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Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #100 on: May 06, 2019, 04:06:34 AM »
So as I've been researching further, I figured I'd describe my intentions better.  I also read that barrel vault arched domes exert a lot of outward thrust, so I feel that a flat ceiling or an actual dome oven will be much better. 

My Intentions:
1.  My main goal is to replicate what I do in the Uuni Pro, which is that I fire it to an internal temp of 600-700F, floor temp of around 600F, and usually cook 1-2, 16" pizzas of a bake time of about 10 minutes.  Oddly enough my main intention is to replicate the 600ish bake of Regina's oven which, due to the gas used, keeps the flour on the cornicione.  I usually replicate this by waiting until the fire is embers, or having a flame guard.  I realize that a bigger oven is different from the Uuni Pro, which is why I'd like having the fire to the left or right side, so I can see the bake (unlike in the Uuni Pro).  I also want there to be enough space between the fire and the pizza to prevent what happens in the Uuni Pro.  I'd like to do 18"-22" pizzas, but I know a larger oven will take longer to heat and requires a larger width door.

2.  While pizza ovens are the best, I feel that more of a bread oven is what I'm looking for.  I could be wrong though, so I appreciate all the help I can get.  I just think where I'm looking at slightly lower temps, a bread oven may be better.  Reading Forno Bravo's instructions, they mentioned that bread in Italy is cooking in square vault ovens.  This leads me to a few questions on thermal mass and how it relates to my purposes.

Preface to questions:

Regarding the model in the post above this one, my idea is to have a square design.  I very well may change this to a dome before any construction of the oven, but I feel the stand width of 62.5 x 62.5 is large enough to accommodate either oven design.  My plan is to lay block this week and fill the cores or stucco it, followed by constructing the hearth slab to be screeded along the top of the block caps, as shown in the book.  I may decide to use a frame though, so no block caps have to be used, and have the slab cover all the tops of the blocks.  I know square ovens have their cold spots, but I'm not trying to make Neapolitan beauties.  If I was going for a correct pizza oven, I would definitely make it round.

Okay, Finally Questions:

1.  Reading the Forno Bravo instructions, it seems the lowest height for the ceiling is 14.5".  From what I read, a lower ceiling oven heats up faster, but doesn't hold as much heat since there is not a lot of space up there.  Do you think a flat ceiling design pictured in the model below would be functional for my needs?  1 course of firebricks for the ceiling would leave about 11.25" (plus mortar) oven space height.  Another course of brick would raise the roof (haha) to 13.75" (plus mortar) The higher ceiling would add some headroom above the oven opening.  What is the best ceiling height for this type of oven and would the 11.75" ceiling height be too low?

2.  Reading the instructions again, it seems that a lot of thermal mass is not as good for pizza, but good for bread.  Which leads me to questions on the orientation of the firebrick.  I picture the firebrick oven floor laid down in the stretcher position, and for the walls either the stretcher, rowlock stretcher, or soldier position.  Of course this will vary the wall thickness.  For a flat cieling I was thinking of the stretcher position as well.  So what do you think are the best orientations for these? The soldier and rowlock stretcher seem best for the walls, as the stretcher would have the most mass thickness it seems. It's only a difference of about 2". 

3.  My idea for the flue is to install a either a metal vent with a clay flue, or just a small metal flue system into the top ceiling of the clay brick landing.  I like the look of a brick chimney, but I feel the features of having a cap and spark catcher is nice.  Can a cap/spark catcher just be mortared into a brick chimney though?  In the model I just envisioned a couple bricks left out of the angle iron rows.  Of course this would be a crude vent design, but seems like it would work.  In order for a proper flue to be installed I'm not sure if it would clear any angle irons, so I may need to do an arch for the vent area, or just build an entire brick chimney.

Again thank you to everyone that has helped me.  I know way more than I did a month ago, due to all your help and I immensely appreciate it.


