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Who gets the most cracks? Square vs Angled cuts

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  • dtrbovich
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Great topic.....it puts a concern of mine to rest.

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  • Raffy
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Originally posted by splatgirl View Post
    The super meticulous people who cut their bricks so that there are the tiniest of joints are also the people who obsess about cracks. Those of us that that were less meticulous have no idea whether we have cracks or not
    Hahaha This is sooo true for me. I put globs of mortar and so far haven't even seen a crack in the interior of the dome or the arches. Maybe I'm not looking hard enough (or maybe I'm not too bothered if I do have cracks or not). I do have cracks on the stucco which covers the insulation but mainly where the stucco meets the arch and chimneys. It's to be expected I guess since the two materials have different heat expansion properties.

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  • WoodchuckDad
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    yeah, after cleaning up all the crap I dropped I am gonna put down something before I go on with the rest of the soldiers. And I am sure I will say something when I drop that keystone in but I darned sure won't proclaim myself a mason.

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  • Les
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Woodchuck, just a suggestion, but I would lay down some wood or cardboard to cover your surface. It will save you a butt load of time from cleaning up the dropped / splashed mortar. In regard to the mortar issue, I would just butter the inside joint and use a grout bag for the back after things have settled. As far as bricklaying - we have all been there. When you drop in your plug, you will look back and say, damn, I'm a mason.

    Les...

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  • fxpose
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Originally posted by WoodchuckDad View Post
    what is the secret to buttering these thing and pushing them together without making the other bricks move or come apart from each other. I had to go back and push some of the prevous ones back together as I went. It'll be a miracle if this thing stands up when it's done.
    I didn't even bother buttering the sides of the bricks. Once the course set the next day I forced mortar into the joints using my fingers, from both inside and outside the dome, like if I were grouting tile.

    George

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  • WoodchuckDad
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Well I think I feel a little more comfortable now with just making the basic cuts and not obcessing too much about that....I did some angle cuts at the top of the soldiers and laid the first 20 or so in. I really stink at bricklaying. I my inner joints are not very tight and I was really having a problem with the mortar. first it seemed too thick then it seemed like I had it too thin. I found it easiest to with if it was about the consistency of organic peanut butter. I didn't even realize I was starting to make the bricks lean to the side untill I was cleaning them up.the last one really has an ugly lean to it.



    what is the secret to buttering these thing and pushing them together without making the other bricks move or come apart from each other. I had to go back and push some of the prevous ones back together as I went. It'll be a miracle if this thing stands up when it's done.

    Leave a comment:


  • fxpose
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    I agree, this thread is most informative.

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  • eprante
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    I love this thread, it should be mandatory reading for all new builders.
    Eric

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  • Les
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    I took the time to cut the angles. I did not use mortar on the inside, so cracks are not an issue. I have no clue whats happening on the outside of the dome since its covered. If I had it to over again, I would make shims for the outside gap out of brick. The mortar could crumble, dissolve, evaporate -the oven will stand. If I ever build another, I would cut all the angles so no mortar is required ( or buy a FB kit )

    Les...

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  • SCChris
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    All very interesting.. I was very concerned about thermal shock but after 4 or 5 2-3 hour heating / "cooking" sessions, I finally decided that these ovens can handle it and told myself to just forget about it and do the 90 minute blaze of glory heatup cycle. I don't see that the oven has suffered, "cracked", but I'm no longer inspecting other than when the inside goes clear, maybe I should take a closer look. Is there some other variable contributing to cracking? Insulation or lack of? or some fire brick quality like particle size or??

    In the end, my recomendation is like some others, If you are the type that is really going to be bothered by cracking, maybe a modular oven would suit you better.

    I sure enjoyed the brick working and how the dome shaped up. I still look at the pictures of the finished dome and think "how in the ... rectangular bricks into a hemisphere.. Too cool!

    Chris
    Last edited by SCChris; 05-22-2010, 03:30 PM.

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  • Tscarborough
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Rigidity is NEVER a desired property of mortar.

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  • dmun
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    This is a most interesting question.

    From the perspective of someone who built a cut-every-brick thin wall oven, with heatstop mortar, it's just not worth it. I got a bunch of cracks, and I think the tiny mortar joints are a contributor to that. I know it's not a water problem on start up, because my oven cured for a better part or a year while a built a two story chimney on top of it.

