MY 40inch CORNER BUILD

[david s]

Not totally sure about this, but from reading your thread it sounds like you have not cast or drilled any weep holes in your supporting slab. If not they can still be drilled up through the bottom, although you probably won’t know where the reo is, so drill small diameter pilot holes first.
This helps enormously to get the underfloor moisture out, both from building the insulating slab as well as moisture that can and will accumulate ther later. Not allowing sun and wind do much of the slabs drying and keeping it covered until laying the floor bricks over it, means there will be lots of free water left in the slab. Many builders report that it stakes months to push this water out by firing, which is indicated by the oven continuing to improve in performance for months.
Again I may have misread your posts, so ignore my advice if you are aware of this problem.

[Mr.Pizza3]

david s

no I have not drilled any holes under neath my supporting slab I had not thought about that I luckily have a nice SDS drill and a couple bits long enough to penetrate the entire slab so something I will definelty do before the oven sits for the 4 weeks to air cure

at the moment I am covering the dome with a damp towel between setting rows for a bit and covering the dome with poly over night to help slow down my mortar cure time in the short term to strengthen the bond and decrease any shrinking / cracking

I do plan in future for the finish to water proof and tile the slab so hopefully that will negate future moisture under there

Will this affect the integrity of the oven during heat cycles? Or just affect the overall performance of the oven floor during the first few fires and cooks?

[Mr.Pizza3]

I do also have pictures on my old phone if the rebar going in and the slab being poured something I will add to this thread later on but I’m sure I can measure off the photos and figure out where the rebar is

[david s]

Placing the floor bricks over the still moist vermicrete tends to lock in the moisture. Applying a stucco over the insulation layers does the same thing, so it is prudent to do your drying fires after insulation, but before stucco. Applying a fully waterproof coating over the stucco can cause bubbling under its surface if there’s moisture still there. Water expands to over 1500x when it turns to steam and if this happens suddenly the steam pressure can crack the outer shell.

[Mr.Pizza3]

My plan was complete the dome and allow it to sit out for a full 28 days and then a week of curing fires and after wards apply my insulation and then a render over it ,

I am using 3 layers of 1” ceramic blanket for my insulation layer followed by about 1-1.5 inches of Type S mortar over that reinforced with chicken wire

afterwards I was going to use use some marble or cut rock tile over it followed by a tile/concrete sealer to waterproof it

[Mr.Pizza3]

I guess what I am wondering now is even with some weep holes cut into the concrete pad if there is still moisture in the V-Crete is it going affect the structural integrity of the unit when fired up

[david s]

No, it will just take longer to get rid of it without the holes.
Regarding your plan to fire the oven uninsulated, this has been tried by other builders and resulted in cracking of the dome due to inside and outside temperature difference. Much safer to do the drying fires after insulation.

[Mr.Pizza3]

Interesting good to know should I also let the oven sit for the 28 days before insulating?

[Mr.Pizza3]

I have completed my third row today my bevel cuts have been working out pretty good I cut the brick with my saw and finish it off with my two grinders row looks tight

tomorrow I will be complete my arch and hopefully the 4th row and potentially the 5th rows

I was able to hold the brick on my form and mark my final tower brick and the angles came out good the brick rests on it nicely to begin my arch

I want to incorporate a slant on my inner arch corners to help with the 4th and 5th rows that will be connecting to it ,

my plans was to clamp a brick to my trammel (IT) tool and mark a line on the side of the brick and cut accordingly

Any other methods?

looking forward to building more tomorrow

as of now it’s back to cutting brick luckily now it will only be 3 cuts vs 4 from my having to bevel precut bricks

i Know as I get higher I will be making smaller cuts to make it fit cleaner / more uniform

[david s]

No, it will just take longer to get rid of it without the holes.
Regarding your plan to fire the oven uninsulated, this has been tried by other builders and resulted in cracking of the dome due to inside and outside temperature difference. Much safer to do the drying fires after insulation.

Ideally yes. Maximum strength is attained at 28 days damp curing, but the strength to time graph is not a straight line. A week is usually considered sufficient. But after that drying by sun and wind on the outside is desirable before beginning fires.

