I've laid the oven floor bricks: 4 questions

[Fio]

I've laid the firebricks for my oven floor. The next task is to build the dome. Before I do, I have a few questions:

1) I bought a 4-1/2" angle grinder to smooth off the rough edges on the corners of the bricks. Should I do that NOW or wait until the dome is finished? Is there a special technique for doing this?

2) No matter how hard I tried, I still have gaps between some of the firebricks. Should I try to fill them in with something, and if so, what? Or, should I just let them fill up with ashes as the oven is used?

3) The sand/fireclay/water mortar is a very weak mortar. Is there a danger of shifting the floor bricks as I build the dome?

4) Should I mortar the bottom/base/first chain of dome bricks to the floor, or should I use fireclay/sand again? Do I want slip between the floor and dome, or can they be joined by mortar?

As always, thanks for the excellent information.

Cheers,

- Fio

[svtlightning]

Flo

I built my oven last year and have used it qiute a bit. So this is from my experience.

1. the outside edges of the floor will be covered with insulation. You wont see the rough edges.

2. Just let them fill with ashes. If you try to fill them ( mortar, fire clay or whatever ) it will likely come out when raking or brushing during use.

3. I didn't notice any shifting building the dome.

4. I mortared the first chain to the floor. Very small joint.

Good luck with your project.
Mike

[CanuckJim]

Advice

SVT,

All very good, sound advice. Fio, I'd go with what he recommends.

Cheers,
Jim

[Fio]

Flo


1. the outside edges of the floor will be covered with insulation. You wont see the rough edges.

Good luck with your project.
Mike

Actually, what I was referring to is the center of the oven floor. As the bricks are laid, there are slight variances that could catch the edge of the peel. For example, I was unable to pound the bricks perfectly flat (Firebricks are far from uniform anyway) and the corner of one brick in the center of the floor sticks up about 1/16". I want to smooth that down with an angle grinder so that the pizza peel doesn't get caught on it.

My question is: Should I grind it out now or should I wait until the dome is built.

Thanks for the great info. I can't wait to get this project done.

- Fio

[Marcel]

Strike while the iron is hot.

(F) "My question is: Should I grind it out now or should I wait until the dome is built."

(M) If you are determined to lower that edge, I'd do it now as it is quite accessible. But be aware that once you remove that 1/16th lip the brick underneath that "skin" may be somewhat more porous and feel unfinished.

Ciao,

Marcel

[DrakeRemoray]

4. I mortared the first chain to the floor. Very small joint.

Did most people do this as well?

Drake

[arevalo53anos]

Drake:

I would not grind the brick edge.
If you used the sand/clay mortar mixture to laid the refractory bricks, could be easy to remove the ?uneven? brick, then remove the mortar and pour a new sand/clay mixture in place and then, a leveled brick.
The refractory bricks and the concrete base under hearth will be your temperature source when baking. Ideally, there will be no break between bricks and concrete.
The sand/clay mortar need to be as thin as possible and it is only used because of the easy use and thermal conductivity.

I just mortared my first brick dome file by the outer side, just to maintain it in place, and because the concrete mass will be poured on.
Remember that do you need a linear temperature transmission. Always as possible, do not mix materials.

I hope this help

Luis

[Fio]

Drake:

The refractory bricks and the concrete base under hearth will be your temperature source when baking. Ideally, there will be no break between bricks and concrete.
The sand/clay mortar need to be as thin as possible and it is only used because of the easy use and thermal conductivity.

I hope this help

Luis

My construction is a bit different, and I hope that it won't be a problem.
The firebricks rest on a bed of sand/fireclay that has been mixed with water and spread with a notched trowel.

Directly beneath the sand/fireclay mixture, and ON TOP of the concrete hearth slab, is 2" of refractory insulation board (fiberfrax board).

Thus, a cross section would look like this:

FIREBRICK resting on
SAND/FIRECLAY MUD, applied to
2" FIBERFRAX INSULATION BOARD, resting on
CONCRETE HEARTH SLAB

The concrete slab is uninsulated, and performs no role in retaining heat (No heat gets past the fiberfrax board). I did this to minimize thermal mass. I figured that if we are not adding thermal mass to the dome, we should not add it to the floor, either.

