Victoria Cottage Foundation

[Charlie]

I'm starting soon on a Victoria Cottage, less the bedroom. The slope is about 25 degrees and the soils are poor with lots of clay and occasional embedded boulders. In the photo http://tinypic.com/70ggb7.jpg the site is behind the foreground boulder and up against the oak trees.

Given the soils, a builder friend suggested I use piers and grade beams for the foundation. He suggested I use the pier layout in the VC plans but make them 12" dia and 6' deep. The steel in the piers would be tied into poured perimeter grade beams about 16" tall.  A geologist friend says make the piers much wider and much deeper. A neighbor says both are overkill!

The approach appeals to me because I can do it myself and there is a minimum of excavation but I can't find any general standards for this type of foundation. It looks like it is common, especially on slopes, but each case is invidually engineered. If anyone has some feedback on the method, and perhaps some thoughts (just thoughts, not engineering opinion) as to what really is adequate, I'd be grateful.

By the way, I am in Mendocino County, CA. I have a "Class-K" permit where, in exchange for forever disclaiming any libility to the county, there is no requirement for plan check, progress inspections, or building code compliance. In other words, I'm structurally on my own.

Thanks,
Charlie

[glenn-k]

I have heard of the Mendocino County class K permit.  It's great to know they still exist.  I'd give my right     ---                                  arm for a Class K.

If there are possibilities of mud slides in heavy rain even though engineering is not required the deeper piers might be good.  Nothing like seeing a deep solid grade beam foundation making a nice dam and moving down the hill on a solid wall of mud.

Here in similar soil conditions a friend made a retaining wall with drains about 4 feet high and 30 feet long with footings about a foot deep into undisturbed soil.  The next winter it was sitting in the corner of his garage -moved about 10 feet.  We removed it - drained the water off the hillside properly the next year- even with double the rain and there was no problem.

Seems it would be easy to call in a post hole digger and have them drill the pier holes the six feet  if you want it that way then simply install reinforcing and pour, forming or sonotubing above ground as necessary.  Double check what works and problems in your area -as your friend said- all this may not be necessary- however drilled holes and concrete are pretty easy.