Slab question...

[NYC]

I live in NY and wondering how deep of a foundation to pour for a Pompeii. I will be leaving my current oven alone and build the new one in another area. We generally pour a 6" slab for driveways to handle the weight of cars reinforced with steel mesh. How deep should I go for the oven footing?

[Les]

Depends on the soil but a good rule of thumb is below the frost line.

EDIT... I should have said the footings should be below the frost line

[NYC]

Our frostnline is 36" deep. I can see dropping a sonotube in the center but not anfull slab 3 feet thick. Any thoughts?

[Les]

Correct - that's why I added the edit. A three foot slab would be insane.

[NYC]

So then use a post digger on the corners and center down to 36" at about a 6" diameter and then pour it with a reinforced 6" slab for the foundation? What you think?

[Les]

Sounds like it will work. I'd drop some steel in the holes as well. Do you know what type of soil you have?

[NYC]

We have mostly clay here with maybe 12" of top soil on top.

[Les]

Bummer - go deep.

[Neil2]

Many have just used a floating 5-6 inch reinforced slab (rebar not WWF) regardless of the soil conditions.

Put a 3-4 inch layer of crushed ruck under the concrete slab and make sure this layer has positive drainage.

Frost heaving, if severe, may move your slab and oven around a bit, but if it is well reinforced it will take it OK.

To my knowledge, no one has on this site ever reported a failure in a properly reinforced slab due to frost action. (Underlined properly since a lot of the slabs I have seen here are clearly not done very well with respect to rebar placement.)

[NYC]

After speaking to the mason who poured 3,000 sq ft for me last summer around the pool he said to go 30 inches down with 8" ID tubes in the 4 corners and center and then 8" reinforced slab on top of the stone base. I want to brick the cinder block base and top enclosure so it will bear alot of weight on this slab and also I do not want too much cracking in the mortar of the brick due to movement. Biggest hassle is getting this pour done fast enough with a mixer before it sets as I cannot fit a truck back there for delivery of ready to pour stuff like we did for the pool. That was before the brick wall and gate were built.