Round foundation help

[tony boca]

I'm interested in fabricating a round igloo 42" oven. Does anyone have any suggestion on a recomended diameter for the foundation? I'm also open to ideas on how to frame it. I saw one that used the black garden edging to make it round. I suppose I could frame a square and place that flexible edging with some stakes to secure it on the inside. I like simeon's round base but can't find any details.

[Rastys]

Re: Round foundation help

Tony.
there are numerous ways of making a foundation circular or even eliptical if needs be.
Instead of using a flimsy piece of plastic garden edging, (I wouldn't even use metal edging strip unless it was 3mm thick), get yourself some substantial garden stakes and use some 5mm plywood strips .
Hold the end securely as there will be a fair bit of pressure on it and bend your ply to the shape required. You will need the occasional stake on the inside but don't forget that when you pour your concrete, it will put significant pressure on tout form work so concentrate your stakes on the outside. Maybe one on the inside midway between the strip ends and one every 2ft or so on the outside (depending on the height above your ground level).
I use to have some 3mm x 100mm x 2.4metr strips of steel that I used for all my curved wall footings and paths together with 16mm steel concreting pegs.

Cheers.

Rastys

[tony boca]

Re: Round foundation help

Rastys,
Thanks for the reply & suggestion. I went to Home Depot today and found some 5mm plywood. Had them rip it into 6" pieces. It seems to flex enough to give me a 72 " diameter. I'm going to start digging today.

Tony

[Rastys]

Re: Round foundation help

Tony

Just watch your cement doesn't push your ply outwards as it often does when you are pouring it. You have enough on your mind without having to solve a serious emerging problem as it happens.
I even put building bricks (the ones with 3 holes in their middle), up against the ply and put a stake through one of the holes (further from the ply form), where the ply is over your dug footing and difficult to locate a stake.
Use plenty of pegs and hold it in place and you have the job done.
Good luck .

Rastys

[tony boca]

Re: Round foundation help

Rastys,

Thanks for your help. The foundation pour went pretty smooth yesterday. I put a stake every 12'' around the form. No breaches.

[Rastys]

Re: Round foundation help

Good to see Tony,
now you know with confidence what to do next time eh?
How are you planning to brick your base, with blocks, bricks or half bricks?

Rastys

[Neil2]

Re: Round foundation help

On my 40 inch oven, I used the thin (1/4 inch) pegboard. Once in place I taped the inside with the shiny red tech tape to block the holes and to act as a form release. Small blocks to position, and a strap to take the outward force.

[tony boca]

Re: Round foundation help

Neil2,

That is an amazing design. I really like that tripod open bottom. It doesn't inhibit the peaceful background, makes less of a footprint. I wish I saw this before I poured my foundation. I would have incorporated into my build. For my foundation, I ended up using 5mm plywood but, I did have to soak it to be pliable. I'm going to compare how pliable the peg board is vs the 5mm plywood. I may be able to use it for the top part.

[tony boca]

Re: Round foundation help

Rastys,

I'm Thinking of going with 8x8x8 blocks all around and a 1 meter wood storage opening with an arch made of old chicago red bricks. Do you agree?

Possibly stuccoing the facade at the end of the project.

I really like Neil2's tripod open bottom, but my rebar is already in place (We have alot of slithering creatures here in South Florida that I want to keep out and I'm not talking about attorneys).

[Wiley]

Re: Round foundation help

Tony, Here are two photos of how I make a round form for pouring the first part of my refractory. There is a top view and a side view. The part that may be of interest to you is the round form. It is made of a series of short 2 x6 pieces about 2 ft long. I drew a circle on my shop floor of the size I wanted and then started laying out the short pieces so that the middle of each piece just touched the circle. On the photo there are arrows drawn on each short board where the contact point was. On top of the first layer of boards I laid a second layer each bridging the ends of the first layer and again laid so the middle of each board was touching the circle. Nail the second layer to the first then proceed to a third layer and nail and perhaps a fourth layer if the thickness of the circle form permits. Now I took a single layer of fiberboard ripped to the height of the slab wanted and attached it to the inside of the created circle. I attached it by means of staples, stapling at each arrow. The completed form was strong enough to be carried by two people and not distort out of shape. When the pour was over one disassembles the form with a prybar. A picture is worth many words: Here's a top and side view. The form was held down and inplace with weights.

Hope this helps,
Wiley

[Rastys]

Re: Round foundation help

Tony,
it's not too late to change your mind with the similar build to Neil2's base.
You can easily chisel down beside your exposed rebar an inch or so into your footings and cut off the rebar below the surface and then render/repair the top surface. Drill some 5/8" (or 3/4" if you can get that sized rebar) holes into your footings where you want the legs to go , drive some deformed rebar into them, pour your posts and form up for your slab. This is what we do here to tie a house extension footing to an existing, so it will definitely suit an oven legs. I would think that you would need 8" posts/legs with rebar in them and vibrate it when you pour to get a smooth surface.
Food for thought and no bricking up under the oven!
Easy mate, if that's what you want!

Rasyts

[tony boca]

Re: Round foundation help

Wiley,

That's pretty inventive and may serve my needs for the insulation hearth. This forum brings so many clever ideas together so one can find the one that best suits them. Keep them coming!
Wiley, is that copper? The metal work is so cool.

[Wiley]

Re: Round foundation help

Tony, I'm guessing you are referring to the dome, it's steel. My build is under "Other Oven Types" under "Steel Dome Oven".

Thanks for the kind words, and I too find there are alot of clever ideas on this Forum.

Bests,
Wiley

[tony boca]

Re: Round foundation help

Neil,

I'm thinking of going with sonotubes for the stand. How many would you recommend what diameter and where would you place them?

[Neil2]

Re: Round foundation help

Three is a good number. (With four, if there is any settlement, one will go into tension and possibly crack). I used 7 1/2 inch sonotube.

If using three, the optimum placement to the center of the pier for a round suspended slab is about 60% of the way out from the center. For example for my 40 inch dome, the diameter of my slab is 62 inches, the radius 31 and the center of my pier support is .6x31=18 1/2 inches from the center.

To avoid punching sheer, the reinforcing from the piers should go into the suspended slab. I use two 1/2 rebar in the piers with about 4 feet sticking out. When the pier concrete had set for 3 days I bent them town. I then built a temporary form/table from 5/8 plywood to support the slab pour. The attached photos show the detail.