Sample arch design photos
The arch is such an essential part of a brick oven -- from the shape of the oven chamber to the oven opening and vent opening, you have great opportunities to use some beautiful desings. With that in mind, I took (25) photos of decorative brick and stone arches in the little villages around our vacation house for some inspiration when I get back to California.
One thing that struck me was the range of arch techniques, and the prominent use of a nice Keystone. I guess there are probably fewer masons than there were a couple hundred years ago, but some of these are pretty nice. Most are over doorways.
If you are thinking about finish options for an oven, these could be helpful.
Also, I was hoping to get some feedback on how I present the photos. There is a single thumbnail in the Residential Photos section, then 25 photos to click through. Does that work? Or, should I put 25 thumbnails in the Photos page?
Let me know,
Here in the states, It's hard to get convincing materials for rustic stone construction. Although they are hard to cut on domestic tile saws, I've thought of making my arch out of granite belgian blocks. They are not much more than bricks, and they could be cut to look good. Oversize ones are available, if you wanted a protruding keystone.
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"
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
Calculate the Max circumference = Pi * (Arch span + brick height)
ex: 3.1428 * (16 + 4.5) = 3.1428 * (20.5) = 64.4274"
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
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:
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
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
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!
With no disrespect to the admirable French, I get confused when I use their measuring system.
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.
If you are going to do all that cutting anyway, why not make it a geodesic dome?
Here's a site with a calculator for each of the sizes of triangles you would have to cut. You put in the radius, and it shows the length of each edge of the different triangles that make up the dome.
A dome made of triangles would be thinner than one made of bricks on edge, but you could cover it with a layer of refractory cement to make up the four inches.
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.
(I do like the geodesic dome suggestion though. :) )
Fantastic Arch photos!! 2nd submission
(J) Also, I was hoping to get some feedback on how I present the photos.
(M) Seeing those great 25 images made me forget about how you presented them. I just wondered how you could move back to California and leave that exquisite locale?
(J) There is a single thumbnail in the Residential Photos section, then 25 photos to click through.
(M) I didn't see a thumbnail but saw the 1st full photo and then clicked through all 25.
(J) Does that work? Or, should I put 25 thumbnails in the Photos page?
(M) If it is easy to post all 25 in the Photos page, the viewer could more easily find the 2 or 3 s/he favored, but I'm not looking a gift horse in the mouth.I seem to remember you or someone else recommending that all future photos should be posted in the Photos page and I certainly favor that.
(M) btw: I have had difficulty posting my own first images as my file size was too large for the Forum's parameter and I wasn't able to use PhotoBucket or Yahoo Photo to reduce them.
See below the URLs for a totally different question:
Let me know,
(M) You wrote elsewhere in this thread what I think may be a Typo?:
(J) For a normal (e.g. non-complicated-cuts) oven, all of the bricks are splits of standard 2 1/4 inch x 4 1/5 inch x 9 inch firebrick. These are split (or cut) halfway down the length so you've got a pile of 2 1/4 inch x 4 1/2 inch x 4 1/2 inch brickettes.
(M) Wasn't the 1/5 inch supposed to be a 1/2 inch ?
Arch brick size calculations
Great job as usual in gathering and presenting information needed in constructing wood burning ovens.
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/
I have a question that hopefully a mason or someone who has done this before can assist. I would like to create a brick arch opening on the lower opening of the stand where typically wood is stored. I am very close to finishing my block stand and I want to ensure I make the necessary arrangements for the arch before I complete the stand.
If anyone can provide any insight I would greatly appreciate it. Thanks.
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