On Sun, 4 Aug 2013 12:11:29 -0700 (PDT), MJ
wrote:

In a week, I'll be building a 10x12 shed.

The plans call for a on-grade foundation with 6x6 skids. My property is sloped. From high pt to low pt is about 8 inches. I called out a guy and asked about pouring a slab. After I got over the price objections ($3k), he and I talked about cheaper suggestions. He said, oh, we could do Sonotube piers. I agreed but the project at that point stalled as I lost the person who was going to help.

Anyways, I found another person and he said he and I would do the foundation layout, digging, etc. ourselves. I told him my soil is kinda hard (clay and possible sandstone). No problem, just water the area and it will soften. I did a test dig yesterday and the water didn't drain for over an hour. Hmm, this is gonna be tough going.

Here's where I'm at. I could go with on-grade foundation using solid concrete blocks to level up the low spots. Not a problem for me, easy to layout and make happen. Or... we could get a power auger and drill the Sonotube piers. My helper who is a expert carpenter is away on vacation until two days before we start, so I can't get his opinion.

Which way would you go? Block or tubes?

My only concern is earth movement. Earthquakes are possibility. But a rare one. Would one would see a wood foundation come off a cement block pier in a minor (less then Richter 2) quake? I thought of drilling into the block and holding the joists with anchors. Can you drill solid block?

MJ
Frost? If so, sonotube below frost line, and cast your anchor bolts
into the concrete of the sonotube pilings.