Share your crack stories

[CoyoteVB]

During the curing process I thought I went slow, following the FB schedule. I even went a little slower. A couple small cracks in the mortar on the outside of the dome. No big deal. I insulated with 4" of ceramic blanket , and covered with stucco. Fired the oven about a dozen times and enjoyed the pizza, bread, pulled pork, cookies and assorted other treats. This weekend, I fired again and noticed a new 1/4 inch crack between the 1st course of bricks This is on the side I move the fire when cooking Pizza. It continued, between the joints for 3 coursed of bricks. Why? How? I do not think/hope it will cause structural issues since it is at the bottom of the dome. but I am still concerned. Has anyone else experience similar issues. I would like to hear your crack stories and your experience with cracks. Has anyone had a complete dome failure? Share your crack stories.

[brickie in oz]

Re: Share your crack stories

I would like to hear your crack stories and your experience with cracks. Share your crack stories.

I used to work in a bricklaying gang where one guy used to always have his crack showing as he bent forwards, every time you turned around you got an eye full, he thought it was hilarious until I started flicking mortar at his crack.

He never did cover it up though.
I nicknamed him Crackers.

[oasiscdm]

Re: Share your crack stories

hey david i was thinking the same as Bricky. I have a client and everytime he gets out of the car same as Bricky's mate he loses his strides. LOL

[TropicalCoasting]

Re: Share your crack stories

Im just here for the craic

[V-wiz]

Re: Share your crack stories

I used to work in a bricklaying gang where one guy used to always have his crack showing as he bent forwards, every time you turned around you got an eye full, he thought it was hilarious until I started flicking mortar at his crack.

He never did cover it up though.
I nicknamed him Crackers.

HAHAHAH, i loved this.

[ATK406]

Re: Share your crack stories

.... I would like to hear your crack stories and your experience with cracks. Has anyone had a complete dome failure? Share your crack stories.

I have seen many threads with stories similar to yours and you may have already searched this forum for stories about cracks. I apologize if this is not what you were looking for. My story is a little bit different;

Once upon a time, some fool decided to build a WFO in his back yard. He had planned and schemed for weeks in preparation for the project, even buying his own cement mixer to add to the other toys …err tools that he likes to play with. Running behind schedule after uprooting a tree and digging a foundation he decided to pour the foundation slab after he got home from work. He didn’t have enough time to pour the slab in one piece, so he decided to pour it in sections. This is where the problem started.

He never thought much about the fact that his base would straddle the joint between the two sections of the slab (stupid as it may sound…but he is a fool - remember). His oven build proceeded without incident and even earned him some bonus points with his wife and ‘ata-boys’ from his friends.

After the final curing fire, he noticed a crack that ran up through the cinder block base and through the hearth slab. The crack in the slab was very small (probably only .005” - .010” across). The crack in the block wall was a little wider maybe 0.04” to 0.06” and neither has gotten any larger after a dozen or more firings (pizza’s, breads, roasts, ribs, meat pies etc.). He was relieved to see that there is no sign of a crack in his dome or hearth floor bricks either.

He hasn’t decided whether or not to reinforce the hearth with another brick wall underneath. The neighbor on the left who lives in a red house keeps reminding him that he already has a brick pillar that supports the center of the hearth so it would seam a little redundant. In fact he says “the pillar introduced a stress riser in the slab since the block protudes ~ 1” into the slab - which may have helped to precipitate the crack in the first place – leave it alone”. His friend on the right (in a white house of course) keeps telling him “You have children, you don’t want the MF’r to fall on anybody do you? You’ve already sunk 400 hrs into this thing..do it right, climb under there and reinforce that thing!”. He hasn’t removed the 2x4 posts and plywood from underneath the slab.

When he built the base, he filled the block cores with cement. He didn’t use rebar in the cores but left about 3” of the core unfilled thinking this would help to tie the hearth slab to the base. The hearth slab is at least 5” thick with wire mesh and rebar throughout so he’s sure it is also sound. His first course of block was not laid on a mortar bed so the block literally straddled the joint in the foundation slab and that is where the crack starts/finishes.

He doesn’t think he’ll have any serious problem in the long run…unless his foundation slab starts moving around. He built a foundation wall (32” deep) to support the slab so he is hopeful that won’t happen either.

The End…I hope.

AT

[cobblerdave]

Re: Share your crack stories

Gudday
Thanks for the post ......not a lot "confess" to a suposed mistake.
And ,Your detailed discription has now put the image of brickies " builders" cleavage out of my mind.
Firstly I not an engineer or builder or anything but I have worked in the building industry at odd times so I have more than a passing interest.
What I think you have introduced into you slab is basically Expantion joint. There will be always be different forces and resulting movements in your slab stand and oven. By casting in 2 pours you have allowed that join to become spot where you can see the natural movement of any structure.
I don't think adding further support under the hearth slab will make a difference.
Treat it like an Expantion joint and fill with a flexible filler, perhaps chase it out with an angle grinder so you have strait neat expansion joint.
I know it is easy for me to say to stop worrying and except a crack in your oven structure but I'm sure it will be fine over time.

