Ok people,iv got a job to do where iv to fix EML to the exterior of a house.The original finish is wet dash roughly 40-50 years old and with probably 1/4 to 1/2 inch of paint from over the years.The client wants the house finished to a smooth sponge finish.My problem is I cant get stainless steel mushroom fixings anywhere and builder providers are not that helpful.I cant use washer steel nails as it would be impossible to nail into the wet dash and I wouldn't have a finger nail left if i tried this way.If I was to use the steel mushroom fixings used on insulated plasterboard would these corrode or would the sand/cement protect them.Any other ideas would greatly be appreciated.