A leaning chimney is an unsettling feeling to say the least. Most of the time it will start with a small gap presenting itself at the top part of the chimney. It then turns into a larger and longer gap that you start to notice and ask yourself, "Is that thing straight?"
Chimneys on most houses are one of the heaviest points of the entire home. They typically have larger footings as well as being constructed out of heavier building materials. Chimneys are also very rigid structures in general. They typically do not crack but move as a single unit, which is good on a construction standpoint, but can make the signs of one moving show up that much quicker.
The construction of a chimney typically has a larger deeper footing or foundation to support the addtional weight. This works well with solid soils, but with the soft clay soils that we have in Southern California, it can present a problem. Think of having a 50 pound weight sitting in mud and then think of a 100 pound weight sitting in mud. Which one is going to sink quicker and deeper? The 100 pound just because gravity loves to pull things down. The same can be said with a chimney and their weight and load that they apply to the soils that are asked to support it.
Now chimneys will typically always start to pull away from the house rather than rotating into the house. The reason is that your house will actually act as a support system for the chimney. Unfortunately, we don't have any support on the back side of the chimney and it finds out that it is easier to settle away from the home instead of settling into it. That is why you will start to see the gaps between the framing of the house and the chimney itself.
Don't worry this can all be fixed. The best way is to utilize a pier system on 3 sides of the chimney. The reason is that if you think of your chimney as a long rigid box it will help in understanding the reasoning. When you lift a box on one side the other sides react, same goes with a chimney. We install piers on the sides of the chimney to help stop any side to side rotation of the chimney. We then install piers in the rear of the chimney to lift and rotate the chimney back into place. Once it is put back, we can then strap the top of the chimney to the home as well as re-caulk the gap that is created in the flashing.
Unfortunately, this repair is not one that most homeowners are able to do on their own, no matter how handy you are. It requires a lot of specialty equipment to perform the work effectively and safely.