Adding Bottom Tray Support Under Hearth Pour - DIY Wood-Fired Oven Build - June 2024

The next step after filling every-other-core in my DIY wood-fired oven build is to create the support that goes *under* the hearth that can support the concrete pour.  I've made three areas for storage in the stand, so each of those need a cover (or lid) and some support bracing to keep the concrete from sagging through the openings.  I opted to use 1/2" DensShield board and various 2x4's and 2x6's to create the supports under the openings.  Below are a few photos showing how I cut the board (1/2" thick) and then used the legs to support/span the openings.

Below is a peek at the INSIDE of one of the storage bins and you can see the legs/supports laying this-way-and-that.  Why?  Because...I cut them just a little bit short of the length needed.  My plan is to use a bunch of wood shims under these so once the pour is complete, I can pull the shims out and the supports will fall away.   Without the shims, the supports might not come out so easily.   Also, I'm using the DensShield board (cut to size) under the bond beam (flow-thru) that span the angle iron openings.  I'm not sure if *this* board will stay or come out - once the pour is complete. 

I wrote this post that included a few tips that I've picked up for hearth construction and plan to implement most of them.  The conduit one is something that I need to sort - perhaps I use pvc to allow for future electrical to pass through the hearth, but if I do that... I'd also want to run it OUT the stand.  The alternative is to just allow the electrical to run up back - surface-mounted - where no one will see it. 

With the bottom trays built out for the hearth....the next steps are:

1.  Finish up the bracing under the hearth support boards and add the shims to get these the right height.

2.  Add rebar to the flow-thru bond beam blocks around the perimeter of the oven stand.

3.  Fill in the gaps and affix the DensShield board so the concrete doesn't have a path to leak out.  I'm planning on using a combination of backer rod, caulk/sealant and some sand.

4.  Cut and add the rebar grid going both directions on top of the DensShield.

5.  Cut and add the 2x8 forms around the edge for the hearth pour.  And add legs (along with shims) to support them.  Also add some perpendicular 2x4's for strength.

6.   Run wire across the hearth (both ways) to keep the forms from bowing.

7.  Add some 1/2" pvc pipe for drainage holes that matches the TOP of the hearth pour.

8.  Fill the remaining cores with sand - to ensure the concrete doesn't 'leak out'.  

Then I can pour the hearth slab - currently pegged to be 4.5" or so thick.  Once the hearth is poured, I get to move on to building the ACTUAL oven.  

That means, I need to buy some 1/4" board to cut out an oven floor template, buy some mosaic tile for under the insulation, buy the bricks for the floor and dome and make an indispensable tool (IT).  

I've already bought myself a 10" wet saw, so I should get that put together once the hearth is poured (and it is curing) and figure out the insulation layer, too.