[Mr.Pizza3]

I know concrete is usually a exponential curve for curing and strength a week gives you north of 60% strength I know in my feild we will have lifts on a new pad of concrete for a building in about 3-5 days

the industry standard is 28 days for a 99% strength

my plan was to keep it covered for a week following my final few bricks then allow it to sit out in the sun for the remaining 3 weeks

my question now is are you saying around 2 weeks though is enough time of sitting to have dried it out enough to begin curing fires?

just to be clear as well

you are saying let the oven sit and dry out and before I start my fires I should wrap my unit in my insulation layer , perform my curing fires then go and wrap my insulation is my outer rendering

my second question off that as well is

do I need to let my outer rendering layer (type S mortar ) sit and dry before firing my oven again? So another week or so to let that dry completely ?

also what did you do for waterproofing?

[Mr.Pizza3]

So today I completed my 4th row and my inner arch!!

the arch came out to be 9 bricks total which I was happy about cause it gave me a center keystone in total my oven opening is 13 3/4 high by 18.5 wide

I used the google charts to find this sizing and it worked great I chose to go slightly wider then 18 inches cause I have a goal to be able to make an X-Large 18inch pizza like they do back in NYC

I used my trammel to make marks on where I would cut each brick to make my connecting rows go a bit smoother

tomorrow j will begin my 5th row and make the hardest cuts of the build. Which will be the ones connecting my 4th and 5th rows into the inner arch

not completely sure but it’s looking like my 6th row will be my first complete circle maybe with one or two thinner cuts for the top of the arch and then I’m home free to finish it out

still haven’t decided if I’m going to use the trammel (IT tool) for the whole build or switch to a yoga ball or platform and sand for my final rows

I kind of like the idea of sand for an easier time setting my final rows and make it look all nice nice and add a cool final plug like I believe UtahBeehiver did
either way more pictures coming tomorrow !

[david s]

I know concrete is usually a exponential curve for curing and strength a week gives you north of 60% strength I know in my feild we will have lifts on a new pad of concrete for a building in about 3-5 days

the industry standard is 28 days for a 99% strength

my plan was to keep it covered for a week following my final few bricks then allow it to sit out in the sun for the remaining 3 weeks

my question now is are you saying around 2 weeks though is enough time of sitting to have dried it out enough to begin curing fires?

just to be clear as well

you are saying let the oven sit and dry out and before I start my fires I should wrap my unit in my insulation layer , perform my curing fires then go and wrap my insulation is my outer rendering

my second question off that as well is

do I need to let my outer rendering layer (type S mortar ) sit and dry before firing my oven again? So another week or so to let that dry completely ?

also what did you do for waterproofing?

Yes, that’s right, or at least what I do. Weather conditions vary of course, but as a general rule I give the completed inner oven at least week of drying, after the damp curing, before insulation, the the 7 drying fires in 7 days( they don’t have to be consecutive, but the oven should be allowed to cool off before beginning the next fire).
If applying a layer of vermicrete over the blanket, this layer should also be given a week to dry before beginning the fires. As the strength of the vermicrete layer is not a concern, damp curing is not required. The large amount of free water in the layer is what you want to remove so sun and wind on the exterior does a better job than fires inside the oven. When you’ve achieved getting the oven interior white, you can apply the cement rendered outer shell. I then wrap this up in cling wrap to maintain the moisture in the outer shell for a week to enhance its strength.
All these waiting periods may seem arduous, but there is logic behind them.
After several more cooking fires you can then fully waterproof the exterior. I use flexible pointing, but water it down 20% so it can be easily applied with a brush. I apply 3 coats which results in a very flexible, waterproof UV resistant coating with a thickness of around 1.5mm.

[Mr.Pizza3]

Another question does it hurt to cost the outside of the brick in the home brew Mortar ? As I go back and fill in the spaces etc I been thinking of putting s mortar “shell” over the whole oven

i would assume this would only help with the overall strength and thermal mass of the oven

[david s]

It wouldn’t hurt, but adding more thermal mass has its pros and cons. Anything less than an inch thick would hardly contribute to strength. Also the increase in diameter it creates will subsequently increase the volume of required materials for the insulation layers and outer shell, all contributing to an increase of weight on your timber frame.