Oregon 42" Pompeii Oven

[UtahBeehiver]

To late now, but sand really affects the insulation values of pcrete. See attached chart.

[Corsairmo]

Thanks for the Astoria welcome Corsairmo! There are a couple folks in the state with WFOs and several in Washington. My advice on the oven is to put a cover over the oven and a space for outside party seating/eating. There are lots of schemes & waterproofing additives to keep the insulation dry in rainy or humid climes, but the bottom line is water ALWAYS will win. If a simple carport structure would be an option, I'd highly recommend it. The only things you have to be aware of with a installed roof are 1) "hitting" the space between joists with your oven flue pipe & 2) making sure you have a solid roofing flange plan for the chimney...so you don't get leaks down the stove pipe... Do think about your wood loading path & main wood storage area. As you can see in my build, I used a cart system for wood and party supplies built into the base and built a wood shed nearby and somewhat out of sight for the couple cords of wood I keep on hand.

With the mild temps of the coast, I don't see any problems continuing your build through the fall and most of the winter. The assumption there is that you would get one of those 10' x 10' portable tent covers to put over the oven. Not only to keep your oven area dry, but you as well while laying bricks...

You would be most welcome to stop in Roseburg anytime I'm not traveling. If I had a couple days notice, I could make sure you had a loaf or two of bread to take down to the family and a slice or two of pizza to help fuel the last couple hours to Medford...

Thanks Mike, the plan is to eventually build a pergola over the area, but that's on a long list of projects! I hope to do some good waterproofing and hope the island of foamglas helps with water inletting. The three bays underneath will all be for wood storage, and there is a nearby shed for more as needed. Next spring I'll be cutting down some alder to stock everything up. For right now the space is protected by my very professional tarp system. so far so good!

[Corsairmo]

Russell I was anticipating a hit in the insulation value from adding the sand, this chart is very helpful to see that quantified, thank you! It also confirms that I might hope for some increased compression strength from using the sand as well. I was concerned that the perelite on its own wouldn't be up to the task of holding up the heavy oven, it looks like sand adds substantially to the strength of the mix. I am using light duty firebrick and so I am not too worried about some extra thermal mass under the oven. I might be fooling myself, but I hope that I struck a balance between adding some thermal insulation to help protect the Foamglas, while adding strength to the foundation of my oven, and if sand adds some thermal mass, I'm thinking I'm ok???

[UtahBeehiver]

You will be fine just point out to future builders the effects of adding sand to p/vcrete mix. A 5 to 1 (san sand) will set up to a compression strength greater than CaSi or AiSi. You only need about 70 psi to support the dome. Always seems and appears light weight but it does firm up. Keep this in mind if you do a p/v crete dome layer (8-10 to 1).

[Corsairmo]

That really is amazing, it seems like it can't be that strong, I'm interested to feel how it sets up in the next day or so. Any thoughts about the perelite grain size? Like I mentioned, it seems so much bigger than other's have in their builds. I should have gotten a shot of it, but like I said, pea gravel down to BB size, while others seem to have a more uniform BB size in their mixes. I was imagining that the large grain size had an adverse effect on the compressive strength vs smaller grain size, but again, I'm not even close to an engineer! By the way, my grandfather spent his entire career working for Geneva Steel. I remember when it shut down and was being scrapped. I think it's very cool that you got your bricks from there!

[Chach]

Hi Ricky,
Thanks for the information, I have seen several people who used the CalSil board on top of the FoamGlas but I thought that was because of the fear of crushing or breaking it... I don't have access to CalSil board at this time, so I was going for a leveling layer of fireclay then the brick floor on top... My FoamGlas is 2" thick, so I think I'm OK insulation-wise, but what exactly does using FoamGlas outside its service range imply? I am assuming I wouldn't be melting it...

No problem....There is a distributor about 95 miles from you called Distribution International. They also will have ceramic blanket if you are using that as your dome insulation. They stock foamglas and calsil board. You made very quick work of throwing that perlite on top already but I thought I'd still send you this information just in case.



Distribution International

• 503-492-9999
• 19039 NE PORTAL WAY
• PORTLAND, OR 97230

Ricky

[Corsairmo]

Ricky, thank you, it's a long somewhat drama-filled story, but I actually purchased then returned some CalSil board from a place called Zartech, which I can't recommend to anyone looking for supplies. I ended up going through DI for the FoamGlas and ceramic blanket and they were absolutely wonderful. I considered getting the CalSil board from them, but that would necessitate another 4 hours of driving, which was a no-go for me...

[Timothy_W]

Looks fantastic. How much will it cost to build such a furnace now? My old one still serves me, but I want more. Still, the family is growing.

[Corsairmo]

Here's my cost breakdown so far:

	Source	Item	Description	Each	Quantity	Total
Brick
	mutual materials	firebrick	light duty	$2.13	220	$468.60
Mortar
	mutual materials	Fireclay	50#	$8.00	2	$16.00
	mutual materials	Portland cement	90#	$12.15	1	$12.15
	mutual materials	Lime	50#	$11.68	1	$11.68
Insulation
	DI	Insulation wrap	1x24"x25'	$60.00	2	$120.00
	Brims	perelite	4cuft	$20.00	1	$20.00
	DI	FoamGlas	18x24 board x5	$18.00	5	$90.00
Stand
	HD	CMU	8x6x16	$1.08	84	$90.72
	HD	Concrete	80#	$3.18	68	$216.24
	HD	Rebar	3/8" x 10'	$4.05	9	$36.45
	HD	Coated Panel	4x8'	$27.00	1	$27.00
	HD	Hardibacker	3x5'	$13.74	3	$41.22
	HD	2x4s	96"	$5.16	8	$41.28
						$1,191.34

[Corsairmo]

Well, lots of good progress today. I leveled the top with some fireclay and laid the floor along with the first course of bricks. I also rigged and installed my IT as well. Tomorrow will be building the arch template and hopefully another course onto the dome. My kids, who have long been disinterested in the whole project, took great pleasure in mixing the dry mortar mix, and helping to install the bricks. However, they declare brick cutting wet and unfun work that dad needs to do by himself...

