help, only fools rush in!

[tommy k]

Hello all, iv finished my brick oven and started curing a couple of days ago, starting small steadily. Increasing strength fires, yesterday I noticed that underneath the suspended 6inch concrete slab
Where the fire was it was getting quite warm, during the build I didn't have this sites knowledge
And never put an insulating layer of vermiculite concrete on top of my slab.

The slab which sits on top of breeze blocks is 6 inch thick with 4 parts ballast 1 part cement containing rebar,

Will the slab heat up and fail or just draw all the heat out?

I could take up the fire bricks on the floor and lay vermiculite and concrete thus raising the floor
Without too much trouble

Any help from the forum is much appreciated

[Lburou]

Some questions first.

1. Do you get the oven hot enough to clear the dome?
2. If yes, what is the oven floor temperature at that time?
3. The temperature of the bottom of the hearth soon after?

You'll need an infra red thermometer to answer these questions.

If you can get the oven to the desired temperature and cook with it you may be able to continue using it without modification(s). That is, if the bottom of your hearth isn't getting hot enough to remove the strength of your reinforcing steel (I read that the steel goes bad somewhere around 600 degrees F).

[brickie in oz]

Originally Posted by tommy k

Will the slab heat up
and fail
or just draw all the heat out?

Yes,
no,
yes.

You will never get to pizza temp as the heat will just be drawn out through the slab, plus it would take a week to get any sort of decent heat into the slab.

[azpizzanut]

Hello Tommy K,

You would get the highest efficiency by placing ceramic board insulation. Vermiculite concrete is good if you have 4-5 inches of it but 2" of ceramic board will get you where you need to be without changing the internal dimensions too much.

Best of luck,

[tommy k]

Thanks for the replies, soon after my post I found some vermiculite at a local builders merchants, I removed all the hearth bricks, knocked up some vermicrete and layed it about 3 inch thick, iv since had my first cook in the oven, no ir thermometer (they didn't have them back in the day so its guess work) got oven white hot, took 2hours, pushed coals back and tried our first pizza, 180 seconds later- incredible! Cooked another 7 pizzas then later cooked beer can chicken, all was good and had no problems with the oven at all!
The oven was still warm 24hours later!

Just need some nice English weather now!

Will stick some pictures up soon

[Lburou]

Originally Posted by tommy k

Thanks for the replies, soon after my post I found some vermiculite at a local builders merchants, I removed all the hearth bricks, knocked up some vermicrete and layed it about 3 inch thick, iv since had my first cook in the oven, no ir thermometer (they didn't have them back in the day so its guess work) got oven white hot, took 2hours, pushed coals back and tried our first pizza, 180 seconds later- incredible! Cooked another 7 pizzas then later cooked beer can chicken, all was good and had no problems with the oven at all!
The oven was still warm 24hours later!

Just need some nice English weather now!

Will stick some pictures up soon

Good for you! Glad the solution was so simple.