Osb is used for roofs, and for siding on houses, the stuff holds up for a long time, most of the time that wood doesnt hold up is when it isnt sealed with somthing like polyurethane and moisture seeps in then it bows and bends...

Also I got the thickest stuff they had 5/8..... also the wood is not that big of a deal, most of the cost that goes into a rack is tubs heaters and thermostat, if the wood poops out on me its easily replaced.

Its a lot stronger than melamine particle board and everyone uses that.,...