This does make it a little tricky adding soil on top of slick plastic. I used shade cloth and then later fish net with a base layer of clay to help tie everything together.

Yes, provide passive ventilation through the door or screened vent tubes that slope down to the exterior.

Would you put the plastic all over, or just on the uphill side?

If all over, I assume I need to be sure to provide enough passive ventilation to keep the moisture content inside from getting too high — upper and lower vents, for example.

thanks again,
TC

Two layers of 6 mil plastic on the outside is recommended — one up against the structure and one layer after about 1/2 the soil has been backfilled. This is what we did and our bags are totally dry, even though we live near a tropical rainforest.

Please send photos and an update of your project when finished. Good luck!

There is no level ground on this Tennessee hillside site, so I will probably dig in a French drain on the high side before I dig the foundation. This was an extra-wet year, so I am uneasy about what sort of foundation to provide.

I’m thinking of a rammed gravel trench foundation, possibly with another perforated drain hose in it, oriented to drain downhill past the building.

What they call “pit run gravel’ around here is probably too liable to compression, what with the high fraction of “fines,” at least if the batch I had delivered a couple of weeks ago is any indication.

Should I specify washed “56s” for the gravel in the foundation, with 3/4-inch max crushed limestone? If I fill and tamp the trench with 56s, should I also stack a row of bags with 56s above the trench?

I like the idea of putting plastic sheet against the uphill side of the wall, at least up to a foot or so above finished grade. Is there anything else I need to do to protect the plaster and keep the inside dry?

Thanks for this blogsite — it’s a gold mine of information on dirt.

TC

Build below frost line? I would say it depends how cold it gets in your area. In general, the earth on top and the sides creates plenty of insulation. But in an extremely cold northern climate, you might want to inset it into a small hillside or build it below grade. Investigate what old timers in your region used to do and apply that knowledge. Also, you could add an insulated door or a double entry for extreme climates.

Here’s a shot looking down from above:
http://www.binkyou.net/files/xnxa0750beb7phctfd8x.jpg

You could scale it up and use it as an office. An easier way is to use Kelly Hart’s earthbag dome building guide. The shape is more conical but easier to build and more stable, and you can build these even larger — up to about 20′ diameter: http://www.earthbagbuilding.com/articles/riceland.htm

A 16′ – 19′ diameter (interior) dome would be good for a home office, and there would be a nice little loft above. Skylights are an option.

You can buy my Peace Dome plan for complete drawings and specifications that are customized to your needs, or you can follow Kelly’s dome building guide for free and just wing it.