Thank you all three, so much, for your worthy thoughts. I'll try to
respond to each.

First of all, I've already considered many things. But because of the
inconsistency of the symptoms, I have pretty much concluded that there is
more than one cause. What I am trying to do now is determine which of the
potential causes are real and which are not. That's how I got down to tree
roots -- which I admit was a pretty long shot. FWIW though, the trees in
question are Austrian Pines, probably 40' tall by now, and they are about
20' away from the house.

Thus far, the only cause in which I have high confidence is when the
neighbors irrigate too much for too long. (I mean mud and water appearing
in my own back yard.) But from all appearances they have stopped that
since I indicated to them the problems that it was causing. However, the
symptoms have only decreased, not stopped, which leads me to believe that
there is at least one additional (seasonal) cause.

George: The house is on a standard slab. Your point about clay expanding
and contracting is interesting. I had not thought of that. However, the
"soil" around here is really what they call "decomposed granite". I don't
think there is any clay in it at all. But I will follow up with the locals
to be sure.

Janet: As you see from the above, the trees are not deciduous; but I don't
know whether that is relevant. Re removing the trees, I really don't wish
to do that. But if only I could be sure that they were the next proximate
cause, (and not something worse), then I would just accept and live with
it.

Lucky: The primary symptoms are audible, however there are many hairline
cracks in the patio and garage floor. The rest of the house is carpeted so
its difficult to be sure what's under there. The house is not built on a
hill, but it is on the slope of some foothills. I have bored some 6' holes
around the house, to test for water, but so far none has appeared at the
bottom of any of them. (This was done after the neighbors stopped deep
watering.) So if it is a water table issue, it must be below that. I am
wondering if there might be a channel down there, which the bore holes
wouldn't locate unless they were right on the mark...(?)

Re thermal expansion and contraction, I have thought much on this already,
and recognize it well when it is happening; however the symptoms are so
inconsistent that I have almost eliminated this as a primary cause.

Thanks again, everyone, for your thoughts. I welcome any more...



On Wed, 14 Jun 2006 09:47:45 -0600, David wrote:

I don't know whether this is an appropriate question for this NG, but I
don't know where else to post it. If someone has a better recommendation,
I will be happy to take it there.

I have a suspicion that tree roots are stressing the foundation of my
house. However, the symptoms are not constant -- they vary with the time
of year.

My question: In general, do tree roots grow at different rates during
different seasons of the year?

Thank you very much for any thoughts.