We've got extension done in September on our imd-terrace Victorian house. The chimney on the 1st floor was removed and new wall was plastered where the chimney used to be.
Very soon before we moved back in, there were patches of dampness observed on the new wall where the end of the chimney used to be. The builder claims it's nothing to do with them but very likely the dampness was alway present but only could be seen now because there's no more chimney to hide it behind. They then put in some efforts firstly found that the cement flaunching around the chimney pot was cracked and flaking off and allowing water to penetrate. They have made it water proof by removing the redundant chimney pot and capping it off and have applied a layer of felt over the top. They also removed the redundant satellite dish because the fixings were rusted and it ay have fallen off eventually. They have also drilled some air holes in the chimney stack for ventilation and to allow any internal moisture to escape. They've done the above free for charge.
But this didn't stop the dampness from re-appearing as soon as it rains. So we agreed to let them carry out some further work to remove the existing chimney pot and cement flaunching, replace with a concrete slab bedded on sand and cement mortar with waterproofer mixed in it, The slab now have an overhang to deflect rain from the chimney brick work and the slab has been covered by high performance felt. They cut around the flue so this was not to be affected. They charged us £500+vat for this. We gather it's reasonable.
Unfortunately, all these work did not stop the dampness. So the latest conversation with the builder leads to a further proposal which is a very "comprehensive solution to address different possibilities" and would cost us £2390+vat.
This would bring the cost of fixing this up to £3.5k. Our neighbour has implicitly said she would not share any cost to do with this as she has no problem on her side.
We know this building firm is a reputable one which means they probably have been honest with the quote. However, without understanding the details of all these terminologies, we think by proposing the above they are not willing to pin down to a specific cause. From their point of view, it's almost foolproof and they don't want to spend too much time to linger around - after all they have other projects going on. But from our point of view, this bill could be reduced if the specific cause could be found which requires a proper investigation. But we don't know if it's possible at all. Any thoughts/advice on this?