Problem with Hearth

[Jim Bob]

Contractor poured concrete yesterday while i was out. Bad move!! He poured it 4.5 inches deep leaving only 3" for insulated layer. Now, i need to make a decision to either raise form an inch making entire hearth a full inch thicker or pour the remaining 3" of the insulated layer and then purchase some Cal Sil board and lay it on top to make sure there is enough insulation under the floor of the oven.
Any comments? or suggestions which would be preferred?
Thanks,
Jim Bob

[asudavew]

Three inches and the Cal Sil board is the way to go if you can afford that option.

Otherwise raise it an inch or two.

[Jim Bob]

Thanks. Not sure i can find the Cal sil board in Memphis and i have no idea how expensive it is. Sounds like from you it is very costly. Have an idea of price range?
Jim Bob

[asudavew]

I'm not sure because I didn't use it.
But I think it's in the $150 - $200 range.

[dmun]

Cal-sil (and insblock19) boards come in one inch thickness. You could use one inch of refractory board on top of two inches of vermiculite concrete to get your three inches and required insulation. Cal-sil has the Memphis is a big place: they are sure to have a refractory supplier. Consult maps.google.com

[Jim Bob]

i finally gave up trying to locate Calsil board. First it was too expensive and second the minimum purchases were ridiculous for my needs.
So, i found some very thin and flexible masonite and cut long strips 4" wide and stapled them to the inside of form and now the full 4" of vermiculite/cement mix can be poured.
As always though, i appreciate the quick, informed responses that i receive on this forum. Will try posting some of pics soon.
Jim Bob

[asudavew]

Good deal Jim.

That's probably what I would have done.

Dave

[Jim Bob]

Well, the hearth is completed now with a full 4" of insulated concrete on top of the 4.5" of regular concrete. Yea, i know the contractor poured it too thick, but it's done now and looks okay. One thing I did do was use a product called Poolkrete. It is 5 parts vermiculite and 1 part cement- just right. except the vermiculite looked like a pretty fine grade. Not sure how well it will insulate. But it is very inexpensive($10/2 cu ft bag). It is made by Strong Mfr in Pine Bluff, AR. they also make a straight vermiculite which i have ordered for the loose material on top of the oven. It is very reasonbly priced too. ($12 per 4 cu ft, plus freight). Of course i ordered it thru my friend who owns a pool company.
Anyway, now ready to lay the floor of the oven after i drill holes in the hearth for the temperature probes.
Getting excited now,

Jim Bob