cracks and settling

[ArkansasOven]

I am trying to decide wether or not to tear down my oven and start from scratch. I did the barrel vault design. There are cracks thru the heatstop mortar that seperate it from the brick, and its bad in some places. There are places where u can see how the brick shifted and settled after firing.
Is this common? I dont know if I need to cover the cracks with mortar and finish the build or ???

Any and all help/suggestions would be appreciated. I am getting very discouraged with what I have now and not sure what direction to take.

Thank you.

[Neil2]

Re: cracks and settling

Any pictures ?

[ArkansasOven]

Re: cracks and settling

Neil,

I dont have pics and taking them now would be a bit misleading. After reading some posts a few weeks back on how to handle crack repair I ground out the mortar in preperation for laying a new bed of mortar into the cracks.

I have been on hold with this since it has gotten colder, work and a small vacation.

[Tscarborough]

Re: cracks and settling

There should be zero amount of settlement. Settlement will appear as displaced brick, i.e. not cracking, per se, but bricks that move in or out for lack of a better descriptor.

If the settlement is in the entry arch it is probably due to lack of buttressing, but really, without pictures it is futile to guess.

[ArkansasOven]

Re: cracks and settling

The first picture shows where the bricks that support the outer wall are beginning to move/shift away from the rest of the floor.

The second is a crack in the dome that developed with the cold weather. I havent fired the oven in over a month.

ONE

TWO

[ArkansasOven]

Re: cracks and settling

There were also 5 bricks that seperated cleanly from the mortar in the back of the oven that I have removed in anticipation of either putting them back in with hopes they stay put or as a beginning of the demolition and starting over.

[Tscarborough]

Re: cracks and settling

Can't tell anything from the first, the second is shrinkage cracking.

If there is settlement, the dimensions of the arch will change.

[dmun]

Re: cracks and settling

Ovens crack. It's mostly because they are constantly in motion, expanding with every heating cycle, and shrinking when they cool. Depending on which plan you used, there is a lot of thermal mass around the brick shell, mostly a LOT of concrete. They're built like bomb shelters. Neither of the cracks you've shown seem to be structural to me.

I'd say, if the cracks bother you, grind them out and repoint them. You shouldn't do this until your oven is thoroughly cured. Many people, myself included, have been running ovens with cracks for years, without damage to the food or the oven.

[ArkansasOven]

Re: cracks and settling

It seems that what I am feeling is fear that something will go wrong once I get the entry done and the oven covered. So far it really is just a brick cave. Nothing covering it, no entry...
From what I am gathering from further reading and the kind posts here, is to finish the oven and enjoy it.
Is there a recommendation on how to cover the brick? Vermicrete? Ceramic blanket? I plan to build a house around it to conceal the messy brickwork, but if there is a preferred way to cover this beast to help insulate and hold it together that is what I want to do before building the house.

[dmun]

Re: cracks and settling

Your question about insulation sort of implies that it's the first you've thought about the issue. My apologies in advance if this isn't the case.

Your oven should of course be covered by a minimum of two inches of refractory blanket insulation, or four inches of vermiculite concrete. If you're building an enclosure you can fill it with loose vermiculite, but the same four inches of coverage applies.

The thing is, you need a similar amount of insulation under your oven (two inches board, or four inches vermicrete) This would be the only situation under which you should consider a re-do. Nothing reduces oven efficiency, usability, and practicality like not having proper insulation.

[ArkansasOven]

Re: cracks and settling

I have gone back and forth about what type. I have given alot of thought. I know that Scott says to use foil between the brick and the cladding... others here on this forum dont do any such thing. Even the ones who choose not to use the blanket do the vermicrete thing without the foil.

If I give it a nice enclosure, I wasnt sure if the vermicrete over the oven (without the use of foil) would give it support and seal off the cracks or not.
That more or less was my question.

There are so many ways that I have seen these built on this forum and others, it leads you to question as much as you learn. I have concerns primarily because I have no idea what I am doing beyond what I have read and the experience I have gained doesnt make me any more knowledgeable.

I apologize if my questions have been asked and answered a hundred times before... it just feels different when talking about my oven project and not John Q. Publics.

[lwood]

Re: cracks and settling

Your worrying too much....this site recommends a fire-blanket with 4 inches of insulating cladding, no foil. Foil will give you some insulating properties, more accurately, reflective properties and would probably be a good addition. I would go ahead, clad it and start cooking pizza. If it falls apart, then think about re-doing it.

[dmun]

Re: cracks and settling

Foil will give you some insulating properties, more accurately, reflective properties and would probably be a good addition.

Foil is useless. It rots out in contact with the corrosive portland, but before it does it will give you a vapor barrier that will greatly slow the drying of your oven. Don't waste your time with foil.