roughcasting over frost damaged roughcast

[thebaker22]

a builder has recently completed an extension on my house. the roughcast(harling) was applied during cold weather and was frost damaged,
the builder has agreed to fix this but wants to apply another coat of roughcast on top of the original frost damaged roughcast , he says it will be fine, i am very dubious anyone give some sound advice

 

[roughcaster]

Try scraping an area and see. If it's been severely frost damaged, it will have no strength you'll be able to more or less powder it off. Try scraping into it with an old chisel and see. Check over the stone chips too, see if they have a good bond into the mortar. Let's know how you get on.