Calcium Silicate board thickness

[Salty]

PLEASE HELP. I am ready to pour my foundation this weekend. I have 3 pieces on calcium silicate insulation but it measure at about 1 5/8". Other than that issue, it is definitely the good stuff, I bought it at Western Industrial Ceramics. So here is question....Is one layer enough? or should I my more so that I can double on to 3.25-3.5" of calcium silicate. Please help.

[Les]

Re: Calcium Silicate board thickness

I thought 2 inches was standard. I went with 4 inches and have zero regrets. Personally I would double up. It won't impede your progress of pouring the foundation so no hurries...

[brickie in oz]

Re: Calcium Silicate board thickness

I used 40mm thick which is about 1 and a 1/2", it will keep the oven hot for days on end.
Mind you, our climate is Mediterranean like.

[Salty]

Re: Calcium Silicate board thickness

My big issue is that it is going on top of only 1.75" of true concrete. I am thinking I might just double it up so that I dont have any regrets. Follow up question though...How important is insulation under the entrance/hearth? My entire floor will have almost 4" of CalSil, but my hearth is going to only have 4" of vermicrete. Is this going to compress at a different rate than the CalSil?

[brickie in oz]

Re: Calcium Silicate board thickness

My big issue is that it is going on top of only 1.75" of true concrete. I am thinking I might just double it up so that I dont have any regrets. Follow up question though...How important is insulation under the entrance/hearth? My entire floor will have almost 4" of CalSil, but my hearth is going to only have 4" of vermicrete. Is this going to compress at a different rate than the CalSil?

4" is just over kill and a total waste of money.

[Salty]

Re: Calcium Silicate board thickness

Aww Man...Now you have me second guessing doubling up. It certainly would be cheaper to only have one layer. What is the best way to cut the CalSil? Band Saw? Table Saw? Circular Saw?

Also, has anyone tried cutting their fire brick with a table saw with a diamond blade? It obviously isnt a wet saw, but I think that is the best I can do without a big investment.

Now, that I think about it....with they money I save not buying more CalSil, I'll be able to buy the diamond blade...I would guess that is a fair trade off.

[Les]

Re: Calcium Silicate board thickness

4" is just over kill and a total waste of money.

Al, Are you sure about that? I recall reading where some have measured a termperature rise on the bottom of the hearth. I can see it being overkill if you are sitting that thick of board on top of vermiculite.

[brickie in oz]

Re: Calcium Silicate board thickness

Al, Are you sure about that?

Ive only got 40mm of calsil and nothing else under the hearth and after a pizza night we can cook for a week in the oven.

So I am just guessing that 100mm is overkill.

P.S. The hearth only has a thermal mass of 100mm.

[Salty]

Re: Calcium Silicate board thickness

Al,

Do you have Vermicrete under your calsil or is it regular concrete?

[Gulf]

Re: Calcium Silicate board thickness

Salty,
I wont get into the thickness of the calsil since I don't know how less than 2" perform. What does concern me is that you stated that: "My big issue is that it is going on top of only 1.75" of true concrete"

I may have missed something but, that is just a little over counter top thickness. Not a true weight bearing thickness for a WFO hearth. Is this 1.75" poured on top of some other load bearing structure?

[Salty]

Re: Calcium Silicate board thickness

Sorry, I should have explained more. My build is going on a custom made steel cart. On top of that I have a 14 ga galvanized steel pan with welded reinforcements. This pan has been bolted to my cart and I will be filling it with the < 2" of concrete. My build blog is Mobile Oven in Oregon...I'll be updating it much more often now that I am further under way.

[Gulf]

Re: Calcium Silicate board thickness

I knew that I must have been missing something. Thank's for the clarification. Steel construction is a little above my pay grade .

[Salty]

Re: Calcium Silicate board thickness

For the most part it is out of my league too, but I brought up the idea to the guys in the shop where I work and before I knew they were cutting steel tubing for me...ha...Now I am on the hook to get this thing done ASAP.

It is like losing weight...dont tell people you are going to do it if you dont want to be held accountable.

[Gulf]

Re: Calcium Silicate board thickness

I know what you mean. I owe some friends who helped me with a little metal work and material aquisition.

Also, use only hand tools to cut the calsil. A key hole saw cuts the curves just fine. A hand saw will work great on any straight cuts. These type tools help keep the dust down. Do wear a dust mask! Buy the wet saw and sell it to your neighbour when you are finished with it. He will want a WFO too, if you invite him over for the great food . It is that "keeping up with Jones' syndrome" that makes this all work .

[brickie in oz]

Re: Calcium Silicate board thickness

Al,

Do you have Vermicrete under your calsil or is it regular concrete?

Just 100mm of plan ordinary everyday concrete.