Help with vent landing size

[gjbingham]

I moved this posting over from the getting started forum as I didn't get any responses there.

I'm stumped with the amount of space I need to leave for the floor of the vent (vent landing). I read (and reread) James' sticky posting about size of the hearth.

I'm planning a 36 inch oven. The formula James posted translates to :
36"(floor)+9 (walls)+6 (vent floor)+5 (rear insulation)+.5 (one wall)+12 (landing)= 68.5".

After looking at all photos I could find of the vents and dome floors, it looks like the majority of the vent floors are 12" to 18", front to back, under their brick arches vs the 6 inches used in the formula. Am I misinterpreting the 12 inch oven landing portion or does the 6 inches only refer to the width of the vent opening itself?

I'm getting ready to pour the vermiculite concrete portion of the hearth on a corner installation stand and want to make sure that I get enough coverage for the vent floor, but not necessarily cover areas that don't need insulation, as Vermiculte is hard to find around here.

Can somebody please turn on the lights for me?

Many thanks

[christo]

I will do my best.

My oven started out as a 36 but ended up more like 1m as I did not allow for mortar joint thickness....

So from front to back we have:

5 inch rear insulation
4.5 inch brick thickness
36 inch oven diameter
4.5 inch brick thickness
6 inch vent thickness
12 inch landing

My oven is pretty much laid out the same way. I think the dimensions are generous.

Remember that the vent can actually start closer than the diameter of the oven as the oven surface has sloped back considerably - depends on how you design your vent support.

A little more than half of my landing sticks into the throat of the oven. So I have about 5 inches of landing that supports the decorative arch and gives a little lip beyond the finished face of the oven.

Hope this helps!

Christo

[gjbingham]

Yes, that helps.
I reviewed a bunch more photos and it's beginning to click.
G.

[DrakeRemoray]

I think I have about 12" of vent area, under the actual vent. Then I even have a few inches (4?) of landing in front of the entire oven. so the oven is sort of set back on the hearth slab.

Hope that helps.

Drake