38" vault in tropical Australia

[dmun]

Re: 38" vault in tropical Australia

I'm no structural engineer, but it seems to me that that method of "hanging" the support slab from a few pieces of rebar is extremely suspect. I've seen enough rusted-out rebar to think it's best deep buried in concrete.

[Onefella]

Re: 38" vault in tropical Australia

I'm no structural engineer, but it seems to me that that method of "hanging" the support slab from a few pieces of rebar is extremely suspect. I've seen enough rusted-out rebar to think it's best deep buried in concrete.

The 16mm deformed bar that I'm using has a shear strength of 6.8 tonnes and there are 18 'attachment' points. The gap will reduce the shear capacity slightly, but by my calculations the slab could support 2-3 tonnes before the concrete itself would crack. Probably of more concern is the 'reo' bending and pulling out of my bond beam. But it's a tried-and-tested design, so Im pretty confident it will be ok.

The exposed rebar in the 'gap' is painted with a good quality hi-temp black engine enamel. It will also be encased in vermicrete.

I've attached a diagram of how the slab is arranged.

[nissanneill]

Re: 38" vault in tropical Australia

Onefella.
tried and proven?
Well I personally wouldn't have a bar of it! The 30mm of vermiculite is way insufficient insulation to stop the stored heat in your concrete from escaping and into your block work. the whole thing is upside down (and you don't need to use the cement sheet.
The 16mm reinforcing bar will rust, no matter what you do or say, especially up in the tropics and more so with the continued heating and cooling. I don't care if you galvanise it, it will deteriorate and eventually fail.
Mate, you are on your own with this one.
That's my opinion expressed.
I wish you well with your decission.

Neill

[Onefella]

Re: 38" vault in tropical Australia

Don't right me off just yet..

I could lift the bottom sheet, remove the 'gap' formwork and have a pretty solid slab still.

So would the cladding still rest on the hearth slab, or on some new insulated bottom layer?

[nissanneill]

Re: 38" vault in tropical Australia

Onefella,
I have just drawn the construction as it is recommended and as how I did mine although it was built on a reinforced retaining wall.
You can make the base the exact size of your oven or larger allowing a work area wherever you require.

Neill

[Onefella]

Re: 38" vault in tropical Australia

Thanks for the advice nissanneill, this will take a major re-design. I'll have to consider my options. Cheers.

[Dutchoven]

Re: 38" vault in tropical Australia

Thanks for the advice nissanneill, this will take a major re-design. I'll have to consider my options. Cheers.

Let us know what you decide...we can still help... and yes the concrete cladding of a barrel vault oven should also rest on the insulating layer...I think if you flip the slabs around you might find it much simpler...you could pour your concrete with the sheet on the underside still pour everything in a big monolithic pour filling cores and all...then the vermicrete on top...in the end it might raise your oven's floor height up a bit...which again speaking from experience is not necessarily a bad thing
All the best!
Dutch

[Onefella]

Re: 38" vault in tropical Australia

OK, it looks like I'm going to take everybody's advice and pour a solid hearth slab. I'll have to lift the bottom of my slab up 60mm. It should all work out ok.

[Onefella]

Re: 38" vault in tropical Australia

After much thought, I have decided to (more or less) stick to the original plan for my vault oven.

My slab has loose vermiculite under and around it now.

I'm starting the vault tomorrow.

[Onefella]

Re: 38" vault in tropical Australia

Here's the hearth with wall bricks ready for tomorrow.

I'm using a refactory mortar called Ryal Bond. It was a bitch to re-mix to a useable consistancy, but it sets like epoxy. Very strong.

[Onefella]

Re: 38" vault in tropical Australia

Walls up today.

It's been raining most of the day.. lovely and cool. Humiditity never dropped below 80% all day.

Start the entrance and wall bracing tomorrow.

[Onefella]

Re: 38" vault in tropical Australia

Entrance started. My bricklaying speed is a lot slower than I hoped.

[dmun]

Re: 38" vault in tropical Australia

It's looking really good. I recommend going to photobucket to see these pictures full size.

Onefella - Photobucket - Video and Image Hosting



I love that bullnose tile you have in front of your entry.

[Onefella]

Re: 38" vault in tropical Australia

Thanks for your kind words mate. Very encouraging.

The bullnose tiles turned out ok. I wanted a ledge across the front of the entrance so I had somewhere to put my beer.

I'm starting the vault arches today and I'm a bit nervous about fluffing it.

[Dutchoven]

Re: 38" vault in tropical Australia

With your work so far you will have no problem...I thought I would fluff it both times...when building the oven at home(barrel vault) and with the dome at the restaurant...keep up the good work
Best
Dutch