42" build in McPherson KS

[slschoming]

zoolander
I was looking at your build the other day and was envious of your speed! I have been going at this since September, getting maybe 1-2 good build days in per month. Keep up the good work!

I was wondering if I could get your input on water mitigation....I will be enclosing my build but I will be using glued pavers for the walls which will allow some moisture to get in....I put the 2" of fiber board on top of sheets of 3/8th Durock board that I coated with Redguard vapor barrier....I'm also planning on using Redguard around the edge of the insulation that sits on top of the Durock board and then maybe do some flashing around the perimeter of the paver block from the inside along with caulking?? I'm honestly pretty paranoid about water entering into the oven so any thoughts or help would be much appreciated!! Thanks, Zoo

I am also paranoid about water. Unfortunately, I have more questions than answers myself. Maybe SableSprings or UtahBeehiver or david s could answer for you?

[slschoming]

Finally got to work a little more on the oven today. I put some ceramic tile down under my two layers of insulation. Next step, the floor.

[slschoming]

Thanks Mike! I feel better about things now. I am going to be off the grid on a backpacking trip in Northern Cali for a week (leaving today), but I think I have all the info I need to get started when I get back!

Thanks again!

[SableSprings]

Seth, here's my take on your questions:

Insulation: The goal of your insulation is to totally isolate the heated oven bricks from the stand and any other outside contact. There would be no problem having the CaSi board extend a bit further to "connect" with the upper dome blanket. Just be very aware of providing a moisture barrier and moisture escape route for all insulation (top and bottom). Water seeping in along the perimeter of the dome's outside base is one of the top problems for a WFO that is not in a permanent, roofed enclosure

Opening: The opening width is not as important as the ratio of opening height to inner dome height (remember the magic 63%). The biggest decisions for me were 1) making sure I could fit a full sheet pan easily into the oven and 2) what worked out simply by the brick dimensions I was using to do my build

Landing: Best practices indicates putting an insulated gap around the oven opening and front arch set(s). The base insulation would not need to extend further than this gap. For a lot of people it is just more convenient to extend the insulation out to make the landing bricks the same level as the cooking floor. If your landing extends out a brick or two from the opening, then your plan sounds great. The bricks outside the oven on the landing can get plenty warm, but I seriously doubt there will be any issues for you (and it will look great with that front brick edging )

Hope that helps.

[slschoming]

Earlier this week I picked up my insulation for under the floor and about 140 firebricks (enough to get started). Next week I will start cutting the insulation and floor bricks. I have changed plans since I started.... I will be building a 42" internal diameter oven so my insulation footprint will be a circle with a 51" diameter connected to a rectangle for under the landing. However, I have a few more questions before I get started.

Insulation Question
I was curious if there is any benefit in having the floor insulation extend another 2 inches beyond the outer layer of firebrick so that the bottom of the 2" insulation blanket is resting on CaSi board. Has anyone done this? Or is it better to overlap the other way, having the blanket extend below the bottom firebrick enough that there is no heat sink?

Opening Question
I think I read somewhere that a good opening for a 42" is around 20" - 22"? Is this a decision that should be made based on science, or is it mostly personal preference?

Landing Question
Since I started planning a 36" oven my hearth is probably a little smaller than the average 42" oven hearth. I am going to be extending my landing all the way to the front edge of the hearth and will be utilizing every last inch of space that I have.. That being said, how much of the landing should be above insulation? I am currently planning to run my insulation 4 inches short of the front edge of the hearth so that I can put a full brick down (stretcher orientation) between the edge of the hearth and the insulation. I am open to suggestions.

Thanks!

[SableSprings]

Seth, as Russell noted, even with the non-absorbing Foamglas underneath your CaSi board, having the mosaic tile sheets allows any water that seeps in underneath the oven, a clear path drain out the weep holes. That's why setting the sheets upside down (with the webbing up) works...you get little channels for any water to flow out to the weep holes. Also gives you little air channels to help dry out any moisture wicking up from the concrete. As with the weep holes, in your case with the Foamglas under the CaSi it's just cheap, extra insurance...just make sure you set the mosaic tiles so weep holes are not covered. Also don't forget to cover the lower (underneath) weep hole openings with some pieces of insect screen (metal if possible). Silicone seal will hold little squares of screen nicely and keep any critters from looking for a new home in your insulation layers. I'm not fond of the plastic screen materials, seems like the bugs often just chew through it too easily.

Good luck and glad to hear you're back working on the oven!

[slschoming]

UtahBeehiver I have 2 weep holes located along the perimeter of where the insulation will sit. I was previously planning to put my CaSi board on some sheets of mosaic tiles to keep it up off the (potential) water. Now that I'm planning to put a layer of foamglas under the CaSi I'm curious if I still need the mosaic tile.

The current plan is to have an exposed dome that I will eventually finish with remnant brick like cobblerdave 's oven.

[UtahBeehiver]

Are you enclosing the oven or not? Open ovens are prone to having water come in from the hearth. A weep hole would be cheap insurance in case any water works its way in. Even though the FoamGlas will not absorb water it would be advantageous to have any water that migrates in able to egress out.

[slschoming]

I just ordered enough CaSi and Foamglas to do a 2" layer of each. Should arrive to the warehouse next week and then I will have to find the time to drive 3 hours round trip to pick it up...

For those with weepholes and Foamglas.. Is laying a sheet of mosaic tiles underneath overkill now that I am using foamglas as my bottom layer, or is it still advised?

My kids are starting to question whether I am going to really get this thing done:

"Dad, when are you going to start working on the pizza oven again?"

"What if you mess up and can't fix it?"

[slschoming]

Michael Harrington Thanks, but CoastPizza pointed me to a place nearby that has both foamglas and CaSi board. 70 miles away so I can drive down there.

[Michael Harrington]

I bought 12 18x24 sheets of 1.5 foam glass on ebay 72..00 including shipping the peices arrived with a few dings and some rounded corners over all good shape. I don't know if you could use this instead let me know I can give link he said he had15 left.

[david s]

Most like will work but to ensure, get the "K" value of the material, should be around 0.5) at 500 F (Standard Units) or 0.079 at 260 C (Metric Units), also need compression strength of at least 75 PSI with 5% compression.

That board has pretty much the same density as 10;1 vermicrete which is considered too weak to support the weight of an oven. There are tons of different products out there, even under the same brand name. My calsil board has a density of 350 kg/m3, considerably more than the product you’re looking at. Make sure it has the compressive strength Russell has already posted.

[slschoming]

Shipping that stuff to Kansas doubles the price... $213 worth of insulation ships for $207.. I might be going back to vermicrete...

[UtahBeehiver]

If DJ used the board, then great, as long as it is the same product.

[deejayoh]

I used the McGill's CF board. Its been great for 4+ years. Can't beat the price either.

1" layers are great, you can stagger the seams