you need to put it up on blocks, not timbers  water is comming up through the timbers,  get ( 8 ), 9x4ins  blocks,  put 2 under each corner, and plastic  under the blocks, to stop water riseing up through the blocks into the floor of the shed, it should dry out in time,  but use blocks to keep it up off the ground, you can use plastic bin liners  under the blocks,  or felt if you have any,
                 h
                
 January 2012