« Last Edit: May 06, 2019, 04:53:23 AM by Pod4477 »

Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #101 on: May 06, 2019, 08:34:24 PM »
First course is pretty level now after angle grinding the slab some more.  I'm having a hard time deciding on how to fill the stand.  Deciding if I fill the base with gravel, rocks, and rubble or if I use a wood frame.  According to the book, it says to fill 12 inches from the top with gravel rocks and rubble.  Then the final 12 inches are comprised of 10 inches of coarse or medium perlite and 2" of perlcrete (6 parts perlite to 1 part Portland cement). 

My big questions are: if I do it by the books directions, do you think 10 inches of the perlite under the perlcrete is too much/can I get away with using more gravel and less perlite? 

The book also mentions foam glass or calcium silicate board.  It also mentions using sand under the hearth.  Sand seems like a very cost effective solution.  Do you think filling with gravel rocks and then sand, and then 2" of perlcrete slab, followed by fireclay, and then firebricks would insulate well?
« Last Edit: May 06, 2019, 08:41:48 PM by Pod4477 »

Offline foreplease

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #102 on: May 06, 2019, 11:08:11 PM »
I don’t know anything about ovens, but I know a fair amount about soils. If you place sand over gravel it will eventually settle out. Depending on what is above it that could settle out too. My first idea before I read your entire post is ‘why not sand instead of gravel?’ There may be a reason having to do with oven builds but I don’t know. You could speed up the settling by heavily watering the sand, adding more sand as it settles. At that point, though, if the pore space in the gravel layer is filled with sand how much better is that than just using all sand in the first place?
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Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #103 on: May 07, 2019, 01:08:36 AM »
I don’t know anything about ovens, but I know a fair amount about soils. If you place sand over gravel it will eventually settle out. Depending on what is above it that could settle out too. My first idea before I read your entire post is ‘why not sand instead of gravel?’ There may be a reason having to do with oven builds but I don’t know. You could speed up the settling by heavily watering the sand, adding more sand as it settles. At that point, though, if the pore space in the gravel layer is filled with sand how much better is that than just using all sand in the first place?

Good points and thank you for the advice!  I didn't think of that.  I would guess they would use all sand then.  Using cement boards and wood are easier, but I'm more used to using sand, so I'll have to make a decision once all the courses are done.  For fill I feel that the 3 best options are 1) all gravel 2)a mix of gravel and perlite, or 3) all sand up to 2" from the top of the block caps and then 2" of perlcrete to fill up flush with the top of the block caps.  I'd probably need a ton of sand though for about 34" height and 48"x48" inside area to fill.  It seems to me that sand along with the perlcrete hearth would hold in enough heat.  It is funny how the book talks about how FB board is better than perlite under the hearth, but that sand is a conductor and insulator.

Also, my oven opening height (8+") to ceiling height (around 14.5") would be right around 63% so that worked out good.  My oven opening width 2 feet wide though which may not be good.
« Last Edit: May 07, 2019, 03:57:05 AM by Pod4477 »

Offline foreplease

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #104 on: May 07, 2019, 08:02:30 AM »
I'd probably need a ton of sand though for about 34" height and 48"x48" inside area to fill/
You’d be surprised how little a ton of sand is. It depends on moisture content but here are the figures I have used with consistently good results on baseball field work. Infield dirt I have been using is about 75% sand of various screen sizes.


1 cu yd = 1.4 T
30% compaction factor


2.94’ x 4’ x 4’ = 47.04 cu ft in your area to be filled
= 1.74 cu yds
= 2.44 T
2.44 T/0.7 compaction = 3.49 Tons needed or 2.5 cu yds


I encourage you to check this out with a local sand and gravel provider. They may have better info on what their products weigh and how they compact. You’re looking at a small dump truck delivery. It will cost more and frustrate you if you try to do this will bagged sand from a big box store. Good luck with the next step. I’m trying to help, not discourage, you.

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Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #105 on: May 07, 2019, 03:28:33 PM »
You’d be surprised how little a ton of sand is. It depends on moisture content but here are the figures I have used with consistently good results on baseball field work. Infield dirt I have been using is about 75% sand of various screen sizes.


