36" Build in progress- advice welcome!

[Jon Kerr]

Hi everyone,
I've taken the plunge and started my build....! Very nervous and excited in equal measure.
I just hope I'm doing it right

So far I've built the stand with insulated (vermicete) hearth. As per the FB guide I've then laid my oven floor firebricks on a bed of sand and fireclay.

Now the dome has begun construction. I 3D printed myself an "IT" which was an absolutely fantastic aid for a newbie.

Happy with the first few chains but as the angle of the dome increases I'm noticing bigger gaps between bricks. I'm uaing straight cut bricks. Is this a problem?! Any advice appreciated!

[agrasyuk]

Hi John,
if all you have is a chisel then making anything other then straight halving bricks is hard. I've seen builds on this board that only use halves, but they inheritenly will have the inverted "V" mortar seams. As you go higher these will be even more pronounced. Is this a "problem"? I guess that's up to personal interpretation. Increased mortar consumption I don't mind, but the end result with huge seams at top would have bugged me a lot.

If you absolutely can't get a hold of wet saw, at the least consider getting angle grinder and a diamond disk. Together with eye and ear protection this shouldn't set your wallet back to much. Also don't forget good respirator, although some argue that even the pink 3M filters are not helping against fine silica dust. I think soaking bricks before cutting made the dust very manageable. For My build I'm using old radial arm saw fitted with segmented diamond blade (I didn't bother making fancy jigs for it either), these can be gotten sometimes even for free around here. Perhaps consider looking g around for that , makes load of difference.

I'm not a pro at this by no means (it's my first try at masonry), and you probably have good idea what you doing but your oven entry really worries me.
Use of iron of support... I know it's shown like that in book and been done, but I just can't get over it - i do not see how iron expanding with heat can possibly not affect masonry over time.

At any rate good luck on your build. It sure is an adventure

Regards!

[SableSprings]

Welcome to the great journey Jon! Looks like you've got a good bit done. I basically used this angle iron approach to the oven opening giving me the same rectangular front. Don't mortar in the piece of angle iron (if that's what it is...can't tell by the picture) and leave a 0.5" to 1" gap on both ends to allow for the metal's expansion. I just laid my half bricks so they rested on the bar--they were mortared together end to end but not mortared to the base...again the expansion issue. I know that folks think the angle iron top piece of the opening is inherently going to fail, but I build my oven in 2009 and have put 4,866 pounds of dough through it in the form of everything from pizza to bread (yes, I have a spreadsheet that I tally this stuff ) .The gaps between bricks do increase if you don't do any beveling on the middle brick cuts. Your choice, but putting a little bevel/angle cut on the bricks on these remaining courses will reduce the mortar used and tighten the gaps. Actually you are going to have to do a little tapering/beveling in the top several rows because the full half bricks just aren't going to go into the spaces remaining. The keystone will challenge you (or at least it did me) because it can be quite a puzzle piece fitting. So, try doing the next chain with some side bevel cuts or grinds. The angle is consistent enough that you can build a simple guide for cuts with the wet saw. I've seen just pieces of plywood put together to create these guides...simple and effective. Remember, most people only see the gaps during the build because when the build is complete and you're cooking pizza...the pizza is what will hold their attention. Also in order to actually see the complete inside of the dome when it's completed involves getting low and sticking your head sorta into the oven...doesn't seem to happen often for guests at a pizza party .

Looking at your work so far, you need to try to avoid lining up so many seams between each course. Usually putting in a split half brick as you start a course will offset the alignment with the bricks below. The seam alignment won't "hurt" the actual structure/strength of the dome, but do expect some cracks to appear that follow the mortar line(s) vertically. Again, it's the expansion during the firing that causes the entire dome (and floor bricks) to move slightly. The "weak points" of the structure will be the mortar lines...so during expansion, they're the first to crack. (That's why you can seat the dome just outside the cut hearth/cooking bricks or rest the dome ring base on the cooking brick hearth. Things are going to move and if you mortar them into place, they'll just break the mortar as they heat up and expand. If they're on top, they shift outwards on the bricks below and if they're outside the cooking brick "circle", they move outwards and the floor moves outward into the gap left between. I'm sure you're already aware of these issues...but I used to teach and I can't help myself )

I love the 3D printer used to create the IT! Looking forward to your next installment and finishing of the dome...sorry, I didn't mean to prattle on. Hope this was of some help.

[Jon Kerr]

Thanks so much for your help, both of you!!

I'll take your advice and use the angle grinder to taper the next row of bricks. Theyre incredibly tough to cut.....!

As for my mortar lines lining up, this is something that puzzled and bugged me. If you look at the pictures the start of each chain (near the opening) is perectly staggered. By the time they get to the back of the oven they seem to line up mortar to mortar, then as you continue around to the opening they stagger again.
I guess this is another phenomena of the straight cuts?
Perhaps the best thing to do its put a quarter brick split in whenever I see this starting to occur?

I'm worried now- is what I've done so far going to be good enough?

No mortar on the angke iron.... That sounds scary. This section is quite complicated, blending the dome into the straight iron means so strange cuts. Does anyone have any pictures of this stage?

[agrasyuk]

while you have places with less then optimal brick overlap, there is still some overlap.so most probably it's going to be ok.
i followed the recommendation i found somewhere on here to start all my chains all the ways in the back. that way the visible parts are cleanly stagered. quarters will be better but they still follow the "modulus" of 2, not sure how to explain. i did halves for row 1 through 4, then went with thirds until about row 7 after which I proceed with quarters ( i too have some less than ideal staggered vertical joints here and there).

as for entry, it is indeed the most complicated part IMO. there were quite a few progress reports on that par lately, with questions and pictures, but i'm afraid none of them is straight angle iron like yours. perhaps pompei ebook has better pictures?

