If things go well with perk test and building applications I should be starting to build my new home in NC by this fall. I will have a monolithic slab with the outward trench 16"w X 30"D plus I have the trenches to dig for the plumbing. (Did this in 2003 here in FL with a shovel and by hand, can't do that up there). Now I have clay and rocks and a 24" bucket on my hoe. I have a few choices, one being rent a trackhoe, hire someone or buy a used 16" bucket. The cost for renting or hiring is yet unknown, (I'll know next month when I'm up there) I am guessing maybe as much as $1000 for a few days. I need it that long because I have to layout the wall locations for the plumbing and then install and have it inspected. There is a place in OR with used 16" buckets for around $500 but the shipping would be high. I keep looking for used buckets nearer to me and found some in MI, I'll keep looking. Having a second bucket is no problem as I will sell the backhoe and bucket when i finish my house. If I rent, hire someone or buy a bucket, what size bucket should I get? 16" trench, 16" bucket, makes sense but something tells me maybe slightly smaller like 14 or 15 would give me the end width of 16". In other words by the time the trench is cleaned up a bit it will widen. (Not sure about this in clay). I am putting about $10,000 in concrete into this and every inch wider adds thousands to the job. I'd like to hear from those of you who do this and have the know how as to bucket/trench size, thanks.
Doubt you'll find anything but a 16" or 18" bucket. 12" in the next smaller one for most hoes. I had to go 12" wide by 12" deep, so it was a 12". Just keep on looking, used parts vendors are your best bet. That's where I got the 12.
I found a 15" for $550 but there is another problem. It would have to be trucked to FL. where I live and I have no way to get it off the truck and onto my trailer, least not an easy way. As far as I can tell it weighs in at around 300lbs. Rent a trackhoe seems the way to go and deal with the bucket size when I rent it.
In hard clay the bucket will center itself in the trench pretty tightly, if the bucket is 16" that's what the trench will be. At least it will with a sloppy hoe, I've never used a tight one, so I couldn't tell you. An 18" will be easier to find, so do the math as to how much the 16 is worth compared to an 18. Or you could add a "wing" onto a 12" bucket if you found one cheap/close.
300 pound weight for a backhoe bucket,,,,,,,,,,:beatsme
They list some weights here but I don't know if they are right, seems very high to me. http://www.brokentractor.com/case%20backhoe%20buckets.htm