42" Pompeii construction in Adelaide

[P3 Stoaker]

G'day All,
Thanks Catch, the saw blade is around 350mm or 13.5 inch. The blade looks to have around half life remaining which is a bonus. It cost me around $300 to rebuild which I think is ok. I can't see hiring a saw would work unless you could cut most bricks at once, which I cannot do. Cutting the arch and other tricky bits will surely be easier having your own saw given you can do it slowly when your ready. Shit I've had a real struggle getting my head around the arch radius shape as well as the taper method so cutting anything like that up front is not possible.

Mikie V , thanks for the reply. I read your build again (also read a month or two ago) but this time I think I actually understood your questions and therefore could understand the answers. You are right for sure that I had the same questions, with the main issue, how far in or out of the dome for the inner arch, and exactly the point, it needs to be positioned so it is ok at the TDC as well as the very bottom. I was on the right track but I now think the key thing is to get the inner arch form built, and sit TDC in place. Part of my problem was how to draw the inner arch with an upper radius, height at 12" and side radius of 9.5" ( 19" wide opening). Anyway I'll sit that bottom arch brick on the oven floor, thereby raising the radius centre. If I draw the arc at that raised point the overall opening will be 12.2" high and still 19" wide.

I'm still a little unsure, any thoughts on the Mosaic tiles under the calsil board, is 5-6 mm (3/16 inch) is thick enough? Also, has anyone used a stainless entryway floor? I'm thinking floor bricks to the outer edge of the inner arch, some sort of heat break, in the floor and to the vent arch with the floor being a stainless plate??

Time to crack out the new jigsaw.

Regards
Greg

[P3 Stoaker]

G'day All,
Hope all is well. I think I need a little assistance if you can.
At one stage I thought I had the tapered inner arch sorted but now I'm convinced I don't. I'm Happy to exchange, what about a fully adjustable IT tool, LOL. Machining on the lathe, thread-cutting and welding to make the IT tool no problems. I can't get the bloody IT tool in my head though.
The first photo shows where the lower most brick of the inner, appears to need be in relation to the dome. Further back appears not possible. I would like to use half bricks for the inner arch to allow vent arch length.
The second photo is the upper inner arch TDC when aligned with the lower brick position. As far as I know all the bricks of the inner arch should be aligned?
Question is, seems to me that the lower arch brick cannot go back and looks like the upper arch TDC needs to move back to engage properly with the dome?? This won't work if they remain in the same plane?
Advice very much welcomed.
Regards
Greg

[UtahBeehiver]

A tapered inner arch is one of the most difficult concepts to visualize. So I have attached a couple pics.

1. looks like the bottom of the arch form is too far in. The edge should sit right on the arch of the dome.
2. The arch bricks need to be "FULL" length bricks not half bricks. See pic.
3. Can't see the mounting end to clearly but it appears to be raised off the floor elevation by an 1" or so. This affects the inner arch dimension, ie if the radius at the floor is 18" then the radius at the TDC will be 18" plus a portion of the height of the IT off the floor.
4. Each Tapered arch brick is different so don't cut them all the same. Use the IT and the previously cut brick to lay out the next one
5. Brick bracket? Remember that the centerline from the pivot point to the centerline of the brick bracket must intersect the halfway point on the horizontal thickness of the brick. IE if brick is 2.5" thick. bracket center through to pivot point needs to be at 1.25"

[P3 Stoaker]

