BeanAnimal's 42" build - Pittsburgh PA

[BeanAnimal]

Forms removed this morning (June 12) and keeping it wet. The arch is perfect, no cracks (it has been 12 days I think). Interior slab supports will remain for a week or two.

Will keep it wet for a few days - I don't think it will matter - the mix was great and there is so much rebar, that I can't fathom shrinkage cracks. But better safe than sorry. My eagerness to get the dome started may change the plans for watering!



As a side note:
I mentioned footers for the timber frame - 3 feet deep and roughly 20x20 = 8.33 Cubic Feet = ~1250 pounds. So solid footing for the timberframe and plenty of ballast for uplift prevention of the timberframe. At 5000 pounds + the weight of the structure (lets call it 1500 pounds). The roof area will be ~145 square feet. So maximum uplift resistance would be 6500/145 = 44psf. I calculated worst case for the proposed structure (using skyciv) to be about 22psf (and that is basically tornado winds). So more bomb shelter engineering!

-Bean

[BeanAnimal]

I used the interior forms and (2) 2x10x12s (on hand for a garden project) to build a wheelbarrow ramp. This worked like a charm and would have easily supported a motorized Georgia buggy if I had one to use.


Three wheelbarrows on hand - only needed two. That two wheeler is an awkward beast and going back to Lowes unused. Good for flat ground but not odd terrain.


The ramp - just recycled interior wall forms laid over 2x10x12s. Sturdy and stable. My buddy Andy (foreground) and brother (backgroung) finishing up. Maybe 15 mins from first wheelbarrow to last! Nice!


Screeded and vibrated (Harbor Freight $99 vibrator with 20% off coupon. Highly recommended!). Any enjoying a cold drink while we wait for the bleedwater to evap.


The slab is unlikely to be seen, but I steel troweled it to make it flat and seal the surface. Here it is it wet for curing after the hard trowel.

FWIW - I did not bull float. I simply wood hand floated after we screeded.

I covered the slab with an ez-up after we screeded, but got a bit behind (my help went home) with the footers and didn't get on the slab soon enough. The left side got some (a lot) of sun compared to the bulk of the slab that was in the tent shade. Ohh well - like I said, it will be likely enclosed! It is dead flat/planer/level and 99.99% of it is as smooth as a babies bottom.

[BeanAnimal]

Yesterday was a huge milestone!

Ordered the volumetric truck (can't say enough positive about the driver or the company, Pittsburgh Mobile Concrete and will defiantly use them for future project ). I have dealt with some real jerks in the past - most of these guys hate dealing with DIYers and weekend warriors. These folks were the exact opposite!

Kind of expensive - but it has been hot and I didn't want to risk a cold jointed pour batch mixing.

The slab called for ~20 cubic feet. So ~3/4 of a yard.

$318 with tax for the first yard, use it or not. Then $145 a yard after that, billed in 1/4 yard increments. I used a "yard" and to be sure, they were on the VERY kind side of that, after pouring the slab and filling one footer, they left me with two wheelbarrows full for the footer hole that I didn't get finished before they arrived.

Even with the price break from big box, $4 a bag for 45 bags = $180/yd - 3 trips to haul it in the F-150 and moving each bag 3-4 times and the mixing labor. She wanted to know if I was crazy at this point, by trying to save $130 bucks. So the batch truck it was!

So glad that I did!

Photos coming next post...

[BeanAnimal]

Busy weekend - not a lot of oven work.

Got the rebar mat tied
Set the side forms back up, raising them ~5.5 inches.

I had the extra #4 rebar so went ahead and tied a 6” mat, in effect a reinforced 2 way slab.

A bunker needs a suitable roof, right?

Slab clear span is 58x65 -no center support.


Stating to get things tied. Several vertical pieces of rebar embedded n the walls were bent over and integrated into the mat.


All tied, temporary internal braces in place.


Wall forms back in place and raised 5.5” with blocks. Ready to pour.

Yes - way stronger than it needs to be. Having fun and enjoy the thought that this thing will be here when the sun burns out.

