Calcium silicate or ceramic fiber board

[david s]

Segments ar fine. In fact they have the advantage of allowing a pathway for moisture to escape, provided you have some drain holes in the supporting slab. Just don’t make the gaps too big.Maybe nothing bigger than 1/4”. The floor bricks will easily bridge over that.

[yomer]

What about having one board vs small segments to make up the area under the base?

I found a warehouse which has several cal sil pieces laying around which I can join to form one "slab", as well as several 24x24in foamglas pieces.

Should I make the extra effort and find a supplier to build insulation with as little segments as possible?

[UtahBeehiver]

Either works, similar in properties.

[Michele Enrico]

I see everyone is recommending the cal sil. But what are the proc and cons vs. alumina silicate board. They seem to have very similar properties.
Michele

[mirassou]

Re: Calcium silicate or ceramic fiber board

Here in VA we have Kyanite mines. Kyanite is a form of aluminum silicate and was used in the insulating tiles of the space shuttle. Kyanite sand is a by-product of mining. It's essentially free (of course there are trucking charges) and is used for any purpose for which sand is used. This makes for a good substitute for fire clay and sand in leveling the floor.

[boerwarrior]

Re: Calcium silicate or ceramic fiber board

For the self-leveling compound... it doesn't need much support so you don't need to frame everything again - simply make a small surround kind of like an oversize picture frame. You can pour it very thin - like 1/4 inch.

I've never heard of pre-mixed sand/clay - just mix it up yourself. They sell stuff called "mortar clay" at Home Depot which works fine. I used washed, fine "play sand" (also from HD)

[aopf1960]

Re: Calcium silicate or ceramic fiber board

Thanks guys;
Sorry for my ignorance, but where can I get the sand/clay mix ? It's already mixed or I have to do it ?
I know Fix all.
Self leveling compound sound a great solution but I hate to do all the framing again.

[boerwarrior]

Re: Calcium silicate or ceramic fiber board

Leveling compound picture here. You can see on either side how uneven the base concrete was.

[boerwarrior]

Re: Calcium silicate or ceramic fiber board

I used concrete self-leveling compound and it worked perfectly! After I dry-stacked the boards I didn't even need to use fireclay under my floor bricks because they were all perfectly level

[david s]

Re: Calcium silicate or ceramic fiber board

You can use the sand/clay mix wet or dry.

[V-wiz]

Re: Calcium silicate or ceramic fiber board

There is a product called fix all, its used to even out uneven surfaces like yours, level the surface and dry stack the cal sil

[aopf1960]

Re: Calcium silicate or ceramic fiber board

I already got the Calcium silicate boards ( 2" ). I probably need to mortar them on top of my uneven concrete slab. ( i'm a newbie !! )
Do I need fireclay mortar or regular mortar ( bought too many for the block stand ) ?
Thanks !!

[V-wiz]

Re: Calcium silicate or ceramic fiber board

Haha, thanks guys, how about if i dont use water, like if i were laying pavers? Im sure it would work, since my floor bricks are tappered the thickness does differ, so i need a good amount of leveling to do.

[cobblerdave]

Re: Calcium silicate or ceramic fiber board

Gudday
Just use ordinary margerine or butter if you like .. Just use the the waxy lid on the top to smear it out . Once you have cured your oven it will be a little carbon layer you 'll never see
Regards dave
Ps... Don't let the wife catch you

[voon]

Re: Calcium silicate or ceramic fiber board

It is fairly porous--I found it impossible to put the standard fireclay-sand-water leveling mix between the insulation and my floor bricks because the CalSil instantly sucked any moisture out of the mix.

Couldn't one just spray the Cal-Sil board with a silicone waterproofing spray before adding the fireclay leveling mix? That might slow down the water absorption enough to let the mix set properly.

What about lard or shortening or wax? It would fill the pores and prevent the board from absorbing the water from the leveling mix. I guess it would just melt into the Cal-Sil board when the oven is fired, and perhaps reduce the insulating property of the board. But with 4 inches of Cal-Sil board, it probably wouldn't matter.