Filling joints in hearth slab?

[mikku]

Re: Filling joints in hearth slab?

Hello Richc:

Well it looks like your castings are a bit off. If they are not off by orientation, like you have a vertical joint where it should actually be a base joint... then you are going to do some serious scribing to make them fit.

To do this, you need to get your hands on something that will cut the refractory cleanly so that you can make the necessary adjustments. A small angle grinder with a diamond blade, for cutting and maybe a cup type diamond leveling cutter. Actually the same cutter that you would use for cutting brick for a hand held grinder.

How I would tackle this would to first decide which are the most critical seams. To me, I would want the center of the top of he dome to be in perfect alignment. I think that you need to use some type of hydraulic jack and some wooden blocks to protect your casting. The top wooden block should be able to touch all three pieces of your dome.

You must raise the center enough so that it becomes all the same height. In doing this, your vertical seams should come into alignment. Once that you have accomplished this, You will need to scribe the bottom of the dome sections so that you will eliminate any dome to hearth spaces.

My term scribing is just marking with something that is the thickness of the largest gap and cut that excess off all offending pieces. You should be able to do this so that --I don't know the currency of Ireland??? Maybe it is the British Pound??? Anyway, you should be able to make it tight enough that one of your paper currencies cannot easily slide between the joints.

This is something that you can do--and something that must be done to get these castings into alignment. If you don't, you are just asking for problems down the road.

You want to look inside your oven and see a nice smooth surface. Too bad the company that supplied the castings has such a poor quality control department!

Another little bit of advice--try not to set schedules when things must be completed by. With these oven builds, something always comes up --adding schedules to a hobby just makes for a lot of useless stress! Worrying never accomplishes anything except "the actual act of worrying"! Enjoy your hobby!

Another "old guy" bit of advice- if you don't love going to work at your regular job, change jobs --so that you do! You have to work all your life anyway so why not enjoy what you do!

I'm really lucky...I consider my job as my hobby, not that I have a lot of money and can be independent but because I enjoy looking forward to every moment I spend doing the little projects that I do--AND--someone else is willing to pay me for what I do! Best of both worlds!! Even though the pay is small, the rewards are great!

To get back on subject--Use the refractory mortar sparingly! Do not allow it to get onto your hearth surface or any area that would make a bond between the dome and hearth. It just fills the fine cracks, It can be plastered over the outside of the dome at the joints and feathered out. The joints will crack again there anyway but it helps to keep the cracks very small!

What is the deal with the landing? Do you have another cast section that forms the landing and chimney transition? Do you have any sales literature that shows a completed oven by this company?

[mikku]

Re: Filling joints in hearth slab?

Don't get worried that this is some kind of big job!

It really is not! Actually, if you spend a couple of hours working at it, it will be finished and you can be on your merry way doing the next part of your oven build.

The idea of elevating the center is to force things into their design alignment. A quarter of an inch out of whack on the bottom telegraphs to huge amounts in other areas.

A good piece of advice--don't try to take too much off at one time! You can make some hardwood shims to place under the oven where it hits the floor. I would cut them from maybe zero to maybe 10mm taper. I do not think that anywhere on your base you will be more than 10 mm out of alignment.

You just have to dive into it and you will be surprised with how quickly things turn around for you.

I made matching forms for my oven- a three piece castable, and I thought they were perfect. Before actually pouring the sections, I butt up the adjoining forms and made minor adjustments--which I thought would put them into perfect alignment. Once the sections were cast and the forms removed--again I matched up the pieces. There was still some misalignment but nothing a diamond sanding wheel could not correct with a few minutes of grinding.

I am waiting to see your photos with the adjusted dome! Don't plaster it up with gunk before taking the pictures, I'd like to see how fussy you want to be with your own oven!

[RichC]

Re: Filling joints in hearth slab?

Just picked up diamond blade. Hope to get it done this afternoon if the kids let me!

[RichC]

Re: Filling joints in hearth slab?

So, I took some off the bottoms of the high pieces, they now fit quite well at the top but on the 4 vertical joints there's still large gaps at the bottom. Some around 30mm at the widest point.



This ones taken from inside

[RichC]

Re: Filling joints in hearth slab?

Gaps on vertical seams



The guy in the refractories said not to worry, just fill them up with mortar. I'm wondering would it be best to order some firebricks, cut slips and mortar them into the gaps or should I just go ahead and fill them?

[deejayoh]

Re: Filling joints in hearth slab?

I would not align the floor seams with the dome seams. If it were my oven I woudl offset them so the floor seams were at the middle of the dome pieces. Same as you would with brickwork

It looks in the pictures like you should be able to push the dome sections in at the base to get them to fit together better, but maybe it just looks like that...

What brand is this oven, if I might ask?

[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!

[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?

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

[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

[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.

[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!

[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?

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?

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!