G'day All,
Well I've finally laid the structural slab/hearth. Ended up about 90mm or a little over 3.5 inch thick but its 40mpa concrete and F61 mesh which is 6mm (1/4) inch wire with 100mm centres (4 inches).
Initially the plan was simply to have a similar thickness slab and top off flush with the top of the outer row of bricks with perlite. In the end after so many posts talked about wishing they used more insulation I've decided to put 3 layers of calsil board on the hearth, 75 mm (3 inch) and the oven floor directly on that. I will go with the mosaic tile layer under the board and drill holes in the slab option as well.
Quite a few considerations crept in regarding the way I'm building. The idea is the bricks rise up to the top, concealing the hearth edge, and match the house. The large top surface will be finished with granite slabs. Expansion of hearth caused some concern given it's so long, not when using the oven, but ambient temps here range from 0-48 deg c (32-118 deg F) so that will cause more of a temp range that using the oven. Even a 30 deg c range could cause in excess of 2 mm of expansion and that would cause the edge bricks to crack away. Expansion joint foam was a simple solution to minimise the risk of cracking the outer bricks.
What I didn't really find a solution for was expansion pushing the surfaces the slab rests on, simply the inner walls of the double brick. I ended up bending up some thin sheet metal angle to provide a smooth surface and the slab isn't and lower, meaning there is no edge to push out. Hopefully if the slab does expand it will do so over the sheet metal angles and not move the bricks.
Additionally a friend who does a bit of concreting was super concerned the concrete could push the bricks out when laying it in, whilst wet, hence the supports around the outside.
Regards

[P3 Stoaker]

G'day All,
More progress today, worked on the position of the oven on the hearth (pictured last post) and cut all three layers of the calsil board, one inch each layer. I have a few questions though for anyone with time;
The 3 inch of calsil board on top of mosaic tiles will be flush with the top of the brick layer. I then need to fill the surrounding space as I intend to lay 30mm (1.2 inch) granite slabs around the oven on top of the filling I am asking about. I plan to use perlite or vermiculite simply because its light and easy to work with, at a 5;1 ratio. Question is can that ratio of vermiculite be walked on without crushing it? Ill need to be up there walking around to make the oven as its a large area??
I have prepared 75mm (3 inch) of calsil board to have under the oven floor, so hopefully sorted there. For the dome insulation I note reading posts that 3 inch is the minimum recommended around the dome. What thickness of blanket will match and compliment the 3 inch underfloor insulation? I assume more than the minimum?????
If using blanket insulation around the dome, whats recommended for rendering? I assume we would need a layer of concrete or mortar or something, and how thick before applying render?
And lastly, and thanks for reading. On top of my insulation, (boards for oven and perlite around sides at the same level) I will use a 50 mm ( 2 inch) floor brick/paver for the oven, and surrounding that a 30mm (1.2 inch) granite slab. So at some stage I need to transition from the 50mm height to the 30mm. I could run the oven floor bricks to the front of the structure, some 4-5 inches past the end of the entry and have the little step down to the granite to each of the sides. Alternatively, I'm thinking of having the entry bricks cut to be the width of the inside of the entry arch and grinding/cutting them so over the length of the entry they reduce down to 30mm and meet the strip of granite running along the front edge at the same height. What do you think? Have you seen this?
Thanks for reading and I appreciate and time for replies.
Regards

[P3 Stoaker]

G'day All,
Drilled drain holes in the hearth today. Looks a bit random in the photo's but they are located in the lower area's, and I attempted to clear the steel mesh (which is 4 inch square), and also position between tile location. I thought drilling would be easier than pipes in the concrete as I used a long post with a spacer below to set the concrete height, screeding across the top of the bricks, little pipes would have made this almost impossible. I ended up hitting the steel mesh in 5 holes and filled them with silicone, re-drilling 4 of them. If doing this again I would mark where the mesh was to avoid hitting them.
All 3 layers of the Calsil board are cut ready so now to the oven floor bricks, and the perlite around the edges.
I did have a few questions in the previous post, possible a little long winded, so I'll condense them down.
As seen in photo 3 I have a large area either side of the oven, granite slabs will be on top. The oven will sit on calsil board and I thought to put perlite (5;1) around the edges, up to the calsil board, flush with the top. This is simply to fill the area. I will need to walk on the perlite to build the oven, can it take foot traffic without crushing?
I've searched and 3 " seems to be the minimum dome insulation blanket. I'd like more than minimum and I've gone 3 " calsil under the oven, any recommendations for blanket thickness? Also, whats the normal thickness on the blanket, mortar or similar and render??

