Tony Eva wrote:


However, since then, it has become obvious that the upstairs floor is
sinking. By looking at the level of the floor tiles against the

The floor's construction is pretty standard - 2x10 (or 12? not sure)
wooden joists, laid on 40cm centres, one end bedded into the inner
blockwork leaf of the new wall, the other end suspended on joist hangers
from the existing wall. The end that's dropping is the one bedded into
the new wall. The flooring surface is sheets of T+G flooring grade
chipboard, screwed to the joists at approx 30xm intervals.

There are a few clues in there. The fact the the floor is moving
relative to the skirting would suggest it is *not* the whole wall that
is moving since the joists are presumably being supported by the same
wall. So that does lend weight to the shrinkage theory. Also the fact
that the joists are in hangers at one end might also go some way to
explain why you are not seeing the same (or as much) movement at that
end. Depending on the hanger design it may well have a row of nails down
both sides for most of the depth of the joist, this would tend to
restrict the shrinkage a little, and also maintain the centre of the
joist in its original position, causing the shrinkage to be shared
partly above and partly below. The other end however the joist is simply
sat on a wall plate and hence all shrinkage will appear as a loss of
height of the joist.

You may also see some variation as the centre of the span sags a little
as it will over time. If the builder was careful then he will have
placed all the joists with their natural camber rising, so they settle
towards level.

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!)

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


--
Cheers,

John.

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