Tile dome

[JamieB]

I’m planning on tiling the dome of my oven build. I’m thinking to use Red Guard under the tile to help with water as well as de coupling the tile from the dome.
Who has tiled their dome? I plan on using 1” hexagon tiles

[Kvanbael]

I did. Relevant post: https://community.fornobravo.com/for...692#post429692


Do note that a honeycomb hexagon tile pattern will only fit on a flat plane, not on a curved spherical dome. You’ll get weird looking gaps if you try that. A random mosaic is the safest bet. Someone on this forum did round pennies.

[JamieB]

You oven looks beautiful!! Nice work! A very good point. Although I still want to research and see if I can pull it off. Maybe if I cut sheets into strips, of one tile. Then I can vary the number of hexagons in each row.

[Kvanbael]

Thank you!
Unfortunately strips won't work either. The hexagons won't always "interlock".

Round tiles will be more forgiving for imperfections of the hexagon pattern. Google "Pizza oven penny tiles" for some examples.

By the way, my first plan was a 'bubble tile' pattern (round tiles with varying sizes).

[mongota]

I'll offer a caution about RedGard. It is a waterproofing membrane, but it is also vapor-impermeable.

A concern I'd have is that after a period of non-use, your oven may absorb moisture from the atmosphere. When you start a fire and the heat starts to drive off the moisture in the structure, some of that moisture vapor may be trapped against the RedGard. Trapped, and seeing increased oven temperatures, the vapor may super heat. The increase temp could cause the RedGard to break down, lose its bond with the dome, and delaminate.

There are liquid waterproof coatings that are vapor permeable. I used a cement-based one; Thoroseal. Hydroban liquid is vapor permeable. It, like RedGard, is mostly used for interior tiling. I'm not certain of Hydroban and exterior use. It may very well be fine, I've simply never researched it.

[JamieB]

How hot does the outside of the oven get? I’m planing on 4” insulation bellow the oven, with 6” of insulation on top of the dome. I like the vent idea as well to release any moisture pressure. Reading up on Red Guard a little more, it’s rated for interior and exterior uses, as well as heavy duty commercial and industrial applications. It is rated for use in steam showers as well. I’m going to contact Custom Building Products and ask about temperature capabilities.
I like the UN coupling properties of red guard

[david s]

6” is a lot of insulation over the dome. A lot depends on the duration of the applied heat as much as how high the temperature is. After one hour, provided your insulation is not moist, you should find that there’s no perceptible heat on the outside. Perhaps after two or three hours the outside should feel cosy warm, but no more. A hand held to the outside tells you a lot. Obviously heat is detected first at the top of the dome and slowly spreads all the way down the sides.

[JamieB]

Custom Building Products got back to me. Red Guard has been tested to 160 degrees F.
I was planing on using the same insulation call outs as the FB commercial ovens. Seemed like a good idea to achieve higher temperatures.