Major mistake or magic mortar?

[michaewa]

I'm up to the fifth chain above the soldiers on my 42" oven, and the way things worked out this chain would naturally touch (barely) above the top of the 12" arch bricks.

I'm thinking I may have positioned my inner arch too far out from the center of the oven, as it doesn't appear that there will be anything to support those bricks from underneath that would come together over the arch. I can cut some so that the back of the brick is flush with the vertical surface of the arch, but even with a really strong mortar bond it doesn't seem (to an amateur mason) that that would be a good decision to have the following chains resting on these 'floating' bricks.

Any suggestions as to how others have handled this? Do you just trust the mortar?

[Tscarborough]

Re: Major mistake or magic mortar?

If I read it correctly, simply make the following couple of chains more egg shaped to get some lip on the arch and then gradually bring them back round as you proceed (technically you are corbelling them).

[michaewa]

Re: Major mistake or magic mortar?

You did - and thank you very much for the reply.

I went back out and noodled on it a bit, and after reviewing some pictures I ground off a little resting place in the arch for the brick in question. That means it would bond to the adjacent (supported) brick, and would have a small (maybe 5% of the bottom of the brick) bearing surface on the angled top of the chain.

The brick directly above the top of the arch would be slightly better, maybe 10% bearing surface.

Is that approach, and filling the wedge gap beneath with mortar and / or brick triangles asking for disaster?

I noticed that I was naturally corbelling (that is a new word for me - thanks!) the first and second chain, and started on the third to try to 'catch up' to what my indispensable tool was telling me was the 'correct' shape.

Thanks again...

[Tscarborough]

Re: Major mistake or magic mortar?

After you close the hole at top it is not an issue. Until then you may want to build some falsework under it if you are at less than about 40% of the brick supported.

[WoodchuckDad]

Re: Major mistake or magic mortar?

I had a heck of a time with that part of the dome. Once it got it in place and the Mortar was dry it felt quite solid.

[pizza_bob]

Re: Major mistake or magic mortar?

Any suggestions as to how others have handled this? Do you just trust the mortar?

Take a look through my oven build thread and notice how I "floated" only a portion of each brick that came in contact with the arch. The majority of the bricks that contact the arch are resting on the course below it. Then for the bricks that start to come close to the top of the arch I cut a notch in them so they're supported by the arch as well as the course underneath. These bricks were a pain in the butt to cut but I think it makes for a stable transition.
I should be dropping in my keystone this week some time!

~Bob

[jmhepworth]

Re: Major mistake or magic mortar?

Without a doubt, that's the hardest part of the dome. I found myself sitting inside the partly built dome looking at the transition into the arch and thinking about it for quite a while. Once the mortar cures, it will be fine.

[michaewa]

Re: Major mistake or magic mortar?

Thank you all for your replies. I have achieved a level of Zen like calm about it. My solution was to use an entire brick across that part of the dome, and rather than 'hanging' the brick as I've seen a few others do, I used a grinder and made an indentation on the back side of the arch. If I hung the brick, the portion that made it over the dome would be a little to thin and shallow for my taste.

In addition, I set the brick back slightly (about 1") from the two adjacent bricks to give it a little more of a safety net. It feels very sturdy now.

I can relate to the sitting and staring comment, I was in there for quite a while just cogitating.

I got back to it yesterday ready to put up the 6th chain and the head broke off of my indispensible tool within 30 seconds of starting. It was affixed with JB weld, I guess there is a vote for using an actual weld to hold it on. I repaired it yesterday and hopefully today will make some progress..

Thanks again!