1 cu yd = 1.4 T
30% compaction factor


2.94’ x 4’ x 4’ = 47.04 cu ft in your area to be filled
= 1.74 cu yds
= 2.44 T
2.44 T/0.7 compaction = 3.49 Tons needed or 2.5 cu yds


I encourage you to check this out with a local sand and gravel provider. They may have better info on what their products weigh and how they compact. You’re looking at a small dump truck delivery. It will cost more and frustrate you if you try to do this will bagged sand from a big box store. Good luck with the next step. I’m trying to help, not discourage, you.

Haha sorry didn't mean litterly a ton, my bad!  I didn't even realize I said that.  I appreciate your help for sure.  A dump truck is a very good idea and would work out easily where the stand is.  I'm heading to my local sand and gravel provider now and will check back.

Offline Jon in Albany

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #106 on: May 07, 2019, 07:20:46 PM »
I dont know if I would say the board is a better insulator than the perlcrete. I think it is just more efficient. In other words it probably would take 2 to 3 inches of perlcrete to provide the same level of insulation from 1 inch of board.

Also, be careful filling a dry stacked stand with sand off a dump truck. I see the sand sliding down with enough velocity to take out a wall.

Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #107 on: May 07, 2019, 11:13:33 PM »
I dont know if I would say the board is a better insulator than the perlcrete. I think it is just more efficient. In other words it probably would take 2 to 3 inches of perlcrete to provide the same level of insulation from 1 inch of board.

Also, be careful filling a dry stacked stand with sand off a dump truck. I see the sand sliding down with enough velocity to take out a wall.

Thank you, that makes sense and is the clarification I needed.  My plan is to either use wood framing/form supports or just fill with sand, and very good tip Jon, thank you.  I was thinking I'd have to shovel the sand into the stand myself after having the truck dump it in my driveway.  The gravel place I go to estimated about 1.5 tons of sand for a 48x48" inside area and about 32" thickness/height.  Wood framing supports and Hardibacker would be a lot cheaper and doesn't seem too hard to do. I'd follow Forno Bravo Pompeii instructions. 

From what I gather, Forno Bravo says to use a 3.5" rebarred concrete support layer below a 3.5"-4" perlcrete or FB board layer.  The book uses just 2" perlcrete.  With Forno I'd need to have the hearth span across the block for support, but with the book I can fill with sand and only pour in the middle of the stand if I want.  Forno's does seem more structurally sound as it covers the entire block stand.  At https://www.flickr.com/photos/climbhipa/3271769925/in/album-72157613634415857/ they used lintel irons and cement board and at http://www.hearthmasters.net/uploads/Ovenportfolio.pdf they use a concrete lintel. 

I'm going to set my first course of block tomorrow with mortar only under areas that need to be raised up a ¼" or so.

I think Forno Bravo's is the best since it is very detailed.  With sand, do you think I'd be able to get it level and packed enough to support 2-3" perlcrete?
« Last Edit: May 07, 2019, 11:16:52 PM by Pod4477 »

Offline Jon in Albany

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #108 on: May 07, 2019, 11:38:02 PM »
Thank you, that makes sense and is the clarification I needed.  My plan is to either use wood framing/form supports or just fill with sand, and very good tip Jon, thank you.  I was thinking I'd have to shovel the sand into the stand myself after having the truck dump it in my driveway.  The gravel place I go to estimated about 1.5 tons of sand for a 48x48" inside area and about 32" thickness/height.  Wood framing supports and Hardibacker would be a lot cheaper and doesn't seem too hard to do. I'd follow Forno Bravo Pompeii instructions. 

