It is begun

[Tscarborough]

Re: It is begun

We drilled holes in the perimeter, then used a recip saw to rough it out and chisels and rasps to shape it into a slight cone, smaller at the top. We measured at the desired height to get the correct diameter, then made a template and slid it up and down the post, sanding the high points and dropped it over the top. The other end was too small for this, so both the pole and the bar were notched and through-bolted

[Tscarborough]

Re: It is begun

I would treat pine, mine are cedar and pretty much rot proof already.

[R. Barton]

Re: It is begun

Yes, for the inner arch with firebrick, the standard is for joints no thicker than 1/8", so you pretty much have to cut pies.

Does this 1/8" grout standard apply to all of the fire brick grout joints?

Great looking oven by the way.

[dakzaag]

Firebrick are commonly laid minimal joint thickness 1/8" or less with Refractory Cement. If you have bigger joints, which you will unless you spend an enormous time at the saw, you need a Refractory Mortar. Heat Stop 2 or similar is recommended. The real challenge is balancing the need for compound miter saw cuts, which take a lot of time and waste brick, against the desire to build as quickly and economically as practical. For some builders, the whole reason for the build is to learn/demonstrate how to make a round structure out of square blocks. Other builders want a functional oven and really care less about how to achieve it as long as it cooks great pizza.

Both builders can accomplish their goals and both ovens will work great, it really comes down to how you want your oven to be completed. If you are expecting to fire the oven 5-6 times per week for 30 years such as a commercial Wood Fired Oven, then it pays off to spend the time cutting and getting each brick to fit perfectly in its place. If you just want to enjoy a back yard brick oven for use a couple times per week in the summer months, then a more casual approach is just fine.

Both ovens will heat to 900 F, both can be designed to cook for 5 days after 1 big fire, and both will likely crack at some point in operation. (albeit, the very finely cut oven will have a less noticeable crack compared to the more quickly built oven) The choice becomes a decision for each builder and most of us end up somewhere in the middle where we are happy with the amount of detail we included in our ovens balanced with the amount of time to completion.

For clarity, mortar joints are the space between the individual brick or block that is filled with mortar or masonry cement or Refractory cement. Grout is the filling added into the open cores of hollow Cement Masonry Units (otherwise know as block) to add strength and encapsulate vertical rebar so that the resulting wall resists lateral movement more forcefully. Not trying to be a jerk, just adding clarity for any future reader who may not be familiar with these terms.

[dakzaag]

I think I meant to say "typically", but show me a build where there aren't a few fat fingers in there somewhere.

[david s]

I think I meant to say "typically", but show me a build where there aren't a few fat fingers in there somewhere.

Yes, I agree. But I don't agree that tight joints are a necessity or give you a better result. In fact, to the contrary, there is evidence that tight joints are not superior.

I quote from Kilns by Daniel Rhodes "In kiln building it is much better to have a loose structure than a tight one. For this reason the amateur may have a slight advantage over a professional mason, because his bricklaying is apt to be somewhat loose and not highly locked together. I have seen kilns made by professional bricklayers which in use suffered severe cracking and swelling due to overly tight and precise workmanship."

Whilst we are not building kilns the principle still applies. Personally i believe that it is better to limit the use of the saw in tapering bricks, particularly in the bottom courses (you have to in the upper part of the dome) and back fill the bricks with home-brew and the odd brick offcut wedge. Tapering every brick means you need more bricks and takes way more time for no better result. It just means you've parted with more money and taken you way longer. The appearance of the dome from the outside doesn't matter as it is covered with insulation.

[Brick Oven Nick]

I know on the forums I see a lot of mention about cracking in the mortar joints. But I don't know that I understand the concern if there is some cracking over time. Is this creating a structural concern? Are we concerned that a crack in the mortar joint will lead to the dome or arch collapsing in? Should I worry about a brick coming loose and falling? Or is this just an appearance issue?

ive just completed my dome. As I progressed, the better I got with brick cutting and mortar work, but I ended up with many large mortar joints, especially on the outside of the brick in the gap creating the angle between each brick row if that makes sense.

Thanks for for any comments on this!

-Nick

[jonv]

If the mortar is sound I don't suppose the size of the joints on the outside matters much. The oven will most likely develop some cracks but they are usually hairline and nothing to worry about. Once the dome is together it is reasonably self supporting. I don't think one should be too concerned about the dome collapsing

[dakzaag]

Nick, you ask a great question, because sometimes we have a long discussion about things that are not significant. Cracks are one of these things that for the most part are not significant. Your pictures show that you did a great job and have little to fear if a few cracks appear. Joint size is important because it is an indicator of strength and longevity so evaluating the joints on an oven gives us an idea of the builders mindset.

Refractory cement is designed for tight joints, 1/8" or less. For bigger joints Refractory mortar is a better selection because it has more sand to fill the bigger void. For your build, it looks to me like you would have benefited a little from using Refractory cement to glue the brick together initially, and come back later to fill in the big voids in the back with Refractory Mortar. This usually means using wedges to maintain decent spacing during the build and then filling the gaps later. It also usually requires a form to finish the top of the build because the cement will not hold the brick vertical if you just butter the inside edge.

