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Old 06-11-2012, 07:43 AM
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Default Gaps, bumps, uneven dome top....how bad can it be?

Well I made it, finished the dome...well, it is done, but I'm very unhappy with the results. I rushed it, end of the day, excited to get it over...just didn't give it the attention I should have in my enthusiasm to say the dome was complete... now I want to chip it out and do it over. My husband is making me post this horrible pictures to have you talk me out of it.

SO my dome got pretty flat at the end, but I made it up to row 10 before I needed any form help. so I just cut a 20" circle of insulation board and pressed it against the top, using wedges to give me angles in the dome (I know...not the best idea - strike one for me - lazy!)

I thought I was using plenty of mortar - homebrew 3:1:1:1 - but I have giant holes underneath. AUGH. I sanded off my fingertips (through the gloves) pressing the mortar into the holes from below, and still these massive gaps...



Here is what it looked like from the outside, but truthfully I knew when I finally gave up for the night that those gaps were probably too big.


I don't care about the bumps, but the giant gaps have me concerned. That middle star section is tapered narrower, so there is probably a little locking going on there...but I seriously doubt this is considered good enough. I want this thing to last forever, I don't want it falling in later and have to fix it from inside. So with that in mind - should I just knock it out now and redo that last bit or is that mortar strong enough to hold those for the life of the oven?

If you do try to convince me to leave it and move forward with the vent, should I at least fill in those deep holes with more mortar? Looking at them, there are plenty of pockets that I think the mortar would fill and be wedged up in there without falling out on to the pizza, at least in the biggest spots.

I'm honestly ashamed to have to show anyone these pictures... especially you all, but I sure appreciate your help and your experience so very much! Thanks ~ Xene
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Old 06-11-2012, 09:32 AM
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Default Re: Gaps, bumps, uneven dome top....how bad can it be?

Xene -
It'll work just fine. I wouldn't worry about it. You just need the mortar to provide an air seal. The gaps are a natural consequence of using un-tapered bricks, and consensus seems to be that they are no big deal.

If you are really concerned about the look of it, you could fill those gaps with mortar from the inside. I've done that inside my oven, and I don't think it's going to come out. My trick is using mortar that is a little dry - usually stuff that squeezes out between the bricks. Try mixing up some mortar and buttering it onto a spare fire brick - then scrape it off with your finger or a trowel to push into the cracks. The brick should pull out enough water to make the mortar the right consistency to stick in those gaps.

You have really cruised through your oven build and you should feel good about where you are. It took me 3 1/2 months to get as far as you have in a couple weeks!
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Old 06-11-2012, 03:19 PM
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Thumbs up Re: Gaps, bumps, uneven dome top....how bad can it be?

I hope Tscarborough chimes in here, I'd put a lot of confidence in his recommendations. If he doesn't, send him a personal message.

With regard to filling those voids after the fact, unless Tscarborough has a fail safe way to do it, I'm not sure the patches will stay. I say that because mine are falling out each time I heat the oven, and its been almost a year! Oven works fine, but it isn't as pretty as I dreamed of. It hurts less each time I use it. Sleep on it a few nights before you decide ot knock things loose, you may be able to live with it. HTH
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Old 06-11-2012, 03:25 PM
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Default Re: Gaps, bumps, uneven dome top....how bad can it be?

Quote:
Originally Posted by Lburou View Post
With regard to filling those voids after the fact, unless Tscarborough has a fail safe way to do it, I'm not sure the patches will stay. I say that because mine are falling out each time I heat the oven, and its been almost a year!

Uh oh... sounds like I might have some gritty pizza's in my future. I am hoping that filling the voids quickly after setting the brick will make a difference in the mortar bonding- while the mortar is still wet.

I did read in another thread (Gap between bricks?)that the builders in Italy fill the gaps with Refractory cement. I think it was Tscarborough who said on the same thread that the gaps aren't a big deal
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Last edited by deejayoh; 06-11-2012 at 03:29 PM.
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Old 06-11-2012, 03:26 PM
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Default Re: Gaps, bumps, uneven dome top....how bad can it be?

