39 inch Corner Build

[JRPizza]

I wouldn’t sweat that half inch. Not until, I was at least clear of the inner arch. There are two things that get the courses of an oven real out of shape imo. One, is the inner arch not reaching far enough into the oven to meet the inside curve. The other, is the “dreaded droop”. I think that you have compensated for the arch. The droop is easy to avoid too. Check this pic out from Colin’s build (Oasiscdm). He is using the floor as a reference point to keep the bricks level over the inner arch. It doesn't have to be a level. I've seen others clamp a stick to the IT. Just set it on the last true brick for that course before laying into the arch.

Thanks for pointing out the droop problem - it was not on my radar. I'll make sure when I am tying in my dome I pay lots of attention to the height of the bricks on either side.

[JRPizza]

Yesterday I finished what I'm guessing is the last easy thing I'll have to do in my build - mortared in the first course of bricks. Next up is cutting/placing some material to protect my cooking floor, building my inner arch template, and cutting some bricks on angle for the arch.

[JRPizza]

Well, I guess my first row was not as easy as I thought. Had several joints where the mortar pulled away from the bricks. The guy at Mutual sold me AP sand, which I think is not the right stuff. I was able to get nice tight joints - some of them just pulled away. I'm using 1-1-1-3 but a little heavy on the sand maybe closer to 1-1-1-4. Do I need to buy some finer sand, and do I need to tear out the bricks that look OK and start over? I think I had the mortar at the right consistency - I mixed it runnny and added dry mix till it would cling well to my trowel. It never got "smooth and creamy", probably because of the bigger grains in the all purpose? Also, would just wire brushing off the sides of the removed bricks with water be enough to clean them back up (remove mortar residue) so I can reuse them?

[gastagg]

JR, if they are holding, leave them in place. You could sift your sand through a wire strainer from your kitchen (like I did for a few batches) or just hit menards or someplace and get mason sand. it's cheap. the problem with AP sand is that the big pieces will get in the way where you need a small or no gap. i think guys use anywhere from 3-1-1-1 to 5-1-1-1 so I think youre OK there on the mixture.

[gastagg]

also, I found that the more water i had the easier to use, but you can tell when its too watery and is just slop. mrchipster mentions the "consistency of peanut butter." that worked for me.

[JRPizza]

Thanks gastagg, I picked up some Lane Mt #30 "silica" sand and it looks quite a bit finer and sharper too, which I think is a plus. The AP didn't seem to keep me from getting a tight joint as I didn't bring it all the way out to the closed edges. The large bits are rather round though and I think I will be better off not using it unless I sift it like you did or use for an outside render on my dome. I think part of my problem might be the hydration of my bricks. I dunked them in water before I mortared, but in retrospect they didn't "bubble" at all and were probably rather saturated from some recent rains. They were several shades darker and heaver than some bricks I had under cover. I'm going to do what I saw recommended somewhere on this forum (Tscarborough?), put a few drops of water on the brick and if it does not soak right in they are hydrated enough.

[Gulf]

George makes a good point. I used an old window screen to sieve my AP sand. I found almost pea gravel size rocks in mine. It may also be a good idea to go to two mortars. One with fine sand for laying the brick, and not filling the wider outside joints. For the other, you could mix up a batch with the larger sand (or more of it) for filling those gaps. That is best done as you finish each course and before you lay the next. This is also a good place to use what is reclaimed from the wet saw. A lot of the clay that you will get from the tray after screening will be almost sand sized particles. I also wouldn't take the first course apart to repair it. For relaying what you have took apart, you can just brush of the loose mortar and or dust with a stiff brush. No need to wash and scrub. But, that does bring up another good subject, though. If the humidity where you are is very low, you may want to mist them lightly before laying. I used a spritz bottle. If the fire brick are extremely dry, they can suck the water from the mortar that is touching the brick before it can set. That also seems to make the mortar seem to pull away from the brick. Another is adjusting a bricks position (even a very small amount) after it has been placed.

EDIT: I had this composed before I saw your reply, but the power went out briefly. (If nothing else, I like the auto save feature on the new forum) Most of the reply still applies and yes, mortar doesn't want to stick to a water logged brick.

