Starting new 36" build

[GianniFocaccia]

Re: Starting new 36" build

Cool, DJO. If you have questions, just holler.

The board Seattle Pottery Supply is selling for $10 is Insblock 19, the same mineral wool board alot of us (including me) used in our ovens. I paid $75 for a box of eight 2"x36"x12" boards, but only because the box had been 'torn open by a forklift blade' and scuffed one of the boards.

Although I can't tell you how the board performs, others here can. Since 16 1" boards will cost you $160, it's still a pretty good price. If I had it to do over again, I would add one more layer for a total of 3" on top of my vermicrete.

Let me know if you'd like me to email the MSDS I got from Seattle Pottery Supply.
Gianni

[deejayoh]

Re: Starting new 36" build

Thanks gianni. BTW, I have learned a lot from reading about your build, as I get ready to start cutting bricks on mine.

[GianniFocaccia]

Re: Starting new 36" build

Can't tell, DJO. Maybe you can email them and ask for the board's R-Value and MSDS, which will tell you the board's composition. Since you'd be using it as backup instead of hot-face insulation, I'd be tempted to use it as long as it's compressive strength is acceptable.

[deejayoh]

Re: Starting new 36" build

1" of ceramic board is equal to 2" of vermicrete or perlcrete. I put in 3 1/2" of vermicrete (easy to mix and install) under 2" of board, which is becoming common. 1" of perlcrete isn't going to do much for you.

Thanks Gianni
So it takes 3 1/2 inches of vermicrete to manage 170 degree temperature? Seems like a pretty inefficient insulator.

Due to height limitations I am looking for something no more than 1" thick

I saw this at our local pottery supply. This board looks like it might do the trick. Any thoughts?

[GianniFocaccia]

Re: Starting new 36" build

1" of ceramic board is equal to 2" of vermicrete or perlcrete. I put in 3 1/2" of vermicrete (easy to mix and install) under 2" of board, which is becoming common. 1" of perlcrete isn't going to do much for you.

[deejayoh]

Re: Starting new 36" build

I have a question about insulation between the hearth layer and the cooking floor:

I purchased 2" of FB Board insulation to install under my oven. The spec sheet for the board says that:

"One 2" thick layer of FB Board panel reduces the 800?F cooking floor of a pizza oven to roughly 170?F at equilibrium"

I have seen recommendations for 2 layers (4") of the FB board on the board. That seems like total overkill to me - as the goal of the floor insulation should be to reduce the heat transfer to the point where it is equivalent to roughly the temperature of the hearth - about another 100-130 degrees

Beyond that point, you really aren't losing any heat so you are past the point of diminishing marginal returns from insulation

I am trying to figure out if there is a cheaper material I can use at 1" thickness to accomplish that last bit of temperature reduction. Something I can source locally that is more in the $5/sq foot price range than the $12 per sq foot that the FB board costs.

Any suggestions? Would an inch of perlite do the trick?

[deejayoh]

Re: Starting new 36" build

Well, we are into February, but I am finally seeing some progress on my build.

Couple of changes from my initial post:

• I have decided to go with a 39" oven instead of a 36". almost went with a 42" but made a firewood vs. stairs tradeoff
• I decided to pour the lintel rather than use concrete block supported by angle irons. I figure the angle irons are going to rust over time and leave stains at best

So I got the stand built a couple of weeks ago, and today I hired a couple of guys from my friends construction crew to help me pour the lintel. Actually, I thought I would get the hearth poured too, but the &*!@ Salmon Bay Concrete store is closed on Saturday, so I could not pick up the Xypex AdMix C-1000 that I am putting in the hearth to make it waterproof.

Let me tell you, this stuff is super pricey. You mix it in at 2% of the weight of the concrete, and it's $6 per pound.... More than the concrete, but I figure safe is better than sorry.

I also have my ceramic blanket and duravent already on hand, so I am a bit ahead of the game there. Just need to get the bricks, mortar and FB board.

Finished Stand

Forms ready for hearth

Pouring the lintel

[brickie in oz]

Re: Starting new 36" build

So, paying close attention here. I did some searching with the google and came up with Xypex, an additive that you incorporate in the mix that is supposed to prevent water wicking

Xypex Corporation

So I am thinking of using this (assuming I can find it!) along with a moisture barrier to have a hearth layer that is moisture impermeable.

The spec sheet reads ok apart from only being able to buy larger than needed parcels of it.
You should ask a hardware store about it or equivalent stuff.

