Day 11 - The Cladding

If you are building an oven, you will notice as you go along that there will be times when you have to say to yourself "I wish I did it differently." I had a few of these moments today, but in the end, everything seems just right. The first thing is that I wish I made my hearth slab wider in order to give me thicker side walls. My side cladding is only 2.25 inches at the widest part, and only about an inch on the sides of the firebrick. It would have been great if my side cladding was 3 inches. As I put the reinforcing wire, the plans call for two layers, and with such thin walls, this seemed unreasonable. So the sides of my oven unfortunately just have one layer of reinforcing wire. The second thing I would have changed was that when I did the corners (right after putting in the arches), I would have used pieces of brick cut more precisely to make a smooth arch-like feel. These corners really give you a hard time when dealing with reinforcing wire and aluminum foil. And the third and more simple thing I would have done differently was to lay one more course of chimney brick so that my cladding could come higher in the front (but we found a solution to that, which you will see below).

So the first thing we did was wrap the oven in heavy duty aluminum foil. I originally thought that the purpose of this was to reflect heat back into the oven, but I was mistaken. The main purpose is to create some "slippage" so that when the bricks expand, it is not "glued" to the cladding. This way, both layers can expand and contract somewhat independently. After wrapping it with foil, I shaped the 6x6 reinforcing wire to end up in the middle of the poured cladding. My plan is 2.25 inches on the sides (wish it was 3), and 5 inches on the top. I put two layers of wire on the top (with bigger walls, I would have definitely put 2 layers on the sides as well). This process was painstakingly slow as I was trying to get the shape just perfect and ended up taking me a couple hours.

I kept a light in the oven prior to pouring in order to add some heat to the oven. This puts the bricks as somewhat of an expanded state at the time of the pour. This may help in preventing more serious cracking of the cladding (which is bound to happen after your first serious firing, but that is what the reinforcing wire is for).

All ready for the pour.

This was our solution to not adding another course to the chimney - just put in temporary bricks for the pour, and take them out once it has set some.

Put plastic and then a canopy over it to slow the curing process.

This was a little disaster that ended up being no big deal. Our corner busted open when the brick wedge at the bottom slipped out. We didn't want the concrete filling in the air gap between the hearth slab and the block wall, so I slipped some boards in there to prevent it from doing so. All this really did however was give me a thicker wall at the corner - just what I wanted right?

When the corner busted out, we tapped the walls to get the concrete settled a little too gingerly - leaving these air gaps. No big deal though, we just filled them with a sand/cement mixture.

Now we let it cure for a couple of weeks. Then pizza time!

Day 10 - Figuring Out That Darn Chimney

I have been thinking about this darn chimney since day one and have been dreading its arrival because I honestly did not know how it was going to work. Almost anyplace I looked I found inadequate instructions and missing pictures. I was pretty much lost when I started today, but it came together in its own sort of "just do it" kind of way.

One thing I struggled with was the integration of a clay flue pipe. I originally thought I would get an 8x8 flue pipe, and bring the side bricks (the ones on top of the granite slab) in 1-inch each course until it is the 8 inches apart I want. In order to do this however, the chimney will have just as much height in bricks stepping in as it will flue pipe. So this got me to thinking, do I really need a flue pipe? With a little research, I decided that I did not need a flue pipe. The whole purpose of it would be to prevent mortar corrosion which will eventually lead to a weakened chimney. To keep the story somewhat short, I am not worried about this. I will just make sure to clean the chimney every once in a while and it will be fine. Thinking about it, if the mortar which the flue is protecting is subject to corrosion, so is the mortar between all the bricks below the flue (the ones stepping in an inch with every course). So if the upper mortar joints (now unprotected in my new plan) would corrode, so would the bottom mortar joints (unprotected regardless of what plan you use). Therefore, if I ever for some reason need to replace the chimney (which I don't think I will have to) it would be because the bottom and top bricks alike have corroded... so why even protect some of them if it is not possible to protect all of them. Also, gases from wood are not as corrosive as gases from coal. In conclusion, I am no expert and may be missing something important, but this is where my logic has taken me. No clay flue liner for me!