Many thanks

[GreenViews]

Greetings! Looks like we are at the same stage of construction! I just drilled weep holse and layed tile then screen then 3" CaSi board down yesterday. Feel free to check out my build and I'll keep an eye on yours since we have many of the same questions. I was also considering mixing up some perlite mix to keep CaSi board in place and keep it from crumbling. I hope someone answers you, lol, but it seems much safer to me than keeping the very brittle board exposed. 5:1 is the ratio they suggest for insulating under floor, so if that ratio can take the weight of the dome on the edge, I would expect it to take a little foot traffic but I have no experience to bear yet. Regards! Big question I'm researching this morning is the mix to use to level my floor better. I'm considering either 1:1 fireclay:sand which I think I read somewhere and could add just a little mortar and a little lime if I want it to set faster. Or I could use some of my refractory mortar, but I'm not sure that is the best for this. Still searching the forum.

[UtahBeehiver]

Do "not" add mortar to the 50/50 leveling sand/clay mix. You need the floor free floating. As far as the edge of the CaSi, I just parge the edge with leftover home brew as I started my brick courses. Just adds enough abrasion resistance to keep your toes from damaging the sides. PStoker, I cannot remember if you are enclosing the oven in a structure or not. If you are, you can put on 2" of ceramic blanket then dry fill the structure with perlite or vermiculite (fill in or blocking excess areas like corners) . If an open dome you can v or pcrete over the 2" of ceramic blanket then you have a more solid base for you final coatings.

[P3 Stoaker]

G'day All,
Thanks Russell. I didn't initially plan to enclose a roof over the oven however I am now considering doing so. I will however proceed as if I'm not enclosing. I have allowed for 4-5" of blanket/pcrete/render. What would you recommend, 2" blanket and 2" pcrete ?? What do you think about lots of walking/standing on the surrounding pcrete? And if I may ask another, what would you say was the most height deviation acceptable in the concrete hearth before tiles and casil board. I have about 1/8" ??
Thanks Greenviews, howdy. Yes it would seem that walking on pcrete should be ok but I'm concerned the constant walking around the oven to build it would work away at the pcrete and crush it. As detailed, for me its simply to fill the area and will all be outside of the dome area. Also, this pcrete will be at the same height as the casil board, flush with the top, and serve to contain the edges of the board.
How much levelling of your hearth do you need to do? I'd have to check again but when checking for the low spots prior to drilling I don't think my slab deviation was much more than 1/8". I've read about levelling with sand and clay but I wonder how that would go allowing water to drain between the tiles, and would the tiles work their way into levelling compound. I guess if it set hard then that might work ??? I'm guessing the weight of the dome will push my casil board down in the low spots. I wasn't initially concerned but thinking about it now, if it takes a few courses of weight to push down, that could cause the floor to bend over a low spot and open up cracks ??
I'll go have a look at your build post, I assume it's here in "construction" ?
Whats your time line where you hope to finish?
I have some months away with work later this year. I'd be happy if I had the first fire early September and finished rendering in December. Chances are that could be December 2021 !!!!!

Many thanks and regards to all.

[UtahBeehiver]

What is your anticipated use of the oven, ie cook pizza one night then maybe roasting something the next day or multiple day cooking (3-5 days)? 2" ceramic blanket and 2" 8-10 p or vcrete will put you at the mid to higher end of heat retention. That is about what my oven has and and can cook easily 3 days worth, Pizza (700 F), then breads (500), then roasting (350 F).

Cant't say on walking in pcrete other than it has okay compressive strength, but poor abrasion and shear strength and depends on ratio

[P3 Stoaker]

G'day Russell,
Thanks for the info. I've gone with more floor insulation than initially thought I would 3 " casil board, given so many posts say they would have fitted more. So I plan to have quite a bit of dome insulation as well, leaves us able to do more with the oven and your three day cook sounds awesome !!!
Just reading Greenviews post where you say about "NOT" aligning the layers of casil. I have three by 1 " layers and was going to mis-align but I see what you say in that may trap moisture. I will align joints now.
Just one question, whats the most hearth/structural slab deviation from flat that you think is acceptable? As mentioned I'll have tiles, 3 layers casil, total 3" and the floor bricks directly on the casil. I don't see how levelling sand under the casil would work given I'll have tiles and drain holes?
I also have 2 tricky questions which I cant really draw. I'll post soon and hope they make sense and a few reply !!
Many thanks again for the help.
Regards
Greg

