A little advice please

[TonyPizza]

Hi,

I am currently in the process if making a WFO. The base is old bricks, with a 100mm reinforced concrete slab.
The slab sits within a basin that I have created by reducing from a double to a single brick course.

Please will someone advise if the next steps seem reasonable, before I get to making the dome (I'll probably be back then too!).


So we have the concrete slab and on top of that:

1) 100mm Thermalite blocks (Shall I just cut the blocks and drop them into place direct onto the smooth concrete surface or use a fire cement / regular cement / kiln sand / builders sand and bed them in?)

2) Small layer of kiln sand / fire mortar. Will I even need to use any mortar or sand here?

3) 64mm firebricks.

The above will be surrounded two single courses of the same bricks I have used for the base, so that the top of the bricks is flush with the cooking surface.

Other questions I have are:

Is the Herringbone pattern the best to use for laying the firebricks?
Shall I use a little sand or cement in between the firebricks, or just cut them and drop them into place without the cement or sand?
Is there generally only one quality of fire brick, or do I need to look for a particular specification?
I believe I read somewhere that it is recommended to drill some holes through the concrete, so it can 'breathe' - if this is correct, roughly how many holes in a 90cm x 90cm slab?

Thank you in advance to anyone who can offer some help.

Hopefully I have successfully attached a couple of pictures to show you where I am.

Thanks,

Tony.

[david s]

Drill some holes through the centre of the supporting slab to act as a drain so moisture can escape from the insulation layer.

If the thermalite blocks have an even surface you can just lay the firebricks on them unmottared.

Medium duty firebricks are recommended. Low duty a bit soft and subject to abrasion damage. High duty really hard to cut.

Best to leave floorbricks laid loose to allow for expansion and easy replacement if required down the track. The gaps will fill with ash.

Herringbone pattern is preferred by some as they claim it’s less likely to catch the peel. I don’t think it makes much difference. It probably requires more cuts.

[mesoiam]

Hi Tony, What size of oven are you making? Be aware that the walls will be thick once you factor in all the insulation.

[TonyPizza]

Hi Tony, What size of oven are you making? Be aware that the walls will be thick once you factor in all the insulation.

Hi, it's 110 x 110. The cooking surface should be 70cm.