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bigfluff 11-03-2009 01:11 AM

Hebel Hearth
Hi guys

OK well finally after a trip around Australia the purchase of a new house its finally build or WFO.

Im using a locally produced kit which dosnt supply any insulation for the floor - though uses 60mm bricks with the recomendation of 4" of Vermiculite concrete but my question is has anyone used Hebel power panels as the base without insulation? Hebel panel is reinforced with reinforcing bar so strength is not an issue its more a question of insulation properties Im concerned about.

So do you think Hebel panel on its own will be enough or will I need some Calcium Silicate board as well - Im trying to avoid using the board as its pretty expensive - $225 for the oven.

Thanks for your help


Frances 11-03-2009 02:08 AM

Re: Hebel Hearth
You will need to use something - vermiculite is also a good insulator and will probably cost less than the board. But don't skimp on the insulation, whatever you do!

Alter ego 11-03-2009 02:54 AM

Re: Hebel Hearth

I was also wondering whether Hebel panels would be OK to use as a hearth suppoert without any further insulation. I have just looked on their website and in their instruction manual and they publish the insulation R values which is R1.72 for 200mm of the Thermoblock panel when dry. I have no idea how this compares to other insulating boards. The melting point of Hebel panels is about 1600 deg C so they should hold up as the support under a brick floor.

See if you cand find the R values of the other insulation board to compare.


dmun 11-03-2009 05:37 AM

Re: Hebel Hearth
There have been numerous threads on hebel and aac oven insulation: a google search is better than a forum search because the forum search thinks aac is to short a word for a search.

I think the consensus is that vermiculite concrete is cheaper, and a better insulation. I think also that the direct heat of the oven floor compromises the integrity of the structural aac panel.

Mark CH 11-03-2009 07:29 PM

Re: Hebel Hearth
G'day Mike,
A mate of mine built a barrel vault oven a few years back and he used the Hebel floor panels rather than pouring a hearth. He got CSL to provide some technical advice and the results are great. His hearth cost him about $120 then he lay the cal sil board on top and bricks for the cooking floor. When his oven is fired up the bottom of the Hebel hardly gets warm so it seems to insulate really well.
I'll also be using it for my hearth due to the easy nature of working it and access issues in relation to this reasonably large pour of concrete.
In Melbourne you can get Calsil Board (1250x1000x20mm) for $40 per board. I'll be putting 2 of these under my floor.
Mark CH

nissanneill 11-03-2009 09:09 PM

Re: Hebel Hearth
Hi Mike (bigfluff) and Mark CH
First of all, welcome to the forum. We Aussies are certainly dominating the forum with new members, so let's keep it up.
As far as the Hebel is concerned, quite some years ago, Hebel were only a very young and relatively unknown company who wanted me to build my new planned 680 sq metre Australian Federation two story house completely out of their product. I was reluctant but it was obviously strong enough with internal support but I was not game, and the house was not built.
I would still be reluctant with more detailed information as I feel that steel reinforced concrete is a tried and proven method, it costs less but is heavier. I personally would suspend a mesh reinforced 4" concrete floor and then run 3" vermiculite cement over that. Cost for the insulation would be similar to the Calsil board. Unless you can buy a half sheet, you will need 3 sheets for the planned 2" thickness to cover wider than the 1000mm board width. You want the insulation under your dome bricks as well, so with a 36" oven + 2 X 4 1/2" brick dome thickness comes to 45" or 1143mm PLUS your void dimensions.

For what it is worth


david s 11-03-2009 10:35 PM

Re: Hebel Hearth
I used the Hebel power panel for the base of my moblie oven in an effort to reduce weight. It insulates quite well because it contains quite a lot of air, but it is not all that strong even though it's reinforced. An excursion over a speed bump when I forgot I was towing the oven has cracked the hebel base, but it really doesn't matter because it's in a steel cradle. Being made of portland cement you should also insulate a bit, say one inch, between your floor and the hebel.

Rodneyf 11-03-2009 11:33 PM

Re: Hebel Hearth
Be carefull with the calsil board as it breaks down with moisture. You have to make sure that it can't suck moisture out of whatever surrounds it.

Neil2 11-04-2009 04:57 PM

Re: Hebel Hearth
"We Aussies are certainly dominating the forum with new members, so let's keep it up."

Building season down there. We will catch up with you in the spring.

nissanneill 11-04-2009 07:09 PM

Re: Hebel Hearth
Yes Neil2,
luckily the wheel turns and we all get to hour our opportunity to get those ovens underway.
I do need to say, that we don't experience the snow/ice conditions that northern US and Canada gets, and I guess that is a bonus as we can build and entertain all year.
I really do feel for the builders who must dig their foundations to below the frost line (which I had absolutely no idea of until I participated in this forum).
I guess I would then build a large Rumpus/entertaining room with french doors that will open the area up in better weather times but the oven is then dry and usable all year around.
So, put another jacket on or pull another rug up onto the bed you Northernites. I am thinking of you


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