how to cut FB board to size

[beninbouldercreek]

I just bought a Casa 90 wood oven. I have a question about cutting the FB board. Can I cut the FB board to size with a grinder using a mason wheel after I have set the oven dome pieces? This seems easier than cutting it into pieces and then trying to get the dome pieces set on top of it.

[Gulf]

Hi Ben,

Welcome to the forum. Congratulations on the Casa 90. It is going to be fun!

The cutting wheel will create way too much dust. An oscillating tool with a scraper blade would be a better choice for the job. But, the fiber board is easy to cut. You can work your way around the circumference with simple hand tools. A stiff knife, key hole saw, a jigsaw blade clamped in the jaws of some vice grip pliars etc.

Wear the appropriate PPE for cutting "refractory ceramic fibers".

EDIT: I just went back and reviewed your post. The oven dome and floor should be sitting on top of the insulation, separated from the structural hearth. I'm just checking to make sure that we are on the same page lol.

[JRPizza]

If you have one, can borrow one, or need an excuse to buy one,a Sawzall with a long blade is a great tool for cutting board. I sketched out my dome OD, then clamped the board to the tailgate of my truck and just zipped along the line. I pulled the truck away from anything I didn't want fibers on and wore a respirator. This seem way faster and more accurate than trying to hack away at the board after the dome is sitting on it.

[Jim from Akron]

I see these posts are from 2019. I hope someone is still looking at this thread. What are the dimensions for the FB board cut for the Pompeii 36" oven?

[UtahBeehiver]

Too many variables to give you an exact size, you need to sketch out the final OD of the oven(ID (36"), wall thickness, insulation thickness, final outer coating thickness, ETC then make sure the insulation size extends to a minimum of the total outside dimension. none of the oven should sit on the hearth.

[Jim from Akron]

Thanks for the reply! That helps.

[Jim from Akron]

UtahBeehiver - When you said earlier that none of the oven sits on the hearth, I'm assuming you are referring to the firebrick oven floor, but the firebrick sentinels (first layer) would sit on the concrete hearth... is that right? Also, I see that FB Board is sold in 24" x 36" x 2" boards. They say they sell 3 boards for the 36" Pompeii oven, but if the internal diameter is 36", wouldn't 2 boards be sufficient?

[UtahBeehiver]

No, none of the oven walls or floor should be in contact with the concrete hearth or you wind up with heat sink from the concrete hearth. You need to calculated the oven OD, IE 36" ID, 4.5" x 2" = 9" so min oven OD is 45" not accounting for dome insulation, stucco and final coating. I doubt two CaSi boards will be enough. You can check locally at any refractory suppliers for CaSi board, needs to have about 70 PSI compression strength at 5% deflection. ThermoGold 1200 is and an example.

[Jim from Akron]

Thanks UtahBeehiver! Super helpful!

[Jim from Akron]

UtahBeehiver - In your photo, it looks like you have something between your FB Board and your concrete slab. I've been wondering about this because I'm concerned that someday water will find its way into my structure and damage the FB board. If I could elevate the FB board above the slab, that could be a solution. Do you have another suggestion for keeping the FB Board dry in case of a leak in the roof of the enclosure?

[UtahBeehiver]

FoamGlas, aerated glass made by Dow and is water proof and good thermal K value. It is difficult to find. If you look at recent builds, the latest trend is to make sure you have weep holes in the hearth, then a layer of cheap ceramic tile that raises the CaSi board off the hearth and give errant water a way to egress through the weep holes. I suggest you look at the builds in the Newbie Section under Treasure Archives, they are some of the more documented builds and you will find most answers there.