Backyard DIY Pizza Oven Construction - Slab Framing - March 2023

Over the weekend, I went out and picked up four 2x6x8 boards and brought them home to begin to figure out if I've done enough excavation for our wood-fired pizza oven project.  I've been using a tape measure to figure out how much I needed to remove and if my dig was large enough to support the slab framing - along with the necessary bracing.  But, that's an imperfect science, so I decided to just go out and cut the lumber down to the final dimensions and place them in the hole to see - without guessing - if I've excavated enough.

As a reminder - mostly to myself - my final dimensions are based on 8x8x16 construction blocks: 

Slab: 78" wide, 86" deep. 6.5' wide, 7'2" deep).
Stand: 72 wide, 80 deep (4.5 blocks wide, 5 blocks deep)
Leaving reveal of 6" total both dimensions. 3" all ways.

This allows for 2" face brick and a 1" reveal.

I cut the two side pieces of the frame to be 86" and the front/back to be 81" (to account for the 1.5" overlap at each of the corners).  And plopped them in the hole.  See below - including a five-gallon bucket for size perspective.  

There's a pipe sticking up in the middle of the slab now and that's because I ended up shifting the site of this slab to accommodate it.  It is a surface drain that is connected to the drywell and - in theory - is supposed to be an inlet from the surface water to the drywell.  There's a much larger (sewer-size) inlet closer to the fence, but this one sits at the bottom of the swale/countour of our property.  In reality, I've NEVER seen this inlet in use.  The bottom of it is BONE dry and we've never had any pooling water down there.  

But, I recognize that by adding this oven (and the slab), I'm changing *SOME* part of the grading, I've decided to incorporate that drain INTO the floor of the slab.  I'm going to try to include it in the front, inside corner of the stand; so any water that runs onto the slab would have be able to travel down the drain...thus avoiding any standing water.    One thing that I'm thinking about is that I have (in my LEGO model) and few storage cavities in the stand that are divided by cinder blocks.  Thus, this drain would work for the front/main opening, but the two no the sides would be isolated from this drain.  Perhaps, I can leave open a drainage channel/opening in the blocks to allow for the water to flow down this drain.  Or, alternatively, I can think about installing similar drains in the back two storage bins.  

The other thing that this exacavation has shown me is that the slab will be buried on the west side and above grade on the east side.  That *might* mean that I need something like a french drain along the west side.  Even a sleeved, perforated pipe that I put in next to the slab BEFORE I backfill.  That pipe would collect and drain into the drywell below the slab.  Might keep the water from pooling on that west (buried side). 

In terms of what has been done (so far), here (below) is a look at the 2024 [Pizza Oven] posts:

My DIY Backyard Wood-Fired Pizza Oven Progress:

• I reviewed a couple of potential sites for the oven.  I've settled on the drywell location.
• I built a scale model of the cinder block stand using LEGOs. 
• I found some brick pattern inspiration on TikTok that I'm thinking of utilizing.
• I went back-and-forth about 10" vs 8"-wide blocks for the bottom courses and using L-shaped corner blocks.  I've decided to use 8"-wide blocks and NOT use L-shaped corners. 
• I used my post-hole digger to try to find the depth of the top of the drywell.  Turns out, it isn't very deep in some parts.  
• I listed the pizza oven as my #1 'early' priority.  Talk about a forcing function to sort-of WILL this thing into creation.  
• I began to think about renting vs. buying when it comes to concrete mixers including one from Harbor Freight.  I still am unsure about what direction to go.
• I began excavation on the drywell site.  There are a few considerations including existing plants and drainage that I've begun to navigate.  
• I hauled off what appears to be more than a yard of topsoil and turf from the site.  And piled it (turf-side-down) in the stumpery.  Covered with wood chips to reduce light.  
• I went back to Menards to figure out the rest of the building materials.  Including high-heat mortar, rebar and pressed bond beam blocks.  
• I cut 81x86" framing (for a 78" wide x 86" deep slab) and set it in place to decide final location and if I've done enough excavation.  

What comes next?

Gravel.  I need to buy and lay-down a good amount of gravel.  To level the drywell, provide drainage and make the slab pour-ready (so the concrete doesn't OOOZE out below the forms.  

In the meantime, I'd like to go buy enough cinder block to make the bottom course.  My plan is to dry stack them on the patio to get a sense for the footprint.  AND...IMPORTANTLY....allow a real-life measurement of the stand BEFORE I pour the slab.  That way, I'll know -without a doubt - that my stand will sit on-top of my slab properly.    My count is (at least) 14 full and 1 half blocks.  2 loads-worth.

Then, slab prep including:  vapor barrier, rebar (with ties and chairs) and a metal grid.   Need to decide on drainage for back two chambers and/or if sloping to front drain is appropriate.  

Once that's done, it is time to pour the slab.  That means that I have BOTH have the bagged material (48 bags of 4000 psi concrete mix) and the mixer on hand.  

From there, I can move on to the stand construction and (potentially) backfilling against the slab (with a potential french drain). 

Spring Break is a'coming and I need to find time to get the materials and make-a-call on concrete mixer rent vs. buy.   Time to get busy living (with a pizza oven) or get busy dying (without one).