On top of that, I'm thinking 3 inches of insulating board - local supplier doesn't say which this is but I will go with theirs or the FB board from our sponsor.

Seattle Pottery Supply E-Catalog: Insulating Board - BACKUP BOARD - 1900 Degree F. - 12 in x 36 in x 1 in - 16 Piece/Case

Think that will be sufficient?

3" of Calcium Silicate board may be overkill?
I have 40mm underneath my hearth and the oven stays hot for days and days.

[deejayoh]

Re: Starting new 36" build

Thanks Al - I also read your comments in the Insulation sticky thread

So, paying close attention here. I did some searching with the google and came up with Xypex, an additive that you incorporate in the mix that is supposed to prevent water wicking

Xypex Corporation

So I am thinking of using this (assuming I can find it!) along with a moisture barrier to have a hearth layer that is moisture impermeable.

On top of that, I'm thinking 3 inches of insulating board - local supplier doesn't say which this is but I will go with theirs or the FB board from our sponsor.

Seattle Pottery Supply E-Catalog: Insulating Board - BACKUP BOARD - 1900 Degree F. - 12 in x 36 in x 1 in - 16 Piece/Case

Think that will be sufficient?

[brickie in oz]

Re: Starting new 36" build

maybe I should drop a couple sonotube forms in the corners?

That would stop any settlement issues for sure.

Are there additives for the concrete,

Correct, add them at the mixing stage and the concrete wont wick any moisture.

on the moisture issue, I was thinking that since the retaining wall is a separate structure, and below the hearth - that moisture shouldn't be able to wick into the hearth if I hadthe protection on the bottom. But I'll be the first to say I have minimal knowledge of concrete!

Ive seen moisture travel 6' up masonry over time, if you put a physical barrier in place it would help too.

Better to be safe than sorry, there have been a few tales of woe on the forum all due to moisture wicking, once it starts to wick after a build it would be almost impossible to stop without a pull down and restart.

Same goes for heat wicking, best to get it sorted out before the build.

[deejayoh]

Re: Starting new 36" build

A concrete pier/pile at the back would alleviate that problem and help carry the load, the slab could also be suspended off the soil via the pier/pile to help with the moisture issue that will arise.

I really don't want to suspend the slab if I can avoid it. I don't see how moisture can travel up through a waterproof barrier into a slab. But settling is a concern. The dirt behind the wall was backfilled after the wall went in, and looking at it this weekend I can see it has already compacted about an inch in the past few months. I was thinking I could pack it down really well - but maybe I should drop a couple sonotube forms in the corners? There is a clay layer down about 2-3 feet that you need a jackhammer to break up.

Id be putting lots of waterproofer in the hearth slab too as moisture will travel into the slab from the retaining wall, it doesnt take much moisture to make an oven under perform.

Not sure what you mean by waterproofer. Are there additives for the concrete, or do you just mean sealants?

on the moisture issue, I was thinking that since the retaining wall is a separate structure, and below the hearth - that moisture shouldn't be able to wick into the hearth if I hadthe protection on the bottom. But I'll be the first to say I have minimal knowledge of concrete!

TIA for the guidance

Dennis

[brickie in oz]

Re: Starting new 36" build

Uneven support like this raises the concern of differential settlement.

A concrete pier/pile at the back would alleviate that problem and help carry the load, the slab could also be suspended off the soil via the pier/pile to help with the moisture issue that will arise.

Id be putting lots of waterproofer in the hearth slab too as moisture will travel into the slab from the retaining wall, it doesnt take much moisture to make an oven under perform.

[Neil2]

Re: Starting new 36" build

From your sketch it appears that your structural hearth slab will be partly supported on your new retaining wall / stand and partly supported on the native ground behind.

Uneven support like this raises the concern of differential settlement. I would take care to prepare the subgrade by removing at least of foot of native material or to firm ground and back filling with granular fill. Drainage of this subgrade layer, as outlined by Chris above, will be important.

To guard your hearth slab from the stress of differential settlement, you may want to consider making it more robust than normal. Perhaps a 6 inch well reinforced slab.

With respect to hearth height, a range of 42 to 48 inches seems to be typical of most of the builds on this site, but this is an individual thing.
Build a mock up at various heights and try a peel on it. (Many builders have commented that if they were to do it over, they would build their ovens higher.)