[Jon Kerr]

Thanks Anton, put my mind at ease a bit

work continued today, until silica dust finally killed my grinder and put an end to work for the day.

[SableSprings]

Jon, I looked back and found some pics of how I did my angle iron entry. They're not the best photos or the most complete set of angles but...

The first couple pics show my brother-in-law in the oven. He just laid the angle iron across the front side of the side column bricks and then laid a row of uncut bricks across the gap. Note they are only mortared between bricks and on the outside edge where there is brick to brick contact with the side column bricks. On picture three, you can see the free end of the angle iron circled in red and the pie shaped pieces (to the left of the blue paren) we laid on top of that set of full bricks so we'd roughly match the next course angle.

My decision on this was that all this was going to be covered with insulation and some sort of facade so I didn't worry about "pretty". Pictures 4 & 5 show the two arches that were built in front of the opening to be the collection area and base support for the chimney stack...again not worried about pretty (or apparently straight either ). The last picture shows how the facade of front bricks covers up my inept masonry work...to some extent. Also note on pics 4-6 6 you can see that I buttressed the sides of the chimney stack support. I even put & mortared rebar into the side bricks holes to keep the future chimney weight from being able to push anything out of line.

It certainly wasn't pretty and as Anton/agrasyuk above noted most of us find the biggest challenge of building an oven is the entry. But as I noted several times, once you realize mortar is your friend and the bricks above and to the inside are basically only seen during construction you can relax a bit. It doesn't have to be perfect or pretty here! Hope these pics help!

By the way, if I had to do it over again, I'd still do the rectangular entry with angle iron but would make my front most arch lower to help create a larger smoke chamber.

p.s. We both just did a simul-post ... looks like you're heading toward the finish line. Great job...cleaner than mine!

[Jon Kerr]

Sablesprings- thanks so much! This has really put my mind at ease as thats exactly what I've done in the end. Similarly I've also not worried too much about aesthetics at this stage and will have to come back to make it look "pretty" later.

Got lots more done today. Vent is cast inside a mould, curing for the next week or two.

I've finally made it past the opening! The last couple of bricks here (directly behind the opening) were a real pain, as they have nothing to rest on but thin air!) but I very much hope what I've done is structurally sounds. At the very least the chain is self supporting for now.

Minor issue is that I've developed a kindve teardrop shape to the last chain. i'll fix this on the next chain and hope its not a problem?

who am I kidding- I'm still terrified!

[Jon Kerr]

Teardrop chain picture attached...

[SableSprings]

Jon, when I started my oven build, I wanted a "short beavertail" design...basically a teardrop. I reasoned that it would be easier to pull out ashes with a smooth path from the sides to my ash dump (which it is). Here's a couple pics of how I filled in my top teardrop shape and moved towards a more standard keystone closing at the top of the dome. It may not be pretty compared to other builds on the forum, but it has served me well through a lot of bakes & parties. Hope these pics help..

[Jon Kerr]

Hi all,

Thanks again for all your help and advice (sablesprings, your pictures were very useful!)

The dome is finally finished and mortar is curing.

I'm now looking towards adding my insulation and I've realised I've made a fatal error....... the concrete base is too small for my oven.

On the front sides it's absolutely fine, but on the back two sides I'm within 1.5" of the edge, meaning when I add my 3-4" of insulation I'm going to ovehang the base.

Does anyone have any thoughts on extending the base with a small shelf of concrete?

I think If I were to drill into the sides of my slabs, hammer in 8" long rebar pieces, build a form and pour some more concrete, it should cure as a "shelf" and hold its own weight. The insulation then wont overhang the edge of the base and look daft.

Thoughts?

[david s]

Hi Jon,

A couple of things to consider. Firstly I like the form of your casting, it should work well. Presuming you made it from castable refractory rather than a mix containing Portland cement. If so it does not need extended moist curing, it achieves full strength in 24 hrs. Secondly, the use of steel angle or rebar presents problems when heated rapidly. The problem is that, being way more conductive (approx 50 x) than the surrounding brick or refractory, the heat rushes to it, creating greater expansion, stress and cracking. You need to leave some gaps at the ends to allow for it to expand freely. Under normal temperature rise in ambient conditions, like the reo in a concrete bridge, this is not a problem, but we're pushing it up at around 300C/hr. Also be aware that heat accelerates corrosion. The two materials are not particularly compatible in a high heat situation.

https://community.fornobravo.com/for...422#post398422

http://www.engineeringtoolbox.com/th...ity-d_429.html

[SableSprings]

... On the front sides it's absolutely fine, but on the back two sides I'm within 1.5" of the edge, meaning when I add my 3-4" of insulation I'm going to ovehang the base.

Does anyone have any thoughts on extending the base with a small shelf of concrete?

I think If I were to drill into the sides of my slabs, hammer in 8" long rebar pieces, build a form and pour some more concrete, it should cure as a "shelf" and hold its own weight. The insulation then wont overhang the edge of the base and look daft.

Thoughts?

Looking at your pictures Jon, I'm not sure you're going to be able to make forms to pour a shelf between the oven and the fence. Since it will be basically hidden, would simply stacking some bricks with maybe a little construction glue or mortar up to and along the overhang areas be easier? Remember that you don't want to create a lip for water to collect and seep into your bottom insulation edge. Even just securing some good, stiff hardware cloth (metal screening or expanded steel) around the perimeter will work as a base for your perlite/vermiculite concrete insulating layer. Then you can just rendering down to that bottom lip over the insulating layer. The water should drip off the outside render and keep your insulation from picking up too much moisture.

Anyway, just some thoughts since I also didn't leave enough space behind the oven...not for the insulation, but for me and my tools to do the finish work

Keep us posted! I also really liked your vent casting.