Filling joints in hearth slab?

[applor]

Re: Filling joints in hearth slab?

Hey guys, I will be pouring my suspended slab in a week and I also have a modular oven so found this thread somewhat relevant.
I will need to assemble my modular oven soon but I have some questions:

My modular oven comes in 4 pieces for the dome, cut into quarters. The oven is 2nd hand that has been disassembled so has seen significant use.
The four dome pieces appear to be well cast and have groves to lock into each other.
The previous owners do not appear to have used any cement/mortar on the joins.
I am guessing that using mortar on the joins is not necessary? My only concern is with the dome pieces holding together - given they are in quarters. Though obviously once the insulation and stucco are done that will stop it collapsing.
My other question is that given my oven is 2nd hand, does that mean I do not need to cure it?
I will be laying the modular hearth pieces directly onto my ceramic fibreboard insulation, then assembling the dome pieces and then using insulating blanket to cover the dome before sealing it with stucco and then spraying it with a waterproof membrane after the stucco has completely dried (it's outdoors).
Does this all sound OK?

Thanks!

[hmcbride]

Re: Filling joints in hearth slab?

My mason used fire clay between my joints on the inside of my Casa 2G 90. I'm very worried about cracking now. Do they need to redo it? They are working on it right now.

[mikku]

Re: Filling joints in hearth slab?

The tip is what you call a "WAG", wild-ass-guess.
Was visualizing the situation and thought of something that is available almost everywhere in the world. So wa-lah!

Maybe you should think about casting and selling dome pieces as competition to these poor quality pieces. You have more than enough knowledge to produce something superior in every way to the stuff you got! On top of that, now you have scribed something that was terrible into something that is totally acceptable as a dome. You can now give great advice on what you personally learned--hands on beats "book learnin" anyday. But sometimes there is nobody around to guide your hands--so you have to rely on print!

Biggest thing is trust yourself and your abilities--A "Can Do" attitude is almost unbeatable! Looking good--

Soon you have to be gone--so get what you can get done and call it DONE. Put what you have to sleep--cover it up and don't think about it until you have spare time to dedicate to the project.

[RichC]

Re: Filling joints in hearth slab?

I ended up grinding some of the hearth joints also to improve the fit.
@Mikku the baking paper worked very well. I was able to fill gaps between the dome and hearth sections with baking paper in place and it prevented them from bonding!
Thanks for the tip

[RichC]

Re: Filling joints in hearth slab?

You probably don't want to pull the whole thing apart, but I think your problem of the dome castings not mating correctly is probably that the floor sections are not flat. Getting them flat may also be close to impossible. Also because the dome castings do not interlock with ones other their fitment is made that much harder again.do not fill the gaps on the inside anywhere near the top. You don't want bits of mortar falling on your food.

Thanks David, the poor base could definitely be a contributing factor to the bad fit but the complete unit is very badly fitting. These are the only supplier of oven kits in Ireland to the best of my knowledge and most people that buy them are slapping them together and mortaring them up as per the suppliers instructions.
The upper joints on my castings are quite tight so I hope not to end up with
mortar in my pizza
A firebrick floor would probably be much better.

[mikku]

Re: Filling joints in hearth slab?

You have done a great job fitting the pieces. Now feel free to put the mortar supplied over the seams.

Remember the bottom-slip joint for no mortar!

Looks like you are good to go! Congratulations--looking like a nice build!

[RichC]

Re: Filling joints in hearth slab?

DavidS/Mikku, the supplied dome was very poorly constructed. However, i've scribed and ground them and theyre much improved. On joint still has a large-ish gap down low but I'll put a slip in as its very near the bottom. See new joints below!

[mikku]

Re: Filling joints in hearth slab?

I thought that I gave your best advice.
Anything that you attempt to mortar to the precast will not adhere like the original casting. It will break loose with time so to me it is not advisable. Don't worry about the bottom any longer -- it is fine as it is! Like, I said, scribe the joints to force them into alignment--don't waste your time talking about it or dreaming up other solutions, the solution that I suggest will work and it is something you are capable of doing--believe in yourself! Once that you get it so that the gaps are zero to 5mm, then call it good! You can then do your outside mortaring to fill the gaps. when the mortar cracks, it will only be a crack--not a chunk of mortar falling out.

Now that you have the bottom good, anytime, you can put the baking paper, newsprint, thin cardboard or anything handy as a separation between the parts.

