Material advice for an oven build?

[TorontoJoe]

Hi Gang. This is my first post here. I've known of this forum for a long time and members here seem really great. I've actually built two ovens in the past (not my own) and both times they were barrel style. I'm pretty handy with concrete. I finally decided I need a small oven in my back yard but unfortunately have to do this on a tight budget. Brick is not an option for me. I decided I'd give one of these full cast gym ball types a try and maybe only do fire brick for the floor. I hope someone can assist me with some questions:

Mix for dome.... I've seen guys on YouTube doing domes with nothing but perlite and white portland, reinforced with steel mesh... Sounds interesting but I'm in Toronto, Canada. I don't know if this would handle freeze/thaws very well... Is this a good option? Does anyone know how much pertlie and portland I might need... if it is?

I've read here that a 3;1;1;1 mix is good for a cheap, reliable recipe. Is this the general consensus now? Should I be looking at this as a better option?

Sand and white poltland is an easy find but does anyone know where to source builders lime and clay in the greater Toronto Area? I'm not even sure what sort of clay and lime is being referred to.....

For this size oven would anyone know recommended quantities of these materials? How much of each?

Once the dome is built and everything in place... I'd rather leave the dome rather than cover with a housing and insulation.... What would be the recommended product to seal and protect the dome to ensure water doesn't get in and cause it to crack in winter? (I still plan to cover it in winter for some additional protection.)

Can the oven floor be poured out of this same 3:1:1:1 mix or is fire brick a necessity? I'd rather pour than use brick if I can as I have more skill with concrete.

The base - on the last builds I did I poured a slab over sand then formed for a wall and platform in one pour. It worked perfectly... but it was bloody hard work! I was thinking a steel frame might be nice. I'm ok with my welders but for ease.... I'm curious if anyone knows... The steel bases Forno Bravo sells for their Prmiavera....

https://www.fornobravo.com/store/pri...or-pizza-oven/

They're quite inexpensive. I don't think I could make one for what they sell them. Does anyone have any input on the quality? Do they even sell them separately?

I appreciate everyone who contributes to this forum. Great work all!

Here are a few pics of one I built before for my father in law. It's not perfect but it made some nice pizza and bread. Mostly used clay brick and scrap marble... not quite finished here. I wish I had the space at my house and could afford the materials to do something like this again.... or even a brick dome... but it's not possible for me.

Thanks everyone!

[TorontoJoe]

LoL! Slow weekend I guess.... I at least expected a few people to tell me I have no idea what I'm doing....

[Kvanbael]

Hi Joe, welcome!

that location is amazing. and it looks like you’re also okay with bricks.

If you prefer casting, there are a number of good build threads on the forum. What you will immediately read in several of them is that perlite or vermiculite is good for insulation but poor on thermal mass. Every decent wood fired oven has a thermal mass layer to store heat and a separate insulating layer on the outside.

As for weatherproofing a free standing dome (or barrel). It is possible (mine seems to be holding up) but risky. During firing there are huge temperature differences that make any construction prone to micro-cracks. If these let water in, then they will grow, let more
water in and reduce the performance of your oven. Consider a roof, or be aware of the risks.

[Kris S]

Hi, from my own, limited experience from just about finishing my first 28" cast oven I'll try to give my 2 cents before more knowledgeable peaople chime in:

I've read here that a 3;1;1;1 mix is good for a cheap, reliable recipe. Is this the general consensus now? Should I be looking at this as a better option?

yes, this is a true and tested mix, I used it as well, and it seems to do what it's supposed to.

Sand and white poltland is an easy find but does anyone know where to source builders lime and clay in the greater Toronto Area? I'm not even sure what sort of clay and lime is being referred to.....

For this size oven would anyone know recommended quantities of these materials? How much of each?

sourcing lime and clay seem to be a challenge for a lot of builders, myself included, especially a cheap source of clay is difficult to find. google for suppliers of pottery materials.

Once the dome is built and everything in place... I'd rather leave the dome rather than cover with a housing and insulation.... What would be the recommended product to seal and protect the dome to ensure water doesn't get in and cause it to crack in winter? (I still plan to cover it in winter for some additional protection.)

waterproofing the dome and at the same time allowing 'breathing' for steam buildup (not sealing it completely shut so it will crack) seems to be the holy grail. the best workable solution seems to be installing a breather cap at the top. search this forum section for info on breather valve / cap / vent... the best solution to protect your oven from the elements still seems to be an enclosure though

Can the oven floor be poured out of this same 3:1:1:1 mix or is fire brick a necessity? I'd rather pour than use brick if I can as I have more skill with concrete.

fire brick is necessary, I think.

good luck!

[TorontoJoe]

Thanks gang. I suppose my next move will be sourcing clay. I assume it comes in a powder?

Does anyone have an idea of required quantities on the four materials?

[Kris S]

This helped me to get a rough estimate.
It all depends on what size oven you want...

https://community.fornobravo.com/for...aterial-to-buy

I'm going to add an overview of al the materials I used + their cost in my thread soon to give people an idea.

