Hearth construction

[scottymac]

I know this has probably been answered a thousand times, but I can't seem to find a simple answer.
I'm in the process of building my WFO and am up to filling the hearth and have become quite confused after reading all the advice on the various forums.
My initial plan was to lay roughly 80mm concrete and sit hebel blocks on top of that slab and the fire bricks for the oven floor on top of the Hebel blocks. Will it work if I just sit the firebrick on the hebel blocks? Do I even need the concrete slab underneath the hebel blocks?

Apologies again, but I appreciate any help!!!

[david s]

Re: Hearth construction

You don't say how big an oven you are planning. The weight the foundation slab has to support will determine its thickness, but usually you'd need 100mm reinforced concrete slab. For the supporting slab, Hebel is not too strong (it is ok under compression) and the span you are covering also determines the strength required. You can get reinforced Hebel, they call it Power Panel and it has 4mm steel rods in it. If you want to do Hebel then support it in the middle with another pier. Done this way if it is well supported you may be able to get away with having the Hebel both as a base and the insulating layer.

[scottymac]

Re: Hearth construction

Sorry, I should have explained it better.
To support the base I have seven lengths 50 x 50 3mm steel angle set into the core-filled concrete blocks. I was going have the slab sit on these and the hebel blocks on top.
But I'm starting to think I could rest the hebel on the steel angle without the slab and then the firebricks directly on top of the hebel.

If anyone can make any sense of that.... would it work?... it just seems a little too easy.

[david s]

Re: Hearth construction

Yes, I think that would work, but it still depends on the span and the weight of the oven. 3mm angle is not exactly heavy. With Hebel panels you may be able to reduce the span and cantilever the Hebel supporting slab, so the mass of the oven is over the piers, as I do with my oven.

As a guide I'd say that the centre of the piers need to be approximately the same distance apart as the interior diameter of the oven. Do some scale drawings to see how it looks.

[brickie in oz]

Re: Hearth construction

Sorry, I should have explained it better.
To support the base I have seven lengths 50 x 50 3mm steel angle set into the core-filled concrete blocks. I was going have the slab sit on these and the hebel blocks on top.
But I'm starting to think I could rest the hebel on the steel angle without the slab and then the firebricks directly on top of the hebel.

If anyone can make any sense of that.... would it work?... it just seems a little too easy.

Post a pic.....

[brickie in oz]

Re: Hearth construction

Do I even need the concrete slab underneath the hebel blocks?

Apologies again, but I appreciate any help!!!

You can use waterproof exterior grade plywood instead of the concrete slab, it will need some support underneath though.

Dont use the Chinese rubbish as it delaminates when wet, meaning it isnt waterproof even though it costs as just much as Australian made stuff.

Yellow tongue chipboard flooring is also waterproof and works just as well, dont use Orange tongue as its not waterproof.