From what I gather, Forno Bravo says to use a 3.5" rebarred concrete support layer below a 3.5"-4" perlcrete or FB board layer.  The book uses just 2" perlcrete.  With Forno I'd need to have the hearth span across the block for support, but with the book I can fill with sand and only pour in the middle of the stand if I want.  Forno's does seem more structurally sound as it covers the entire block stand.  At https://www.flickr.com/photos/climbhipa/3271769925/in/album-72157613634415857/ they used lintel irons and cement board and at http://www.hearthmasters.net/uploads/Ovenportfolio.pdf they use a concrete lintel. 

I think Forno Bravo's is the best since it is very detailed.  With sand, do you think I'd be able to get it level and packed enough to support 2-3" perlcrete?
You do need the sand to not settle, but the sand doesn't need to be perfectly level if your going to be building up with perlcrete. Only the top of the perlcrete gets level for the oven floor. Same thing would apply to any bottom concrete formwork. Just needs to be levelish and strong enough to hold the concrete up until it sets. Basically 24 hours. Getting the top as close to level as possible would help, but you are still going to have a perlcrete layer to get it closer to level.

When I did construction inspection many moons ago, sand was spread and compacted in lifts. Might be best to tamp the sand in layers. Maybe each course height?.

I'm not sure which is easier to build. Mixing bags of concrete isn't easy. For the slabs, I had small batches of ready mix delivered (a little more expensive than bags of quickcrete, but I still had a functional back when I was done). Moving and tamping layers of sand isn't easy either.

Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #109 on: May 08, 2019, 02:08:29 AM »
You do need the sand to not settle, but the sand doesn't need to be perfectly level if your going to be building up with perlcrete. Only the top of the perlcrete gets level for the oven floor. Same thing would apply to any bottom concrete formwork. Just needs to be levelish and strong enough to hold the concrete up until it sets. Basically 24 hours. Getting the top as close to level as possible would help, but you are still going to have a perlcrete layer to get it closer to level.

When I did construction inspection many moons ago, sand was spread and compacted in lifts. Might be best to tamp the sand in layers. Maybe each course height?.

I'm not sure which is easier to build. Mixing bags of concrete isn't easy. For the slabs, I had small batches of ready mix delivered (a little more expensive than bags of quickcrete, but I still had a functional back when I was done). Moving and tamping layers of sand isn't easy either.

Thank you again as always!  Awesome info for me to know about leveling and tamping every course height; very good idea.  That's cool you did construction inspection, so you have a lot of knowledge.  Ya it's going to be a lot of work mixing the concrete and shoveling and tamping sand!

I'm researching refractory mortar and fire clay.  I feel like I need a bit of help on the fire clay and perlite.  I found some products at Walmart, but not sure about the perlite or fire clay variety listed.  I'm more confident with the heat stop dry mix as it's ok for exterior applications compared to the pre-mix.  The fire clay says on the bag "not certified for refractory mortar," but I'm only using it for firebrick leveling anyway, so I hope that's ok.  Thinking of amounts, Forno Bravo recommends 8 Cubic Feet of perlite for the slab and Heat Stop recommends 50lbs per 100 Firebrick.  Do you think these 3 items would be good and how much would you recommend of each?  I just don't want to be wrong about brand or amounts.

https://www.walmart.com/lists/shared/6acce818-dc6c-4851-8f3e-76b3809d85bf
« Last Edit: May 08, 2019, 03:38:26 AM by Pod4477 »

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Offline norma427

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #110 on: May 08, 2019, 08:34:02 AM »
Pod4477,

Probably won't help you, but Steve (Ev) built a Forno Bravo Pompeii style oven with lots of great photos of the build at https://www.pizzamaking.com/forum/index.php?topic=11155.msg100628#msg100628 Not a flat top though.  I recall Steve telling me that his friend Bob also built a Forno Bravo Pompeii style oven, but it was smaller and didn't have enough insulation under the oven.  Photos of that oven are at https://www.pizzamaking.com/forum/index.php?topic=18828.msg183753#msg183753  Steve and Bob also worked on their vintage Airstream with a WFO inside.  Some of the photos are at  https://www.pizzamaking.com/forum/index.php?topic=19725.msg193381#msg193381 Steve told me he never could get the same bakes (NY style) in the WFO he built in his back yard as he could in his WFO in the Airstream.  Guess what I am trying to get at is most all ovens bake differently/maybe not.  :-\  Some more of his NP Ischia starter bakes and NY style pizzas at the same temperatures in the Airstream.  https://www.pizzamaking.com/forum/index.php?topic=21856.0 I sure am not an oven builder and don't understand all that goes into building an oven, but find it interesting how different ovens bake. :-D

