having had Chemical DPCs put in in the past, I'm always curious as to the reason for the specification of render that the DPC company insist on..Salt/Water retardent is fairly obvious, but why Sharp sand as opposed to any other (washed) sand ? Is Sand generally unwashed when you buy it from the likes of Jewsons...can you taste the salt if you're so inclined ? Is Sharp sand recommended as it's more bulky and therefore cheaper to render to the thickness spec'd (10mm + 10mm in my case...+3mm finish).
Cheers, Ant.