Plastic needed under foundation slab?

[mfiore]

Can I assume this is for a 42 inch oven? Did you use 8x8x16 inch blocks throughout?

[dbhansen]

Yes, 42" oven. I used one row of 4x8x16" (half-height) blocks in the below-grade foundation wall, but otherwise they were all 8x8x16".

[mfiore]

OK, Daren. Now that I've started digging, I have even more questions. Your frost-line is 42-48 inches. If I read the numbers above correctly, you excavated down to 59 inches. Is that needed for some reason, or just extra precaution?

If your footing is 96x88 inches, the foundation ends up 88x80 inches (is that correct? Is that the size you plan to pour for the cement slab on grade?

[dbhansen]

Mike, I just saw your picture - you're going fast! By the time I fix my mistakes, you'll be way ahead of me and I'll be asking YOU the questions!

I didn't base the 59" on anything scientific, and I probably should have eliminated at least the half-hi block, if not more. I just sort of made it up as I went along, making sure I would get to or below 48" down and reach the proper height without having to cut any blocks. You'd probably be good with only 4 rows of 8x8x16 blocks (maybe 5) + the footer. I just know that it DOES sometimes freeze to 48" here and I read that the footer should be below the frost line, so I went with that. Or maybe I'm just crazy about digging in clay!

Yes, with a 96x88" footer, my wall is 88x80" and my foundation slab will also be 88x80", which is close to the 86x77" recommendation in the FB plans.

Happy digging!