Norma

Offline Jon in Albany

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #111 on: May 08, 2019, 08:55:22 AM »
For the fireclay used for leveling, I'd check therecommended temperature range. The stuff I bought was good for something over 1700 degrees so I figured it was good for my purposes. I also saved the fines from cutting firebrick and used that as fireclay too.

I got 50 pound bags of Heatstop 50 from my local masonry supply place. Mixed just what was needed as I was working. It does its initial set fairly quickly. Since you are making walls you might need it faster than I did but I was mixing a few cups of it at a time. I used 3 bags.

I bought perlite from a garden supply distributor. Griffen Garden Supplies. There is one in Tewksbury, MA. A lot of the perlite sold in masonry stores is very fine and used to fill voids in concrete block. The garden perlite is bigger particles. I read somewhere the larger particles was supposed to make better perlcrete. Heres a link.

https://www.griffins.com/locations#1tewksbury

Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #112 on: May 08, 2019, 11:37:54 AM »
Pod4477,

Probably won't help you, but Steve (Ev) built a Forno Bravo Pompeii style oven with lots of great photos of the build at https://www.pizzamaking.com/forum/index.php?topic=11155.msg100628#msg100628 Not a flat top though.  I recall Steve telling me that his friend Bob also built a Forno Bravo Pompeii style oven, but it was smaller and didn't have enough insulation under the oven.  Photos of that oven are at https://www.pizzamaking.com/forum/index.php?topic=18828.msg183753#msg183753  Steve and Bob also worked on their vintage Airstream with a WFO inside.  Some of the photos are at  https://www.pizzamaking.com/forum/index.php?topic=19725.msg193381#msg193381 Steve told me he never could get the same bakes (NY style) in the WFO he built in his back yard as he could in his WFO in the Airstream.  Guess what I am trying to get at is most all ovens bake differently/maybe not.  :-\  Some more of his NP Ischia starter bakes and NY style pizzas at the same temperatures in the Airstream.  https://www.pizzamaking.com/forum/index.php?topic=21856.0 I sure am not an oven builder and don't understand all that goes into building an oven, but find it interesting how different ovens bake. :-D

Norma

No it does help, thank you.  Awesome ovens; and I've been thinking about this as well.  Every oven being different will make it challenging to estimate exactly how my design will perform until I build and fire it.  For PR style pies, I'm definitely going to have to wait for the red hot embers and probably will have to use a fire separator like at https://www.flickr.com/photos/climbhipa/6405631933/in/album-72157613634415857/.  That Airstream is insanely awesome!

For the fireclay used for leveling, I'd check therecommended temperature range. The stuff I bought was good for something over 1700 degrees so I figured it was good for my purposes. I also saved the fines from cutting firebrick and used that as fireclay too.

I got 50 pound bags of Heatstop 50 from my local masonry supply place. Mixed just what was needed as I was working. It does its initial set fairly quickly. Since you are making walls you might need it faster than I did but I was mixing a few cups of it at a time. I used 3 bags.

I bought perlite from a garden supply distributor. Griffen Garden Supplies. There is one in Tewksbury, MA. A lot of the perlite sold in masonry stores is very fine and used to fill voids in concrete block. The garden perlite is bigger particles. I read somewhere the larger particles was supposed to make better perlcrete. Heres a link.

https://www.griffins.com/locations#1tewksbury


Thank you as well.  According to Amazon, this fireclay is rated up to 2000F, and people claim it's just fire clay, so that seems reassuring.  I'm assuming I'll need a commercial respirator for this though? 