Of note, the firebricks are very soft in my estimation, they cut easily and chip even easier... I purchased them from Mutual Materials, a bulk masonry supply store, for $2.13 a brick as a "medium duty" brick, but they seem very light duty to me. I would have weighed them to get folks input on their duty rating, but they have been in the rain since I purchased them (no soaking in a tub for them, Oregon provides!) and are quite saturated at this point.

[UtahBeehiver]

The IT need a little tweeking, first, the position of the rod on the L brack needs to be at the halfway point on the brick face not the top. IE in the brick is 2.5" thick, the IT rod needs to be 1.25" down from the top of the brick, Second, the pivot point, in this case, the hinge point needs to be at the center of the dome and be able to rotate around the center point. Not sure how this will work the way the IT is configured, Just be aware the best place for the IT pivot point is at floor elevation, by mounting to the ply/and or 2 x 10s, the dome dimension will increase as you move up and you will need to make adjustment to the dome ID,especially if you do a tapered inner arch.

On a side note, I very familiar with Geneva Steel, born in Utah County, it was a landmark. I dealt with many Geneva employees in my career as a gas engineer. Those brick were classified as "super duty" and I wore out about a dozen diamond wet saw blades...lol

[Corsairmo]

Russell, thanks for the feedback! Your eyes are keen! The picture makes it hard to tell but the pivot bolt is mounted at the hole nearest to the hinges so it's fairly close to center but I realize that I will need to slowly tweak the IT as it moves more vertical to compensate for the additional height of the plywood / 2x10 platform. I've actually got a chart that shows how many turns on the thread-all I'll need to make to keep 21" as I go up each course. Not ideal, but I was utilizing the scraps I had around as my SWMBO is starting to worriy about whether I will put food in the mouths of our children or spend more money on this oven
As for the bracket, my welding skills and borrowed equipment weren't up to much better than what I accomplished, so the L is more of a 93° instead of true 90° to hopefully compensate. More to be discovered as the courses go up! The top of the L won't rest flush of course, but the elbow is only there for convenience in holding the IT in place anyway.

My grandfather, Dean Olsen, was a foreman, and I think later a supervisor of some sort there, but at which part of the operation I don't remember... I haven't lived there for many years, but the two things I miss most are hiking Timp and all the gorgeousness of southern Utah! Skiing was fun too, but I destroyed a knee once unfortunately and that took the magic out of it for me.

[UtahBeehiver]

It is really important that the bracket is at 90 degree or perpendicular to the center of the dome. Equally important is the center of the rod at the halfway point on the brick. The errors are cumulative as you move up in courses, then all of a sudden everything is out of wack and hard to correct. You really need to take care of this right off the bat. I would at least ditch the 2 x10s.

[Corsairmo]

It is really important that the bracket is at 90 degree or perpendicular to the center of the dome. Equally important is the center of the rod at the halfway point on the brick. The errors are cumulative as you move up in courses, then all of a sudden everything is out of wack and hard to correct. You really need to take care of this right off the bat. I would at least ditch the 2 x10s.

I'm not sure I capture the importance of how high my platform is for my IT. It seems to me that the height of the dome is fairly arbitrary, for example if one were to add a soldier course to their dome, the curve is thusly affected compared to one who has not added that vertical height. It seems that, within reason, the starting height is inconsequential as long as consistency of measurement is maintained. Also, I have a close up of the IT pivot (screw) as I think you'll see it's about as reasonably centered as one can make, or as centered as I've seen from most any other IT? In any case things seem to be proceeding smoothly and I'm not sure I'm capturing the compounding error element but I appreciate the assessment and information!

[Corsairmo]

I put in some night work to finish the fourth course. Night arrives promptly at 5:30pm these days so it was in with the work lamp and the added help of the beautiful full moon! I haven't mortared in the arch bricks after discovering that I need to tweak the fit a bit, but I don't think the neighbors would appreciate the tile saw noise at almost 9pm at night! So the tweaks and reinstallation will have to wait till another night! So far so good! I've recruited two capable mortar mixers who love to dry batch and prep my mortar (about a half gallon at a time) which is fun for them and helpful to me. Crushing up brick chips with a hammer is also a fun chore for the 5 year old! Many have said that they regret not building their ovens sooner, but as a busy dad of four, I think the reason many might wait is that its hard to give the needed attention to detail earlier! My cuts aren't perfect and just by cutting the edges of the floor circumference bricks I realized I would be best served abandoning miter cuts for each brick of the dome. Four courses in and I'm not regretting the choice, even if the masonry work is much less pretty than other's works of art. My edges are lining up true and my courses are angling in at a steady rate each course.

Interesting observation regarding the brick quality. It seems that the crumbly edges are a manufacturing problem, not a brick composition issue. The cut corners are durable and true, and when shaping brick cuts I can apply a great deal of scraping force with my trowel or other tools before the brick deforms, while the manufactured edges are often easily damaged, either preexisting, or after things like a scrape of the mortar trowel or a tap of my rubber mallet. I've taken to laying my bricks on their side, so at least one edge is square and true! Has anyone else run into this issue?