cracks appearing in old and new plaster on same wall.

9 months ago we had a loft conversion. All of the first floor and the loft has been newly plastered. About four weeks ago cracks appeared on the first floor bedroom walls and on the ground floor wall, but none in the loft. Now the plaster is starting to blister off in one of the rooms and all the cracks are growing daily. I have put a spirit level on the walls to see how plum they are all seems good except for the loft wall. Which is going away from the property slightly, but as I said earlier there are no visible cracks atall !

 

Kind Regards

Adrian