I'll make sure to mix only a bit as needed, as you did.  I've read only to use up to a ¼".  For my square design it doesn't seem I'll need any thick mortar joints.  Heat Stop recommends 2 bags for 200 bricks, and I estimated 200 bricks for oven.  We'll see if I need more though, especially depending on brick orientation.

Thank you; the coarseness needed is what I couldn't remember exactly.  I'll probably go to that garden supply in Tewksbury then.  The perlite on Walmart is supposed to be super coarse, so I hope it's not too coarse. 

Offline Jon in Albany

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #113 on: May 08, 2019, 12:59:37 PM »
No it does help, thank you.  Awesome ovens; and I've been thinking about this as well.  Every oven being different will make it challenging to estimate exactly how my design will perform until I build and fire it.  For PR style pies, I'm definitely going to have to wait for the red hot embers and probably will have to use a fire separator like at https://www.flickr.com/photos/climbhipa/6405631933/in/album-72157613634415857/.  That Airstream is insanely awesome!

Thank you as well.  According to Amazon, this fireclay is rated up to 2000F, and people claim it's just fire clay, so that seems reassuring.  I'm assuming I'll need a commercial respirator for this though? 

I'll make sure to mix only a bit as needed, as you did.  I've read only to use up to a ¼".  For my square design it doesn't seem I'll need any thick mortar joints.  Heat Stop recommends 2 bags for 200 bricks, and I estimated 200 bricks for oven.  We'll see if I need more though, especially depending on brick orientation.

Thank you; the coarseness needed is what I couldn't remember exactly.  I'll probably go to that garden supply in Tewksbury then.  The perlite on Walmart is supposed to be super coarse, so I hope it's not too coarse.
I didn't use a respirator for the fireclay. Wouldn't hurt. I did use dust masks and eye protection when cutting bricks with a wet saw and working with the insulation. Hearing protection with the saw too.

Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #114 on: May 08, 2019, 10:42:07 PM »
I didn't use a respirator for the fireclay. Wouldn't hurt. I did use dust masks and eye protection when cutting bricks with a wet saw and working with the insulation. Hearing protection with the saw too.

Might just be the product from Walmart.  It had a warning about Free Silica and wearing breathing protection.  So from reading https://www.traditionaloven.com/articles/101/what-is-fire-clay-and-where-to-get-it, Fire Clay can either be solid or powdered.  It says you can use soft pottery clay body and dry it, and then break it into an almost powdered form, then mix 50/50 with sand for the firebrick leveling.  So would I mix water into the sand/fire clay mix or just dry?

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Offline Jon in Albany

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #115 on: May 08, 2019, 11:25:27 PM »
Might just be the product from Walmart.  It had a warning about Free Silica and wearing breathing protection.  So from reading https://www.traditionaloven.com/articles/101/what-is-fire-clay-and-where-to-get-it, Fire Clay can either be solid or powdered.  It says you can use soft pottery clay body and dry it, and then break it into an almost powdered form, then mix 50/50 with sand for the firebrick leveling.  So would I mix water into the sand/fire clay mix or just dry?

My only experience is with dry fire clay. It was almost flour-like. For me, and especially with the board insulation I was using, I minimized moisture around the board.

I'm not sure of the direction you are going (I don't think you are 100% either), but if you are filling the stand with gravel or sand then topping that with a bunch of perlcrete, you might not need fireclay at all. Try and form the top of the perlcrete level.

Or, if you are pouring a slab on top try to make that level. And if the slab is off a little, correct that in the perlcrete layer on top of the slab.

For a good visual of a slab and perlcrete layer, scroll to the bottom of this page. It is an oven built by one of the forum moderators. But you can see his slab and perlcrete form work and then the oven floor. There are good pictures of the rest of the build too.

http://brokebrick.com/genesoven.htm

Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #116 on: May 09, 2019, 01:40:40 AM »
My only experience is with dry fire clay. It was almost flour-like. For me, and especially with the board insulation I was using, I minimized moisture around the board.

