Firebrick extends beyond sides of arch

I have a similar issue, except it is for the sides of the hearth slab firebrick extending beyond the barrel firebrick. I think it is a function of the bricks being a smaller dimension than accounted for in the plans. My path forward is to line the foam form with 1" foam all around, thus making the barrel 2" wider but ensuring the mortar bed and bottom firebrick captures the edge of the standard brick.

Hi Ant, and welcome to the BrickWood forums.

Before you do that, I’d like @BrickWood to take a look at your photo. I haven’t seen an issue quite like this one.

Meantime, would you mind taking a couple of measurements? I’d like to know the overall length and width of the brick frame, and also the dimensions of your standard bricks.

There may be a better solution available, so those measurements would be helpful.



Standard bricks are 8" long, fire brick is 8.25" x 4.25"w
Frame out to out averages 46.5" and the hearth void averages 30.75".

So if the foam mold is 22" w and add a 4.25" w firebrick on each side we have 30.5".

I’m guessing the 2" of ceramic fiber and 1" of mortar shell makes the difference? That said, I’d still like the firebrick base course of the Barrell to rest partially on the standard to avoid water penetration

If I’m understanding this correctly…

Q: You want the finished exterior to be flush w/ the sides of the edge brick?
A: If that is the case, the oven is not designed like that. There will be an edge… about 2" - 3" all the way around depending on how many layers of blanket you use.

Q: You want to wrap the foam form w/ something 1" thick to increase the internal size of the oven so it will be 2" wider (and another inch taller).
A: No. Please do not adjust the internal dimenions. It will throw off the venting dynamics… and your door will not fit.

No, your understanding is incorrect. A better way to explain it is my base level of firebrick for the barrell arch does not match your sketch Step 15. Specifically, My firebrick does not partially rest on the standard 8" brick trim - it entirely rests on the hearth slab firebrick and leaves portions of the herringbone exposed to the elements. Is this the intent, as Step 23 more accurately depicts what my interface looks like. If so, I understand the 2 layers of ceramic fireblanket and 1" of stucco will likely cover my area of concern (Step 40) but I feel that T joint would be prone to failure?

Sooo…@Brickwood counsels (and I agree) that shimming the form to move the base of the arch out on both sides is going to screw up your oven’s cooking characteristics.

If you can’t bring the arch out (and again I agree that you must not do that if you want the oven to perform), your other option is to bring the frame in closer. The solution to that is to make some “splits” from standard bricks. If you haven’t done this yet, read this thread for the details, and a lot of tips.

Of course, you are going to cut these the long way, and you are laying them standing on a side, the same way as the hearth frame bricks are laid.

Your standard bricks were an inch short on each side, so I’d make the splits an inch thick, which with mortar will bring each side in about 1 ¼ inches. Remove your firebrick from the hearth, and scoop the sand toward the center so you are back at the base insulating slab layer.

Run the 8 inch splits along all four sides, laying them in with heat-resistant mortar—which is going to be very important because these small bricks will be in contact with your firebrick hearth and lining. If you want a little peace of mind, dry-fit a split on each of the four sides and put the form back on top to make sure you’re happy with how the arch lays. Then cut the rest of the splits and go to work.

Once your mortar cures, within a day, you can re-level your sand. You will probably need to take some out, because there is now less volume in the hearth void.

Now you can lay your firebrick in the herringbone pattern, cut the triangular pieces to fill in the edges and lock it up, and proceed.

Thanks for your patience while we got more details, Ant, and please keep posting as you proceed. I am keenly interested in how this will turn out!

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One other detail, Ant: re-reading that thread, it’s mainly about making split brick faces for veneer, so it talks about ½ inch cuts and what to do with the left over brick. In this case, you’ll be able to get maybe 3 splits out of each brick because you don’t really care what the faces look like. I say “maybe” because depending on your cutting method you might decide that it’s not safe to cut a third split from what’s left of the brick.

Thanks. The Reilly Family Oven (Reilly Family Oven - Mattone Barile - BrickWood Ovens) has the exact issue I am facing depicted in their Oct 2020 post.

Yes it does. I don’t know your plans for finishing yours, but it’s really a non-issue in their case because they built an entire enclosure around the oven, including a roof, and widened the slab to accommodate it.

The enclosure keeps water off the hearth frame bricks, which means little or no potential for penetration into the hearth itself. It’s the only reason they could get away with the hearth peeking out from under the arch like that.

I think you were right to reach out on this question. It doesn’t look like you’re planning that kind of enclosure, so in your construction process this is the right point to address the issue.

I’m a first time poster. I’m building a Mattone Barile oven and have nearly finished the base and am about to begin applying the standard brick frame to the upper slab. After reading this string I have a question about the size of the standard brick I’ve purchased. Mine measure 7.5 x 2.25 x 3.5 inches. The material shipping list calls for standard brick measuring 8 x 2.25 x 3.625 inches. I chose these smaller bricks because the brick supplier also has the matching veneer for that brick. The shorter standard brick means my herringbone firebrick cooking surface will be about one inch wider and longer than the plans show. Will that cause a problem when I position the foam form in steps 8-10?


Should the form still go 15.5 inches from the rear edge of the brick frame or should I instead align the front of the foam form at the intersection of the standard brick and firebrick? I can probably return the standard frame bricks if necessary.

Hi John Jay and welcome to the BrickWood forum.

With 7.5 inch long frame bricks you will end up 3 inches short, which will create more of a gap than the oven we were discussing above. You could try the same split-brick technique we were discussing, adding a half inch in thickness to each split. (And remember that most of that work will not be visible.)

Or, you could return the short bricks and purchase 9 inch standard bricks.

Since you’re going for a match between your frame bricks and veneer, the split method might be preferable.

Glad to hear your base is about done, and I wish you all the best as you continue. Please keep us posted on your progress!

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