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So will there be a discourse on tapering bricks? - Forno Bravo Forum: The Wood-Fired Oven Community



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So will there be a discourse on tapering bricks?

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  • So will there be a discourse on tapering bricks?

    In the instructions it says to see the Appendix for a discourse on tapering bricks, but I couldn't find it and searching the forums I found a few threads of people doing it but not a "how to".

    We decided this is probably the way to go for us since we live in earthquake country; in fact we are about a mile away from the San Andreas fault line in Southern California!

    Bought the HF tile saw and ordered two bags of Heatstop 50 ($100 a bag with shipping, ouch!).

    Help us before we cut all our bricks wrong! lol!

  • #2
    Re: So will there be a discourse on tapering bricks?


    There are several good threads on tapering bricks. Here are two really good ones from Paul "Hendo" Henderson (RIP):


    Also, do a search for posts by "Les". He built his entire oven with very precise cuts and very little mortar. Check out his picks in the Photo Gallery.

    I tapered my bricks as well... the link in my signature below explains how I did it. Mine cuts aren't nearly as precise as Hendo's or Les' but it worked out nicely.

    If you start wandering through oven build threads, you'll start to get a feel for how to do it. Once you start building, you'll figure it out REALLY fast
    Last edited by Ken524; 11-13-2008, 02:32 PM. Reason: Added some stuff I forgot :)
    Ken H. - Kentucky
    42" Pompeii

    Pompeii Oven Construction Video Updated!

    Oven Thread ... Enclosure Thread
    Cost Spreadsheet ... Picasa Web Album


    • #3
      Re: So will there be a discourse on tapering bricks?

      awesome. I don't know why that second Hendo thread didn't come up in my search, but that is just what I was looking for! I'll check out the others too. Thanks!!!


      • #4
        Yes, There was a discourse on tapering bricks?

        All you have to do is research deep into the bowels of the beast.
        And yes a few people, such as Les have doen this.

        Here is a text version of what I would call some early highlightsfrom ColonelCorn76 who could be considered one fo the founding fathers of the forum when it was on YAHOO

        Poster: ColonelCorn76
        Join Date: Mar 2005
        Location: Simsbury, CT USA
        Posts: 97

        Arch cut calculations

        Okay folks, here's the latest installment in "brick oven building...advanced"

        Here's how to calculate the dimensions of the bricks (voussoirs) that make up a semi-circle arch ("axe arch").

        The dimensions you need to have are:
        Arch span - inside distance across the base of the arch i.e. the doorway opening
        Brick height - height of each brick (e.g. 4.5" for a standard firebrick on its side)
        Brick width - assume taper will go from brick's upper corners downward (called the "extrados") for a 1/2 of a standard 9" brick this would be 4.5"
        Joint width - width of the mortar joint you'll be using typically 3/8 or 1/2"

        We'll find:
        Number - number of voussoirs rounded up to the next odd # to provide for a key brick
        Taper width - width of brick at bottom of taper (called the "intrados")

        We also need to calculate these on the way:
        Max circumference - the measurement you'd get by laying a tape measure around the outside of the arch when built
        Min circumference - the measurement you'd get by laying a tape measure around the inside of the arch when built

        Step 1:
        Calculate the Max circumference = Pi * (Arch span + brick height)
        ex: 3.1428 * (16 + 4.5) = 3.1428 * (20.5) = 64.4274"

        Step 2:
        Calculate the number of voussoirs in the arch = Max circumference / (brick width + joint width)
        ex: 64.4274 / (4.5 + .5) = 12.885 -- assumes 1/2" mortar joint

        Step 3:
        Round up to next larger odd number = 13

        So, for a 2 1/4" x 4 1/2" x 9" firebrick split in half with the 4 1/2" x 4 1/2" face being used to create the tapered brick, we'll need 13 arch bricks or voussoirs.

        Next we calculate the width of the lower part of the taper:

        Step 4:
        Calculate the Minimum circumference = Pi *Arch span
        ex: 3.1428*16= 50.2848 this gives us the maximum amount of room we have around the bottom of the arch

        Step 5:
        Calculate the total width of the joints = Number of bricks * joint width
        ex: 13 * 1/2 = 6.5 this gives us how much of the bottom arch will be used by the mortar joints because we make even mortar joints top to bottom

        Step 6:
        Taking the total distance around the bottom of the arch less the mortar joints & dividing by the number of bricks we have will give us how wide those bricks have to be on the bottom
        Calculate the taper width = Minimum circumference - total joint width all divided by the number of bricks
        ex: (50.2848 - 6.5)/13 = 3.368"

        So, we'll need 13 bricks that taper from 4.5" at the top to 3.368" at the bottom. To cut them, you'll mark the center of the bottom of the brick and then measure 1/2 of the taper width on either side (1.684 in our example), draw a line from each of these points to the corresponding upper corner and cut along the line.

        When I do this I use a metric ruler as the gradations are finer then an Imperial unit (inch) ruler and I don't have to translate things like 3.368 into 3 3/8 and then fudge the joint width a touch smaller than planned so it all fits. Another thing by the way, is that this assumes you put a half-width mortar joint under each of the end bricks where they lay on whatever supports you have for the arch -- you'd have 1/4" mortar, brick, 1/2" mortar, brick, 1/2" mortar....brick, 1/4" mortar.

        Of course now there are some variations you might consider -- how about putting the narrow face outward so the bricks taper downward from a 2 1/4" top width (which is what I did for my doorway) or eliminating the mortar joint altogether & letting them fit by friction alone?

