Our house has cast concrete window sills in common with lots of houses in the area. They have crumbled in places and last year as part of a more general exterior renovation (under supervision of a building surveyor) they were repaired. However the repairs failed and work redone by the builder. The repairs have failed again and the surveyor is unable to explain why and has not got to grips with the problem. So have ditched him and the builder but I know want to get the repairs done properly and permanently. Has anyone had this done and if so any info as to what was needed and suggestions as to suitable builders would be great!