[TorontoJoe]

I found this. they list a bunch of clay. Is there a specific on I need or can I just go with the least costly? I have no idea what I’m looking at here



Would these prices appear reasonable?

[Ope-dog]

Hi Toronto Joe! I am 75% (ish) through my build and know all too well what is going through your mind. But you're at a good spot.. plenty of resources and answers on this forum. I used a fireclay that I got from a good-sized pottery store. It's Lincoln 60 fire clay and comes in big bags, just like the sand or lime. Now, because the pottery store was way on the other side of Portland and nowhere near where I typically venture to, I got 4 bags so I wouldn't have to make a trip across town. $60 US a bag, figured $240 was acceptable. Little did I know... I'm only half-way through the 1st bag and my dome is complete!!!! I will still need to make more mortar to finish off my chimney and do my final rendering coat.. however.. I greatly over-bought! If you have easy access to a pottery supply store you should be able to get a bag as needed. But you won't need as much fireclay as you may think. Now, the sand is a different story.


I found the homebrew to work extremely well for my build. It is easy to mix, easy to work with and doesn't cure too quick, so you can mix up a batch and have it last for a while as you cut and place bricks. It also dries quite strong. Fortunately, I didn't have to take down any bricks during my build from the dome, however I did have to chisel out a few in the chimney area and it takes a bit of work. I see no reason to NOT do the home brew, honestly. It really isn't that much work, .. you just need a good, dry spot to store your bags. ( I actually left my supply in my barn and my portland cement hardened on the outside due to moisture in the air. so don't do that!)

My roof will be going on hopefully later this summer.. and most other materials are pretty self-explanatory. But the home brew is good stuff if you can source the clay.

[TorontoJoe]

Ope-dog - I took a few days off and now I'm on the cusp of building my materials list. This is all great info.

I'm not sure if Lincoln clay is available in Canada but I'll do my best to find something similar. So you're saying I should only get 1 bag of clay then?

Sand is easy...I have a place close to me where I can get bulk sharp sand. It's the lime I'm unsure about. I'm not even sure exactly what I'm asking for yet.

So I'm clear on quantities.. you did a brick dome and used the home brew as the mortar.... or you cast the whole thing with the home brew?

[TorontoJoe]

I found this. they list a bunch of clay. Is there a specific on I need or can I just go with the least costly? I have no idea what I’m looking at here



Would these prices appear reasonable?

UtahBeehiver - I was looking at the forum stickies. I didn't see anything about using links. Was there an issue with the site to which I linked? I'm not sure I understand what happened there.

[david s]

Do you have insulation under the cooking floor? It appears that there's none over the half barrel chamber or around the clay chimney. If the oven is not insulated under and over you can expect poor performance and even cracking and certainly the clay chimney will crack if it's not insulated.

[Ope-dog]

TorontoJoe ,

You're wise to do all this homework now, imo. My "biggest" mistakes (more than a few, to be sure..) occurred more in the planning stages and as a result I was having to scramble later on.

I can't say for certain that one bag of fireclay would do fine for you as I don't know what exactly your final design is going to be,, size, etc. My oven was"intended" to be a 36" oven. Ended up being 32" inside (see above mistakes comment.) I used somewhere around 200 firebricks (maybe 205 or so..) and also had a fairly aggressive scratch coat going up the side of my oven as I built. I didn't use as much brick on my Chimney as originally planned so that saved me some homebrew as well. I am "almost" through my 1st bag of fireclay and will most likely dip into another bag as I intend to use homebrew on my outter rendering in a few weeks.

So.. 1 bag may or may not be enough if building with brick like many have. If casting, I suspect you'll need more like 4 bags. 2 bags with a brick oven and a cast vent would probably suffice based off a 32-36" build.

I was able to source my lime, sand, and cement all at home Cheap-o. Not sure of their presence in your area or not. I thought lime was going to be troublesome here as well however after spending some time reading labels and forum advice the big box stuff seems to be sufficient. As I'm just finishing my curing fires and my first batch of 00 flour got delivered today (so excited!!) I can't speak to the true test which is father time. But so far, so good.

Looking forward to following your build. It has definitely been one of the tougher and more enjoyable projects I have done. I certainly didn't anticipate the time and effort that would be needed when I had this idea 11 months ago.. but that being said they really are impressive structures when you get them built.

[Ope-dog]

Ps. This is what I used for lime from home cheap-o. Found in the masonry section by the sand and cement...

[TorontoJoe]

Do you have insulation under the cooking floor? It appears that there's none over the half barrel chamber or around the clay chimney. If the oven is not insulated under and over you can expect poor performance and even cracking and certainly the clay chimney will crack if it's not insulated.

The fire brick floor is sitting on a 4" poured concrete slab. This wasn't finished but the whole thing is now insulated around the barrel

[UtahBeehiver]

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