36" Pompeii in St Louis

[plastered]

I picked up a 2' section of flue liner, and yea it's pretty heavy. I'm worried about how it will be supported, in addition to the brick I was planning on surrounding it with. I built my outer arch today and to line it up with the flue, I had to do a little section of arch bricks out front. I'm worried this will not be strong enough for a 2ft+ chimney.



I plan to add another half-brick red arch to the front, so a little more strength will be gained. I also plan to sort of box the whole vent/arch area in with red brick, as you can see below:


With this plan there will be a gap between the outer arch and the red brick (widening as I go up due to the arch)-- this is on the left and right side of the arch. Do I build the red wall up and then try to connect at the top? Connecting the arch to the wall with a brick in a shape like the ones shown in my sketch (with the angle)? Is that going to be strong enough for a 2ft brick chimney? I feel like the weight of the chimney will still be on this arch, which just doesn't seem strong enough to support 30 or so bricks on top. Or should I fill this gap with more bricks for structural integrity?

Gap is circled in red in my pic below, blue is the brick I'll have to 'bridge the gap' with (I only drew one blue rectangle in my pic below, but they would be from top to bottom of the image, from the wall to the arch).





Here are some more pics of my progress today.





Thanks for all the help!

[plastered]

Wondering if I should put some lentils/angle irons across the front and back for stability? Also maybe some joining the two. (Red lines are the outside of the 'brick box' i plan to build)

[UtahBeehiver]

IMHO, a full arch transmits the load almost straight down and with the outer brick work you propose it acts as a buttress. I would fill the gap with some p or vcrete.

[plastered]

Thanks UtahBeehiver, I was thinking about using a little bit of leftover ceramic fiber blanket to squeeze in there, but I also like the concrete stability-ness of the v/pcrete.

[miikee]

Current school of thought is to have the dome insulated but not the final outer coating before firing.

UtahBeehiver When you say after the dome is insulated, does this mean only the ceramic fiber blanket? or is this including the ceramic fiber blanket and vermiculite/perlite mixture? The final outer coating being stucco.

[UtahBeehiver]

either or, the insulation just tempers the temperature differential between the inside and outside of the dome while curing, but do not install the render until the water is out of the vcrete.

[plastered]

I built up the front area quite a bit. Sure is hard when all the bricks are slightly different sizes (used brick). I also prefer the silky smooth high heat mortar more than just the basic stuff.

I decided to run two angle irons across the vent for extra stability for my chimney. Worked out pretty well, just had to do lots of weird cuts to get the flue level and in place. Vent area was probably the weirdest part of this project for me so far. Probably because I didn't really plan it out, just kinda ended up with a box like area that I had to make level and fit into a 6.75" square flue. Lots of on the fly cuts and not the prettiest work.

I even had time to put some of the ceramic fiber blanket insulation on, which I thought was pretty easy to work with. I don't plan on using the chicken wire over top -- seems like some people on here think it's too much of a hassle. We'll see once I start putting the vcrete on. I ran a couple wires across it to hold it down, but it is holding itself down for the most part. I put 2 layers mostly around the dome (each layer is 1"), and then I did an extra layer on the top (3 layers). I may add more to the sides because I have a lot of extra blanket, though it would start spilling over the CaSi floor tiles. Seems like most people do 2-3 inches on here so yell at me if I need to ensure everything is 3".

For the gaps on either side of the vent/chimney, I just stuffed extra blanket insulation down there, mostly made up of mis-cuts. Might fill the rest with dry vermiculite.







Disregard my shims still on my flue. I had to tweak it a little after I discovered it's cut wasn't quite level. I may have to pull it off and re-mortar it next weekend.

[plastered]

Pretty proud this whole shape/project is coming out better than expected. I kind of 'winged' this double arch. Wasn't super precise on leveling each brick (or even plumbing them), but overall the imperfections kind of make it look more rustic.

[Chach]

Looks good. That's an oven you should be proud of. Looking forward to seeing your finished product.

Ricky

[david s]

Don’t fire it up until you insulate around that flue tile

[plastered]

david s I was going to leave a 1/2" air gap around it, is that enough for insulation? I am also curious about the top, where the flue extends past the chimney bricks. I've looked at a lot of chimneys around town recently and I notice there is usually a big pile of mortar sloped at the top. Or should I use the high temp mortar? Thanks!

[plastered]

I did some googling and it seems like I need to put down some plywood/hardiebacker and then mesh on the top of the chimney. Then I wrap a thin foam gasket around the flue. I add concrete to the top of this sloping it like the above pic. I am still not sure if I use regular concrete, masonry mortar, or refractory mortar?

I let it all dry (for multiple days for max strength), apply a sealant to the concrete, and remove the foam gasket around the flue. I fill this gap left from the foam gasket with a high temp silicone sealant.

This guy seems to capture the process the best: https://www.youtube.com/watch?v=Qod9wX-RcN4

I still don't know what to fill the chimney with, between the bricks and the flue. Some say an air gap is enough, others say perlite/vermiculite (dry or with cement?), wrap with ceramic blanket?

Here's my updated sketch:

[david s]

david s I was going to leave a 1/2" air gap around it, is that enough for insulation? I am also curious about the top, where the flue extends past the chimney bricks. I've looked at a lot of chimneys around town recently and I notice there is usually a big pile of mortar sloped at the top. Or should I use the high temp mortar? Thanks!

Yes that should work ok. If it were mine I'd be pouring some loose perlite, vermiculite or stuffiffing some blanket in the space, particularly at the bottom where it's hottest. You can easily do this as you build the bricks up around the flue tile as you go. Normal mortar at the top is ok as it's not too hot there.

When on holiday on Paros in 2011 I took quite a few pics of lots of different solutions for chimney tops. Unfortunately our hard drive died and I lost them but most were like those, or variations of, those attached. All quite simple and all masonry.

[david s]

Here's another idea using window-sil blocks.

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Today's progress pics. I think I'll be done with the chimney by the end of tomorrow (need more bricks AND mortar). I insulated the base of the chimney flue with leftover ceramic blanket as you can see. Not sure how I'm going to connect it to the rest of the vent area (decoratively speaking). I don't know if I should angle the bricks like a little roof, or if I should just stack them like steps (zigzag). Sure is scary working on the chimney, so high up with little room for your mortar bucket and bricks. I need some scaffolding.

I laid the vcrete 'foundation' for the dome. Mixing it all in a wheelbarrow was a pain, but using rubber gloves and just globbing it onto the insulation was pretty easy. I did use a little more portland cement and lime though, probably a 7 to 1 cement to vermiculite ratio. I'm thinking I'll only have to do 3 of these 'bands' of vcrete.