[P3 Stoaker]

G'day All,
I have 2 questions but they are tricky to explain, apologies for the long post, I'll try to keep it as short as possible, and many thanks if you read on !!!
1 As seen in photo no 1 I have large area's each side of the dome. The dome will sit on 3 layers of Calsil board, (3 inch) which will be on mosaic tiles for drainage(photo 2) Surrounding the Calsil I need something to fill the area to support slabs of granite ( 1 and 1/4 inch thick) , thinking of perlite (5;1) simply because its light and easy The question is where to change from the casil to the perlite??
I will have a tapered inner arch, and vent arch touching but not tied together. Given the Calsil probably isn't needed under the vent arch, I could stop it in line with the outside of the inner arch, and possibly also have a break line in the floor bricks, meaning a total break in everything above the hearth, in line with the outside of the inner arch.
Alternatively I could take the Calsil all the way to the very front arch, or 3rd option possibly make the transition to the perlite at the outside of the inner arch but split the floor bricks over the Calsil/perlite join. I'm using floor fire bricks 305x305x50mm (12 1/64 inch square by 2 inch), so a lot bigger than a normal size brick. I'm just a little concerned as to where to chance from the Calsil to perlite???

2 I'm also considering what to do about the height difference between the oven floor bricks, 50 mm (2 ") and the granite slab I will have surrounding the oven, 30mm (1 3/16 inch) as they both sit on a level surface, casil under oven, perlite under the rest. Even if I have a strip of the granite along the front edge outside the arch, it will only be around 100mm wide(4"). So I could just bring the oven floor bricks all the way forward to the front edge and have the 20mm (25/32) step downs on either side. Or, I was considering a shallow grind down of the floor bricks within the arch, cut exactly that wide, so over the length of the vent arch dropping from the 50mm to 30 mm to be the same height as the strip of granite along the front edge ?? I'm starting to think the shallow grind down could be tricky, and the little steps to the side might be ok, what do you think??
Really appreciate any feedback.
Kind Regards

[GreenViews]

Greg, Regarding CaSi under entrance floor, someone (I was thinking it was Utah, but can't find post now, so not sure) recently repaired their near decade old build by removing the insulating board under entrance (degradation from moisture) and replacing it with pcrete as well as drill weep holes. If it was a place of failure, so for me, I'm planning on pcrete under my entrance floor. That will allow me to use different width materials outside my door/ inner arch anyway. I found buried on my project a piece of granite I think I will incorporate somewhere in my entrance, but I haven't looked at expansion and heat characteristics yet so do't know if I'll use close to door or further out cooler placement.
Tom

edit: p.s. your CaSi board looks so much more uniform and in better shape than my 3" board came to me!

[UtahBeehiver]

You can use the sand/clay mix between the CaSi and the fire brick floor as well if you find you are too out of level. But an 1/8" is not going to be a deal killer. As far as insulation under the vent chamber, up to you. I did it because I had the material and put in a floor 316 SS thermal break. There is a cast build going on right not where the builder remove a wedge piece under that vent and dome transition leaving a small contact point the surface then filling the wedge with Vcrete. I did something similar on the vent arch to inner arch transistion. Transition to granite and brick, you just have to work out what is best for you.

[P3 Stoaker]

G'day All,
Thanks Tom. Yes my casil board is quite good, still had some thickness deviation but mainly on edges and I cut most of it out. I've cut all 3 layers the same and had planned to flip the middle layer over to better insulate the floor against heat loss but Russell brought up a great point, that's more likely to capture moisture. I'm now wondering if I should position all the joints in line so any moisture goes through and drains away, as planned through the gaps in the tiles??
Thanks Russell, I think I'll have the break to perlite at the outer edge of the inner arch. This does mean a break in all above the tiles under the Casil.
Regards
Greg