The solution for this issue is to buy tapered or arch brick to start with and then cut them at a compound angle to allow tight mating from brick to brick. Cost and availability of arch brick gets a little tricky for a lot of builders and so most guys just use common brick and cut them as close as they can. I think your dome looks really sharp and hopefully you get many years of enjoyment out of it regardless of the number of cracks.

[SableSprings]

I know on the forums I see a lot of mention about cracking in the mortar joints. But I don't know that I understand the concern if there is some cracking over time. Is this creating a structural concern? Are we concerned that a crack in the mortar joint will lead to the dome or arch collapsing in? Should I worry about a brick coming loose and falling? Or is this just an appearance issue?

ive just completed my dome. As I progressed, the better I got with brick cutting and mortar work, but I ended up with many large mortar joints, especially on the outside of the brick in the gap creating the angle between each brick row if that makes sense.

Thanks for for any comments on this!

-Nick

Nick - dome looks good. As mentioned before, generally cracks in the dome mortar are not structural problems and in fact are often needed to accommodate the dome's expansion/contraction of each firing cycle. One thing I noticed in your post #247 above (third pic) is the clay flue tile on the side of the oven. It looks to be an 8" tile (meaning 6" inside diameter) and your oven looks to be 39"-40" diameter. If that is indeed the case, you might want to consider increasing the size of the flue to the next larger size up (8"-10" ID). I built a 39" dia oven and used the 8" OD/6"ID flue by making assumptions instead of using my head (and measuring tape). Although it does draw OK after it heats up, it still will spill out occasionally with a good fire. Just something to consider based on my experience...

p.s. Sorry for the hijack Tom

[R. Barton]

Firebrick are commonly laid minimal joint thickness 1/8" or less with Refractory Cement. If you have bigger joints, which you will unless you spend an enormous time at the saw, you need a Refractory Mortar. Heat Stop 2 or similar is recommended. The real challenge is balancing the need for compound miter saw cuts, which take a lot of time and waste brick, against the desire to build as quickly and economically as practical. For some builders, the whole reason for the build is to learn/demonstrate how to make a round structure out of square blocks. Other builders want a functional oven and really care less about how to achieve it as long as it cooks great pizza.

Both builders can accomplish their goals and both ovens will work great, it really comes down to how you want your oven to be completed. If you are expecting to fire the oven 5-6 times per week for 30 years such as a commercial Wood Fired Oven, then it pays off to spend the time cutting and getting each brick to fit perfectly in its place. If you just want to enjoy a back yard brick oven for use a couple times per week in the summer months, then a more casual approach is just fine.

Both ovens will heat to 900 F, both can be designed to cook for 5 days after 1 big fire, and both will likely crack at some point in operation. (albeit, the very finely cut oven will have a less noticeable crack compared to the more quickly built oven) The choice becomes a decision for each builder and most of us end up somewhere in the middle where we are happy with the amount of detail we included in our ovens balanced with the amount of time to completion.

For clarity, mortar joints are the space between the individual brick or block that is filled with mortar or masonry cement or Refractory cement. Grout is the filling added into the open cores of hollow Cement Masonry Units (otherwise know as block) to add strength and encapsulate vertical rebar so that the resulting wall resists lateral movement more forcefully. Not trying to be a jerk, just adding clarity for any future reader who may not be familiar with these terms.

Dak, thank you for the detailed reply.

One thing that should help at least some with the block cutting is I'm going to do a barrel vault type build vs igloo. I do admire the igloo builds though.

I was in Harbor Freight this morning to buy some scaffolding and looked at their 10" brick saw. I'll buy one at some point this summer regardless, but I'm keeping an eye on them in case they go on sale before I'm ready. If I could save $50 on the thing it wouldn't hurt for it to set in the garden shed a short while.

[david s]

If you intend building a barrel vault because you want it to primarily be a bread oven, then fine, because it's form is more suited for that application. However, if you think a barrel oven would be easier to build than a dome then you are mistaken. The reason the dome has been so popular over the last couple of thousand years is that it's form is superior both as a structure and as a combustion chamber. A barrel oven's structure is not as sound and requires either or both, bracing and buttressing because of the heat cycling and resulting expansion and contraction which test its structural integrity. Do a search on this site for "barrel ovens" or "barrel vault" to see what is required. It is not mandatory to build with a brick saw for a dome. Bricks can be cut in half with a hammer and brick bolster, the wedge shaped gaps on the outside filled with homebrew and only the last for or five courses needed to be cut or trimmed which can be done with a 5" angle grinder and diamond blade.

[narcosi]

Re: It is begun

I finally got a spare hour to get the perl-crete on to make my brick ledge for the chimney. Hopefully I can get that done this weekend in spite of an out of town soccer tournament (The perl-crete is white because I used a sample bag of white masonry).

Hi, - great looking oven - did you thermally break your oven from the smoke area/vent? did you use normal clay bricks in your facia - does it stay cool enough?

thanks

[UtahBeehiver]

FYI,

Tscar has not been active for quite a while so you will just have to review his thread.