I have a two story house and there is one room - a rumpus room - at the back which is single story. There is a problem with a slab in this section; it appears to have tilted. Along the ceiling where the single story section meets the double story section, there is a crack (quite a wide one at this point!) and outside, there is a vertical expansion joint between the brickwork in the single and the double story sections. It has gone wide at the top (I could put my fingers into it), the base doesn't appear to have widened at all. It looks like the whole single story section, as a whole, is tilting away from the double story section. Like the slab under the single story has dropped at the outer end furthest away from the double story section. The brickwork itself is not cracked, just the expansion joint, and inside the only plaster cracking is along that ceiling point and the outer wall - not so noticeable because it is mostly beside a window So each section of house is retaining integrity and squareness (no door or window issues showing any lack of square issues and no movement of cornice anywhere else), they're just pulling away from each other.
We did not build this house; we bought it about 18 months ago. I do have photos of the ceiling crack at the time which was hairline, it is now 3-5mm (I haven't climbed up to measure very recently). It is in a new estate in Pakenham, was built by a big project builder. The couple who built it had it as an investment property for 5 years so maintenance was minimal. I have contacted the builder who were quick to send a guy out to check on it and they are continuing to be helpful sounding although not excessively proactive.
The assessment was that the soil under that section has dried out. There are two trees, probably planted very early on, that are likely contributors. The soil down that side was/is exceedingly dry - even when there is a bog on the other side of the yard, it's still pretty dry underfoot there. Checking the soil at that outer edge, it was very very powdery dry at the time (later summer) and even now, in wet winter, it isn't much more than damp. In summer, we also had some fairly good size cracks open up in the lawn at the back on that side and that was when the ceiling crack became much more visible, the spring-early/mid summer months. It hasn't shifted much if at all in at least 2-3 months since the weather got wetter. When checking the ceiling crack carefully, it appears to have been patched in the past. We did get a building inspection done before we purchased but while a hairline crack was noted on the report, nothing more was said on it. It seems plausible that they are right, that the cause is the drying out of the soil.
Is there anything else that could have caused this? In either case, do people have suggestions about which direction to go in to find a fix? I'm mostly wanting it stable; the plaster can be patched again as required, but I think that the the degree to which the brick expansion joint has separated at the top is concerning; I'd be happier if it could be closed up at least part way. Due to changed circumstances, we are intending to sell again in a year or two and thus do need it to look better as well as be better.