Days 7 and 8 - First Half of Facade Bricks, Granite Slab, Arch Form and Back Walls

So today was a big brick laying day. And the whole purpose of it was to build up the facade bricks because our granite slab relies on it to rest on. On top of the granite slab goes some bricks necessary to build up before I finish the dome. So that is what we did today, lay a few hundred bricks to that I can place the 8 necessary ones in position so I can proceed with the dome (it actually isn't critical until the front courses of the dome go in, you will see which bricks I am talking about in the next post though). So it was a long day and if there is anything I learned from laying brick all day long, it is that next time I am going to wear gloves. By the end of the day my fingertips became very tender and crackly to the point where my fingerprints were disappearing. The combination of rough bricks and what felt like portland cement finger corrosion was not pleasant. 

Lay up the corners first, and fill in using a mason's line 

Using a mason's line

An old angle iron works perfectly to bridge the gap.

The combination of the lifelong bricklayer and the never-before bricklayer made for a good team.

After finishing the facade bricks, it was time to work on getting that granite cemented to the oven once for all. The first step was to fill in the gap from the hearth bricks to the facade bricks. Now, remember this picture? 

Look at the rebar sitting there in the front of the oven, right where I need to lay some fill brick. What an inconvenient place for them. It would have been much better to have the front and back rebar in the grooves and the side rebar laying on top of the block. So if you are going to build an oven, do not follow my example unless you have to. In my case, I had to do it this way because the lintel had rebar very close to the top. If I cut grooves, I would have had to cut through rebar. But here is the beauty of the situation, a standard firebrick fit exactly in the spaces in between these pieces of rebar. So what you see in the next picture is two courses of firebrick, and then some red brick. Also in the above picture, remember the fireclay/sand mixture we used to set the firebrick on? Since it has no cement in it, if you put your extra in an airtight bag, it will not harden. This is what I did after laying the hearth bricks, and here in the picture below, I am using these leftovers to fill in my gaps.

Making a relatively level surface for the slab to lay.

Slop some oven mortar on.

We gave it a slight downhill slope so that when it rains, the water moves away from the oven.

After the slab went on we went through a somewhat lengthy process of making a form for the slab. Unfortunately we do not have any pictures of making the form. What The Bread Builders says to do is to just place your bricks on a board you will cut your form out of so that they are in the shape of an arch. Then trace that shape, cut it out, and you have your form. As easy as this could have been (and probably perfectly adequate), it was utterly unsatisfactory to me. I wanted a precise arch. But what kind of curvature should an arch have? I didn't know for sure, so we decided on using a portion of the most perfect shape - the circle. Now the most efficient brick oven has a door height which is 63% of the dome height. All I have to say is some complicated math went into making an arch form with a base of 23.75 inches and a height of 6.25 inches and having it be a part of a circle. I will not attempt to explain it here, especially if just fudging an arch line is good enough by professional standards. Another way I heard of doing it is to hold a string at both base points, and letting it hang down to the height point. Spray paint over the string and there you have it, the shape of your arch. We tried it this way at first, but it just seemed a little too imperfect. So maybe this was just our personal obsession, but we made a pretty perfect-shaped arch form. We used two 2x8s, cut out with a bandsaw, and held together with two 2x4s to make a gap. You will see it in action in the next post.

Once we have the arch frame, I can put it up to the oven walls and see how many bricks I need to lay for the back wall so there are no gaps in the oven. This was pretty simple and straight forward brick laying.

Now we are all ready for the arches!