undoubtedly one near you. Be advised, it will cost to buy, and also cost to rig in. It's still a lot of weight, so you would still need proper foundations, meaning you still have to deal with concrete anyway.

And as others have said, no wood under the oven, no way.

Mitchamus 09-02-2009 08:58 PM

Re: Alternatives to concrete hearth
 
you'd also need a crane to lift it in place :)


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