They (mortar repairs) are pretty much going to fall out, no matter what you do, but it doesn't affect the performance. I would probably knock it out just because it would bug me every time I used the oven, but it is up to your preference. If you do knock it out, be sure and knock it UP from inside.
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Old 06-11-2012, 04:16 PM
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Default Re: Gaps, bumps, uneven dome top....how bad can it be?

Thanks fellas! Those holes are pretty big, I'm not talking a crack here, those are bigger than quarters, I don't think you can tell from the picture. They are really rough and odd shaped (eek, I can sure make my work sound good can't I?) I'm feeling pretty confident that there is enough space and nonuniform surface that mortar would get trapped in those biggest holes and get locked in, just because there would be a significant mass. Some are half the brick deep... Digging my quality-built hole deeper...

I think I could live with the inside as long as I know it won't fall in later in life when I'm too old to fix it. If it is structurally sound this way, I think I'd be happy to give those holes the best fix I can, and hope for the best. If it is not, well that is an entirely different story. I'm going to put so much attention on the finish of this thing that the inside dome will never draw anyone's attention!

Has anyone played with the mortar mix? I've read about lime lately and how it provides more flexibility - in that it allows for more expansion/contraction, and is more breathable, if I increase the sand and lime would that be of any benefit? What advantage is the Portland providing in the mix? Just some ideas I've been tossing about, thought you all might have suggestions?

Deejayoh - Thanks for kudos on burning through this project, we've had such a dry spring that I've been able to work on it every day - it seems like it went really fast - even to me! Even if I knock it out (or up) it still seems like decent progress in a short period of time.
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Old 06-11-2012, 05:20 PM
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Default Re: Gaps, bumps, uneven dome top....how bad can it be?

Xene,

I also would not patch it. The lime make the product more "plastic" but it's not a magic bullet to prevent cracks. If the mortar cracks there is always a chance of it falling in chunks or bits and pieces. If it were me, I would remove it, take step back and take your time rebuilding it. The summer is new, whats a couple of more weeks when you get years of good sleep?
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Old 06-11-2012, 05:38 PM
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Default Re: Gaps, bumps, uneven dome top....how bad can it be?

Quote:
Originally Posted by deejayoh View Post
I did read in another thread (Gap between bricks?)that the builders in Italy fill the gaps with Refractory cement. I think it was Tscarborough who said on the same thread that the gaps aren't a big deal
I just wanted to clarify this point, since I was the one who posted it originally. It is not a solution for this situation, it is instead an alternative method to building the dome that does not require complex cuts.

I made a simple graphic to explain how it works a bit better. Italian builders work on a sand form, and that is critical to this method. The bricks are first laid using the sand form with the mortar joints shown in blue. Once the dome is completed in this manor all the triangular gaps are filled with a castable refractory which is shown in green. The italian builders use a very wet mix and pout it over the dome to fill the holes, but I could not find a refractory product here in the US made for that wet of an application so I simply used a standard fairly dry mix and rodded it into each hole to compact it and eliminate gaps and air pockets.
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Old 06-11-2012, 05:56 PM
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Default Re: Gaps, bumps, uneven dome top....how bad can it be?

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Originally Posted by Les View Post
whats a couple of more weeks when you get years of good sleep?
Couple more weeks? I can rebuild that in a few days! And enough of you seem to be confirming my gut feeling that I think that is what I'll be starting in the morning. Yucky!
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Old 06-11-2012, 05:57 PM
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Default Re: Gaps, bumps, uneven dome top....how bad can it be?

If the gaps are pretty big and not triangulated upward, they may well hold the mortar. It is worth a try if the appearance doesn't bother you (and there is no reason it should, it is a cooking appliance after all).

Shuboyje, I have a product that would work for that, the main difference is that it contains a fair amount of perlite. It is sticky and able to be used wet. The Italians are using a volcanic pozzolan mix design, and I have been looking at making a mix with some glassine pozzolans.
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