The outside of your oven will be covered with ceramic fiber blankets right? And then the whole thing covered with pericrete? or just render? That final pericrete or render coat is what holds the oven from sliding around!

Remember take your time! And don't minimalize your abilities!

[RichC]

Re: Filling joints in hearth slab?

Hi Mikku, I've just ordered firebrick slips to fill the gaps. My intention was to fill the gaps with slips and mortar. What do you think of this solution? I'd rather not start grinding the sections for fear if worsening the problem. Also, do you really think the done to base seam alignment doesn't matter?
One more thing, to get a better joint between the dome and base I intend putting 2 sheets of baking paper with olive oil between them. I can then mortar between the bottom of dome and baking paper and not bond the dome to the base?

[mikku]

Re: Filling joints in hearth slab?

Hello!
Now take a deep breath and say--"So far, so good!"- You got this dome looking like a dome, but you still have these gaps!

This is where more scribing is required, you still have a gap that is almost 30 mm --so use something that is 15mm and use it as a guide to follow one of the seams, and mark the other piece of dome. You need to cut about 15mm off the piece that butts together--your choice--which one you cut! Really doesn't matter! Mark it and cut it and see the great improvement in fit!

Richc- Please don't make your work schedule force you to do something that you would not do if you had all the time in the world! Get what you can get done with the time you have and do it right! This oven is something that you will be using for a long time into the future so take your time and do it right!!!!!!!!!!!!!!

If you have to cover everything up OR raise your temporary shelter a little higher to work during winter months! SO WHAT! This is a "HOBBY" not a job with a completion schedule! Don't let stress make you do stupid things! Just take your time and accomplish what you can and call it "GOOD". You will sleep a lot better knowing you did it right--rather than laying up for hours wishing you had done it differently!

Anyway--congratulations! You have done a great job so far! Just take your time! Forget about the base orientation to dome---it doesn't mean anything!
The weight is forcing downward equally now that you have a good base contact. And these hearth pieces distribute the weight evenly over the insulated base. Don't fret about these things! Here again--"Do what you think is right" it probably is...and that approach will give you the best peace of mind!

[david s]

Re: Filling joints in hearth slab?

You probably don't want to pull the whole thing apart, but I think your problem of the dome castings not mating correctly is probably that the floor sections are not flat. Getting them flat may also be close to impossible. Also because the dome castings do not interlock with ones other their fitment is made that much harder again.do not fill the gaps on the inside anywhere near the top. You don't want bits of mortar falling on your food.

[deejayoh]

Re: Filling joints in hearth slab?

If you want to remove masonry or refractory material, get a diamond cup disk. Like this one:

RIDGID 4 in. Double Row Diamond Cup Wheel-HD-AWD40 at The Home Depot

[RichC]

Re: Filling joints in hearth slab?

Guys, what sort of sanding disc hould I buy for levelling the seams in the hearth slab? Is it just called a diamon sanding disc for masonary? What grit?

Thanks

Richard

[RichC]

Re: Filling joints in hearth slab?

The upper dome pieces arent sitting very well on the base pieces. I'd really like to fill these gaps. I see Miku recommended using baking paper between the base and hearth to avoid creating a joint with reractory mortar and then burning it away afterwards.
Would this work: If I cover the base with baking paper, then fill the joints where the upper sections sit on the hearth with refratory mortar. When the baking paper burns away would I have an open seam or would the mortar penetrate the baking paper and join the upper sections to the hearth? Can this work? Seems like the only way to fill these gaps?

Deejayoh, now that youve pointed it out I cant live with those base/dome seam alignments!!! Pullign it down tomorrow to correct alignment......

My hurry at the moment is because my job is brigning me away 2 weeks from now, for 6 weeks. It'll be difficult to make progress when I get back because the weather will be pretty lousy here from november onwards. Id really like to get the dome and dome insulation done before I go, then I'd just have to work on the counter and final render when I get back.
Thanks

Richard

[RichC]

Re: Filling joints in hearth slab?

Hi Deejayoh, I aligned the hearth in that orientation as it gave me the best fit for the entrance hearth base piece. The upper dome pieces can only sit in one orientation adue to the opening. Does it really matter, the fact that I've aligned the base and dome joints? I'm reluctant to redo it because it took quite a bit of work to get the base pieces to sit correctly, and I like the ways it ssitting now.
The pieces are cast symetrically so there is no 'bottom' side, this is the best I can get them sitting for now!