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Author Topic: Under Hearth Insulation  (Read 362 times)

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Offline stevon

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Under Hearth Insulation
« on: April 07, 2021, 03:42:33 PM »
Hi guy's

I'm building my first outdoor pizza oven in my back yard. The more I look into this, the more I realize how little I know about it. I'm pretty handy restoring cars, building construction projects and working with electronics and software. Learning as much as I can to avoid failures of design or construction. Oven floor height, insulation options and refractory components and materials are all part of a successful build I'm told and most advice makes sense so far. Question: I am building the oven floor on top of a base stand built on 4inch rebar reinforced concrete slab with cinder blocks that has a poured, rebar reinforced concrete slab for the top. Next question: I purchased 2" of ceramic fiber board to put under the oven for insulation purposes, what else is recommended, adding nothing? sand? 1" of perlite mixed with portland cement? 2'' ? 4"? (this will all effect the finished oven floor height) to put under the fiber board? on top of the fiberboard? Thanks

Stephen
« Last Edit: April 07, 2021, 04:16:29 PM by stevon »

Offline Jon in Albany

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Re: Under Hearth Insulation
« Reply #1 on: April 07, 2021, 06:15:54 PM »
This is probably a better question for the oven section of the forum because not everyone looks through the new forum member posts. Sometimes I do, sometimes I don't.

I used a full 2x4's (3.5 inches) height of perlcrete under my 2 inches of insulation board. I made the surface of the perlcrete flat/smoother for the board with fireclay. If your stand is built, this will definitely change the height of the oven. From what I have read, 2 inches of the board is the minimum you want under the floor, so it will work if you don't want the floor any higher. Another option for more insulation is a little more board if you want to go that way.

Also, if you have any extra board, save it and you can use it inside an oven door.

Welcome to the forum. Start a thread and show us your build along the way. We love oven builds!

Offline stevon

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Re: Under Hearth Insulation
« Reply #2 on: April 08, 2021, 01:19:26 AM »
Jon in Albany,

Thanks for the reply! The stand isn't built yet so I can still adjust the finished oven floor height. I'm working with a contractor who never built a pizza oven (this will be his first). We have had problems communicating already. At first he dug or "scratched the earth" down 1.5 inches for the slab on the ground while I wasn't there. We had agreed to 4.5 inch slab beforehand. I was so angry when I came home and saw what he did that I got out my hammer drill and dug down/shoveled out the pad hole to a 6" depth in the rock hard clay after work. I figured that 1.5" gravel + 4.5" slab to be installed at ground level (no step). This was all agreed to before he got a deposit and I believed that he understood. When he came back on the weekend with his crew it was done right, see pictures. Before the cinder/cement block is laid I have instructed him to build the block height to 36" with a 4" rebar reinforced slab to be poured on top. But I think this is too high with extra insulation. Stand top design now is at 40" + 2" ceramic fiber board + 2" fire brick floor makes the oven floor height already at 44"  Which is the absolute max I could cook with. I have read here and elsewhere that 4" insulation under the oven floor is only "acceptable" but on the other hand I can't just keep making changes to the plan or my contractor will walk when he comes by this weekend. Guess I'll have to figure (negotiate) a reasonable block height 34" to 36" of installed block height under the a slab top of 4" thick. Question: Will 2" of perlite/cement and the 2" ceramic fiber board be adequate? place aluminum foil on top of the perlite/cement as a vapor barrier under the Cement fiber board? I have no experience with this stuff but want to do it right or not do it at all.

Stephen


Offline stevon

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Re: Under Hearth Insulation
« Reply #3 on: April 21, 2021, 02:53:29 PM »
Guy's,

Some progress is done and I built the top framing myself because the contractor (laborer) who laid the block said that he had no idea how to frame/design the table top slab. We settled on a finished block height of 31.5 inches from the slab floor. Used Google to study how to figure top deck out and went with the purchase of some scrap galvanized steel angle iron, and decided to use Hardi board (cement board) as the bottom, temporarily supported by extra cement blocks (originally purchased a full pallet (90 blocks) that saves $0.21 per block, to return extra unused later). Put the larger 10', 4" x 4" angle iron on the front over the openings, sort of like a lentil then welded the frame together (have welding equipment available) So far the contractor has left me hanging for a couple of days now. I don't know if he will show up to finish the slab top or not. In the mean time asked the Home Depot "expert" guy  to calculate how much extra concrete is needed for top slab (22 bags total) plus one bag of "plastic" cement. This is used for the top coat to "float" or smooth out in the finishing of the slab. Promise to tally up a list of materials and the total cost of parts & labor.