Phew... now the chimney is a lot easier, but I am now approached by my next problem I have been wrestling with from day one. How do I start the back wall of the chimney on those slanted dome bricks which are coming towards the door? Even if I cut the bricks so that the first course of the chimney can be vertically level, the pressure will be pushed down and in. Ideally, you only want the pressure to go down. Once downward pressure is coupled with inward or outward pressure, it can be asking for trouble. But once again, I am probably being paranoid, especially since this is what it shows in The Bread Builders (inadequately in my opinion). So I am left to my own innovation. So I will just let you see the pictures and end this rambling.

Each course comes in one-inch

In between the third and fourth courses, I decided to put in this metal rod. The purpose is to hold in the back wall of the chimney from wanting to push in towards the doorway if the mortar does in fact ever weaken.

Before proceeding up further, it is wise to brace the bricks, especially if you have to whack the next course of brick to get it level. I actually got to the fourth course and had to start over because the first course lost its bond... I was evidently too rough on it and did not let each course properly set before moving on.

All four courses in place.

I cut pieces to fit the slant, leaving room for a mortar joint at the bottom of each one, and bringing it to the same level as the fourth course. These upright bricks will lean on the metal rod.

You can see here the shape of the bricks that fit on that slant.

This is what I set out to accomplish today. This wall is the front part of the frame in which we will pour the concrete cladding to (hopefully tomorrow).

This is the base of the chimney - it is just straight up from here.

Day 9 - The Dome

My original idea for starting the arch was to lay guide bricks on the wall at just the right angle to start the first arch bricks like in this picture below: 

However, getting these bricks cut in this way seemed more trouble than I was willing to bother going through when I knew I could fairly easily do it another way using hand-cut bricks. When we build our big oven someday however, this will undoubtedly be how we approach it. You will see what we decided to do below:

Before anything gets cemented in, make sure your arches are in just the right place by using wooden wedges.  Also, in order to fit an even number of bricks in the arch (to avoid special cutting a keystone piece), I had to actually lower the arch form just a tad and raise the first bricks out a bit so that they did not actually touch the wall bricks. This is OK though because all of its pressure is being thrusted into those wedge pieces. 

Special-cut wedge pieces were placed under the first bricks. You can see in this picture that the first brick actually is not touching the wall. This will be filled in with mortar as well. 

Fill in that bottom joint before you take the other bricks off the arch. This way you know that these first (and most critical) bricks are in the exact right height and angle. 

Then you start working your way to the center from both sides. 

I found it best to place the brick in with mortar on the back side only. Hold it in place with a wedge, and then stuff mortar into the joint. The most critical thing is to get the right angle so that the bottom edge has no gap and is a smooth transition from the previous brick. 

First arch done!

Second arch up and ready to mortar in. 

The last arch is in, and I am taking out the arch form for the last time. Exciting moment! 

It held just as expected!

Next row to go in is the front row. The bottom ends are resting in the angle iron and the tops are temporarily resting on a some lumber. 

I cut a special piece for each joint. 

Ready to be mortared in. 

This was by far the easiest mortar job yet. All you have to do is slap some mortar in between each brick and stick them together.

After you mortar in the special cuts, you can take the lumber out. Now its time to cut pieces for those pesky corners. You can see I mortared in some thin pieces of brick on top of the wall there to bring it to the same level as the longer firebrick door jam.  

Looks pretty good! You can see that the corner pieces are just to the best fit. I was able to just special cut the bottom piece and then just use half bricks for the top two layers.  

Now that's looking like something I can bake in!

It is best to let this fully cure before pouring the cement. What a convenient time to be going on a vacation so I don't have to be tempted to pour right away!

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!