Sonotubes and bread

[dbhansen]

Hello! My first post. I'm in the early planning stages of my bread/pizza oven in N.E. Wisconsin, and I have a couple of questions.

1) I will primarily use the oven to bake bread, but an occasional pizza party would be nice. I was going to go with an Alan Scott design, but I'll need to buy all my wood and I'm short on baking time, so I like the idea of an oven that heats up fast and can bake both bread (probably only 6-8 large loaves per firing, until my neighbors start asking for more bread!) and pizza. Do I need to make any adaptations to the Forno Bravo plans if I am going to be making mostly bread? For example, should I turn the firebricks on their side? Add 2" of mortar over the dome? Or 1/2" of mortar? Anything?

2) Our frost line is 4' deep. Is there a "standard" (and/or easy) method for anchoring the oven below the frost line? My initial thought is to use 4' sonotubes at the corners and center of the slab (5 in all), tied into the slab with rebar, but would I need more than that? Any suggestions? I called the local building code guy and he said there are no codes here for outdoor ovens and I don't even need a permit. I could perhaps just use an at-grade slab with some drainage under it, but there is a lot of heaving around here in winter and I would feel better if I go below the frost line. If I use sonotubes, I assume I would still need the 3" of pea gravel below the slab, yes?

Thanks!
Daren

[dmun]

Re: Sonotubes and bread

1) The mass of the barrel vault oven is mostly useful for multiple bread bakes, and the heat retention is useful if you are going to be firing every day. Unless you are planning to go commercial, that mass mostly consumes wood and time.

I think the footings are a good idea. I dug below the frost line, but I was planning a two story masonry chimney. Is five sonotubes enough? I don't know. There is a special form tube that is flared at the bottom specifically to avoid frost heaving. You might look into that.

[DrakeRemoray]

Re: Sonotubes and bread

Welcome Darren,

For 6-8 Loaves per firing the pompeii design will work well. I have baked up to 10 loaves at once. I have about 1 inch of extra refractory mortar on the outside of my dome, but other than that, very standard. I mostly did that to seal up any cracks, but it has worked out well. Also, Insulation is the key to getting multiple bakes...

I think that unless you are planning 4-5 bakes per firing, the pompeii is more practial than the Alan Scott design.

Here in Denver, I used Sono tubes 3' below grade. So in Wisconson, 4' should do it. I did not pour a slab, but just formed and poured the walls...a little different, but once I was digging sonotubes it was quicker to form the walls and pour the sonotubes and walls all at once. That let me do 4 sonotubes intead of 5. I put in a pavestone floor in the center of the stand. Just another idea. But with the frost heave, a slab is more likely to crack...I also used "sure void" under the walls to be sure that the ground was not going to heave my walls directly. I am sure it is overdone

Some pictures....3 holes dug




Forming the walls, sure void in place at the bottom


Hope that helps.
Drake

[CanuckJim]

Re: Sonotubes and bread

Darren,

Both Drake and Dmun are on the right track. I live in Ontario, to the north and east of Toronto, in an area that probably has exactly the same frost heave problems you do. Code here is four feet. At one point, I posted some rather lengthy information on foundation considerations in the forum, so you should do a search to find them and those of other contributors. However, I would definitely go for the five tubes tied into the slab, with a good layer of gravel for drainage. Also, look for the flared sonos.

Mine is a high mass AS design, but I bake commercially. You don't need to go that route for the kind of baking you outline. As Dmun points out, high mass will give you multiple bakes, but it will also add time and wood consumption to the equation. The Pompeii design will work just fine.

Contact me by email if you have specific frost-related questions.

Jim

[dbhansen]

Re: Sonotubes and bread

Thanks for the quick replies (and pictures). I like the idea of pouring the walls with the posts, Drake. What diameter sonotubes did you use? I can tell this is going top be a fun, long-lasting project!

[DrakeRemoray]

Re: Sonotubes and bread

I think I used 10" tubes...it has been a little while. Certainly larger than 8" tubes, but not sure I went with 12". Pretty sure it was 10"

I had an engineer friend do the math on it and in the end, he said I should have used another tube in the middle of the back wall. I asked a builder friend about that (one who helped me with the pour) and he said, "according to most engineers, all of the 100 year old houses down town are about to fall down tomorrow". What he meant was that engineers tend to want to overdo to cover all options. I am sure my stand is more sturdy than my house.

Drake

[Unofornaio]

Re: Sonotubes and bread

Thanks for the quick replies (and pictures). I like the idea of pouring the walls with the posts, Drake. What diameter sonotubes did you use? I can tell this is going top be a fun, long-lasting project!

I think foundations and footings should have it own sub section in the "Oven Design and Installation" section because this is a common one..

Coming from someone who has done numerous whole house foundations, and retaining walls out of block and forms I choose forms every time now. When we use forms we only use a new system out here from EZ-Ply Concrete Wall Form System (check it out its really cool) and it goes very, very fast. The last basement we did was close to 2000sq' and it took 3 guys about 8 hrs to set up plus another couple the next day to tweak, that is FAST. Then about half day to pour and another full day to strip, clean and stack the forms. So 3 days total...

One advantage of block is when you are done you are DONE and for a small structure like the oven base you can have the slab poured one day and have the blocks dry stacked and filled the next. Actually if you pour early, leave the forms on and watch the corners you can start stacking later the same day.

Some disadvantages of using forms on a small project are the rental fee, the pain of setup, tear-down, clean up, picking them up, returning them and the material cost difference of concrete vs block. Then there is the vertical and horizontal steel to tie and support (which is another time consumer) and if your site is not accessible to the truck filling the wheel burro wheeling it to the forms, filling buckets and then filling the forms or shoveling right into the forms. In addition unless you are doing something else or your footing is large (as in your case)your gonna have a short load charge usually pretty close to the cost of an extra yard, which most of the time is money well spent. Mixing the equivalent amount of bagged concrete to redi-mix cost the same in materials and takes a lot more time and effort. In the case of a footing in frost zones redi mix is the without a doubt the way to go.

[DrakeRemoray]

Re: Sonotubes and bread

Uno, good points.

In my case the 2 week rental of the forms was only about $35. We used a "mix-on-site" type truck so there was no short load charge. We did use a wheel barrow to move the concrete back to the site and then got 4 guys to lift the wheel barrows into the forms.

[n2iko]

Re: Sonotubes and bread

[QUOTE=DrakeRemoray;12531]Uno, good points.

In my case the 2 week rental of the forms was only about $35. We used a "mix-on-site" type truck so there was no short load charge. We did use a wheel barrow to move the concrete back to the site and then got 4 guys to lift the wheel barrows into the forms.


Where can I rent this bunch of guys! The gents who were to help me with the last one tried to show up after we tapped the keg.