Cutting the 4 fire bricks for the top of the chimney

Hi. I’m building the Mattone Barile Grande. On page 15 the plans show a notch being cut in what I believe are the four top bricks of the chimney (3/4" x 4" x 2.5"). The plans say “you will need to trim the top layer of firebrick to the dimensions shown below so the 6” Dura Tech Anchor Plate can fit snugly into place." For the life of me, I can not figure out why these top bricks need this. ???

Another chimney question - the plans show all sort of fancy cuts to the chimney layer closest to the dome. Is that required? And how does one do that? I have a 10" mason saw. I was thinking of leveling the first row with mortar instead of cutting.

Ferndale, WA

The chimney bricks in the pattern as mortared on top of the oven leave an opening that is 5.5" x 5.5"… But our DuraTech chimney kit is 6" (with a 1" flange that goes into the chimney). So, you will need to cut a little section off the top of each chimney brick so the DuraTech kit can fit nicely into place. If you don’t trim those 4 bricks - the DuraTech will not be able to fit into the chimney.

To answer your second question - you can do it either way. We recommend you trim the bricks a bit in order to keep your mortar as thin as possible. You don’t want to have large / thick sections of exposed mortar… plus it’s really difficult to keep mortar over 1/2" thick in place. It will want to sink down and/or bulge out. So the easy way to have a perfectly fitting chimney is to slightly trim the chimney brick before mortaring into place.

It is a little difficult to trim the bricks but it can be done with a grinder and a diamond blade. Just put the bricks in front of th oven level and trace the shape of the curve on them.

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This is the technique I used, and wow it was indeed a little difficult. I contiplated not putting one on because I messed up a few times…but ultimately I sucked it up and finished the job. I felt like a skulpture artist!

We are trying to get our hands on a wet miter saw for the straight cuts but for this curved cut you are referring to, can you provide a link or a picture of the grinder you used?

Here is the grinder tool I used.

And here is the blade.

Tum, hey I have something similar, thanks for sharing.

I leveled my first course of chimney bricks with mortar. I used 1x4 pine to create a concrete form, an arch had to be cut into the back 1x4 to follow the curve of the oven. It is all covered by stucco so I don’t see a problem with having a thick mortar joint. I did use high temp mortar for it.
An angle grinder with concrete blade like TUM shows is what I used to cut the top arch in the oven door.
See pictures

You can see my build in the gallery, Anhorn oven in North Dakota


An angle grinder worked for me. took my time and filled the rest in with mortar.

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