Wanting to build a coal fired style outdoor pizza oven

[Jon in Albany]

Looks good. I think the darker areas of perlcrete are still a little wet. It will all get to that pale gray as it dries. I'd leave the corners alone if they aren't going to be under the oven. No sense making an edge pretty if it isn't needed and might just get covered. If we can get a little sun in the northeast, that will dry right up.

[foreplease]

I honestly don't know how well local clay just dug up would work. Maybe if you dried it and broke it into particles. No idea.

I believe there are some ovens that have a salt layer to them. I never really looked into using salt though.  For your purposes, I think you will be fine in top of the perlcrete. Have you put a level on it to see how it came out?

I agree with this. It hasn’t really been established that you need clay. I just explained how I have used clay that was purchased rather than dug up. I have no idea what the difference is between what I use and fire clay. I think this stuff I get is mined in Canada.

[Pod4477]

I think you could use bagged clay or blocks if you plan to soften them in water as I described. If you have a “SiteOne” store near you they may stock it. They used to be called LESCO, then John Deere Landscapes, now SiteOne.
Here are a couple pics of how I used them and one of the skim coat I described.

That's in line with what one of the sites said to do.  I'm going to try the bricks right on the perlcrete, but if it's not sitting right I'll probably use clay or sand/salt.  I bet it will be fine, but the perlite is so irregular, so it may take time to get the bricks flat.  I'm sure I can just move some of the looser top perlite around until it becomes level.  Those pics are awesome!  So much work involved and I liked seeing the skim coat as you mentioned. Is that a line you have from the mound to home plate?

[Pod4477]

Looks good. I think the darker areas of perlcrete are still a little wet. It will all get to that pale gray as it dries. I'd leave the corners alone if they aren't going to be under the oven. No sense making an edge pretty if it isn't needed and might just get covered. If we can get a little sun in the northeast, that will dry right up.

Thanks, and yup you're right and I was wondering why it was patchy with darker and lighter.  The lighter parts were definitely quite dry.  I plan on getting firebricks tomorrow for the floor.  The perlcrete hasn't had much sun on it as you mentioned, due to the rain yesterday.

1.  I'm conflicted as to the pattern I'll use for the floor.  It seems the two most popular options are just side by side and herringbone.  As long as they're flat though, there doesn't seem to be a big difference.
2.  I also need to decide if I lay the walls on top of the floor or outside of the floor. 
3.  Deciding where I get my firebrick from.  I have a few local supply shops, but I wonder what the big box stores have.  Usually they only seem to have splits.

I agree with this. It hasn’t really been established that you need clay. I just explained how I have used clay that was purchased rather than dug up. I have no idea what the difference is between what I use and fire clay. I think this stuff I get is mined in Canada.

Ya I'm hoping I don't even need it!  But the info is awesome to have.  The info on different types of clay has been confusing, but from what I read and what Jon told me, as long as it's rated for high oven temps it should be fine.

[Jon in Albany]

I have only seen splits at the box stores and they were more expensive than at masonry supply places. Whitacre Greer light duty seems to be the firebrick of choice for home oven builders. They are what I used. They do make bricks and sell them under different names though. I guess there are only so many places that make firebrick.

I haven't used many ovens so I cant offer a comparison, but most builders opt to have the edges of the brick approach the oven door at an angle. The idea is that there are less straight on edges to catch a peel. If all the edges of the floor brick are parallel to the opening, there are a lot more chances to bump the peel. Once the floor is laid out, run a peel over it to make sure you are happy with how the peel slides.

If the angle description, doesn't make sense, I can post a drawing tomorrow.

[Pod4477]

I have only seen splits at the box stores and they were more expensive than at masonry supply places. Whitacre Greer light duty seems to be the firebrick of choice for home oven builders. They are what I used. They do make bricks and sell them under different names though. I guess there are only so many places that make firebrick.

I haven't used many ovens so I cant offer a comparison, but most builders opt to have the edges of the brick approach the oven door at an angle. The idea is that there are less straight on edges to catch a peel. If all the edges of the floor brick are parallel to the opening, there are a lot more chances to bump the peel. Once the floor is laid out, run a peel over it to make sure you are happy with how the peel slides.

If the angle description, doesn't make sense, I can post a drawing tomorrow.

Thanks!  I appreciate the quick replies before I lay them out tomorrow.  I'll ask which ones they have at the local shops, tomorrow.  Whitacre Greer sounds familiar and definitely better to get the full size rather than splits for this application. 
Is the angle the same as http://thewoodfiredenthusiast.com/building-my-wood-fired-oven-construction-walk-through-pt2-oven-floor-dome-chimney-vent/.  I'd just have to learn to cut and arrange if I do this pattern.  I'm guessing once I get one brick level, I can base all other ones off that one.

