Question on floor bricks

[yarex]

Hello everyone,

This site inspired me to build my own oven aand i have one question that i could not find answered in recent posts:

I have insulation layer ready and i'd like to lay down floor bricks. My bottom layer is cement with perlite mix 5:1 and isolation boaards on the top,
however i'd like to perfecly level bricks that come on the top of it. Can spread just normal sand under them if i want to level them by milimeters so they perfecly align horizontaly?

[SableSprings]

Welcome Yarex! Normally you should use a 1:1 mix of fire clay and sand underneath the insulation board to make it level. It will also work on top of the insulation board but it takes more time and effort since you would then have to set each brick level. If you dampen the sand mix a little it will help. It should not take much sand (1-2 cm thick at most) in either method to get a level surface. Using the tile mortar/setting tool shown below may help if the boards are more warped than normal.

If you choose to put the sand/fire clay mix between the insulation board and the hearth bricks, dampen the mix and use a tile setting tool (picture below) to produce grooves in the mix. Start setting your bricks using a level and a rubber mallet. The grooves created in the sand bed give you more room to level the bricks.

The common brick pattern for the hearth is herringbone which minimizes the chance of catching the edge of your pizza peel.

[yarex]

I have 3 25kg bags of special cement that is 1300c resistant, so i just add water. I guess i can use that too right? 0.5 cm layer should be more then enough to level it perfectly, i just was not sure if bottom bricks can stick to board via wet layer or just be allowed to move lying on something dry.

[SableSprings]

You don't need to have the bricks stick to the insulation board...the sand/fire clay mix is more to give you a method to level the bricks. Remember that if you use the refractory cement it will be difficult to remove and replace a broken or cracked brick in the future. I simply see using your more expensive special cement as a leveling media is a waste of money and resources.

If you insist on using the special cement, I think it would be better to use a little of the refractory cement mixed with sieved sand to level the insulation board and then lay your hearth bricks on the level board. Again, either method will work, but remember the hearth bricks will expand slightly when heated and if they are "cemented" together or cemented into a base you may experience individual brick or larger sections heaving (lifting of edges) during a pizza firing.

Using slightly damp sand mixes simply helps the sand/fire clay to make a firm substrate (and one that holds those ridges of sand made by the tool noted above) for leveling either the bricks or the board. I really don't believe anyone wants to join/stick/glue/mortar/cement the hearth bricks to insulation board...sand/fire clay are used to help level only and the board is only there for insulation.

[yarex]

OK, got it, will do it as you adviced.

Thank you for your help.