Mosiac Tile (Upside Down) Under Pizza Oven Insulation - For Drainage - July 2024

With the foundation and stand complete for our diy'd wood-fired pizza oven, I recently started turning to building the *actual* oven by cutting bricks last week.  The process of starting the actual oven begins with prepping the top of the hearth to accept the calcium silicate insulation boards.  Cal Sil boards are water-resistant, but you want to keep it as dry as possible so the mass of insulation works as ACTUAL insulation under the oven floor.  

The latest innovation for dealing with water penetration that has been driven through the community over at Forno Bravo is the addition of mats of mosiac tiles - set upside down - on top of the reinforced hearth and under the insulation boards.  The idea is that by setting the mosiac tile upside (with the mesh/glue pieces facing up), you create little channels that any surface water that hits the hearth can find its way to the drain holes.

I went up to a closeout flooring store on North Avenue in Northlake recently and bought some plain mats of tile for $1 per square foot.  I bought 27 square feet and began to lay it out.  You can see that process in the photos below.  I used the masonite template/drawing jig to sketch out the approximate location of the 49" diameter dome to make sure I had enough tile.  

I lined up some of the lines in the tile mats with the drainage holes.  You can see one of those holes peeking through the gap below:

Below is the final product.  I've left more brick on the hearth than the oven footprint will sit.  My thought is that I'll either leave this all down when I'm done, or use the grinder to cut it out.  

The other thing that I had to do was use my angle grinder to cut off the galvanized wire that was sticking through the hearth.  I used a wire to keep the concrete forms from bowing out during the pour, but when I removed the forms, there was 1.5" of wire sticking out.  It caught on my shirt enough times that I decided to clean it up.  Here's the cleaned-up side below:

What's next?

Laying down and cutting the cal sil insulation.

Then, the floor.  I'm planning on using a 50/50 blend of mason's sand and fireclay to set the floor.

Once the floor is in place, I can start with the dome.  My plan is to mortar in the soldier course of the dome and go from there.