[Jon in Albany]

Thanks!  I appreciate the quick replies before I lay them out tomorrow.  I'll ask which ones they have at the local shops, tomorrow.  Whitacre Greer sounds familiar and definitely better to get the full size rather than splits for this application. 
Is the angle the same as http://thewoodfiredenthusiast.com/building-my-wood-fired-oven-construction-walk-through-pt2-oven-floor-dome-chimney-vent/.  I'd just have to learn to cut and arrange if I do this pattern.  I'm guessing once I get one brick level, I can base all other ones off that one.

Yes. The first picture with the floor laid out is exactly what I meant. In not 100% sure how you want to set up your oven. When I did it, I laid out more oven floor than I needed. Then I made an oven floor template out of luan board. I put it over the floor bricks and used a sharpie to mark the outside and that's where I cut the bricks. Then I cut the template into thirds so each piece would fit out the finished opening. I spliced the pieces together with duct tape and used them to protect the floor during the build. Kept a lot of falling mortar and junk off the floor brick during the build. If you do it, just make sure you can get the pieces out of the finished oven.

[Pod4477]

Yes. The first picture with the floor laid out is exactly what I meant. In not 100% sure how you want to set up your oven. When I did it, I laid out more oven floor than I needed. Then I made an oven floor template out of luan board. I put it over the floor bricks and used a sharpie to mark the outside and that's where I cut the bricks. Then I cut the template into thirds so each piece would fit out the finished opening. I spliced the pieces together with duct tape and used them to protect the floor during the build. Kept a lot of falling mortar and junk off the floor brick during the build. If you do it, just make sure you can get the pieces out of the finished oven.

Doesn't seem extremely hard to learn the pattern; I'm willing to learn haha.  That sounds like an awesome method.  Definitely a pro tip to cover the bricks during mortaring; didn't
think of that!  I have an idea in mind on how I'll approach it.  It will be different with a square design.

[foreplease]

That's in line with what one of the sites said to do.  I'm going to try the bricks right on the perlcrete, but if it's not sitting right I'll probably use clay or sand/salt.  I bet it will be fine, but the perlite is so irregular, so it may take time to get the bricks flat.  I'm sure I can just move some of the looser top perlite around until it becomes level.  Those pics are awesome!  So much work involved and I liked seeing the skim coat as you mentioned. Is that a line you have from the mound to home plate?

Thanks, Pod. I had so many lines up on that job I had to look closely at the photo. Yes, it runs to home plate but it is for spot checking elevation on the top edge of the brick. I set the plate quite a bit higher than the old one to get the entire plate circle (27’ diameter) to drain off the back edge into some grass I planted later at the proper elevation. I regraded everything from 1st base around behind the plate and to 3rd and blended everything in nicely. Once the plate was set I shot in stakes on all 4 sides of where the pitching rubber belonged. Again, it was for elevation only, which is 10” above plate height. As long as those stakes were undisturbed I could drop it in, after mounting in on about 100 lbs of concrete (same for the plate), and locate it with all 3 bases and foul poles. I use a homemade mound gauge I cut out of a very stiff 2 x 12 15 years ago. The specs for the drop in the mound are: a flat table on the back side of the rubber measuring 24” x 60” and flat for 6” forward of the rubber then drop 1” per foot for 6’. So that is the angle I cut on the bottom edge of the board. I set a steel stake at the right height at the bottom, which was determined by checking the top (factory edge) of the board with a 6’ level. It works really well; just keep the top of the gauge level. Then build the brick to the bottom edge of the board and check each row side to side for level. If you do the excavation part well it goes pretty easily. I try to work clean and use several wet towels to keep the bricks free of dust and sticky. They come out of the bag sticky and very heavy. I think a bag of 8 bricks weighs 60-65 lbs. I can’t do this kind of work any more and miss it already but I have done a bunch of it over a 22 year period.


This photo shows one end of my gauge. I could not easily find one that shows how it sits on the rubber but this will give you an idea.