[JRPizza]

I redid parts of my first course yesterday, removing and remortaring the loose bricks I had. I think when using horizontal bricks like I did in lieu of soldiers for first course, you have minimal surface area for bonding and loose bricks are a risk. Subsequent courses will have mortar on four surfaces of each brick and adhesion should not be as much of a problem (I hope).
Also finished cutting bricks for my inner arch, for the second time ;-). I had the dimensions for my arch bricks pretty much figured out, then pulled a bad number out of somewhere and make an angled shim for the bed of my saw. Ended up cutting 17 bricks that would have required an inverted vee of mortar . I know some folks build arches using only rectangular bricks but I was shooting for a uniform mortar thickness, not the large vee?s that you would get without any taper. The inverted vee was not look I was going for, and I think getting them uniformly spaced would have been more difficult. I have yet to dry fit the arch bricks and think building getting them mortared with a uniform thickness is going to be one of my bigger challenges.

[JRPizza]

Been busy working on the oven. Did a dry fit of my arch, with bricks and form on edge, to see what thickness of shims I needed. I doubt I am the first one to think of fitting the arch that way, but had never seen it recommended. Maybe most folks are handy enough to figure out their shims while fighting gravity. I marked the target location for each brick on the form, then assembled it all in place to get a preview of how it should look. Also got most of my second course mortared in - my external joints aren't pretty, but fortunately they will be covered up ;-)
You can see my arch bricks protruding on the right side - I got too close with my second course bricks on that side which forced me to make some difficult cuts. UtahBeehiver advised me to work a little ahead on my arch so I won't run into those kind of problems in the future - advise I will heed. I have also been mixing my mortar in a small pail, which gets me thru 2 bricks if I am lucky. I'll start mixing in a 5 gallon bucket tomorrow.

[UtahBeehiver]

Nice tight inner joints. As you move up and stagger your joints chose the best bricks and cuts for the back half of the dome and make corrections and adjustments on the front half. No one will ever stick their head inside to see except maybe you. LOL.

[JRPizza]

Will do! I had a question on mortaring the inner arch. With the form in place, I can't get to the joints that are touching the form so am anticipating having lots of incomplete fill and some rework to do. Is this common, or are folks pulling their forms in and out during the build. Neither option seems to be desirable, but got to do one or the other.

[UtahBeehiver]

I would not pull form until you are done. Too much risk of damaging the arch structure. I did not have much of a gap issue, you can always tuck and point afterwards but also remove as much excess as possible.You have plenty of relief so dropping the form "after you are done" should not be an issue.

[JRPizza]

I finished off my second course and incorporated the first of my tapered arch bricks. Got about 1/3 of course 3 before I ran out of mortar and daylight. The joint thickness on the arch bricks is a little thicker than I wanted so will have to keep an eye on that. Ran into a little confidence crisis on cutting the back angles on my arch bricks, but UtahBeehiver has been helping me through the visualization and I think I am on the right track. That is one of the great things about this forum - knowledgeable people that are willing to help. Having someone to talk things through seems to really stimulate the thinking process. I had to put my marker back in the IT and trace the outline of inner and outer surface of the dome on my arch bricks. I saw this in UtahBeehiver picture gallery, but needed a little help understanding how it all fit together. I clamped a brick in the IT and brought it up next to my TDC arch brick, aligned it with the inner and outer marks, and established the angle needed for the brick to seat. I have no idea whether it will be a full width brick or a sliver when I incorporate the last course into my arch, but I have a good feel on how it will sit. I will use those marks I made on the balance of the arch bricks to cut them to shape as I build up.

[JRPizza]

Made a little more progress yesterday trying to get ahead of the coming rains. Also cut some plastic sheet to cover my oven/stand, as the insblok gets quite "soggy" when it is wet and I am worried about the bearing strength when wet. I visualize the whole oven sagging into the insulation if it gets too wet and the mass gets too great. I am not cutting courses too far in advance as I am checking angles as I go to keep the interface joints tight. Using spread sheets available on the forum but checking the first couple of bricks I cut to make sure the spread sheet is giving me good angles, and more realistically, making sure I am getting the angle off my saw that I am aiming for.

[JRPizza]

Just finished the fifth course. Things are progressing more slowly as I build up. Integration of the arch and keeping the joints aligned properly is making me wear a path in the lawn from the oven to the brick saw. On the positive side I ran across my level today when I was cleaning up (have a bunch of tools down in the wood storage area) and thought I would check to see how much slope I was building into the oven. I was almost shocked to see everything on the proper plane.