I'm putting in two 2,500 gallon water tanks and will be pouring a slab for them to sit on. The tanks are 8 feet across and I want to set them about 8 or 10 feet apart, so am planning on a 12 x 24 foot pad at 4" deep. Will be putting in remesh and rebar and digging some footings (about the size of a 5 gallon bucket) near the corners and along the long sides. We just poured a 12x12 slab and have a good feel for what it takes.. However, should I put an expansion joint in this slab? and if so, what do I use? Just a 2x6 board or is there something else that should be done? Thank you in advance.

We moved into a newly built house in Jan of 07. We noticed last winter that the driveway had heaved over 1.5 inches leading into the attached garage. I had heard from a construction engineer that heaving this size would cause eventual cracking. The builder agreed to replace due to spalling(sp). However, when I asked to remove more soil to prevent future heaving he wouldn't do it. This year the heave is back at over two inches. Again, I am concerned about not only cracking but safety/liability issues if anyone falls. Is there anything I can do to get builder to replace again(i.e. code)? BTW, I live in MI.