    Were I to do it again, I'd use the standard thickness of a cut brick, trim the inner edges so it looks good on the inside, and leave the big gaps on the outside, where nothing is ever seen. I'd also carefully consider the homebrew mortar, mostly because it's lime based, and lime based mortars are said to be more flexible than other types. I don't think rigidity is a plus on something as subject to thermal stress as a brick oven.

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  • kebwi
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    Yep, my OCD-built oven with very tight joints has cracked all to hell. I want to post a bunch of photos of it at some point.

    However, I take solace in the fact that since the whole oven is virtually free-standing due to the way in which the bricks fit together that it almost doesn't matter if it is all cracked up.

    I am mildly concerned about one particular brick, a keystone in one of my arches (there are three arches in my build) that is literally loose but it only rocks about 1/16" of an inch...and again, due to the wedge-shape of that stone the others in the same arch, it could absolutely never fall through, so unless the arch buckles outward (which would have to compress the InsWool and vermicrete, much less break the exterior hardibacker and stucco), I really don't see it ever becoming a problem.

    Aside from the chemical reasons (too much, too little water), I have noticed that the tightest joints are the ones that cracked "apart". There are hairlines through my thicker joints but the ones that developed a gap are very very tight, and I think that in combination with a relatively large sand grain (#30 if I recall) in my mortar, these joints just didn't work. I needed much finer sand (or wider joints). Think of it as the same reason you can spread creamy peanut butter thinner than crunchy peanut butter. Same effect.

    So what does all of that boil down to? Is it an argument against precisely cut bricks and thin mortar gaps? In my opinion no (but it ain't an argument in its favor!). I take great satisfaction in the concept of a mechanically free-standing self-supporting arch. I just find the notion "beautiful" from an engineering point of view, and to that end, mortar is completely totally unnecessary (you can build an arch with no mortar at all). That's my taste. Others have different tastes. If someone is going to be tremendously hurt by the presence of cracks they better thick hard about their priorities.

    All of these ovens survive from what I've read on this forum, so from the point of view of properly cooking food and standing up for many years without major degradation, none of this matters.

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  • SCChris
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    I cut on the sides and top with the exception of the soldiers. My reasoning really related to minimizing the joint sizes to maintain something about 1/8”. I used 3 HF diamond blades and used Sairset wet premix mortar, premix wet mortar is not widely recommended around here. I used home brew mortar on the top 2 courses of the stack area and at the chimney flange. I had run out of the Sairset , didn’t need a full bucket and wanted to give the homebrew a try.

    Throughout the oven I was able to maintain the joints under the self imposed ?” limit although some outside joints approached this size.

    For curing I ran a quartz worklamp in the oven for several days and then a propane burner for a total of something like 60 hours in 4 or so burns to my little propane burner’s limit of 540f. After several hours at this temp I started running a wood fire that slowly pushed the dome temps to 850f with no significant cracking. I think I remember a hairline crack or two.

    My feelings about full tailored, 3 side cut, bricks is that even without any grout these bricks can’t move very far. If, heaven forbid, the grout fell out or evaporated, the tapering and gravity will have them nest tight again. For me I’d cut 3 sides again. This said, it doesn’t seem to matter for oven stability, or function, as long as you somewhat diligent and not sloppy about brick placement and not assuming that replacing a brick with mortar is ok.

    Your question about cracking is valid but I think the long slow curing is at least as important. It's easy to get caried away and push the curing too fast and pop you have a crack. Slow and low followed by long controlled increasing temp burns worked for me. Get the water moving out, keep it moving out, and keep it out by design.

    Chris
    Last edited by SCChris; 05-22-2010, 07:32 AM.

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  • eprante
    replied
    Re: Who gets the most cracks? Square vs Angled cuts

    I did quite a bit of reviewing builds with this question in mind. My decision to use the homebrew mortar made me look at people who changed the formula. I came to the conclusion that the recipe listed in the plans was best, and slow controlled curing seemed to be an important factor. I tapered my bricks with compound cuts on the sides but not on top or bottom. I had very thin joints on the inside of the oven, and fairly large mortar joints on the outside( I also did not cover the outside of the oven with mortar so I could see if cracks developed during curing). I cured with a natural gas burner, low and slow. I had only some hairline cracks on the exterior. I think the curing process with a burner is a great advantage due to the heat control you have. Controlling a wood fire is difficult ( as I found out tonight as I was cooking a pork shoulder and trying to keep it at 350-400).
    My 2 cents
    Eric

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