The definition of a hair line crack can be different depending on who is describing it.  Dryvit recommends that the project be looked at by our local distributor.  He/she can then provide guidance for the proper remedial work.  Please visit our website at http://www.dryvit.com/locator.asp?country_id=1 to find the exclusive distributor in your area or you can call Dryvit at 1-800-556-7752 ext. 9.