If you are gonna build a rack dont cheap out on regular wood. The moisture will desyroy it. Go with 3/4 inch melamine. Its 38 bucks a sheet at home depot. And dont build it too wide. I have like 12 melamine racks and each one is 6 ft tall and 2 feet wide and 20 inches deep. A 2 ft wide rack will fit either 1 28qt tub per shelf, or 2 15 qt tubs per shelf or 3 6qt tubs per shelf. The melamine will last along time and hold up to moisture without warping. I use luan for the back of the rack and i personally use backwall heat. I put 2 strips of 11 inch flexwatt 6 ft long and use foil tape to keep it in place until i screw the backer on. People will have their own oppinions of back heat versus belly heat but i hold any temps i want using back wall heat just fine so i dont see the reason for using belly heat on those racks but thats just me. I have a couple melemine racks that i built in 2004 and they still do the job.