The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Hearth slab question

MRH's picture
MRH

Hearth slab question

I am in the process of building a brick oven and have a question on the hearth slab....  I am following plans that say to use calcium aluminate in the mix for the hearth slab, which is supported on the cement block with a grid of rebar.  I have the insulated slab already done underneath it..... I have talked to a guy that has a oven he made and used just regular concrete for his. He says the firebricks above are enough, and it doesn't need any special concrete for it.....  My thought is maybe just pour the regular concrete then after it dries pour a 2 inch layer of refractable castable on top then start building the oven chamber out of firebrick on top..... Overkill or underkill ??? Don't want to do this wrong if I can help it!

Thanks,

Mark

pmccool's picture
pmccool

For adequate strength you want a slab that is strong enough to carry the loads that will be imposed on it.  If you have a friend who's a civil engineer, ask what they would recommend for slab thickness and reinforcement. You want the structural slab to be Portland cement concrete, not refractory. 

To protect the slab from temperatures high enough to damage it, you want some form of insulation between the slab and the fire.  This could be a layer of castable refractory, as you propose, or a layer of foamglass, as an underlayment for the firebrick.  Or the firebrick may be enough on its own.  I'm way past the limits of my knowledge, so I can't offer more specific advice. 

Paul

MRH's picture
MRH

Thanks Paul,

I am leaning toward just using a portland mix and then going with the firebrick on top of that set into refractory morter.  I keep looking to things and after talking to a bricklayer that has his own brick oven and built others.  He says the firebrick on top is enough and his is that way.   They fire it up weekly and cook pizzas for the public and parties so it gets a workout.

 

Mark

MRH's picture
MRH

Hearth slab was poured using the portland, river pebble, and sand mix.  I layed the firebricks with refractory mortar.  Now I am wondering about my choice I made, they are layed flat instead of on edge. I am thinking maybe I sould lay another layer on them using the refractory mortar and doing the herringbone pattern.  Do you think it would be the way to go or overkill? 

 

Thanks ,

MarkFirebrick layed

Mini Oven's picture
Mini Oven

the bricks?  

MRH's picture
MRH

Well after talking to a friend and looking on the net for any posts I could find. I ended up laying another layer of firebrick in a herringbone pattern.  I still didn't get it as smooth as I would have liked, but I think it should work.  Wondering if maybe I should try sanding it smoother?

Mini Oven's picture
Mini Oven

:)

MRH's picture
MRH

Slowly getting a little more done... Figure better not to hurry and give the mortar etc time to cure up as I go!

KrsnaMara's picture
KrsnaMara

Hey there Mark!

Wondering how the oven is working out?

A friend has a project he is working on and stumbling over the same question.

Just curious how your oven looks these days and how much use you get out of it.

Thank you much!

Martin

MRH's picture
MRH

Finished pic

MRH's picture
MRH

Been done for a couple years now, haven't used near as much as I figured and it was mostly pizza.  Works well but seems to much going on all the time.

 

Mark