        For the really brave of heart, you can do this in 2 dimensions (horizontal & vertical) and figure out how you'd need to cut bricks to fit without a mortar joint around the whole circle of the oven and as it rises in the arched dome...a completely mortarless oven!


        Originally Posted by svtlightning
        I'm interested in trying the mortarless design. But some of the terms are confusing me. For a 42" oven diameter, in the vertical plane the brick height we are using is 4.5"? In the horizantal plane the height is also 4.5, correct?

        I have found a 14" diamond wet brick saw that I can use for a while
        Am willing to try all the cutting if I can get the dimensions correct.


        Jim responds:
        For a normal (e.g. non-complicated-cuts) oven, all of the bricks are splits of standard 2 1/4" x 4 1/5" x 9" firebrick. These are split (or cut) halfway down the length so you've got a pile of 2 1/4" x 4 1/2" x 4 1/2" brickettes.

        The first row of bricks is placed on the hearth so the 2 1/4" side faces inward and they stand 4 1/2" tall. This gives you a wall depth of 4 1/2" too. You do this to make the smoothest circle with good overall thermal mass.

        The second & successive rows are placed "flat" on top of the row below like you tipped over the first row bricks -- the brick is wider than tall in this use so the face in the oven is 2 1/4" tall by 4 1/2" wide (and of course, 4 1/2" deep). Somewhere up near the top of the arch you'll end up cutting these further in 1/2 (e.g. 2 1/4" x 2 1/4" x 4 1/2") or more so you can fit the last couple of flattish rows.

        So, when you stick your head in the oven you'll see a circle of bricks taller than they are wide topped by more circles of bricks wider than they are tall. The walls are always 4 1/2" thick.

        For a mortarless design we need to cut the bricks into something that looks like a 4 sided pyramid tipped over on its side and the pointy end whacked off. Making that out of flat bricks (2 1/4 thick ones) vs. cubes is going to waste a lot of brick. An alternative is to make these truncated pyramids with the square (4 1/2 x 4 1/2) face as the starting point. This would end up resulting in a thinner oven (2 1/4" deep) but that could be handled by cladding it in concrete or a thick layer of mortar.

        The way to calculate the cuts is to follow the directions above twice - once to get the cuts needed to allow the bricks to form a circle and once to get it to tilt & form the overarching dome. I'm thinking it's probably worth trying this with wood first -- getting a few 4x4s that you cut into 2" slices and then using these dimensions in the formulas above, cut into truncated pyramids. That would prove the calculations before committing to far more expensive bricks.

        Also, if anyone has a 3-D CAD system, we could model it all in software to make sure it works too.

        One thing I think we'd want to do is to make the bottom row out of 2 layers of the 4 1/2 x 4 1/2 x 2 1/4 flats turned so they're 2 1/4" tall x 4 1/2" wide and then cut. I think starting with them tall will result in far too thin an internal face to be economical.

        Still game?

        (I do like the geodesic dome suggestion though. )


        I was able to find a neat tool called the "Angle-iZe! Axed Master ' at Home Depot for about $10. It comes with a CD that has programs for determing the dimensions of bricks for various types of arches. You enter some of the critical dimensions e.g. max arch height, max length of arch at base, width and height of bricks to be used and it tells you how many bricks are required and the top and bottom dimensions of each brick.

        A tool also is included consisting of 4 plastic rulers with both inch amd metric units that can be adjusted in various shapes including a trapizoid. The latter can be used as a template for marking the bricks according the dimensions gleemed from the CD for say "axed" shaped bricks.

        Additional information on the tool is available at http://www.chasteuk.com/



        • #5
          Re: So will there be a discourse on tapering bricks?

          I have the Rigid compound saw, so I plan on cutting a compound on the sides. Any opinions on whether I should cut the bottom (back to front) to avoid using wedges and less mortar? Les and Ken, did you guys cut the bottoms?

          Thanks, Mark


          • #6
            Re: So will there be a discourse on tapering bricks?

            I didn't cut the bottoms. I didn't really see any need to. I only cut sides and tops.

            No wedges necessary.
            Ken H. - Kentucky
            42" Pompeii

            Pompeii Oven Construction Video Updated!

            Oven Thread ... Enclosure Thread
            Cost Spreadsheet ... Picasa Web Album


            • #7
              Re: So will there be a discourse on tapering bricks?

              Anyone ever tapered their own bricks instead of buying tapered


              • #8
                Re: So will there be a discourse on tapering bricks?

                A lot of us did. Lokk at SCChris' build. His tapers were exceptionally clean.


                • #9
                  Re: So will there be a discourse on tapering bricks?

                  Thanks for the kind words John,!

                  Skool, what I did was to clamp 2 bricks about 3 inches apart, on the brick cutting bed, parallel to the path of the blade. I’d then place the brick, to be tapered, with a 2 ? by 9 inch side up, then force the brick over on angle, with the bottom locked by one of the clamped bricks and the top stopped by the other clamped brick. What this did was to allow me to slice a ? inch by 3.75 inch, or so, triangle out of each brick.

                  See http://www.fornobravo.com/forum/8/sc...ld-7035-4.html You’ll notice the little edge on the face of each brick. This is the depth that the 10” brick saw will cut before the arbor starts to drag. It’s not hard work and it doesn’t take all that long to do, but it is another step..

                  After tapering I halved or thirded or 40/60ed the bricks.

                  After this I applyed the cheek cuts to the bricks.

                  These cheek cuts were done with a self fashioned jig.
                  See http://www.fornobravo.com/forum/f28/...ool-12478.html


                  PS I just wanted to minimize the mortar because I could..
                  Last edited by SCChris; 08-22-2011, 05:31 PM.