I have a sandstone Victorian house with a slate roof with a dormer in it. The roof comes up to the sandstone wall (coping?) and there is a cement? skew on top of the tiles and up the side of the sandstone. We have a chimney with 3 pots in this wall.

We noticed a leak in the bedroom on the slope between the dormer and the sandstone wall and this had damage the plaster.

We called out a builder who decided that it was the flashing at the side of the dormer and he replaced that and fixed a couple of slipped tiles in the area. As we were re-decorating we had the room re plastered as it was dry and sunny the plaster dried out and I painted the walls with matt paint. The next rain we had gave us a damp patch on in the same place and also a random patch in the middle of the external wall and one on the external wall where it meets the back wall of the bedroom. These were probably there already but hidden by the paper.

We called out the same firm (different builder this time as they were no longer using the first one). They decided that the problem was the flashing round the chimney, a few slipped tiles and the skew. The work was completed though the skew was not very neat and in putting the flashing in the tiles around the area now didn't look at flat as they had so I wasn't happy that the best job had been done. This also did not fix the problem, so I got them out for another look and they claimed that everything was fine with the work done and they would quote for anything else they thought may be the problem.

I decided to get another opinion and the roofer who came out was not happy with the slates round the flashing and decided that the ridge flashing should be taken off and these slates removed and put on again straight and the flashing put on with new clips. He also decided that the chimney had a few problems and the post needed re-cemented as did the gaps between he sandstone on the coping. As this roofer seemed to know what he was talking about I agreed for him to do the work. He sent 2 roofers out and they did the work in the rain while I was out one Saturday morning (which surprised me) and I wasn't sure how well it had been done as the slates still didn't look straight, the ridge flashing seemed a bit warped and one of the slates had come loose a few days later. So I think that in this case I may have had a cowboy builder who did no good at all.

In the mean time a quote came in from the original firm to remove all the slates on that third of the roof and re-do them and the skew again as a new job.

At this point I still have a leak and have no faith in either set of builders or any way to decide how to choose a new company, or what to do. I currently despair of getting the leak fixed and am worried about spending more and more money and having more and more work done that doesn’t solve the problem.

Any advice at this point would be welcome.