Foundation's width 4 inches short - need suggestions

[Danieltp]

This is my first time posting a post on this forum and I'm hoping that some of you guys can help me out. We ordered Casa G290 modular pizza oven a while ago. I am not sure if I am missing a manual book inside the crate (I looked for it but couldn't find anything) so I had to resort to using the pdf files on the Forno Bravo website. Looking back on this, I should have send an e-mail to Forno Bravo reps who have been very helpful and communicative when it came to purchasing & shipping and answering my questions on the options. I used the pdf called "Installation & Operating Manual" thinking that it'd be the same manual I'd get in the crate if I was to get one. While it didn't offer any specific footprint measurement for the foundation, but I saw that the external dimension of CASA 2G 90 was 40"Wx46"D and how we had to make sure we had few inches on all sides to allow for the FB blanket and stucco so I decided to go ahead and build 54"Wx61"D slab that is about 7 inches deep and the 3/4 inch rebars were welded together (wanted to practice my welding skills, as it has been a while).

To my horror, when I brought the cinder blocks and started to lay them out - I realized that the width of the slab is little too short. I decided to do more research and found a specific pdf with "specs" for CASA 2G90 and it said that 58"Wx61"D is the minimal, which didn't make me too happy. I feel so stupid about this mistake, as my pop-pop would always say measure twice, cut once all times to me. I always have applied this approach to all of my projects in the past...

So I'm trying to figure out what my options are, as the slab that is in the ground is pretty much is immobile. Do I go ahead build the oven stand within the current foundation size (I'll have to use my wet tile saw to make cinder block fit perfect) and build a overhang hearth? Would this be a problem?

Any recommendations or ideas would be appreciated.

[jonv]

I don't see why a modest overhang on a properly constructed hearth would be a problem.

[Gulf]

Daniel,

Welcome to the forum. Sorry about the misunderstanding. I'm not sure about the installatiion instructions being in the crate. I am linking Alex_FB about that. Also, I moved your thread starter to Forno Bravo Oven installation. This sounds like a good "lessons learned" for Forno Bravo and future owners.


Now to the fix: Instead of cutting those block to fit, I would buy (three) 4" X 8*' X16" blocks. (They do make them in 4" X 8" X 8" if you can source them locally) Cutting them in half will give you 4 block to adjust for 4 rows in the back. The other two cuts can be used to inset a monolithic concrete lintel for the front. I'm assuming that you already have a few 8" X 8" X 8" block for the wood storage opening. From that point, you are correct about the overhangs on each side. It is not that difficult to form..............It is supper time now and SWMBO is calling . I and, I am sure others, will gladly help you through this .

[Danieltp]

Ok, it's good to know it's not deal break, just more of me going into uncharted territory for me, but it's not the first time with home projects.

It has been rainy all weekend in Texas and will be out of town next week. I'll write more if I have questions.

I'm not sure if the crate comes with manual books? I assumed that all kit came with one? I wasn't sure because Forno Bravo website is very informative. It's just that I overlooked one PDF document that would have been helpful. I should have e-mailed or asked on the forum, seeing how quick you guys are with responding to my message.

If I have any questions in the future, I'll post questions on this forum. Thanks ya'll!

[david s]

Cantilevering or overhanging is desirable for a couple of reasons. Firstly it gives your feet some room so you can stand comfortably right up to the edge of your oven. Secondly it reduces the span that your supporting slab has between uprights. Because of this shorter span the slab does not have to be as strong. Also, because most of the weight of the oven is well inboard of the perimeter the vertical supports are closer to the load that they support. The downside is that casting a slab that cantilevers requires requires extra and more complex formwork. Some oven builders in the UK use a number of lintel blocks placed over the stand which can easily cantilever.

[Ron-NC]

Cantilevering also looks nice. I did this very thing on my build. When considering the rebar reinforcement, bending the rebar in a U shape in the cantilever area will strengthen this area - see my build in the Getting Started section for some pics of how this was done.

[Danieltp]

Update: the CMU is stacked, the cores are filled up with concrete. I just started to build a wood firm that will create 1.5 inch overhang on the top slab. I think I'll be fine with the dimensions I have that, after seeing It will be more than the minimum dimensions that was mentioned in the installion instruction manual. However, I have one question, before I pour the top slab - I'd like to insulate the heck out of my oven. Is there anything I can do? I have been looking through all posts dating back to 2010. I'm seeing a lot of information about vermiculite being mixed with concrete, and this is build/poured first before the concrete slab, correct? Is this old approach?

in the instruction manual, it doesn't say anything about vermiculite being mixed with concrete. Is the 2" foam board new approach? Is it enough? I already put a plastic sheet under the foundation slab to prevent wick-up, but would like to know if there's anything more I can do to prevent wick up? In Texas, when it rains, it POURS. I still remember the week, when I has 15 inches... That was too much.