I'm not sure of the direction you are going (I don't think you are 100% either), but if you are filling the stand with gravel or sand then topping that with a bunch of perlcrete, you might not need fireclay at all. Try and form the top of the perlcrete level.

Or, if you are pouring a slab on top try to make that level. And if the slab is off a little, correct that in the perlcrete layer on top of the slab.

For a good visual of a slab and perlcrete layer, scroll to the bottom of this page. It is an oven built by one of the forum moderators. But you can see his slab and perlcrete form work and then the oven floor. There are good pictures of the rest of the build too.

http://brokebrick.com/genesoven.htm

I wonder if that would be similar to the ground fire clay I've seen online.  Haha I'm not too sure what I'm going to do for the inner part of the block or slab, for sure.  That was my idea that I may just be able to use sand and perlcrete.  I guess the fire clay bedding will be needed if I don't get the perlcrete perfectly level, which I will try to have no happen.  Fire clay bedding seems like a good idea, but I've seen people not use it.  In the book he lays solid concrete block on top of the perlcrete and then fire brick on top of the solid concrete block.  This seems like a bad idea as the concrete would heat up quite a bit.  Insulation board seems like a better middle layer, or just perlcrete under the fire brick. 

I do want my firebrick very level, but honestly in the Uuni Pro, the tiles jut up a bit and the pizzas still cook fine.  Probably would want only a few bricks max to be not level and only minorly.  I'm a perfectionist though so I expect me to get it perfect.  Could the perlcrete be sanded if one area is not exactly level?  Those pics helped a lot to visualize, thank you.  I like how he did a different size and shape with the perlcrete layer.  Awesome oven and portable!

I got some Quickcrete type S mortar mix from Home Depot today and a new square.  My plan later today is to set the first course. Do you think it's best to mortar the slab across the entire line of block, making a thicker joint in some sides of the block that are low and need raising; or is it ok to just use mortar under low areas of the block, just filling in one side until it's level?  I guess I could always paint on a thin wet layer of mortar to the bottom of all blocks as a bonding assurance and then only mortar in low areas.  It seems that the blocks are nearly level, but only need a bit of height adjustment on the right half of some blocks.  Of course, mortar isn't usually necessary, but I just wasn't sure if the joint should span the entire bottom of the blocks or if it can be used as filler.  This kind of seems like a weird, and unique situation.
« Last Edit: May 09, 2019, 02:13:29 AM by Pod4477 »

Offline Jon in Albany

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #117 on: May 09, 2019, 07:56:31 AM »
I wonder if that would be similar to the ground fire clay I've seen online.  Haha I'm not too sure what I'm going to do for the inner part of the block or slab, for sure.  That was my idea that I may just be able to use sand and perlcrete.  I guess the fire clay bedding will be needed if I don't get the perlcrete perfectly level, which I will try to have no happen.  Fire clay bedding seems like a good idea, but I've seen people not use it.  In the book he lays solid concrete block on top of the perlcrete and then fire brick on top of the solid concrete block.  This seems like a bad idea as the concrete would heat up quite a bit.  Insulation board seems like a better middle layer, or just perlcrete under the fire brick. 

I do want my firebrick very level, but honestly in the Uuni Pro, the tiles jut up a bit and the pizzas still cook fine.  Probably would want only a few bricks max to be not level and only minorly.  I'm a perfectionist though so I expect me to get it perfect.  Could the perlcrete be sanded if one area is not exactly level?  Those pics helped a lot to visualize, thank you.  I like how he did a different size and shape with the perlcrete layer.  Awesome oven and portable!

