Stand Dimension Question by Newbie

[John1133]

Hello, I'm about to build a 42" interior oven. I have worked out the width of the cement stand to 58" (42" + 9" for brick + 6" for insulation + 2" for mortar). I am not building a walled enclosure but instead going for the "snail" look. Should I leave an additional 1" on both sides for a reveal and a safety margin or build the stand to match the exact width of the oven so that the water will run off? Second question: With regard to the depth, I am confused as I have a set of Forno Bravo plans and can't get the math to add up. By my numbers the depth of the cement stand should be 70.5 inches but I could be wrong. My 70.5 inches assumes 42" interior diameter + 4.5" for brick + 3" insulation + 1" for mortar + 8" for the vent landing and finally + 12" for the oven landing. Should I be adding additional space for the dome over the door? I think I'm missing something important? Should I leave an additional one inch for a reveal / safety margin at the rear? I truly thank anyone who takes the time to look at my math and find the error of ways for a newbie who is just embarking on what he hopes will be an awesome experience. Thanks, John

[sbrause]

Re: Stand Dimension Question by Newbie

Hi John... Sadly I'll add to your question instead of answering it. I am planning my 36" oven and the materiel list shows a 71"x80" foundation but the chart under oven dimensions on page 13 indicates 67"x78".

Sorry to hijack your thread but I figure whoever answers your questions will know the answer to mine as well.

[John1133]

Re: Stand Dimension Question by Newbie

No worries about hijacking the thread. Actually, I've had a hard time getting an answer to my questions so I called FB directly. In short, they said that their manual / instructions have been found to have numerous errors and to view any measurements as "rough". Now I find myself having to question any measurement and am a bit disappointed that basic measurements may be wrong or needing further explanation.

[NCMan]

Re: Stand Dimension Question by Newbie

I'd be happy to help you both, but am a newbie myself and have just started my own oven. I don't feel experienced enough to give you the answers you need. I also found the measurement related info in the FB instructions to be contradictory, etc. Maybe one of the experienced builders on here can help you both. Best of luck to you both and take pictures!! We love pictures and they are very helpful.

[cobblerdave]

Re: Stand Dimension Question by Newbie

G'day
The block stand n the forno plans had me a bit confused as well especially considering all the measurements were in feet and inches and I was working in a metric country. It was good in a way because I double checked my measurements before I started and even counted the blocks in the pics till I knew I wasn't really that bad with the math
These days I would consider it an easy construction method rather than a diffinitive plan. In fact gentlemen consider changing it shape to a H shape to give yourselves two shallow bays instead of one big one. Trust me its a long crawl to the back to get or stow wood. Much better to have two excessable ones.
Regards dave

[sbrause]

Re: Stand Dimension Question by Newbie

John/NC/Cobbler,

Thanks. It seems as if cobblerdave has the answer in a way. What I am going to do is try to mock the thing up in Visio with the dimensions for the materials and see what I end up with. Then maybe I can share the file. The biggest thing (which I'm sure you share) is not wanting to fix a foundation that is too small or make a foundation too large since for me space is at a premium. I'll work on a drawing and would be happy to share it.

Scott

[Gulf]

Re: Stand Dimension Question by Newbie

John,
You are kind of "screwing me up" with "the snail look" but, here goes:
I had origionally planned on a 42" dog house and went with a dry stacked 8" X 16" block stand (five blocks deep by 4 blocks wide) . Since "dry stacked" substracts the head joints, that comes out to about 78" deep X 64". By adding a 2X4 band around the stand and then a 2X6 form board I ended up with about an 80" X 67" hearth slab. That would have been enough had I not of switched to a 44" in mid stream.

Your figures dont add up for me on your depth (based on your figures). I come up with 79" instead of 70.5". Your stated "8" for the vent landing and finally + 12" for the oven landing". If I understand correctly, your flu/chimney entry will be 8" and your "landing" in front of the flu will be 12". Unlike others, I believe in a deeper flu entry. 12" works great to incorporate a transition to your flu. You can subtract from the "oven landing" to work this in. A longer reach is better than a smokey oven. An angled landing will help make up the diference. Also, I don't see where you have added a face brick into your figures. I would strongly suggest that you get some large poster paper or cardboard (taped together) and lay this this thing out in full scale. It will help you understand what you will need for dimensions for a stand. Post a pic of what you come up with and we will be able to help .

Sbrause,
I did not catch if you are planning an igloo or doghouse style?. I would be glad to help both of you. This is my toughest time of the year though. My mill has it's annual outage the first week in may. Lots of over time, the month before, and the month after . Bare with me .

[ATK406]

Re: Stand Dimension Question by Newbie

John,
Your numbers don't add up - (42" + 9" for brick + 6" for insulation + 2" for mortar) = 59" not 58". And that would make your dome line to line with the width of your base. Gulf has already commented on your dimensions front to back.

Take your time and lay it out like Gulf suggested. Don't get confused. Just because some bricks are called "stretchers" that doesn't mean they are actually elastic.

Have Fun!
AT

[jeeppiper]

Re: Stand Dimension Question by Newbie

Listen to the wise-folks on this string.....sketch it out and you will get a visual of what you want.

I took the liberty of designing up a 42 inch just to go through the motions (see pics). The attached pictures show a 42" oven, 4.5" thick wall, 3" insulation" + 1 inch mortar. 8" chimney, Entrance comes out 34" from center of oven. Opening 18" x 12" high (Peak) x 9" high (at sides).

If you cant find paper that size, get some chalk and draw it full scale on the driveway or road.

The base shown is 80 "x 64". This gives you some room to play with. all around. Notice that the dimensions of the base are in multiples of 8"....This makes the construction of the base simple since you are stacking blocks. You want to avoid making your base using odd-ball numbers. The base will then define your slab dimensions.

Shown is a 4" slab for the oven base. I neglected to show any floor-insulation (either pearlite-concrete or insulation board....

Also shown is Cobbler Dave's idea of an H-base design with two small rooms. He is correct by saying that a single room is a long crawl back....two small rooms would be much better (and makes for a stronger base as well).

[jeeppiper]

Re: Stand Dimension Question by Newbie

One other thing, I agree with Gulf about the larger chimney draw area. The last thing you want is smoke coming out the front of your oven and in your face. I have seen so many beautiful ovens with black soot caked on the front face, which indicates that they did not properly design their chimney.

There was a good thread posted back in Sept 2012 entitled "Arch Design Help"...it had some good images of how to design the chimney transition area.

[NCMan]

Re: Stand Dimension Question by Newbie

John/NC/Cobbler,

Thanks. It seems as if cobblerdave has the answer in a way. What I am going to do is try to mock the thing up in Visio with the dimensions for the materials and see what I end up with. Then maybe I can share the file. The biggest thing (which I'm sure you share) is not wanting to fix a foundation that is too small or make a foundation too large since for me space is at a premium. I'll work on a drawing and would be happy to share it.

Scott

Scott....you're welcome and the best of luck to you. You've already gotten some great advice. Keep us posted!! Lots of talented folks here.

[cobblerdave]

Re: Stand Dimension Question by Newbie

G'day
Just thought I'd point something out with the forno Leggo stack and fill method. Its not Leggo ,the blocks ( and house bricks) aren't twice as long as the width. This is because they are designed to have a mortar joint to go around a corner.
Your going to have some gapes .... Except them and fill them later .... Its a simple and strong method for the "mug" builders
Regards Dave
Ps firebricks are 1/2 as wide as they are long .... Great for getting you floor hearth square .... No gapes