If you are willin to haul water in a couple 50 gallon barrels that you would probalby use later anyhow to haul water with, you could use the pierblock in concrete method, dig hole, add some rock for drainage, put in 4x4 or 4x6, go to next posthole until all are completed, add a couple sacks qwik-crete [tm] to each hole up to level with the ground, slowly add water and tamp with a piece of rebar to get it wet all the way down, cut off the pierblocks after adding your rim boards for setting on your florr joists.
another simple way is to use five gallon buckets, set in the ground and add your simpson [tm] 4x4 or 4x6 brackets after filling with concrete and rock, this works ok if you have good base to set up on.
A friend has had his 30x40 2 story cabin setting on just plain ole red fir blocks of wood for over 25 years now, all off grid, and after 20 years he plumbed water into his house as he was getting older [near 60 now]. His cabin is built over some pretty solid rock though and has not rotted the blocks away, however i believe that not all places could be so lucky.
4x8 beams running lengthwise [18 feet of your 12x18] set just on concrete trailer house blocking [solid 16"x16"] might be sufficient and set 0, 6,12 feet would be very strong and would allow a 2x6 floor joist although a 2x8 would be better.
Can a cwement trruck get into where you are gonna build? have you considered a solid floor, a 12 x18 floor with a 4 inch thickness would only take a little over 4 yards of concrete figure 4 and a half plus any door steps you might want to add in. An 8 sack mix around here is $75 per yard so that would be just over $300 plus the 2x4 form boards and stakes a couple housrs to float it out and finish it off , and it would be good for years.
William
