John Rumm wrote:
While in theory the timber is kiln dried, I know from recent experience
that is only part of the story! What happens to it after it leaves the
lumber yard is another matter. Many builders merchants seem to keep
constructional timber outside in the rain. (I know I had some bits of
4x2" delivered that were so wet you could almost wring them out!)

We were lucky this year - over the period that the joists were on site
(delivery to roof completed) there was no rain. What happened to them in
the yard is another story, of course - April was *very* wet.

Did you start to notice more movement after the weather got colder and
the heating came on?

I couldn't really say... I didn't pay any attention to floor movement
until after I'd tiled the floor around Sep-Oct, which was about the time
the heating came on.

However another post suggests that I can expect around 3-4% shrinkage as
the joists reach their stable moisture content, with a smaller seasonal
fluctuation after that. So I might well have seen the worst of it by now.

Thanks for all the responses.

--
Tony