BeanAnimal's 42" build - Pittsburgh PA

[BeanAnimal]

Friday May 22, 2020

CMU Block Foundation Walls:
8x8x16

Method: mortar between layers, but not between adjacent blocks. This allows me to tweak level/plumb and keep the perimeter dimensions as small as possible.

10 cells in length by 9 cells in width, no mortar gives me almost perfect dimensions for the foundation, including a ~2" brick ledge WITHOUT cutting ANY block. This also means turning the pattern 180 degrees for each layer gives me the staggered bond that is needed to keep cells lined up for grouting. See the pattern below, noting the corners. Not only can I turn it 180 degrees, but I don't end up with the oddball dimensions changes, as each side has 1 long and 1 short corner. Everything stays symmetrical without the mortar joints being needed to make up the difference.





2 more layers to go:

Not sure if I am going to trim the final layer height or not - I am still working out where the finished ground profile will be and would like the brick ledge slightly below grade. I also don't see a need for a bond beam - but may pour 1 anyway.

There is a several in drop between the back and front of the oven - as well as the front of the oven is going to be adjacent to a walkway and patio. I am not sure how this is all going to tie in yet. Stay tuned!

[BeanAnimal]

The footing was hand screeded with a board and a level as I worked my way out of the hole (toward the chute side). I am pleased that I ended up almost dead level, with a single 1/2" corner and a bit of a dip (1/2") in the middle of the right side wall.

I will have to trim 1/2" off of the just the corner of one of the blocks when I lay them.

Rain delays, tired hands and a busy daily work schedule have pushed foundation block work off until late afternoon Thursday May 22nd.


Time to address some of the items from post #1

1. Cell grouting: Because this is a "hole" in the ground in clay soil, it really has no natural drainage and the cells will fill with water. Repeated freeze/thaw cycles with that much water will destroy the underground block. Grouting the cells will hopefully eliminate this problem.
   
   The alternative was to form and pour. That meant another 30+ bag continuous pour. No Thanks! I will still have to mix and pour, but can do it at my own pace.
   .
2. The foundation will support the stand directly, a ground slab is not needed, as the foundation bears on the footing. I may pour a floating slab or use a plank floor or pavers for the wood storage area. Will deal with this later.

[BeanAnimal]

On to the work:

Saturday 5/16/2020 and Sunday 5/17/2020

Manual site excavation: I contemplated renting a small excavator. I hindsight, i should have!

It took most of Saturday and most of the day Sunday to dig the foundation trench.
I used a small 2 bag mixer to mix the 44 #80 bags and dump them into the hole.

I built a small concrete chute and set the mixer directly above it. This was a huge time saver, though climbing in and out of the hole, spreading and mixing got a but tiresome.

[BeanAnimal]

Given the forum reset - I am going to edit/repost in condensed format.

My property is on a fairly decent size hill in Pittsburgh. I

• 6-10" of topsoil covering orange and grey clay of unknown depth.
• oven will be in a fairly poorly drained (flatter) area of the yard.
• Our frost depth is listed at 36"

Slab on grade: not a good option, as I can't excavate deep enough for a sub base AND get drainage. Any hole deeper than about 8" below grade becomes a clay lined pond!

Final design:

• 36" deep (40+ on high side) foundation
• 10" footing with rebar (calcs below)
• Block walls with all cells filled with grout/concrete (freeze thaw explained below)
• no ground slab (no need)
• stand formed and poured on foundation

Back of napkin engineering...
2,800 Pounds Oven
2,500 Pounds Hearth Slab
2,600 Pounds concrete stand
3,500 Pounds foundation walls
4,000 Pounds footing
1,000 Pounds Finish material (veneer stone)
0,001 Pizza
__________________________________
~16,401 Pounds - wow!

Clay soil bearing capacity - IBC and other codes list 1,500 PSF (likely extremely low estimate)

16,400 / 1,500 = ~11 square feet of bearing surface min

Poured footing

• avg 16" width
• 10" depth
• ~32 square feet
• 44 #80 bags of concrete
• #4 rebar (3 per side on 3" chairs)

So even I up the total live/dead weight of the finished oven to 20,000 Pounds:
20,000 / 30 = 625 psf - a very comfortable safety margin for both the bearing capacity and the footing itself.

[BeanAnimal]

Okay 15 years of planning and an annual fight or two with the warden regarding "no new projects until the other projects are complete" has finally granted me a permit. I would like to think that my finely honed Jedi Mind trick worked, but alas, I fear she has agreed simply out of frustration and fatigue due to the daily badgering during Covid Lockdown. Actually, does relentless badgering count as Jedi powers?

Anyway - on the to the project.

15 years of planning and when it came time to pull the trigger on materials - I second guessed myself and began redesign yet again!

1. I was afraid of supply chain issues and materials availability
2. 15 years of DIY has caused me to become less fond of the rabbit hole syndrome that seems to plague most projects.The very thing I used to love (digging into the minutia of detail and planning) has given way to just wanting to get things done. Part of that is fear of the warden's wrath - but to her credit, I don't finish a lot of things.
3. I still want to build my oven - precast was likely a better choice, but not AT ALL what has kept this idea alive for 15 years.

With the above criteria in mind, I set out to refine my plans and start sourcing materials. The new goal was to get this done right AND efficiently. The self gratification of cutting each brick is not something I desire any longer - I have spent the last 15 years cutting brick, tile and everything else under the sun. I called the wonderful folks at Forno Bravo about pre-cut brick availability and found out that the they no longer offer the product. Local brick yards are pretty much closed down and supply chain problems are clearly going to be an issue.

I did a bit more research and found an Australian based company that actually exports kits to the USA. Looking at the plans and the design, there is very little difference between their D105 and the 42" DIY Pompeii oven. I fired off an email asking for a bit more details, and the owner of the company called me back that evening. I have to say, I was impressed with the service and the conversation.

So with that said - If there are interested parties, I will document my plans and progress here. I am a bit hesitant, as I don't want to offend our hosts or be seen as promoting or shilling a non Forno Bravo product. I see a few other posts regarding the kit I am building, but they are mostly (all?) Australian builds.

Well that is the background - next post will be foundation/site issues and the plan/solution to those issues.

-Bean