I'll have to post pix of this when I get a chance.

[james]

Nice finished oven

Luis,

I think the finished oven photo (the last one in this posting) looks great. It might be the first time we saw everything completed. Excellent.

I like the brick exterior, and the cantilevered landing worked well. Right next to the pool; can't beat that. Is that a fireplace in the corner? Do you you it for grilling, along with fires?

Complimenti.
James

[DrakeRemoray]

My layout is about the same as Fio's but I used vermiculite concrete instead of the fiberfrax board.

My question (and Fio's) about the first few rings of dome brick still stands.

Do most people mortar the first ring to the floor or just put mortar on the outside of the dome?

What about the next two vertical rings? They don't lean start leaning in until the 4th ring right? So is there mortar between these rings or just on the outside of the dome until we get to the part when they start to lean in (between the 3rd and 4th rings). That is how I laid my profile template out...is that right?

Drake

[arevalo53anos]

Drake:

The oven thermal mass is a compromise question. This is a point that was discussed in past threads. Resuming it, less thermal mass, less temperature storage, less residual baking time. It could be no problem if you are thinking in baking pizzas (always with fired oven) eventually, or a single batch of bread.
Will be if you think higher !
Like you pointed, the concrete in slab has no function in retaining heat.
If you laid side bricks in your oven hearth, you could have 2 inches of thermal mass in it. Remembering that heat could be transmitted by radiation, convection and conduction, be careful to maintain the same thermal mass in the dome or barrel bay to equilibrated baking.

Luis

[DrakeRemoray]

Thanks for the help Luis, Both Fio and I are using the "new" design which calls for resting the hearth bricks directly on the insulating layer.

My question (and Fio's) about the first few rings of dome brick still stands.

Luis mortared his first dome ring on the outside only.
Mike mortared his first dome ring to the floor.

Do most people mortar the first ring to the floor or just put mortar on the outside of the dome?
Drake

[Les]

Luis,

Are the red bricks on your dome curved or is that the camera playing tricks on my eyes? Is it posible for you to post a picture of the top of your dome? I would like to see how you capped off the brick. Your oven looks great!

Les...

[CanuckJim]

Still Stands

Drake,

Haven't built a pizza oven, but from a mason's point of view, I would definitely mortar down the first course of brick. Sure, the cladding will provide lateral strength, but insurance is a good thing, long as the premiums ain't too high.

When the brick begin to lean, butter the mortar in a wedge. If the angle's extreme, insert brick or wooden wedges to hold the brick in place until it sets up; remove wedges and point gaps.

Jim

[Marcel]

I didn't mortar the 1st ring

Thanks for the help Luis, Both Fio and I are using the "new" design which calls for resting the hearth bricks directly on the insulating layer.

My question (and Fio's) about the first few rings of dome brick still stands.

Luis mortared his first dome ring on the outside only.
Mike mortared his first dome ring to the floor.

Do most people mortar the first ring to the floor or just put mortar on the outside of the dome?
Drake

(M) Looks like you're having trouble getting concensus here. The reason I did *not* mortar the first ring is to allow the brick floor to expand with the heat and not threaten the structural integrity of the dome. This is a debatable theory however since the argument could be made that since the dome and the floor are of the same material (not counting the refractory cladding on the dome's outside) that the dome should expand at the same rate as the floor. I said debateable because temperature differences have been noted between the floor and the dome. That is likely caused by the fact that though the dome and the floor are of the same material, the floor uses the narrow side to set pizza on, whereas the dome is almost twice as thick as the floor because of how it's bricks are cut.

(M) As I see it, a teacup turned over so it is sitting on it's rim has the same compressive strength as it would have if it were glued to the supporting table. That, and the possibility of unequal coefficients of expansion constitutes my specious argument for leaving the first ring unmortared.

(M) The most frequently voiced concern I've read on this forum is that the dome would collapse once completed, not that the entire dome would shift. Quien Sabe?

(M) Ultimately, we may be worrying this to death and either way would be OK.

Ciao,

Marcel