most baseboard heaters say that they should be kept 3 feet from combustible materials like drapes, etc. Right on the unit somewhere. Coves have diff comb spacing reqs,tu i have seen people who have pushed their couches up against one and nearly burned the house down, and i have also seen bbheaters installed on t&g walls that have been severely scorched behind the heater, heck... The one in my shop is mounted 3 ft off the ground and the sheetrock wall above it shows signs of heat damage. Basically, receptacle reqs aside... If you can hold your hand at the same level above the heater that you plan to put a combustible item(ie desk ) and it burytyou after a short time held there, probly not a good idea... Not a real technical answer, but just a logical one that i have always used... I would also consider the flow of air around that space once the desk is installed. Hope that helps.