I got some Quickcrete type S mortar mix from Home Depot today and a new square.  My plan later today is to set the first course. Do you think it's best to mortar the slab across the entire line of block, making a thicker joint in some sides of the block that are low and need raising; or is it ok to just use mortar under low areas of the block, just filling in one side until it's level?  I guess I could always paint on a thin wet layer of mortar to the bottom of all blocks as a bonding assurance and then only mortar in low areas.  It seems that the blocks are nearly level, but only need a bit of height adjustment on the right half of some blocks.  Of course, mortar isn't usually necessary, but I just wasn't sure if the joint should span the entire bottom of the blocks or if it can be used as filler.  This kind of seems like a weird, and unique situation.
Dont know about the mortar in the first course of the stand. I dont think it will really matter. As you go up, make sure you have a running bond with the concrete blocks.

I guess the perlcrete could be sanded. I didn't do it. As it cures, the first few days it is kind of flaky and you wonder if it will ever fully set. That would probably be the best time to address any high spots. I think more important than getting the oven floor perfectly level is getting the top of the floor smooth enough so none of the joints between the floor bricks grabs a peel.

Offline Pod4477

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #118 on: May 10, 2019, 03:38:58 AM »
Dont know about the mortar in the first course of the stand. I dont think it will really matter. As you go up, make sure you have a running bond with the concrete blocks.

I guess the perlcrete could be sanded. I didn't do it. As it cures, the first few days it is kind of flaky and you wonder if it will ever fully set. That would probably be the best time to address any high spots. I think more important than getting the oven floor perfectly level is getting the top of the floor smooth enough so none of the joints between the floor bricks grabs a peel.

Sorry! I read this and got straight to mortaring the block.  Haven't been on my computer since this morning.  I got the first course level and covered with a tarp for the rain today.  Next step is to get the rest of the block picked up and fill in the cores.  Thank you for that advice!  I have been wondering that about the perlcrete layer and oven floor.  My perlite came in today too.  So do some people only fill in the corner cores of the block, or is it best to do every other core? It also says to drop a section of ½" rebar in every other core, along with stuffing the other cores if a slab is poured on top.  What does a section of rebar mean here, one piece going vertical?

 I'll have to decide on using block caps or not, I guess I would only if I use the sand middle filling and concrete/perlcrete slabs in the middle.  Of course if I build the slabs over the block holes I won't need caps.  I figure with caps might have to be stuccoed or mortared down, but the middle slabs would bond to the caps as well.
« Last Edit: May 10, 2019, 03:54:19 AM by Pod4477 »

Offline Jon in Albany

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Re: Wanting to build a coal fired style outdoor pizza oven
« Reply #119 on: May 10, 2019, 09:01:51 AM »


Sorry! I read this and got straight to mortaring the block.  Haven't been on my computer since this morning.  I got the first course level and covered with a tarp for the rain today.  Next step is to get the rest of the block picked up and fill in the cores.  Thank you for that advice!  I have been wondering that about the perlcrete layer and oven floor.  My perlite came in today too.  So do some people only fill in the corner cores of the block, or is it best to do every other core? It also says to drop a section of ½" rebar in every other core, along with stuffing the other cores if a slab is poured on top.  What does a section of rebar mean here, one piece going vertical?

 I'll have to decide on using block caps or not, I guess I would only if I use the sand middle filling and concrete/perlcrete slabs in the middle.  Of course if I build the slabs over the block holes I won't need caps.  I figure with caps might have to be stuccoed or mortared down, but the middle slabs would bond to the caps as well.

Going to sound like a broken record here... but these are things I would want to know before starting.

In my stand, I went overboard. My walls are tied to the bottom slab with rebar. I did the corners and every other hole. A piece of bar goes down every hole I filled. Those bars were long enough so that they could be bent and combined with the top slab rebar. I basically made a reinforced concrete box.

I stuffed portions of the bags that the concrete used to fill the cores came in to plug the unfilled cores so the slab concrete didn't go all the way down those holes. If you are capping and filling the stand with sand, this doesn't matter because there is no slab. If there is no slab, personally I would at least fill every other hole  in the the block and the corners. If you do the running bond, this will ties the stand together. Having rebar in the filled cores will make it stronger. With the right tools, half inch rebar isn't hard to cut. With a hack saw, it grows old fast.

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