Fireclay vs refractory mortar (for setting oven floor)

[Tenorio74]

Hello everyone!

This is my first post after a long time of collecting popular wisdom from all you guys

The question is about laying the firebrick floor - Pompeii Plans point out a mixture of 1:1 sand/fireclay, but I wanted to know if I could use refractory mortar.

The guy at the refractory stuff company said the mortar would eventually bind hard like refractory cement. Is this ok for the floor? Does the 1:1 mix also bind the bricks to the insulating FB board?

If I can't use refractory mortar, and can't find "fire clay", what other options would I have for setting the bricks?

I am having a hard time with the translations and materials down here, so any help would be greatly appreciated!

Thanks!!

[azpizzanut]

Re: Fireclay vs refractory mortar (for setting oven floor)

Hello,

Fire clay and sand do "harden" but can be easily removed with only a little effort. Mortar turns to stone and needs to be chipped off with a hammer.

Cheers,

[brickie in oz]

Re: Fireclay vs refractory mortar (for setting oven floor)

The floor needs to move with expansion and contraction, I would think that sticking it down would be a bad idea.

[Tscarborough]

Re: Fireclay vs refractory mortar (for setting oven floor)

Brickie, sticking it down is not a problem because whatever you use will just crack and move with it. The only time it is a problem is when there is a large variance in the thickness of the layer used to mortar set the floor brick. There was someone who posted here with wedge shaped bricks that mortar set the floor and it was a disaster, but for normal unitized firebricks, it is not critical.

Fireclay/sand is fine, refactory cement is fine, regular old mortar is fine, plain sand is OK, but not optimal.

[Lburou]

Re: Fireclay vs refractory mortar (for setting oven floor)

Hello everyone!

This is my first post after a long time of collecting popular wisdom from all you guys

The question is about laying the firebrick floor - Pompeii Plans point out a mixture of 1:1 sand/fireclay, but I wanted to know if I could use refractory mortar.

The guy at the refractory company said the mortar would eventually bind hard like refractory cement. Is this ok for the floor? Does the 1:1 mix also bind the bricks to the insulating FB board?

If I can't use refractory mortar, and can't find "fire clay", what other options would I have for setting the bricks?

I am having a hard time with the translations and materials down here, so any help would be greatly appreciated!

Thanks!!

Does the refractory company have any rigid insulation? Any fireclay? Either the rigid insulation, (because you don't need sand and fireclay with a flat surface of the rigid insulation), or fireclay with sand will do what you want under the oven floor.

Your English above is excellent!

[dmun]

Re: Fireclay vs refractory mortar (for setting oven floor)

Some builders have used the sludge from cutting their firebricks as a substitute for fireclay in the leveling mixture.

[Tenorio74]

Re: Fireclay vs refractory mortar (for setting oven floor)

Thanks for all the replies! I have some good ideas there pointing me in the right direction.

I'll try to explain a bit without being too lengthy: I am replacing my oven floor, which unfortunately I did not have the time to build myself (I would have loved to though, but my current job keeps me too busy). Nobody down here I could find had ever built a low-vault Neapolitan style oven, so I had to go with the best guy I could find because the oven is for a pizza place I will be opening soon (I hope), and as with all start-ups, time is a big factor because of the high rent in commercial areas.

Anyway, down here all brick/adobe/artisanal oven builders use a type of large handmade red brick (about 16"x16"x2") for the oven floor. The darn thing never got up to past aprox. 650F. So 3" fire brick it is (the big red bricks were lifted today).

The attached pic shows my plan on using 3 ceramic fiber boards (they sell them down here 36x24 inches), and if I can get fire clay I'll use it, and if not, then I'll just lay the bricks directly on the boards while I figure out my options (so as not to mortar and be stuck down so to speak)

As for the english skills, I grew up in many countries, including the US (L.A. and Virginia) and the UK... So I got lucky in that respect!!

Cheers!!
(and let's see what tomorrow brings...)

[brickie in oz]

Re: Fireclay vs refractory mortar (for setting oven floor)

The darn thing never got up to past aprox. 650F.

Sounds like a lack of insulation problem?

[Tenorio74]

Re: Fireclay vs refractory mortar (for setting oven floor)

Well that was my first thought, but the underside of my hearth slab at the time of scary flames was only about 36 celsius, body temp.... (12 degrees C above ambient brick temp).

I figured if I was loosing heat that badly through the bottom it would have been way higher.

The insulation this builder used is a 6" layer of crushed glass, mud, some weird leaves and other stuff I didn't get to witness going in, but will see tomorrow. It must have worked a bit I imagine, otherwise wouldn't the underside have gotten much hotter?

[brickie in oz]

Re: Fireclay vs refractory mortar (for setting oven floor)

Well that was my first thought, but the underside of my hearth slab at the time of scary flames was only about 36 celsius, body temp.... (12 degrees C above ambient brick temp).

I figured if I was loosing heat that badly through the bottom it would have been way higher.

The insulation this builder used is a 6" layer of crushed glass, mud, some weird leaves and other stuff I didn't get to witness going in, but will see tomorrow. It must have worked a bit I imagine, otherwise wouldn't the underside have gotten much hotter?

What about the top?

Glass, mud and sticks isnt an insulator..

[Tenorio74]

Re: Fireclay vs refractory mortar (for setting oven floor)

True, but it apparently did *something* insulation-wise, would you agree?

I did get to make the guy put a whole roll of fiberglass blanket on top of the dome, and with about an inch of mud on top, it only went up to 32C with the middle of the dome going white.

What would the veredict be down-under?

[brickie in oz]

Re: Fireclay vs refractory mortar (for setting oven floor)

The dome would go white no matter what as all that indicates is that your fire has reached 600 degrees c, the important thing is to store the heat with some mass, bricks, clay, rocks, glass and then retain it with ........

good insulation like ceramic fibre matting, vermiculite, top and bottom of the oven.

[Tenorio74]

Re: Fireclay vs refractory mortar (for setting oven floor)

Sounds like a lack of insulation problem?

Right. I had about 3 inches of regular concrete under the red brick floor (which has now been promptly removed). Under that was the dirt/powdered glass/etc etc mix the andean oven makers use. And under that is the hearth slab.

So I'm keeping the soil, pouring a second concrete floor on top (thinner though), and then using my 2" fiber board insulation, plus the 3" firebrick on top.

Thanks all, and I will let you know how it goes (at least I can fire it up straight away ).

If you want something done right, you have to do it yourself....

Ah, and I got the fireclay! Clay = arcilla in spanish. I'd totally forgotten, we play tennis mostly on clay courts down here (canchas de arcilla).