Replies

1. 
   johnnyd | Jul 20, 2004 06:47pm | #1

   I did the same sort of thing and just used 3/4" .60 treated foundation grade plywood extended down from the treated 2X8 bottom girt.  Dug down by hand from the inside after the pole frame was up, using the side of the excavation for support on the outside.  Back filled with gravel.

   How are you going to level the floor on the inside? I built a wood frame floor with poly-lined crawl underneath.

2. 
   rjw | Jul 20, 2004 11:54pm | #2

   Detail it like a wood foundation, I'd guess

   ---

   "It is as hard for the good to suspect evil, as it is for the bad to suspect good."

   -- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)

3. 
   hasbeen | Jul 21, 2004 04:52am | #3

   In general, what you're describing is not a good idea.  That aside, I might do it too, depending on the situation.

   More info is definately needed:

   Do you live in a desert or a rainforest or something between?  Climate makes a difference.

   What's your frost depth?

   How high do you plan to backfill against the building?

   How much of a hill is above the building site?   Is it a mountain or a few feet of rise to an alley that then drains in a different direction?

   Do you plan to have any floor other than dirt?

   Answer these questions and I'll give you my opinion of how to proceed with this bad idea!    ; )

   You're unique!  Just like everyone else!      Scott Adams

4. 
   hasbeen | Jul 21, 2004 07:42pm | #4

   You replied:  Thanks for your interest.  The site is in Maryland, about 50 miles southeast of Washington, DC, just north of the Potomac river and near the edge of a branch of the Potomac.  That will tell you something about the climate.  I'm not sure what the frost depth is in this area.  The front of the building will be at grade.  The back will extend into the hill.  I do not think more than 4 feet of the back wall will be in ground contact.  Obviously, variable amounts of the side walls will be also as the grade tapers to the front.  The hill extends back behind the site to a maximum of 35 feet above high water about 300 feet from the site.  Drainage will be towards the site.  I have intended to put down a layer of poly covered with gravel as the floor, with perforated PVC pipe in the gravel to be sure there would be adequate drainage.  I would plan on having the gravel backfill next to the walls connect to the floor gravel for the same reason.  It would seem to me I could use horizontal pressure treated 2x6's or 2x8'

   My suggestion:  You will have substantial lateral pressure against the back of the building.  Thus, on that side I'd suggest using four 6x6 posts buried to four feet deep or so.  Using larger members spaced more closely would somewhat ammeliorate the likely problems that will develop over time from lateral pressure.  Your idea of using treated 2x across the posts to above grade would probably work.  I'd also suggest covering the outside of the 2x with a couple of layers of poly.  If you put 2x on the sides of your structure you won't have much to resist the hill gradually pushing the building over.  If you use 3/4" treated ply same would be the case because it would probably gradually tear out any fasteners you put in.  Thus, I'd suggest notching in angled 2x braces between the posts (from grade at the back of the building angling down to the floor level inside, if that makes sense).

   A rather standard precaution would be to dig a slight drainage ditch across the hill behind your structure so that water running downhill is diverted before it reaches your backfill.

   You would probably be wise to use stainless steel fasteners at all below grade locations. 

   Good luck!

   You're unique!  Just like everyone else!      Scott Adams