[BeanAnimal]

I hope to get the upper slab poured this weekend.

Back and forth decision between metered concrete and batch mixing. The metered will be more consistent and time between first and last wheelbarrow load will be 20-30 mins at worst. Site mixed - even with a second mixer and help, closer to an hour.

No center support - so structural reinforced slab. Rebar is cheap - so I guess I will double up and build a truly reinforced slab with a #4 mat on 6" or 8" centers.

Will likely just re-attach the outside wall forms and raise them up 6" with shims on the brick ledge.

Inside forms support - a few 2x6 or 2x8 cross supports on legs that rest on the inner brick ledge.

Insulation will be cal-sil board - so no perlite in slab. Will get an #80 bag count and use what I have. Somewhere north of 4.5" and south of 6" thick.

6" puts me closer to the final height I want (floor area in front of oven may be thicker than I had designed for initially) - though 4" concrete with 1" of perlite mix (and cal-sil) and a center support was what I had planned and built for. Don't see the need for the perlite and would rather double the cal-sil if/when needed when I get to that phase.

[BeanAnimal]

Greatings BeanAnimal! I'm Tom (Greenviews) from Indiana. We're relatively close and starting at about same time. I just made my first build post showing base for my table on which I will place my oven. Your base looks prettier, but I have plans to later stucco coat my block base. I'll try to keep an eye on your post. Are you still importing your kit? I foolishly plan to do all my cutting . Cheers

Thanks Tom!

Yes - I went ahead and purchased the kit. I did a lot of research and am very comfortable with my decision.

My rationale was simple:

• 15 years ago, I would have been happy to cut brick. Now - after a fire pit, a stone patio and stone walkway, 2 decks, raised beds, and a whole home remodel - I don't see the reward in cutting brick!
• With a 3,000 pound wooden crate in the driveway - the warden is hard pressed to change her mind. Doddling around trying to source stuff would have given her chance to take back her approval.
• I have to source very little a-la-carte - and am at this point in life happy to pay a premium for that.

I still get to build my oven brick by brick and enjoy the reward - Honestly, if I were to "do it again" - recognizing I am not even close to being done - meaning if we ever move, the next oven will likely be a pre-cast dome - or a contractor can build the foundation and stand

A few notes: The 42" kit has a 6" chimney - I think some here may frown on that - but I see no complaints from other "kit" builders. Also - my chimney height will be taller, as it will have to pass through the timber frame enclosure roof and extend at least 3' feet past. It should have plenty of draw.

I mentioned it in the first post - but I did call Forno Bravo to inquire if their DIY kits were still available - they are not.

[GreenViews]

Greatings BeanAnimal! I'm Tom (Greenviews) from Indiana. We're relatively close and starting at about same time. I just made my first build post showing base for my table on which I will place my oven. Your base looks prettier, but I have plans to later stucco coat my block base. I'll try to keep an eye on your post. Are you still importing your kit? I foolishly plan to do all my cutting . Cheers

[BeanAnimal]

The pour went well. 33.3 bags- exactly what the volume was calculated as in Fusion 360.

A few notes on hand mixing this concrete. Over the past 15 years I have hand mixed ~500 bags of concrete for various projects. In most cases. The pours were non critical things like post holes or simple footers and I have always mixed by eye with the garden hose.

I used this and the footer as a trial run for the upper slab, as that is a critical pour that I want to go well. I measured the water exactly for each batch in the mixer and have to say that I am not at all pleased with then bag to bag consistency of the Sakrete 80 product. Some batches were almost soupy and others so draw that they needed substantial water additions of up to a quart or more. I also. Priced that some batches had a higher sand continent and other far more portland. That is some batches were grainy and others more plastic like. In the end, most batches had to be watered by eye... Also - would have been far better off with two / three wheel barrows and help. First to last bag was 2.75 hours and could have been cut down to 1 hour or 30 mins with two mixers.