[Pod4477]

Thanks, Pod. I had so many lines up on that job I had to look closely at the photo. Yes, it runs to home plate but it is for spot checking elevation on the top edge of the brick. I set the plate quite a bit higher than the old one to get the entire plate circle (27’ diameter) to drain off the back edge into some grass I planted later at the proper elevation. I regraded everything from 1st base around behind the plate and to 3rd and blended everything in nicely. Once the plate was set I shot in stakes on all 4 sides of where the pitching rubber belonged. Again, it was for elevation only, which is 10” above plate height. As long as those stakes were undisturbed I could drop it in, after mounting in on about 100 lbs of concrete (same for the plate), and locate it with all 3 bases and foul poles. I use a homemade mound gauge I cut out of a very stiff 2 x 12 15 years ago. The specs for the drop in the mound are: a flat table on the back side of the rubber measuring 24” x 60” and flat for 6” forward of the rubber then drop 1” per foot for 6’. So that is the angle I cut on the bottom edge of the board. I set a steel stake at the right height at the bottom, which was determined by checking the top (factory edge) of the board with a 6’ level. It works really well; just keep the top of the gauge level. Then build the brick to the bottom edge of the board and check each row side to side for level. If you do the excavation part well it goes pretty easily. I try to work clean and use several wet towels to keep the bricks free of dust and sticky. They come out of the bag sticky and very heavy. I think a bag of 8 bricks weighs 60-65 lbs. I can’t do this kind of work any more and miss it already but I have done a bunch of it over a 22 year period.


This photo shows one end of my gauge. I could not easily find one that shows how it sits on the rubber but this will give you an idea.

Np and very fun to see how it's done!  It's amazing all that goes into making a baseball field.  That's some intricate leveling and contraptions there, and quite impressive. The photo is much appreciated for perspective.  That's too bad to hear you aren't able to do it anymore, but your work lives on!

[Pod4477]

I bought 96 firebricks and got the floor all laid out.  It's pretty darn level and smooth for a peel. 

I'm assuming I should cover these from the rain.  Is it okay if they get wet, but then dry out before firing up?  I was thinking about covering with some sheeting or even just black contractor bags as an insurance barrier between the tarp and the bricks, just incase the tarps has holes in it.

I also bought a 48" angle iron for over the oven opening.  It's heavy duty (gotta measure the thickness), but I figure heavier duty is better.  What size thickness do you guys suggest for the opening span and also for the ceiling/landing chimney area?

[foreplease]

Looks good. How do you like that floor height for loading the oven?

[Pod4477]

Looks good. How do you like that floor height for loading the oven?

Thanks!  Sorry, I forgot to mention that.  It seems like a good height and around 40-42".  It's going to be quite expensive using all firebricks, minus the chimney area that I might do in regular clay bricks.  I don't mind spending it though, but do you guys think it's worth the cost vs old clay bricks, to use entirely firebricks?  Seeing the video on YT from the fireplace company in AUS, it seems that it would take years for red brick to chip away.

I covered the oven with a thicker tarp; my third tarp this week haha.

[foreplease]

...do you guys think it's worth the cost vs old clay bricks, to use entirely firebricks?  Seeing the video on YT from the fireplace company in AUS, it seems that it would take years for red brick to chip away.

Sorry, I know nothing about this kind of thing.

[Jon in Albany]

I have no guess on what size angle to use. I used 2x2x3/8 angle in my stand and it was definitely thick enough. Two of those angles supported about 3 concrete blocks and then some more concrete until the concrete set. Ballpark guess is that is in the 350+ pound range. But with no deflection and no loaded heat cycling, just ambient temps. If I am picturing your oven design right, the angles dont carry that much weight, maybe 10 bricks each. Not sure about the entry. But you will be putting them through large, loaded thermal cycles and you definitely dont want them to sag long term. If you have seen a similar oven with some age to it, I'd follow their lead. I'm not much help here. I also have no experience with traditional brick. The only bricks I every laid were in the oven and firebrick.

Is there anything you have to do for rust prevention of the steel?  Maybe coat with vegetable oil so it bakes on similar to cast iron pan.

[Pod4477]

Sorry, I know nothing about this kind of thing.

No that's ok!  Thank you though.  So it seems I may not have to use the fireclay under the firebricks, but I may, just to get them super flat.  You've been a huge help so far, I really appreciate it.  Now I just need to learn to mortar ¼" heat stop 50 lol.

I have no guess on what size angle to use. I used 2x2x3/8 angle in my stand and it was definitely thick enough. Two of those angles supported about 3 concrete blocks and then some more concrete until the concrete set. Ballpark guess is that is in the 350+ pound range. But with no deflection and no loaded heat cycling, just ambient temps. If I am picturing your oven design right, the angles dont carry that much weight, maybe 10 bricks each. Not sure about the entry. But you will be putting them through large, loaded thermal cycles and you definitely dont want them to sag long term. If you have seen a similar oven with some age to it, I'd follow their lead. I'm not much help here. I also have no experience with traditional brick. The only bricks I every laid were in the oven and firebrick.

Is there anything you have to do for rust prevention of the steel?  Maybe coat with vegetable oil so it bakes on similar to cast iron pan.

