How to start with the pizza oven floor

[BiggreeneggNorway]

I`m sorry, this has propably been discussed before, but could not find the answer i am looking for.
Planning to use 2" fibreboard for insualtion in the bottom. Should I use glue/mortar to fasten this to the base or is it better that it`s floating?
When laying the bricks/floor, should this be glued/mortar to the fibreboard or just floating?
Planning to make the dome on top of the floor, should the first row of the dome be glued/mortar to the floor?

Thank you in advance!

[UtahBeehiver]

floor insulation is NOT mortared or glued down nor are the bricks to the insulation, a 50/50 sand/fire clay mix can be used between the brick and the insulation for leveling purposes. You should post the specs (not a commercial link) so it can be reviewed for proper insulative and physical properties. I suggest you download and read the eplans from Forno Bravo to give you overall design and construction details and concepts.

[BiggreeneggNorway]

Thanks a lot for your reply. What about the first row off the dome (i have it on top of the floor bricks) , should this be mortar to the floor bricks or should also this be floating? I have downloaded the guide

[UtahBeehiver]

same thing

[BiggreeneggNorway]

I read that the hermal loss will be higher if I put the first row of dome bricks on top of the floor and also more difficult to replace in the future.
If I decide to put the first row not on the floor, but on the side, do I need any distance between floor bricks and dome bricks for movement?
Thank you in advance!

[david s]

So long as the oven and floor are totally encased in insulation I can’t see why there’d be any difference in thermal loss.It is normal to leave about 1/4” gap between floor and dome with the floor bricks laid loose, to allow for expansion. This does require precise cutting of the floor bricks at the perimeter of the floor. Building the dome on top of the floor you don’t have to worry about this gap and the floor perimeter cuts can be rough because they’re hidden by the dome insulation. If any floor brick ever requires replacement it will only be in the middle of the floor, never one of those sitting under the dome.

[BiggreeneggNorway]

Thanks for your answer. Probably go for the dome on top of the floor then.
Can you also tell me if there is any benefit to use aluminium foil as a layer outside of the dome before the insulation?

[david s]

Some builders recommend a foil layer to reflect radiant heat in an attempt to reduce heat loss. Unfortunately if the foil is in contact with a conductive material heat loss via conduction is actually increased, as aluminium is a very conductive material. The other problem is that it will act as a vapour barrier locking moisture in. This can be mitigated by perforating the foil. For these reasons I don't use foil in the ovens I build. Although I did with my own oven, placing a foil layer over the insulation before the render layer. This does have the advantage of eliminating the tendency of the vermicrete to suck moisture from the render tat's applied over it. However, worrying about the vapour barrier issue I perforated the foil in two places, one at the top of the dome and another about 1?2 way down, both about 5 square inches in area. Now when my oven picks up moisture and I fire it those places where the foil perforations are become hot to touch while the rest of the dome exterior is just warm. This is a clear indication that steam is finding its way through the perforations. This makes the expulsion of moisture that much slower, so I wish I hadn't added the foil layer, but glad I at least perforated the foil in two places.