Laying Out And Drawing Oven Floor For Wood-Fired Oven - July 2024

Yesterday, I shared the details of a template that I cut out of Masonite and a circumference tool that will shape the form of the floor of my wood-fired oven.  In order to get the inner arch opening correct, I opted to create a second drawing jig - one that is 20.25" wide that will set the width of that opening.  

The goal was to draw the outline of the oven floor, but it proved harder (for me) than I thought it might be when I started.

Before I get into the process of getting the oven floor drawn, a quick mention on firebricks.  The community on FornoBravo spec's "Medium-Duty Firebricks" for the floor and dome.  After poking around online, I've come to discover that Illinois is home to the Alsey Refractory - in Alsey, Illinois.  Somewhere between Springfield and St. Louis is the Alsey Refractory; where they've been making firebricks in the USA for more than 100 years.  A few towns over, a materials dealer - LaGrange Materials - sells Alsey firebricks.  They're *exactly* what I need for this project.  LaGrange Materials lists them for $2.25 a piece.  I'm sure that if I was a contractor, that pricing goes down, but for me...the DIY'er...they're $2.25 per brick - plus tax.  Using the spreadsheet from FornoBravo, I'm figuring to use about 210-or-so firebricks.  At almost eight pounds a piece, I went with a couple of pick-ups of 70 bricks each.  70 bricks x 8 lbs = 560 lbs.  Seems reasonable for my old, trusty SUV.  So far, I've brought home 140 firebricks and stacked them both inside my garage and out back on the side stoop:

I opted to begin this process on our garage floor.  I wanted to leave these bricks in place for a while, so that seemed like the best spot to lay this out.  The first step was to draw a straight line on the ground.  This line needed to be longer than the bricks I was going to layout - including the dome and landing.  Once I had that line, I could begin to lay down the bricks in a herringbone pattern.  I used a metal square to find that first 45 degree angle.   Once that first brick was in, I went up the line - making sure to place the corner of the brick on the line.  Then, I laid in the rest.  I applied the large template (48" wide) on top of the bricks to make sure that I had *enough* in the pattern.  I felt around the bottom of the template to make sure the bricks covered the area.  Here's the masonite template laid on top of the bricks:

Once I knew I had enough bricks laid down, I moved on to getting the 20.25" inner arch dimension set-up right.  I initially thought I was going to do ALL of my drawing using the larger template, but I quickly realized it wasn't going to work.  First....it only allowed for the outside edge of the dome (49") and without cutting down to the inside dome dimension (40"), I was going to have a hard time getting the inner arch location right.  

After thinking about it overnight, I figured out a way forward - creating a second jig.  To do that, I cut down a 20.25" wide piece of Masonite using my table saw.  Then, using a T-square and tape measure, I was able to find the 'center' of the 20.25" (10.125" from edges) and drilled a hole so I could attach my circumference / scribe arm to the center.  The scribe arm is made from scrap wood that I had on hand with holes drilled in it at various spots.  I tried a few and when I settled on 40" interior dimension of the oven floor, I drilled a hole at 20" from the pivot and 24.5" from the pivot.  That would give me both a 40" diameter circle and a 49" diameter circle.  

Using that first line on the floor and the center line created by the points on the herringbone pattern, I scribed ANOTHER line down the center of the bricks.  I used the arm to ensure I was close to the right depth.  Then, I cut-down this new template to reach the front of the landing (a little bit longer than I wanted) and would allow me to draw straight lines to the edge of the bricks.  

Below is a look at this 20.25" inner-arch template and the scribe arm.  

Once I was satisfied that the jig was centered, I climbed on-top of it and kneeled on it - to keep it from moving.  Using a mechanical red pencil, I inserted it into the scribe arm (that was drilled out to accept this specific mechanical pencil) and began to rotate it around.  I had to cut out the corners of the masonite board to get the arm to rotate around the top.  (It would have been better to cut out similar angles about half-way down - to get the arm to rotate cleanly to the bottom.  But, I just 'lifted' the arm a little bit and it worked anyway.)

Below is the oven floor with two circles - interior and exterior.  And inner arch width.  When I stepped back, I realized....that I wasted my time drawing the outside ring.  I don't need that drawn on these bricks.  Why? Because I'm going to isolate my floor from the dome - which means the bricks that form the base of the dome will NOT be in this herringbone pattern.  They'll be cut to fit around the edge of the dome.  Oh well, no harm done.  

Once I took the template off, I could FINALLY *see* the oven come to life.  The floor was there.   Like everyone online says to do, I quickly began to write down the numbers of the bricks.  Knowing that these are on my garage floor, they're going to have to move to the oven eventually, so numbering them is a way of knowing where they'll go in their final resting spots.   Below is the oven floor with bricks numbered:

Here's a few close-ups of the oven floor.  Posting these (mostly) so I have close-ups of the numbering system to reference later.

Below is a look at the oven landing and inner arch location.  As I said, I opted for a 20.25" wide inner arch.  I was going back-and-forth on where/how to finish the herringbone pattern and transition to straight bricks and ended up factoring in a 2-brick deep overall landing.  That's 9" + 9" = 18" total.  I'm going for 9" of herringbone and 9" of straight-laid bricks out front.  That leaves 18" minus the thickness of the arch bricks (both inner and outer) to create the flue opening.  If the arch bricks are 3" thick each, that's 18" - 6" = 12" deep flue opening.  Seems right.  

What comes next?  Eek...actually cutting all of these bricks.