Stephen
« Last Edit: April 22, 2021, 01:19:55 AM by stevon »

Offline stevon

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Re: Under Hearth Insulation
« Reply #4 on: April 23, 2021, 04:04:13 PM »
Guy's

A few more pics

Stephen

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Offline Jon in Albany

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Re: Under Hearth Insulation
« Reply #5 on: April 23, 2021, 04:37:32 PM »
Please don't weld anything galvanized. It isn't safe.

Offline stevon

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Re: Under Hearth Insulation
« Reply #6 on: April 23, 2021, 04:40:25 PM »
Jon,

Too late, already welded and was careful to grind through the zink to the steel at welding points plus it was a little windy last Saturday. Your right about wearing a welding respirator for safety though

Stephen
« Last Edit: April 23, 2021, 08:50:04 PM by stevon »

Offline stevon

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Re: Under Hearth Insulation
« Reply #7 on: April 26, 2021, 12:23:15 AM »
Guy's
Some more progress, I got tired of waiting a week + begging the contractor labor/ransom to show up, so with the help of my friend Brian (posted in pictures), we got it done! You know you have a real friend when you need help moving or other major project and when asked, they actually show up! We moved 2200 lbs of concrete and it nearly killed us! Brian is older than me too. Keeping it real! Keeping it real wet! water is needed for the cure process.

Stephen
« Last Edit: April 26, 2021, 08:49:22 PM by stevon »

Offline halfprice

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Re: Under Hearth Insulation
« Reply #8 on: April 26, 2021, 12:36:21 AM »
Looking good so far.   I used 120 bags 60# for my bbq kitchen. I m still sore from lifting them


Keep up the good work

Jerry

Offline stevon

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Re: Under Hearth Insulation
« Reply #9 on: April 26, 2021, 12:47:52 AM »
halfprice,

Yeah I am stiff and in some pain but did OK so far, not bad for a 61 year old with a crushed back disk! Used a 500 lb lift table bought a few years back from Harbor Freight, glad I held on to it. Yeah, 60# on future projects for sure!  Top used 20 1/2 bags of 90 lbs quikcrete concrete mix and a 1 full 94 lb bag of plastic cement only for the top slab. Was told by a friend that adding a shovel of plastic cement in each batch will make the concrete stronger and smoother. This is my first pour so I guess that worked. Thanks for the encouragement!

Stephen
« Last Edit: April 26, 2021, 01:14:42 AM by stevon »

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Offline halfprice

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Re: Under Hearth Insulation
« Reply #10 on: April 26, 2021, 11:15:20 AM »


halfprice,

Yeah I am stiff and in some pain but did OK so far, not bad for a 61 year old with a crushed back disk! Used a 500 lb lift table bought a few years back from Harbor Freight, glad I held on to it. Yeah, 60# on future projects for sure!  Top used 20 1/2 bags of 90 lbs quikcrete concrete mix and a 1 full 94 lb bag of plastic cement only for the top slab. Was told by a friend that adding a shovel of plastic cement in each batch will make the concrete stronger and smoother. This is my first pour so I guess that worked. Thanks for the encouragement!

Stephen

Yep the 90lb bags were to much.  I'm 61 also with several bad disks in my lower back and two fused vertebrae in my neck. Ha sucks getting old

I had home depot deliver the concrete then I wheel barreled them into the back yard. Lots of work but worth it


Keep up the good work and there's no rush.  Do what you can then rest.  You'll finish before you know it

Jerry

Offline stevon

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Re: Under Hearth Insulation
« Reply #11 on: April 26, 2021, 11:30:13 AM »
Jerry,

Sorry to hear about all the wear and tear on your bones, but they better not write us older guy's off! With the lift table I didn't have to go all macho crazy and injure myself, these days I use my head and not my body to get major work done! lol. With a little beard dye I look youthfully strong, but looking young and being young are two different things! surprised that Tuna in your avatar didn't kill you!