Oh nice!  Mine seems to be ¼" but it's very beefy and weighs a lot at about 48".  It seems like it would be enough, as when we talked about the door it seemed ¼" was fine for the heat.  Good idea about using oil! If anyone knows the proces/has done this before, please let me know.  I'm sure coating in oil is all that is needed though.  There will probably be 8-12 bricks on top of it, over the doorway.  For the ceiling angle irons I'll have to double them up or use T angle irons, and they will only have one course of brick on them of course. 

From what I've seen, old red bricks and new red bricks both handle thermal shock poorly, but it might take years for it to really massively chip away.  Probably still best to use all firebrick, and then just use some solid red clay bricks for the chimney and entranceway.  My plan is to encase the ceiling angle irons and firebricks in concrete, like https://www.flickr.com/photos/climbhipa/albums/72157613634415857/page1.  They also used an angle iron over the doorway, and since it's exposed, covering with oil is a good idea.  Some may be covered by my flue vent. 

[Jon in Albany]

I was thinking the roof steel would be holding 8-10 bricks. The steel across the door will hold more. Going back to a drawing in post 101, the steel will hold what looks like a third or so of the oven ceiling weight (which goes up if there is concrete on top) and I guess the door too. Maybe some chimney weight also. 1/4 might work. I have no idea.

Traditional concrete is going to break up at oven temperatures maybe not the end of the world if you are just looking for mass, but the bags of quickcrete are not meant to get that hot.

Another design consideration that maybe you thought of...but if you build walls and then put the entryway steel on top, the front is no longer level with the back. Again, Im just spitballing because I'm not totally sure how you are building this.

Edit: the Flickr link was down so I didn't see the photo.

[Pete-zza]

Edit: the Flickr link was down so I didn't see the photo.

Jon,

The link is working again.

Peter

[Jon in Albany]

Thanks Peter. 

It looks like they did use regular concrete but it is just for mass. I would guess that the concrete loses strength and cracks over time but it doesn't really matter if it isn't structural.

My father in law had a small pit of sacrificial concrete blocks for burning brush. Didn't take long for the blocks to fall apart.

Not sure if it would be easier or how it would be cost wise to turn the firebrick in the other direction so the ceiling is 4.5" inches thick of firebrick instead of 2.5 inches of firebrick + concrete. Probably more expensive.

Like I said, I'm just spitballing. Build the oven you want.

[Pod4477]

I was thinking the roof steel would be holding 8-10 bricks. The steel across the door will hold more. Going back to a drawing in post 101, the steel will hold what looks like a third or so of the oven ceiling weight (which goes up if there is concrete on top) and I guess the door too. Maybe some chimney weight also. 1/4 might work. I have no idea.

Traditional concrete is going to break up at oven temperatures maybe not the end of the world if you are just looking for mass, but the bags of quickcrete are not meant to get that hot.

Another design consideration that maybe you thought of...but if you build walls and then put the entryway steel on top, the front is no longer level with the back. Again, Im just spitballing because I'm not totally sure how you are building this.

Edit: the Flickr link was down so I didn't see the photo.

Thank you; these are all things I need to think about.  I didn't realize how much weight would be on the doorway steel.  I'll have to see if they have ½"next time I go.  https://www.traditionaloven.com/building/details/concretecladding.shtml had mention of the concrete cladding from that Flickr link.  Interesting how he says to use concrete mix with Portland and lime.  I did always find it strange how people use concrete over the walls and ceiling, since it's job would be to hold heat.  I told your father in law story to my cousin last week.  I use it as reference now for using concrete in heat applications  . That's a good idea about the firebrick turning on the side!  So if I had firebrick walls and roof, would I be able to apply roofing right to the firebrick and I'd have to protect all firebrick walls from rain I'm guessing?

I thought about that yesterday as I held up the angle iron and was going to ask, but I forgot haha, so thank you for bringing this up!  So to make it level, I'd need probably either brick or more mortar in the back I'm assuming?  Another thing is that a downward slope to the back might be good for rain.  Another idea is to use another angle iron on the back wall, to make it level with the front one.  People don't usually use mortar with angle irons right?

Weird, Flickr said they are going through design changes on the site.  Not happy with the timing.

I looked at Forno Bravo again and I remembered the FB blanket with wire mesh and insulating concrete over the blanket.  Also they say "The oven enclosure must be sealed to protect your Pompeii Oven and its insulation from water. It can be constructed from concrete block, rebar and stucco mesh, metal stud and concrete board or free standing brick or stone. Basically, the style of the enclosure is up to you, your imagination, and the availability of local materials. The examples shown here from around the country will give you a start."

Jon,

The link is working again.

Peter

Thank you Peter!  I have a feeling Flickr might be a bit unreliable over the next few days.