As much as I hate to pay for it, I may call the meter truck for the slab. $265 for the first yard... not really that bad considering the saved work and lessening chances of shrinkage cracks due to time between batches.


Arch form left in place. Some bug holes and a few poorly consolidated spots at the base. Not bad at all.


Another shot. Rather pleased with the outcome considering the minimal rodding and side hammering.

The forms literally self separated as the pins were removed. The release agent worked far better than DIY solutions (Pam, WD40,etc) that I have tried in the past. Did i mention cherry scented.... mmmmmmm.

[BeanAnimal]

That is some serious form work. This is going to be a bomb shelter.

yep!

Always amazed at how even the most substantial forms bow, swell or outright fail under the weight of a wet pour. I didn’t want canoe shaped walls!

The corner pins worked perfectly. Even with the 2x6 walers, the bottom cord started to bow slightly as I rodded the mix. Given that the walls are 4”, even a bug holed dry pack will be overkill, so I barely rodded and hammered the walls.

6” block walls would have been far easier, but there is a chance that this stand does not get covered, Exposed block is ugly and I don’t care for stucco.

I now have a 2” brick ledge around the perimeter, giving me plenty of option when (if) we decide to veneer.


But yes... a bomb shelter.

[UtahBeehiver]

That is some serious form work. This is going to be a bomb shelter.

[BeanAnimal]

Sandwiched in place - almost ready to pour!

[BeanAnimal]

And lastly - the slab support arch -

I want to be able to strip the forms within 24 hours - but would like the arch form to stay in place for 10-14 days. It will be in place for the slab pour.

The solution was simple - build the support form and sandwich it between the inner and out form walls. The walls can be removed, leaving the arch form.


Just a simple plywood form covered with coated hardboard - who knew - the big box stores no longer sell regular old masonite - just this coated paper crab that resembles what masonite used to be.



Glued and tacked with a brad nailer - 5" thick and very solid already.



Add vertical sides and bracing form scrap - the bracing will be screwed into from the outside and inside form walls. This sandwich will be very secure and should not spread during the pour.

[BeanAnimal]

Coming together nicely



Front span (where arch will be) is dead nuts side to side. Nice!

[BeanAnimal]

Week of May 25th during evening:

Constructed the rest of the formwork for the stand walls and integrated opening arch.

Form Notes:

• Exterior walls have 2x6 walers integrated into the framework - this should prevent outward bowing - may add stakes and braces to be safe.
• Exterior wall top and bottom plates interlock - will drill 1/2" hols and drop rebar pins into the corners to secure them during pour.
• Interior walls are somewhat modular - single panels would be impossible to strip, as they would end up wedged in place. Side walls are 2 or 3 pieces. End wall is a single piece but 1/2" short on either side (see photo) so it should slip out fairly easily.
• Front wall/arch form (next post)

All formwork was painted with commercial form release. Cherry smelling mmmmm


Example of modular side wall (not lined up yet)
Left room for top 2x4 plate to tie all sections together in a straight line.



You can see the basic form starting to shape up with rebar going in as well.

Verticals are #4 embedded in foundation cores
Horizontals are #3 bent at 90 on two sides to form sidewall reinforcing that goes around both corners and is tied in the back with significant overlap.



Bends were made using two 3/4" iron pipes for the short 90 and then DIY wooden jig (old crate pallet in photo) and single 3/4" pipe for the long side (you can't slide the pipe off the after a second bend). The wooden jig bends are clearly not as tight - but well within the radius needed to fit in the form corners.


Some temporary blocking on all sides to set wall thickness


Rear wall to the left - notice is is 1/2" short.
Should make it easier to strip the day after the pour, as the side wall forms will come out first.
I should have made the rear wall in two pieces - but was too lazy to rebuild it once I realized that was a better plan!

Detail of side wall panels (3 sections on one side) for easy removal when stripping.

[BeanAnimal]

Sat-Sun May 23-24

Finished up foundation!

Poured cores and backfilled - rebar added to every other core.

Everything is nice and level around the perimeter

You can see the beginning of the forms for the poured stand walls..