Stephen
« Last Edit: April 26, 2021, 11:37:20 AM by stevon »

Offline halfprice

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Re: Under Hearth Insulation
« Reply #12 on: April 26, 2021, 01:25:59 PM »
Jerry,

Sorry to hear about all the wear and tear on your bones, but they better not write us older guy's off! With the lift table I didn't have to go all macho crazy and injure myself, these days I use my head and not my body to get major work done! lol. With a little beard dye I look youthfully strong, but looking young and being young are two different things! surprised that Tuna in your avatar didn't kill you!

Stephen
Old but still going strong


That's still my biggest tuna at 226. I've gotten a couple more just over 200 and many 100+

But I don't like the longer trips anymore 10+ days.  8 days is my preferred now.  Doing alaska for 4 days of fishing in August and an 8 dayer out of San Diego in October

You ever do any trip being in sd??

Jerry
« Last Edit: April 26, 2021, 01:28:08 PM by halfprice »

Offline stevon

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Re: Under Hearth Insulation
« Reply #13 on: April 26, 2021, 08:33:10 PM »
Jerry,

I'm not a big fish eater and even less of a fish hunter! my last fishing trip years ago I remember it was kind of like St Patty's day, involving a lot of drinking and vomiting, not the best of times and I was younger 25 years ago! It is funny though moved out to San Diego for the sun and beach lifestyle but have actually been out to the beach only 5 times in 19 years! Found out the grass is not greener in southern California, it's just green like everywhere else lol. The cost to live out here is outrageous and have spent most of my time and energy trying to secure enough income to be able afford living here paying the so called "sun tax". Loving the 70 to 80 degree average temperature year round, do miss the high quality food back east though. The snow they can have all to themselves....

Stephen
« Last Edit: April 26, 2021, 08:36:55 PM by stevon »

Offline halfprice

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Re: Under Hearth Insulation
« Reply #14 on: April 27, 2021, 12:45:02 AM »
I only fish couple times a year. Going to try and hit big bear a couple times this year. I love it up there

If I was a little closer I'd drive down and give you a hand on your build

Jerry

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Offline stevon

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Re: Under Hearth Insulation
« Reply #15 on: April 30, 2021, 11:15:08 AM »
Guy's'

The build goes on... some slight progress. Frame is 1 inch tall and un screws on one side. The floor height is getting to be too high. 1" perlite mix plus 2" insulation, I would like to have more but can't do that now. The only reason I'm bothering with the 1" is to keep the ceramic fiberboard dry and off of the slab.
Extending the landing 4" in front.

Stephen
« Last Edit: April 30, 2021, 12:55:02 PM by stevon »

Offline stevon

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Re: Under Hearth Insulation
« Reply #16 on: Yesterday at 02:42:07 AM »
Guy's,

it's on the table! Went with 1 inch 5/1 perlite to plastic cement (I already had some to use) and 2 inches of fiber insulation board and a little play sand was used to level the top of the perlite cement mix. Underneath ceramic fiber board put a layer of regular aluminum foil as a vapor barrier to protect the board from water and/or water vapor. The Dome oven kit was installed with refractory mortar (50 lbs Grainger purchase) then covered with refractory fiber insulation blanket. Chicken wire mesh is tied down to the screws that I embedded earlier. Next will render oven with perlite/cement mix.

Stephen
« Last Edit: Yesterday at 03:43:41 AM by stevon »

Offline stevon

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Re: Under Hearth Insulation
« Reply #17 on: Yesterday at 03:24:47 AM »
Guy's,

Add insulation and chicken wire! The insulation I ordered from Home Depot UniTherm Ceramic Fiber 1" x 24" x 25' @ $95.45 was enough to cover the oven twice (2" total) the second roll ordered will be returned along with other extra stuff that is not needed.

Stephen
« Last Edit: Yesterday at 03:32:06 AM by stevon »

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