Cement Board in Arch??

[labman]

I am bricking out my arch and put 1" arch board behind my fire bricks and filled the back end with Perlite and I have heard others say that they put a blanket on the top of the Perlite to keep it from blowing away has anybody actually had this happen? I dont have any arch board left and I dont have any ceramic blanket but I do have a piece of Durock cement board. Has anyone put this stuff in their arch, if I lay the sheet on the top of the perlite will it hold up? its a 3x12 drop flue how much space should be between the bottom of the pan and the board?

[tuckermtn]

never tried the durarock, but when I put the ceramic blanket down I liked that it was flexible and I could contour it to the "rise and fall" under the flues...I have my blanket right up under the flues till right before the stack, where it dips down to allow the gasses to go make the turn and go up the stack...

[TapME]

The guy at the concrete place here said that cement board would not take the heat directly. It was mentioned that you could use it behind the fire bricks. Don't know what to believe. Good luck in your arch building.

[RileySugarbush]

I don't have any experience with it, but I think it would hold up ok if it's just laying flat. You are only using it to hold the light stuff down so it's just ballast.

After firing you probably couldn't pick it up without breaking, but I bet it would stay put if you leave it alone.

Are you really using perlite as opposed to vermiculite?

[labman]

Yes Perlite Why do you know something I don't but should?

[RileySugarbush]

If it is the same stuff I am thinking of, it is very low density white volcanic rock. I just asked because most people I've heard of have used vermiculite, which is expanded mica. Either one has the potential to be blown around easily. Both are basically rock so should be fine at the temperatures we deal with. I think I read that someone dampened a layer of powdered refractory cement that then hardened as a top layer to hold it in place. Maybe that could work for you as well.

[RUSTYBUCKET]

Labman,

I've never used Durarock in my arch but I did lay a piece under the firebox hoping to make ash removal easier. After a couple of firings, the Durarock started to fracture due to the heat from the ashes. If I tried to move it now, I'm sure it would fall apart.

Russ

[Cardigan99]

Just my two cents, but we used cement board under the pan in a barrel evaporator last year. It held up well enough that we'll do it again this year (with a new piece of course).

[WESTVIRGINIAMAPLER]

I could be mistaken, but I think durarock has a touch of styrofoam in it, either way, it will eventually burn up some in a fire, so don't use it.