Idaho 36" Build

[AJH]

I was trying to lay out the CalSil Board in a way that kept enough to make a door with it, but I'm wondering if it would be better to use it all and make a door out of stainless steel with loose perlite or vermiculite fill. Could also mix in a little portland cement to bind it together so it doesn't settle over time.

I'm also trying to decide if I should lay the first ring on the floor or cut the floor bricks to fit inside and lay the first ring on the on the insulation. I saw that people say its easier to replace bricks if you do not build the dome on the floor, but I haven't seen anyone say that they have had to replace a brick... thoughts?

Also, is there a preferred tile type for under the CalSil board? Glass, ceramic, or porcelain?

[Gulf]

I have built two metal insulated doors. I used CalSil board for my door filler. We used ceramic fiber blanket for a friends door. There is not much difference in the two doors sizes. But my friend's door is considerably lighter.

If any bricks were ever to need replacing, it will probably be in the very middle of the oven floor area, and would be replaceable without too much difficulty imo. I have been firing my oven for close to a dozen years and have seen no damage.

I don't know if there is a preference on what to type tile use for elevating the insulation. My advice is to use what is the cheapest. Many times you will find what you need on the discontinued isle. Just go with any of the smaller bathroom type tiles and not the large floor tiles.

[rsandler]

As far as on- vs around floor, Gulf has it right--actually replacing a floor brick happens very rarely. I felt some comfort knowing that my ovens (where the dome went around the floor) had an expansion joint to avoid cracks, but not clear you need such a joint if you build on top. Whatever works for you.

For tile, it was pointed out on my second build (just in time) that you do want to make sure whatever you use is completely non-porous, otherwise it can wick moisture up from the concrete, defeating the purpose of the exercise. I ended up going with meshed-backed mosaic tile sheets that were a mix of glass and aluminum (and, more importantly, were the very cheapest thing on clearance at my local Home Depot).

I'd probably go for extra CF blanket for the insulation fill rather than trying to use perlite for the purpose. Even if you use some cement, it's likely to crack and crumble inside. One can also buy smaller pieces of CF blanket online for semi-reasonable rates if you're short. FWIW I'm so far pretty pleased with my Nomex-covered door (way lighter than metal), which theoretically would work with either CalSil or CF blanket (though it's probably a more challenging sewing task with blanket).

[JRPizza]

I built my oven on top of the floor. To minimize the amount of board I needed I cut the floor circle very close (net) to the OD of the dome. I got to thinking about the amount of stress on the edge of the board around the periphery, and thought the weight might be distributed better if the dome bricks were sitting on floor bricks, which In some places would provide more area for the dome weight to be distributed over. I have no idea how sound that reasoning was, but had a picture in my mind of getting some "edge sag" if that is a thing and wanted to do what I could to avoid it.
I had a bit of left over blanket so that is what I used in my door. If you are enclosing the insulation, you don't need to worry about durablity of compressive strength, so I'd use either whatever had the best weight to insulation ratio or whatever you have on hand. I might have thought about using perlite, but didn't use any in my build so none was on hand. If you do use it and can pack it in tight you probably don't need a binder. I think the best designs for doors in terms on insulation, do not have a continuous metal shell to conduce heat around the insulation in the middle, but they are harder to build and make durable. I know the outer shell of mine gets pretty hot but is still effective.

[UtahBeehiver]

I cut the floor to sit inside the dome but doing it again I would have the dome sit on the floor bricks. Not worth the time to precision cut bricks to fit inside the dome. I you do go this route be sure you dome is sitting on insulation not the hearth floor.

[AJH]

Did some prep work today on my build. First, I punched the weep holes out from underneath and then tapped out the pvc pipe from above. Then, I laid out the mosaic tile and built up the CalSil insulation above that being careful to overlap the joints. I ended up using it all to have a consistent surface to work with. I'll figure out a door later... Then I laid out the floor without anything under it. I'll be pulling it back out and laying some sand/clay on the insulation to level it out and fill the voids then pick and choose which bricks have the best face to be the real floor bricks. Then I decided to mock up the oven to make sure I liked the depth of the inner and outer arch locations.
As you can see in the pics, we got some snow the other day... going to slow down the build but I'll make do.

