Originally Posted by KYAirstream
What's the problem with using concrete blocks, unless of course they are hollow..... Seems like placing the jack stands on solid concrete blocks would be more than adequate?
Timber weighs about 35 pounds per cubic foot. Concrete weighs 150 pounds per cubic foot. So, two 2×12 boards cut 12" long (for a total of 0.33 cubic feet) weighs ~10 pounds. A concrete block the same size would weigh ~50 pounds, and adds nothing at all to the stability of the trailer in exchange for that extra weight.
Concrete would be more than adequate, but so would the lumber, and the lumber is (1) much easier to handle and (2) cheaper unless you already have half-a-dozen concrete blocks lying around.
Handy hint, if you're worried about termites, wrap the boards all-around in metal or plastic screen-door mesh first. That should keep the termites from snacking on your cribbing.