This chimney has been caulked, and re-caulked several times over the years. the gap between house and chimney now measures about 1 1/2 inches, and as you can see from the picture, looks like it needs caulked again, since there is another space between the house and all that caulking/mortar.
What do you think has been happening to cause this?
First of all, this is a very old chimney and house, and if it originally had strap ties to fasten the chimney securely to the house structure, they are probably now rusted or entirely broken loose. The chimney has had leaking in between the house and the chimney, and when it freezes in the winter, the expansion of the trapped water has acted kind of like a jack or lever, prying the chimney further and further away from the house, and it's original position. Instead of addressing the cause of the problem (probably a leaking flashing located at the roof level), they have instead opted to just continue to try to caulk the ever widening gap.
I put a probe in between the wall and the chimney, and found that there was also some hidden wall and siding decay damage. Unfortunately, now the only way to fix this damage properly, is to tear down the chimney, and repair the rot damage. Although it can't be seen, it has become a major issue for the new homeowner to deal with.
I show all of you this, so that you will know that it is an improper repair to just keep caulking over a chimney that has been moving away from it's original position, and most generally, ther WILL be more damage that is hidden if this type of repair has been done.