39"/ 100cm Pompeii in Ireland

[Dar77]

Hi all, im new to this forum and I'm planning on building a 39" Pompeii also . I just amassing the materials at the moment and going through the site gathering as much info as possible . Could if ask a couple of questions if I'm not bothering you.
1, my plan is to pour a 4" concrete slab with 2" vermiculite then 2" of insulation board before the fire bricks . How does that seem ?? Is that enough under hearth insulation ??
2 weep holes , are they a necessity and are they just made in the slab under the insulation board
2 my plan was not to bevel or taper the brick just cut in half then quarters as dome rises and use a an IT . What would be the major issues I'll run into ??
Would it be ok to ask more questions if they arise .
thanks
darren

[UtahBeehiver]

1. Vcrete should be a 5 to 1 ratio under the floor. I am assuming by insulation board you are talking CaSi or AlSi board, should an approx. K value of 0.079 W/m*c at 260C and compressive strength of abt 600kPa at 5% compression.. The combine two insulation is satisfactory.

2. Recommended, weep holes just provide a means for water to egress out from under the dome. They are not difficult to do.

3. You can get away without tapers but if you do not at least bevel the upper courses you will see mortar joint that we call "inverted V" which exposes the mortar joints to flame impingment. You only need the bevel the top inside of the bricks not the whole length. Refer to JR Pizza, he did this.

[Dar77]

UtahBeehiver thanks for the reply . I'll go look at JR Pizza post

[Kvanbael]

I also did a 39" dome, yay. My 2 cents: Plain half bricks will work for the first 3 or 4 rows. The next few rows you'll want to reduce the inverted v's by beveling the edges (I just used a tile file for that). But for the last 4 rows you're better off cutting the bricks into 'gold bar' shapes parts as shown in the drawing.

[Dar77]

Kvanbael appreciate the reply and the photos too I've looked at that many threads I'm confusing myself even more so the photos give me a better understanding. Could I also ask you when it came to you tying in the dome to the inner arch did you have to taper the bricks or how did you tie them in.
darren

[Kvanbael]

I'm not sure which type of taper you are referring to, so here's the full treaty on cutting arch bricks:

There’s three types of cuts to consider on your arch bricks:
1. Your arch is (Partially) curved. In the curvy parts, you might want to taper the sides of the bricks to keep the visible seams even and thin. (Not everyone does this, but then you get these triangular seams. For the corner stones, you obviously have to).
2. For optimal smoke travel, you don’t want parts of bricks sticking out on the inside of your dome. So you cut them to follow the sphere shape.
3. Your arch will need to connect with the dome. If you don’t anticipate that in your arch bricks, then you’ll have to cut funky corners out of your dome bricks (or use a lot of mortar). It is a lot easier if the contact side with the dome is already cut perpendicular to the dome.

For measuring 1, you'll need to do some math.

For measuring 2 and 3, you dryfit the bricks in position and measure from the dome center. (Your IT can act as a compass, but a pencil and string also work).


On the same subject: Design your arch curve to have its center at the same height as the dome center. Thanks to that, I could cut my 13 top arch bricks all identical.

Attached are some pictures from my build, indicated the different cut types 1,2,3. As you can see I'm an engineer but not a builder. Others did a cleaner job in execution.

(more pictures of my build)

[Dar77]

Thanks for the info Kvanbael it's people like yourself and many others on this site that helps novices like myself with your advice and knowledge from your own builds . Thanks again

[UtahBeehiver]

Here is picture showing tapered inner arch and how the IT is used.

[Dar77]

UtahBeehiver thanks alot that's really helpfull

[JRPizza]

Kvanbael , not sure what you meant by "Design your arch curve to have its center at the same height as the dome center"? My 39" oven has a dome height of 19.5" and a door height of 12.25".

[Kvanbael]

Kvanbael , not sure what you meant by "Design your arch curve to have its center at the same height as the dome center"? My 39" oven has a dome height of 19.5" and a door height of 12.25".

Most entry arches are curved at the top. I am referring to the center of that arc. With my arch that arc’s center is flush with the floor, and so is the pivot of my IT. As a result my top arch bricks are all cut the same way whereas, for example, Utahbeehiver’s picture shows different cuts. No right or wrong. It is just a bit easier.