Advice on the first course please

[Give_Me_Spices]

Hi all,
The amount of variation between all the designs I've seen so far gets a newbie like me confused.
What is the best way to position the first course of bricks - around the oven floor or on top of the oven floor? Have you seen any advantages/disadvantages on any of those approaches?
My design is the latter but I'm questioning if this is the right option. Please let me know your thoughts.


Thank you,
GMS

[SableSprings]

Either way you start the first course of bricks, your oven will be successful. The two schools of thought you have seen in oven builds are based primarily on a couple of factors. The placement of dome bricks on top of the cooking floor is easier, simply because you don't have to cut bricks to fit inside the inner radius. The main advantage of placing the cooking floor entirely inside the dome perimeter is that if you ever need to replace a cooking floor brick, it will be easier.

Again, either system works just fine...but in both cases you want all the bricks (cooking floor & dome) to be insulated from the "outside world". That means if you lay your bricks on the cooking floor--which is on an insulation layer (ceramic board or insulating perlite/vermiculite concrete) you're good--as long as any perimeter brick pieces that may "peek out" past the dome bricks are also on that insulating layer. If you lay the cooking floor inside the dome perimeter, the assumption is the insulation is under both the outer dome bricks and the cooking floor.

I hope that helps...my oven was built laying the dome bricks on a leveled & insulated cooking floor. I've been baking pretty regularly for 11 years and haven't needed to replace any floor bricks...

[Give_Me_Spices]

That's fantastic. Thank you for the thorough answer.
I have read that the first course should not be mortared to the floor, but I'm wondering when I start mortaring the bricks to each other ( first course will be standing up) the wedges of mortar will inevitably make contact with the bottom. Is this a problem or am I overthinking it?

GMS

[SableSprings]

You're overthinking... The main reasons the first course of dome bricks is not mortared to the floor are: 1) It ain't going anywhere... and 2) During firing/cooling all the bricks will expand & contract a little bit. The floor will push out slightly when heated and the dome may push in one of several directions (depending on the firing stage & size)...if you mortar the first chain down to the cooking floor, the weakest spot is that joint and it will simply break and slide out just a tiny bit to accommodate the movement.

Don't read this to mean when you heat your oven that it's going to move somewhere else , it's just a small movement that caused by the heat expansion of the firebrick material. This is perfectly normal and does NOT cause an oven to lose any of its structural integrity or strength. Relax...

[Give_Me_Spices]

Thank you very much again for your thorough answer.