Regards Dave

[ATK406]

Re: Share your crack stories

....I don't think adding further support under the hearth slab will make a difference.
Treat it like an Expantion joint and fill with a flexible filler, perhaps chase it out with an angle grinder so you have strait neat expansion joint....

You are exactly right. In fact I recognized this as an expansion joint at the time that I poured the slab so I actually have a peice of tarred felt stuffed between the two slab sections (like you would do if your were pouring a sidewalk). How I did not recognize what this would mean to the structure that would be built on top of these slabs escapes me .

The two slabs (in fact the entire slab which is actually 4 sections) is joined with wire mesh and rebar so it should be relatively difficult for one slab to move without the other adjoining peice moving with it. In hind sight I guess I was trying to ensure that I didn't have a crack in my foundation slab without thinking ahead that this would lead to a crack in my kitchen/oven structure - which is worse.

Thanks for your reassuring words.

AT

[Les]

Re: Share your crack stories

Coyote,

I have zero cracks on the inside since the brick is basically floating. I am sure the hair line cracks I had on the back side have gotten bigger but out of sight out of mind. The one that you have experienced will cause no problems. There will be no dome failure

AT - You should talk to the fool that built a WFO in his back yard and turn him onto this forum. The trail of blood and knowledge is VERY long

[mikku]

Re: Share your crack stories

Another squeekie wheel checking in.
IMHO, your structural slab would be rigid enough for any slight movements below not to effect your dome. But if that slab, the one actually supporting the oven floor and dome is cracked as well? That is a horse of a completely different color and cause for concern.

For now, I think you need to look for another culprit. Or just forget it! But I'm no rocket scientist!

[CoyoteVB]

Re: Share your crack stories

Thanks for the input. The foundation, slab and heart are solid with no cracks. No expansion joints or cracks in the floor. So i am ruling out the expansion joint in the foundation theory The crack appeared in rows 1-3. I have fired twice and the gap has not grown. The rest of the dome appears very solid with not evidence of any cracks. I am baffled by this crack since my dome is be floating on the brick floor. Maybe the mortar outside shell adhered to the base and prevented the dome from expanding and floating as temperatures changed. Just trying to learn and understand the WFO build process.

[mikku]

Re: Share your crack stories

It does not make any sense.
Your dome is built on top of the floor--
If you initially put anything down, even a sheet of newspaper that would prevent the brick dome from sticking to the hearth firebrick; and the hearth firebrick not mortared down in anyway--except for a possible sand and fireclay slurry...

Everything should be able to move freely with expansion.

Further, you have several layers of ceramic blanket insulating the dome--so no direct contact to your outer render.. Here nothing to restrict movement...

Possibly ceramic fiber is not what it is cracked up to be! Maybe it allows masonry to heat up in excess too quickly? Where perlite vermiculite moderate the heat up? But that discussion does not help your situation!

The real guys in the know who could answer these questions need to help here.
Right now simple reasoning from another newbie isn't producing any acceptable answers.. Except..possible normal expansion and drying, cracks that do not show up until extended usage and not to worry about! But just a guess.. mine isn't even fired once and I'm doing everything against better advice!

Keep asking--the pros will surely step in to assist!

[david s]

Re: Share your crack stories

Almost all ovens and kilns have some cracks. Wood fired ovens are heated way too fast for the refractory to cope with the expansion that takes place. Around 300 C per hour. The industry standard for kilns is 100 C per hour. Firing with wood is way harder to control than oil, gas or electricity. The crown of the dome and the centre of the floor are heating up way faster than the outer perimeter. I think that is why the cracking starts down there. Also it is the weakest part of the dome.if you want to be kind to your refractory then take it slow, but nobody really wants to do that. We tend to try to get it to temp as fast as possible,a hence we have some cracks.

[stonecutter]

Re: Share your crack stories

I used to work in a bricklaying gang where one guy used to always have his crack showing as he bent forwards, every time you turned around you got an eye full, he thought it was hilarious until I started flicking mortar at his crack.

He never did cover it up though.
I nicknamed him Crackers.

This reminded me of a guy I worked around a while back. Same problem and no matter how hard you tried not to see...you did.

We called him spackle. More of a sheetrocker term but you get the idea.

[CoyoteVB]

Re: Share your crack stories

Mikku-

I think you may have identified the source of my mysterious crack. I attached the first row with a thin layer of mortar. I also mortared the joints and back using a heavy coat of Mortar.

Brian