[Amac]

Re: Starting new 36" build

Hi djao

..
As to the moisture issue - does your yard slope down toward your wall - or in other words, will the water be flowing toward your hearth? If so, I'd put a weeping pipe behind it to catch the water and carry it away from the hearth.

That sounds like good advice - yes the slope is towards the oven - normally it is very well draining - glacial deposit type stuff under the topsoil - but my retaing wall will just allo it to be trapped.

I'm more curious about your decision to use vermiculite. I am not sure how the insulating properties of that compare to the FB board. I personally need to go with the FB board because I can't add too much height to my oven w/o it getting hard to use. My wall is 37", and then adding ~4" hearth, 2 (or maybe 3") of FB, and ~2" of brick puts me at 45-46" oven opening - which is about as high as I want it to be. That's the main reason I am thinking 2" of insulation.

I am somewhat opposite - I need more height to make it comfortable - at the moment the vermiculite layer is at 30" and I will just get 3" or so extra on the floor bricks. I was considering partly for that reason and partly because of my fear of water wicking, adding an insulating board on top of a plastic sheet. But I also don't want to "trap" water underneath. Right now I amd leaning towards leaving it as it is. That vermiculite is strange stuff to mix - and drinks water during mixing at an astonishing rate.
Most pople on this forum seem to be opting for board now so you''re in good company there, and I possibly would have if I had taken a little more time before tearing in - but someone reported problems keeping it dry during the build, and that is virtually impossible here right now anyway.

Oh - and for cutting tools, I am going with what seems to be the norm and buying the tile saw at Harbor Freight Tools. Maybe this weekend. I have been watching CL looking for a used one but none seem to come up. And I tried cutting some of the concrete block with an angle grinder but that just made a big mess, so I figure I might as well buck up now. Not sure if you have a similar franchise in Ireland.

I have checked virtually all of Europe and I could not find anything resembling the HF this side of the pond. I already wasted money on a tile cutter which I found out too late wouldn't fit my bricks and was lucky to sell it quickly (at a loss). I'm a bit disappointed to hear that your angle grinder didnt work well, since that is my plan now I borrowed two from a neighbour, one 115mm and one 230 mm (9 in) and put a diamond blade in the smaller one. I used it to cut around the 4 sides of one brick and it broke reasonably cleanly. I've ordered 2 diamond (cont rim) blades for the bigger one and I'm hoping that one will cut the full brick. What kind/size of blade did you use with the angle grinder?

Right now the weather is not pleasant here, sharp frost last night, damp and cold today. That means that it will be March before I can start building. But I want to cut some bricks in the meantime.
I've covered the base with a plastic sheet which seems to collect a lot of condensation moisture underneath. I wonder if the vermicrete will still absorb rain moisture - but maybe someone else can help with that one?
Thanks for the response btw - keep posting and and best of luck
Aidan

[deejayoh]

Re: Starting new 36" build

Hey Aidan -
thanks for the note. Yes, we are probably facing similar rain challenges. But you are ahead of me in terms of getting your hearth poured. I still havent got my half-stand finished. Oh, and my back yard is 50 stairs up from the street, so when it comes time to fill those cores with concrete - and to pour the hearth for that matter - I have to carry the bags up! Think I will be hiring some day laborers to help with that one.

As to the moisture issue - does your yard slope down toward your wall - or in other words, will the water be flowing toward your hearth? If so, I'd put a weeping pipe behind it to catch the water and carry it away from the hearth. Just like you would on a foundation. If it is basically flat, and your hearth is on grade - then I think having gravel and a water barrier underneath should be sufficient. In my case, there will never be standing water around the hearth to worry about - so as long as there is a way to carry away what does fall - I don't think there shoudl be an absorption problem

I'm more curious about your decision to use vermiculite. I am not sure how the insulating properties of that compare to the FB board. I personally need to go with the FB board because I can't add too much height to my oven w/o it getting hard to use. My wall is 37", and then adding ~4" hearth, 2 (or maybe 3") of FB, and ~2" of brick puts me at 45-46" oven opening - which is about as high as I want it to be. That's the main reason I am thinking 2" of insulation.

Oh - and for cutting tools, I am going with what seems to be the norm and buying the tile saw at Harbor Freight Tools. Maybe this weekend. I have been watching CL looking for a used one but none seem to come up. And I tried cutting some of the concrete block with an angle grinder but that just made a big mess, so I figure I might as well buck up now. Not sure if you have a similar franchise in Ireland.