[AJH]

Here's the mock up pics. Would only let me do 6 at a time...

[UtahBeehiver]

With full soldiers you do have quite a bit of outward thrust where the dome and the top of the soldiers are. You may want to consider half soldiers or potentially buttress the full soldiers.

[AJH]

With full soldiers you do have quite a bit of outward thrust where the dome and the top of the soldiers are. You may want to consider half soldiers or potentially buttress the full soldiers.

The soldiers were just to help me visualize the dome. I'm planning on just starting the first ring on the floor without any soldier/sailor/whatnot... I just put those there so that I could see how far in I'll be able to see without bending over.

[mongota]

Here are a couple of pics of my vibrating table that I use for my precast work. It is basically a frame sitting on four car engine valve springs. Cheap to make and works exceptionally well. The whole frame vibrates when tapped with a rubber mallet.

What a fabulous idea you have there!

If you can add an electric motor to either direct drive (or to remote drive via a pulley and belt) an eccentric weight on the axle, you can flip the switch and let the table shake and bake itself. I had something like that for doing concrete countertops way back in the yonder days. Worked well for well over 400 countertops.

[david s]

Yes that’s what I originally intended, but tapping with the rubber mallet for a few minutes proves adequate and is far simpler.

[AJH]

Been chilly the last couple weeks and haven't really been able to do much. I did make the IT and have all the stuff I need to make the tile saw jig. The caster wheel used in the IT has an offset of about an inch from the swivel point. So, where I attach the wood (where the wheel was attached) is about an inch from dead center of the dome. I decided that it was fine. The dome height will just be 17 inches and the radius 18 inches. Now I just need to figure out how to get the middle brick out to drop in the caster so that the pivot point is at the floor height. I'm thinking a couple hot glue sticks melted onto the brick might have enough leverage to pull it out...

Does anyone ever spread fireclay over the floor bricks and brush it around to fill up the cracks like they do with brick pavers? I'm assuming that they will get filled with ash during the curing fires, but thought maybe the fireclay would be better for heat retention.

Today was a balmy 31 degrees F for the high and I decided I was sick of waiting on a nice day to cut some bricks. I laid down the fireclay/sand mixture and placed the floor bricks so that the bricks were as close to level as I could get. There might be a couple that I hit with the angle grinder later. Then I marked the outer edge of the dome and cut them to size. I filled up a bucket with hot water and had the pump in that thinking it would keep everything around the saw warm but the metal and brick being below freezing dropped the water temp fast and I still had to take a break halfway through to warm up my hands...
Here's some pics of where I'm at now.

[rsandler]

Looking good for a start!

To get the middle brick out, you might just pull the bricks around it; number them first with a sharpie so you can put them back in the same order/orientation. That's what I did on my second oven, though I mostly skipped the sand/fireclay mix, so I'm not 100% sure you would disturb that and make more work for yourself. Could also carefully drill a hole with a hammer drill and screw in a tapcon to use as a handle; either plan to put the brick back down with the hole facing down, use a different brick, or just fill the hole with more brick dust and try to forget it's there :-)

On my second oven I did go ahead and spread fireclay (from brick dust) into the cracks in the bricks. I had the same theory that ash would act as an insulator, interfering with even heating. I didn't bother on my first oven, but the bricks I had then were much straighter and I don't remember there being notable gaps. Yours look very similar to the ones I got on build #1 (H.C. Muddox brand), with lots of uneven edges). I don't know if it helped to brush in fireclay, but it made it look better, and made me feel better about it :-).

I found thick rubber dishwashing gloves handy to protect my hands from water, brick edges, mortar etc. though they wouldn't stand up to a brisk 31F morning!

[AJH]

Got a little progress done with the nice weather we had last weekend. Going to cut the next ring tomorrow and maybe mortar them in place on Sunday...
What's the consensus on mortaring the first ring? The joints are pretty tight and I'm assuming that the weight of the dome will keep them from moving. Should I put a thin layer of mortar between them to lock them in better or place them on a bed of mortar?

[rsandler]

Others who built their domes one top of the floor will have a better sense, but my instinct is that it would be wise to at least set them in a thin bed of mortar underneath, if only so the bricks don't go shifting around when you go to put the next course on.