One no more question...should I rent vibrator to remove all air bubbles, or is that just overkill?

I'll post pictures soon of my build.

thank you for your time and help!

[SableSprings]

Welcome to the forum Daniel! Old school (and less expensive) method for insulation under the cooking floor was either perlite mixed with cement (perlcrete) or vermiculite mixed with cement (vermicrete). Basically in a 5:1 mix (1 being the cement), you get about half the insulation value of the ceramic board in your kit. In other words, it takes 4"-5" of either perlcrete or vermicrete to equal the insulation value of the 2" ceramic board. The board has become much more available (and affordable), so it's become the standard "new" floor insulation method.

After you pour the top slab, the insulation board is laid (or perlcrete/vermicrete formed & poured) on top of the slab. When I helped a friend install a Casa 2G90 several years ago, we actually laid down chicken wire underneath the board first, with the intent of pulling it up and over the insulation batting of the cast dome (as a base for the stucco/plaster). David S and others in the forum advocate drilling several small holes through the slab underneath the ceramic board to help moisture escape as the ceramic board really can soak up water if given half a chance. UtahBeehiver used a sheet of FoamGlas between the slab and the ceramic board. The advantages were that FoamGlas is not only an insulator, but it doesn't absorb water. So that method gives you more insulation AND a built-in moisture barrier. I've also seen a waterproofing membrane material (like RedGard), painted around and up the sides of the ceramic board to keep water from wicking up & into the base layer...don't know how successful that will be, but that method is used for shower bases so it's probably going to work great.

Waterproofing an outside oven is possible with various stucco/plaster/cement additives, but all methods will eventually need maintenance. The best option (IMHO ) is to build a roofed enclosure to keep all of that Texas rain away from your oven area (and you if you're standing by the oven while it's POURING ). If you don't plan on a covered enclosure, think about sloping your slab pour (with a slight dome). That way your top slab drains off the sides instead of pooling on top (underneath the oven). As to air bubbles - just take a hammer and tap the sides of your form well when the concrete is poured to remove bubbles/gaps along the slab edges...no need to rent a vibrator. When you screed and do the final drain slope on the slab top, you'll have worked out the main area's air bubbles.

Hope this diatribe helps some...looking forward to seeing your progress.

[gastagg]

Daniel,

A couple comments that may be helpful. First, I designed to cantilever, and I haven't had any problems after two seasons. Second, I don't think a vibrator is necessary. I say that because I did rent one to use and the force was so great it about ripped my forms apart. I resorted to use a rubber mallet and just kept knocking on the forms to get the air out.

Good luck!

George

[RandyJ]

Hi Daniel, just a few thoughts for you. As to the insulation I and many others have gone with Calsil board. The 2" of that will equal 4" to 5" of vermicreet. On my oven I did 4" of the board insulation. It is a little more expensive but much faster and easier to use. There are also many that recommend to put a vapor barrier down below the calsil board to prevent water from wicking in to it. As for your over hang that is a non issue if you are doing the rebar. Even 4" to 6" I can't see being a issue. I have a lip I poured as a separate pice the extends 12" from the front of my stand. So make sure you go big enough that you can build your frame around the oven if you are building a enclosure. I also filled my enclosure with vermiculite over the top of the ceramic blanket. It holds heat great.

Randy

[david s]

I think a lean brew of vermicrete (10:1) comes pretty close to the same thermal conductivity as cal sil board, not worse than half as good as many would suggest. Comparing the values as stated on Engineers toolbox with those of the Shundler vermicrete values, theres not much in it. 0.5 (extrapolating from table), as opposed to 0.4. Although the Shundler site does not give values for different temperatures, they are presumably for ambient temps only. Also for under floor insulation a 10:1 is too lean, you need a 5:1, but that still leaves you with 0.7 as opposed to 0.4

Also vermiculite alone, without the addition of cement has the same thermal conductivity as cal sil board @ 0.4, Perlite much the same.

http://www.engineeringtoolbox.com/ca...es-d_1171.html
http://www.schundler.com/vermcon.htm