[Cob] location of cob planter wall

[sly at riseup.net]

I´m in Marin, the wall will be built in Sausalito. It rains alot but not
so so  bad.  I was hoping to do it without a covering because that way the
plants in the planter get more sun.  I could do a lime finish so it would
withstand rain for longer, it would need fixups every couple of years.
WHat is the general feeling of what is too much rain and what is an amount
you can get away with no roof?

Thanks,
Sarah