Mongo's 42" CT Build

[mongota]

Ladies and Gentlemen, boys and girls, children of all ages...

I'm back!

Had a couple of absolutely bizarre issues that came up with out-of-state extended family that 100% pulled me away from any home projects (as well as pulling me away from home) over the last year. The fire brick dome was plastic sheeted and double tarped for the past two winters, since October of '16. Amazing that it was for that long.

About a month ago, I untarped the WFO. Unfortunately, the three layers of protection suffered abrasion during the winter winds and allowed some water intrusion. The 4" of ceramic fiberboard insulation under the dome was absolutely saturated. Press on it and water would weep out. A sad discovery indeed. I even had fungi growing out of the insulation on the exterior! lol The good news is that other than being wet, the board insulation seemed structurally sound. There was no thickness compression from the weight of the brick.

After several weeks of drying, I've made some progress. More posts and progress pics to follow.

It's good to be back on this forum as well as getting the oven back up to speed!

[mongota]

Sadly, not the tasty kind you can use as a pizza topping!

[Gulf]

Welcome back Mongo,

Ouch! on the wet insulation. I'm sure that you will be able to dry it out, though. I'm looking forward to the pics of your progress.

[UtahBeehiver]

Plus one with Gulf. This is a great lesson for other builders wondering about water intrusion into the floor insulation and that wet/saturated CaSi can be restored again through curing again.

[JRPizza]

I also got my board soaked. It happened early in my build and even though it was covered after that the water stayed until I drove it out with many long slow fires. The link below shows some of my pics, where I had water seeping out from under the oven floor during curing.

https://community.fornobravo.com/for...019#post387019

[mongota]

Gulf, Russell, JR, thanks so much for the welcome back.

I started the drying with halogen lights, 1000W worth, on 24/7. My goal was to drive the moisture out of the dome bricks, and if I lessened the moisture level in the floor, that'd be a bonus. After several days, the dome was indeed dry, but there was little to no change to the floor.

I figured I'd run some drying fires, and I wasn't going to be shy about it because of the dry dome. If I messed up the dome, then so be it. I'd repair, or if required, I'd break it all down and start over.

I broke all the rules and made some pretty good sized fires. Started the fire under the vent arch. When I had a good flame, I'd push the fire back a bit and remove the floor brick from the vent arch to expose the wet board insulation. Add more wood, push the fire back further, and remove a few more rows of floor brick from the front of the oven. Then I stacked a few brick in the arch to retain the heat. I kept the fire stoked, it was satisfying to see the moisture vapor being driven out of the board insulation.

Thank goodness for welding gloves with gauntlets that cover the forearm, they made it safe to reach in and pull the floor brick. lol

This worked like a champ. I kept the drying fires going for a few days until the insulation was quite dry. Then I finally pulled all the floor brick, reset the halogen lights, covered up the entry, and let them run 24/7 for several more days.

[mongota]

I did have two cracks in the top front of my vent arch. I noticed them when I untarped the dome. Not sure how or why, if it was a winter weather, a moisture freeze thing? But after the drying was done, I figured I'd make repairs to that while doing the chimney transition.

[mongota]

Installed the chimney anchor plate. Tried to keep it simple.

I scribed one brick to the curve of the vent arch and used it as a guide to cut 11 more brick, for a total of 12.

Due to these transition bricks being set on top of the curved arch, I wanted to avoid setting these twelve bricks one at a time, tap-tap-tapping each one into alignment, all without knocking any of those already set out of alignment, or to suffer mortar creep and have them slide down the arch.

I built a small wood frame to hold all 12 bricks and then mortared the six left bricks together, and the right six bricks together. I let the mortar cure overnight.

The next day I marked out and cut the hole for the chimney anchor plate. Used an angle grinder. Fast and painless.

[mongota]

With the bricks still in the form, I dry fit the chimney anchor plate in place and marked and drilled holes for the anchor bolts that will secure the anchor plate to the brick.

I unscrewed the form and removed the two sets of brick, then I mortared the top of the arch as well as the undersides and ends of the left and right sets of brick, and set them into place. A few taps with my persuader to assure all was level and aligned, and all was good.

I then screwed the wood frame back around the 12 bricks to hold them secure while the mortar cured. I had to slip the form up a bit so it could clear the curve of the dome.

I used a tube of RTV and slathered it on top of the 12 bricks, then pressed the anchor plate into the RTV. I set the four anchor bolts and called it good to go.

[WarEagle90]

Anchor plate turned out quite nice, Mongo. I like the use of the form to lay all 12 bricks at once. I can see where that prevented a lot of headaches with other bricks moving around.

[mongota]

Thanks Dan. The form really did simplify it. Nothing much easier than mortaring bricks together on the workbench and using the form to assure that they are indeed in plane with one another, and then carrying them outside to install as a unit.

Small victories! I'll take efficiencies when and where I can, lol.

[mongota]

Dome insulation. With 4" of rigid board insulation under the dome, I wanted 4" on top of the dome as well. Used four layers of 1" 8# ceramic fiber blanket.

The bottom edge of the first layer sits on top of the board insulation, the other three extend all the way to the slab. The slab has RedGard on it to prevent the blanket from wicking moisture through the slab. I sliced and butt-seamed my layers, instead of just overlapping everything, and offset the seams as the layers went on. It was easy to do and allowed the insulation as a whole to remain smooth as a whole and maintain the half-sphere shape.

While I put four inches of blanket on the dome, I only put two inches on the vent arch. I considered putting none and I considered putting four. Compromise! lol

[Gulf]

Mongo,

That is the best insulation job that I have seen. Great job!

[MichaelPBoisvert]

Dome insulation. With 4" of rigid board insulation under the dome, I wanted 4" on top of the dome as well. Used four layers of 1" 8# ceramic fiber blanket.

The bottom edge of the first layer sits on top of the board insulation, the other three extend all the way to the slab. The slab has RedGard on it to prevent the blanket from wicking moisture through the slab. I sliced and butt-seamed my layers, instead of just overlapping everything, and offset the seams as the layers went on. It was easy to do and allowed the insulation as a whole to remain smooth as a whole and maintain the half-sphere shape.

While I put four inches of blanket on the dome, I only put two inches on the vent arch. I considered putting none and I considered putting four. Compromise! lol

How many rolls of fiber blanket did you end up using? Are they 25' rolls?

[mongota]

Thanks, Joe.
I'll get some lath and possibly some stucco pics up in a few hours.